Text

Attachment 8 - Netco Report NET-259-03, Revision 5, Material Qualification of Alcan Composite for Spent Fuel Storage
	ML13199A039
Person / Time
Site:	Quad Cities
Issue date:	07/30/2009
From:	; Northeast Technology Corp
To:	; Exelon Generation Co, Office of Nuclear Reactor Regulation
References
	NET-259-03, Rev 5
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ATTACHMENT 8NETCO Report NET-259-03, Revision 5"Material Qualification of Alcan Composite for Spent Fuel Storage" NET-259-03 MATERIAL QUALIFICATION OF ALCANCOMPOSITE FOR SPENT FUEL STORAGEPrepared by:Northeast Technology Corp.108 N. Front StreetKingston, NY 12401August 2008Rev. Date Prepared by: Reviewed by: Approved (QA):'/4L4~4 4J .h.

NET-259-03 Rev 5Table of Contents1.0 Introduction and Summary .........................................................................

1-12.0 Description of the NETCO-SNAP-IN and Installation Tooling ...................

2-13.0 Manufacturing the NETCO-SNAP-IN Neutron Absorber Insert ................

3-13 .1 B illet P rod uctio n ..................................................................................

3-13.2 NETCO-SNAP-IN Production

............................................................

3-23.3 Applicable Codes, Standards and Regulatory Guidance

....................

3-23.4 Q uality A ssurance

...............................................................................

3-34.0 Engineering Evolution of the Alcan Composite

..........................................

4-14.1 Comparison of the Alcan Composite with BORALTM ...............

............ 4-14.2 In-Service Performance of Aluminum Matrix NeutronA bsorber M aterial ...............................................................................

4-9 54.3 N ETC O C redentials

..........................................................................

4-155.0 Accelerated Corrosion Testing ...................................................................

5-15 .1 T est D escription

..................................................................................

5-15.2 Test Matrices and Coupon Description

...............................................

5-1 45.3 W ater C hem istry .................................................................................

5-45.4 Corrosion Test Results .......................................................................

5-85.5 Discussion of Test Results and Conclusions

....................................

5-306.0 Fast Start Coupon Program Description

....................................................

6-17.0 Long Term Surveillance Program ...............................................................

7-17.1 Tree and Coupon Description

.............................................................

7-17.2 Coupon Inspection and Testing ..........................................................

7-17.3 Frequency for Coupon Inspection

.......................................................

7-3Appendix:

Determination of Equivalent In-Service Time for Rio Tinto Alcan 4W1 100 N Series Neutron Absorber Alloy Based on Accelerated Corrosion Test Conditions NET-259-03 Rev 5List of Tables3-1 Insert Quality Assurance Testing Summary ..............................................

3-54-1 Comparison of Aluminum Alloy Matrices

..................................................

4-24-2 Comparison of Boron Carbide ..................................................................

4-34-3 Room Temperature Mechanical Properties of BORALTM and theA lca n C om posite .......................................................................................

4-554-4 Partial Listing of Research and Test Reactors WhereBORALTM Has Been Used ........................................................................

4-94-5 Partial List of LWRs Where BORALTM Has Been Used inSpent Fuel Storage Racks ......................................................................

4-10 44-6 Partial List of LWRs Where BORALTM Has Been Used inD ry S torage C asks ..................................................................................

4-135-1 Coupon Test Matrix for Accelerated Corrosion Testing ............................

5-25-2 Number and Type of Coupons per BathTested After 2000 and6 0 0 0 H o u rs ...............................................................................................

5 3 Number and Type of Coupons per BathTested After 4000 and8 0 0 0 H o u rs ...............................................................................................

5-35-4 Water Specification for Corrosion Baths ...................................................

5-55-5 Summary of Coupon Thickness Changes by Coupon Type ...................

5-205-6 Summary of Coupon Weight Changes by Coupon Type ........................

5-20 45-7 Average Corrosion Rates ........................................................................

5-305-8 Equivalent Exposure Time ......................................................................

5-306-1 Pre and Post Test Coupon Characterization

.............................................

6-37-1 Long Term Surveillance Coupons .............................................................

7-17-2 Long Term Surveillance General Coupon Characterization

......................

7-27-3 Long Term Surveillance Bend and Galvanic Coupon Characterization

.... 7-27-4 Frequency for Coupon Testing .................................................................

7-3ii NET-259-03 Rev 5List of Figures2-1 NETCO-SNAP-IN Insert Installed in a Spent Fuel Storage Rack .........

2-22-2 NETCO -SNA P-IN Insert .......................................................................

2-32-3 Insta llatio n T oo l ......................................................................................

2-54-1 Comparison of Manufacturing Processes

..............................................

4-44-2 M icro Photograph of BO RALTM ...............................................................

4-5 54-3 Neutron Attenuation Comparison:

BORALTM vs. Alcan AluminumM atrix A bsorber ......................................................................................

4-8 45-1 pH versus Time: BWR Accelerated Corrosion Test ..............................

5-65-2 Water Conductivity versus Time: BWR Accelerated Corrosion Test ..... 5-65-3 pH versus Time: PWR Accelerated Corrosion Test ..............................

5-75-4 Water Conductivity versus Time: PWR Accelerated Corrosion Test ..... 5-75-5 Comparison of Post-Test Coupon Appearance with Archive Material:

16 vol % Boron Carbide Loading after 4000 Hours ..............................

5-115-6 Comparison of Post-Test Coupon Appearance with Archive Material:

16 vol % Boron Carbide Loading after 8000 Hours ..............................

5-115-7 Comparison of Post-Test Coupon Appearance with Archive Material:

25 vol % Boron Carbide Loading after 4000 Hours ..............................

5-12 45-8 Comparison of Post-Test Coupon Appearance with Archive Material:

25 vol % Boron Carbide Loading after 8000 Hours ..............................

5-125-9 Comparison of Post-Test Coupon Appearance with Archive Material:

16 vol % Boron Carbide Loading at 8X Magnification after 4000 H ours ..................................................................................

5-135-10 Comparison of Post-Test Coupon Appearance with Archive Material:

16 vol % Boron Carbide Loading at 8X Magnification after 8000 H ours ..................................................................................

5-135-11 Comparison of Post-Test Coupon Appearance with Archive Material:

25 vol % Boron Carbide Loading at 8X Magnification after 4000 H ours ..................................................................................

5-145-12 Comparison of Post-Test Coupon Appearance with Archive Material:

25 vol % Boron Carbide Loading at 8X Magnification after 8000 H ours ..................................................................................

5-145-13 Photomicrograph of 16 vol % B4C Composite As-Fabricated (45X) ..... 5-155-14 Photomicrograph of 25 vol % B4C Composite As-Fabricated (45X) ..... 5-15iii NET-259-03 Rev 5List of Figures (con't.)5-15 Photomicrograph of 16 vol % B4C Composite after 8000 Hoursin Dem ineralized W ater (45X) ..............................................................

5-165-16 Photomicrograph of 16 vol % B4C Composite after 8000 Hoursin B oric A cid (45X ) ...............................................................................

5-165-17 Photomicrograph of 25 vol % B4C Composite after 8000 Hoursin Dem ineralized W ater (45X) ..............................................................

5-175-18 Photomicrograph of 25 vol % B4C Composite after 8000 Hoursin B oric A cid (45X ) ...............................................................................

5-175-19 BWR Thickness Change (Pre-Test vs. Post-Test)

...............................

5-225-20 PWR Thickness Change (Pre-Test vs. Post-Test)

...............................

5-225-21 BWR Weight Change (Pre-Test vs. Post-Test)

....................................

5-235-22 PWR Weight Change (Pre-Test vs. Post-Test)

....................................

5-235-23 BWR Coupon Weight Change versus Time: 4G alvanic Couple Coupons ...................................................................

5-245-24 PWR Coupon Weight Change versus Time:G alvanic Couple Coupons ...................................................................

5-245-25 BWR Thickness Change (Pre-Test vs. Post-Test)

After Acid Cleaning:

General and Bend Coupons ...............................

5-255-26 PWR Thickness Change (Pre-Test vs. Post-Test)

After Acid Cleaning:

General and Bend Coupons ...............................

5-255-27 BWR Galvanic Coupons After Acid Cleaning:

CouponThickness C hange ...............................................................................

5-265-28 PWR Galvanic Coupons After Acid Cleaning:

CouponT hickness C hange ...............................................................................

5-265-29 BWR Coupon Weight Change (Pre-Test vs. Post-Test)

After Acid Cleaning:

General and Bend Coupons Only ........................

5-275-30 PWR Coupon Weight Change (Pre-Test vs. Post-Test)

After Acid Cleaning:

General and Bend Coupons Only ........................

5-275-31 BWR Galvanic Coupon Weight Change versus Time ..........................

5-28 15-32 PWR Galvanic Coupon Weight Change versus Time ..........................

5-28iv NET-259-03 Rev 5List of Figures (con't.)5-33 BWR Coupon Areal Density Change versus e .................

T..............5-29 1 45-34 PWR Coupon Areal Density Change versus Time ...............................

5-296-1 Fast Start Surveillance Coupon ..............................................................

6-26-2 Fast Start Coupons String .....................................................................

6-2v NET-259-03 Rev 51.0 Introduction and SummaryThe purpose of this topical report is to demonstrate that aluminum/B 4C sheet producedfrom DC (direct chill) cast rolling billets supplied by Rio Tinto Alcan Inc. is a suitable 3material for use as a neutron absorber in spent nuclear fuel storage applications and inparticular it is a suitable material from which to fabricate NETCO-SNAP-IN neutronabsorber inserts.

The NETCO-SNAP-IN neutron absorber insert is installed in existingspent fuel storage racks to restore the reactivity hold-down capability of racks withdegraded Boraflex.

Once installed, these neutron absorber inserts becomepermanently affixed to the storage racks.The suitability of Rio Tinto Alcan Inc. material as demonstrated herein is based upon:" detailed comparison with highly similar material with a successful record ofindustry-wide, in-service performance

accelerated corrosion testing in simulated BWR and PWR spent fuel pool 4environments

evaluating and testing of mechanical properties to verify acceptability of installed insert retention force" measurement of B10 areal density to confirm satisfactory neutron absorption capability

short term and long term in-situ coupon surveillance programs.

These evaluations are detailed in the various sections of this report.The Alcan material is supplied as 6x6 inch rectangular DC cast rolling billets that are hotrolled to final gage. The material is designated as aluminum boron carbide composite W1 100N.XYB where XY is the boron carbide content which can range from 16 to 301-1 NET-259-03 Rev 5volume percent.

The reinforcing phase of the composite is boron carbide powdercontaining at least 76 w/o boron and with an average particle size of 7.5 +/- 2 pm (D50).As stated above, one particular application of the W1 100N.XYB composite in spent fuel 4pools is the NETCO-SNAP-IN neutron absorber insert. The NETCO-SNAP-IN isproprietary to NETCO and is protected by U.S. Patent No. 6,741,669 B2.11 The firstuse of NETCO-SNAP-IN absorber inserts will be at Exelon's LaSalle Unit 2 Station.Other applications of the W1 100N.XYB composite include newly fabricated spent fuelstorage racks and dry spent fuel storage and transportation casks. With respect to thelatter use, this material has been used in dry storage/transportation in the U.S. andextensively in Europe.Recent guidance has been published for the qualification and acceptance of new boronbased metallic neutron absorbers for storage and transportation casks. (1-21 Using thisdocument as a guide, the qualification process described in this report consists of thefollowing elements:

" Review of the composition and manufacturing process of the W1 100N.XYBcomposite and a detailed comparison with the composition and manufacturing process for BORALTM, a neutron absorber material that has been successfully used extensively worldwide for spent nuclear fuel storage racks for the last 40years." An accelerated corrosion program has been completed in both demineralized water and boric acid (2500 ppm as boron). The program ran for one year in 5duration.

Interim and final results are reported.

" A fast start surveillance coupon program has been initiated (March 08) at LaSalleUnit 2 to provide in-service performance data on the W1 100N.16B composite inthe actual proposed service environment.

This will provide performance datathat will always lead the installed NETCO-SNAP-IN inserts in both time ofexposure and absorbed gamma dose. The faststart coupon program consists ofa string of 24 coupons connected by stainless links. The coupons have beenprecharacterized with respect to dimensions, dry weight, density and boron-101-2 NET-259-03 Rev 5areal density.

Periodically coupons will be removed from the string and sent to aqualified laboratory for post exposure testing and inspection.

A long term surveillance assembly will be placed in the LaSalle pool prior to theinstallation of the first NETCO-SNAP-IN inserts.

These coupons will differ fromthe "Fast-Start" and, in particular, will be composed of 17 vol-% B4C instead of 16vol-% B4C material.

This modification is due to a manufacturing revision of theNETCO-SNAP-IN inserts intended to ensure compliance with minimum arealdensity requirements.

The tree will hold the following types of coupons:-unclad Alcan W1100N.17B composite coupons-W1100N.17B composite coupons with 304L stainless steel, In-718 andZircaloy samples-W1100N.17B composite bend couponsPeriodically coupons will be removed from the assembly and sent to a qualified laboratory for testing and inspection.

The following sections of this report describe:

-NETCO-SNAP-IN and Installation Tooling-Manufacturing process and quality control used for NETCO-SNAP-IN inserts-Composition and physical properties of the Wi 1 OON.XYB composite

-Description of accelerated corrosion testing and interim results-Comparative evaluation of W1 100N.XYB composite and BORALTM-Anticipated performance of W11 OON.XYB in spent fuel pools-Detailed description of the "fast start" coupon surveillance program-Detailed description of long term coupon surveillance program-Conclusions References Section 11-1. Lindquist, K. 0., U.S. Patent No. 6,741,669 B2, "Neutron Absorber Systems andMethod for Absorbing Neutrons,"

May 25, 2004.1-3 NET-259-03 Rev 51-2.ASTM C 1671-07, "Standard Practice for Qualification and Acceptance of BoronBased Metallic Neutron Absorbers for Nuclear Criticality Control for Dry CaskStorage Systems and Transportation Packaging."

1-4 NET-259-03 Rev 52.0 Description of the NETCO-SNAP-IN and Installation ToolingNeutron absorber materials are incorporated in spent fuel storage racks to permit thesafe storage of LWR fuel assemblies in close proximity to each other. One or twopanels of a neutron absorber material are placed between each face of every fuelassembly in order to maintain the stored fuel in a sufficiently sub-critical condition.

One neutron absorber material used for this purpose,

Boraflex, has been observed toexperience in service degradation well in advance of its design service life. Asdegradation

proceeds, the matrix intended to retain the neutron absorber (boroncarbide) dissolves and the boron carbide slumps to the bottom of the pool. As thisoccurs, less and less of the neutron absorber is in place to maintain the fuel in a sub-critical condition.

The NETCO-SNAP-IN insert mitigates the boron carbide loss from Boraflex byinserting a thin chevron-shaped metallic sleeve into the fuel storage cell of the rack.The sleeve is fabricated from an aluminum/boron carbide composite.

When installed, this sleeve, or insert, abuts two adjacent faces of the rack wall. It is intended that aninsert be installed in all the storage cells of a given module as shown in Figure 2-1.With each insert installed in the same configuration, every face of all fuel assemblies willhave neutron absorber material between it and one face of the adjacent fuelassemblies.

Since the inserts are fabricated of a neutron absorbing

material, replacement of the initial reactivity hold-down system is effectively achieved.

2-1 NET-259-03 Rev 5NETCO'SNAP-INSJ InsertFigure 2-1 NETCO-SNAP-lAIN Insert Installed in aSpent Fuel Storage RackFigure 2-2 shows a typical NETCO-SNAP-IN.

The insert has a length equivalent to thelength of the fuel storage cell and the lower end is tapered to facilitate insertion into thefuel storage cell. The chevron is formed with a central bend angle along its lengthgreater than 90°. The width of each wing of the chevron is slightly less than theminimum inside dimension of the fuel storage cell. Each edge of the wing is roll formedand it is this feature that accommodates cell to cell Variations in inside dimensions.

Near the top of the NETCO-SNAP-IN is a hole in each wing that engages theinstallation tool.It is noted that the chevrons are formed with a greater than 90° bend angle and thiscauses compression of the insert as it is "pushed" into the rack cell and assumes the2-2 NET-259-03 Rev 5900 angle between adjacent rack cell walls. The insert is designed to become anintegral part of the fuel rack once it has been installed.

This is achieved through theelastic deformation of the insert bearing against the rack cell wall and the associated friction force. The force exerted due to this deformation is predicted by the effective spring constant of the insert, which is described in detail elsewhere.

The force betweenthe insert wings and the rack cell walls in conjunction with the static friction betweenthese surfaces serves to retain the NETCO-SNAP-IN and make it a permanent part ofthe rack once it is installed.

01% o05IFigure 2-2 NETCO-SNAP-IN InsertThe installation tool with a NETCO-SNAP-IN engaged is shown in Figure 2-3. At thetop of the tool is a bail that replicates the bail on a BWR fuel assembly.

As such theinstallation tool can be engaged with a fuel grapple or with the refueling mast. The bailis attached to an anvil assembly that provides a bearing surface on the top edge of theinsert. Immediately below the anvil assembly is the head assembly.

The headassembly contains two spring loaded cylinders, that engage the insert while it is beingmoved to the storage cell into which it is destined for installation.

When, duringinstallation, the cylinders come into contact with the rack cell wall they retract, thusallowing full insertion of the insert. The curvature of the upper edge of each cylinder isso configured that when the insert is fully installed, upward movement of the tool allowsthe cylinder to clear the engagement holes in the insert, leaving the insert fully seated inthe rack cell.2-3 NET-259-03 Rev 5Again referring to Figure 2-3, a counterweight is suspended from three rods below thehead assembly.

In addition to partially providing downward insertion force, thecounterweight, which contributes to insert stability during installation, lowers the centerof gravity of the tool. The insertion tool is constructed entirely of stainless steel andweighs less than 1290 lbs. 32-4 NET-259-03 Rev 5BailCylinderNETCO-SNAP-INAnvil-AssemblyHeadAssemblyCounterweight Figure 2-3 Installation Tool2-5 NET-259-03 Rev 53.0 Manufacturing the NETCO-SNAP-IN Neutron AbsorberInsert3.1 Billet Production There are two basic methods for producing aluminum/boron carbide metal matrixcomposites:

powder metallurgy and liquid metal mixing. In the case of powderedmetallurgy, atomized metal powder is blended with boron carbide particles, compacted and sintered to form a billet for further processing.

The billet is generally extruded toproduce rectangular preforms for rolling to final gage. This method has proved to beexpensive due to the high cost of atomized metal powders and time consuming processing steps. In addition, wear products from the extrusion die on the surface ofthe preform need to be removed by cleaning or machining so as not to result in galvaniccorrosion in wet storage applications.[

3-1I Furthermore, and depending on the processused to produce the billets, the final rolled sheet may have limited ductility making thesheet difficult to form by bending.

[3-2]Alcan has developed a liquid mixing process for producing aluminum/boron carbidecomposites that use mechanical stirring to mix the powdered B4C in the moltenaluminum.

As this mixing process is conducted at temperatures well over the meltingpoint of aluminum, significant aluminum and boron carbide interactions can occur thatcan result in degraded mechanical and physical properties.

[3-3] A significant physicalproperty effect can be the agglomeration of B4C particles resulting in a non-uniform boron distribution in the composite.

Alcan has found that by adding small amounts of Ti(< 2.5%) to the molten aluminum, the B4C particles become stable in the moltenaluminum, eliminating particle

clusters, and a uniform blend is achieved.

It is thoughtthat a Ti rich zone forms around each boron carbide particle, preventing AI/B4Cinteractions.

The molten aluminum/boron carbide blend is direct chill cast into 6"x6" rectangular billets.

The length of the billets is determined by the size and gage of the final rolled3-1 NET-259-03 Rev 5product.

The rectangular billets can be rolled directly without an intermediate extrusion step and the potential problems and cost associated with extrusion.

3.2 NETCO-SNAP-INI Production The Alcan billets are heated to -950°F and hot rolled to final gage. After onetransverse rolling the billet is rotated 900 and reduced to final gage in 33 passes in therolling mill. The rolled sheet is trimmed on a shear to final blank size.Once the blanks have been produced, the final fabrication steps required to produce thefinished NETCO-SNAP-IN inserts are as follow. The two long edges are trimmed on ashear to provide a tapered lead-in at the bottom of the inserts to facilitate installation.

The inserts are then formed on a press brake to an angle somewhat larger than 90' andthe two remaining long edges roll formed. The holes that engage the installation toolcan be formed by stamping or water jet cutting.3.3 Applicable Codes, Standards and Regulatory GuidanceThe following codes, standards and practices are used as applicable for the design andmanufacture of the NETCO-SNAP-IN inserts." ANSIANS 8.1 -Nuclear Criticality Safety in Operations with Fissionable Materials Outside Reactors.

" ANSI/ANS 8.12 -Nuclear Criticality Control and Safety of Plutonium

-UraniumFuel Mixtures Outside Reactor." ANSI/ANS 8.17 -Criticality Safety Criteria for the Handling,

Storage, andTransportation of LWR Fuel Outside Reactors.

ANSI/ANS 57.2 -Design Requirements for Light Water Reactor Spent FuelStorage Facilities at Nuclear Power Plants." ANSI N45.2.1 -Cleaning of Fluid Systems and Associated Components duringConstruction Phase of Nuclear Power Plants -1973 (R.G. 1.37)." ANSI N45.2.2 -Packaging,

Shipping, Receiving, Storage and Handling of Itemsfor Nuclear Power Plants -1972 (R.G. 1.38).3-2 NET-259-03 Rev 5a American Society for Nondestructive Testing SNT-TC-1A, June 1980,Recommended Practice for Personnel Qualifications and Certification inNondestructive Testing.0 ASTM C750 -Standard Specification for Nuclear-Grade Boron Carbide Powder.* ASTM C992 -Standard Specification for Boron-Based Neutron Absorbing Material Systems for Use in Nuclear Spent Fuel Storage Racks.* ASME NQA-1 -Quality Assurance Program Requirements for Nuclear Facilities.

ASME NQA-2 -Quality Assurance Requirements for Nuclear Power Plants.* General Design Criterion 62, Prevention of Criticality in Fuel Storage andHandling.

Memorandum from L. Kopp, SRE, to Timothy Collins, Chief, Reactor SystemsBranch, Division of Systems Safety and Analysis, "Guidance on the Regulatory Requirements for Criticality Safety Analysis of Fuel Storage at Light WaterReactor Power Plants,"

August 19, 1988.0 "OT Position for Review and Acceptance of Spent Fuel Storage and HandlingApplications,"

dated April 14, 1978, and the modifications to this document ofJanuary 18, 1979.S1OCFR21

-Reporting of Defects and Non-compliance.

0 10CFR50 Appendix B -Quality Assurance Criteria for Nuclear Power Plants andFuel Reprocessing Plants.* 10CFR50.68

-Criticality Accident Requirements.

0 USNRC Standard Review Plan, NUREG-0800, Section 9.1.1, New Fuel Storageand Section 9.1.2, Spent Fuel Storage.* USNRC Regulatory Guide 1.13, Spent Fuel Storage Facility Design Basis, Rev.2, December 1981.3.4 Quafity Assurance The NETCO-SNAP-INs are designed and fabricated under control and surveillance ofNETCO's Quality Assurance Program[341 that conforms to the requirements of 10CFR50Appendix B. Since the NETCO-SNAP-INs are used for reactivity control of fuelassemblies stored in close proximity, they are classified as nuclear Safety Related (SR).3-3 NET-259-03 Rev 5As such, and as required by NETCO's Quality Assurance Program 3"4, they aredesigned and fabricated to preclude the use of any material or manufacturing processthat deviates from a rigorous set of specifications established by the NETCO designteam. Process controls for materials and fabrication are established to preclude theincidence of errors and inspection steps are implemented to ensure that all criticalattributes, as identified by the design team, for the feed material and rolled sheet aremet in the final product.The raw materials including AA 100, B4C and Ti used to make the cast billets areobtained by Rio Tinto Alcan from qualified suppliers.

The material certifications supplied with the feed material are independently confirmed.

An independent massspectroscopic measurement of boron-10 fraction is performed on each lot of boroncarbide powder used. Each cast of B4C and aluminum is chemically analyzed to assurethat the composition conforms to the design specification for weight fraction of boron, Aland Ti. Permanent records of these analyses are retained in NETCO's qualityassurance files. Each completed NETCO-SNAP-IN has a unique identifying numberetched along the inside upper surface and this number is fully traceable to the billet,cast and feed material lots.For these purposes, coupons are cut from each rolled insert blank, which is of sufficient size to manufacture two NETCO-SNAP-INs.

Samples from the coupons are subjected to neutron attenuation testing to verify as-manufactured boron-10 areal density andmechanical testing to assure sufficient ductility to permit forming.Quality Assurance procedures are enforced on the fabrication shop floor that provide allcontrols necessary to comply with all quality assurance requirements.

One hundredpercent final inspection at the shop includes dimensions, formed angle, bend, twist,cleanliness, identifying markings and freedom from imperfections.

A summary table of critical characteristics and qualification tests performed in support of 5those characteristics is listed below:3-4 NET-259-03 Rev 5Table 3-1 Insert Quality Assurance Testing SummaryCritical Characteristic Qualification Testing Acceptance CriteriaPerformed Minimum B-10 Areal Neutron Attenuation

> 0.0087 g B10/cmA2Density TestingMaterial Composition ICP Analysis Boron, Carbon, Titaniumand Aluminum withinspecification limitsMechanical Properties Tensile and Bend Testing Tensile Strength

>10 ksiElongation

> 3%Bend Test to supportdesign specification forinsert retention force.5References Section 33-1."Qualification of METAMIC for Spent-Fuel Storage Application,"

EPRI Report No.1003137, Prepared for EPRI by Northeast Technology Corp., Kingston, NY,10/2001.3-2. "Handbook of Neutron Absorber Materials for Spent Nuclear Fuel Transportation and Storage Applications, 2006 Edition,"

EPRI Report No. 1003721, Prepared byNortheast Technology Corp., Kingston, NY, 10/2006.3-3.Z. Zhazy, A. Charlette, R. Ghomusheki, X.-G Chen, "Effect of Titanium onSolidification Microstructure of A-16% B4C Composites,"

Light Metals, 2005,Calgary,

Alberta, Canada.3-4.Quality Assurance Manual, Rev. 1, Northeast Technology Corp., 2007.3-5 NET-259-03 Rev 54.0 Engineering Evaluation of the Alcan Composite The Alcan composite is very similar in composition to another neutron absorbermaterial,

BORALTM, that has been used extensively for more than 40 years for both wetand dry storage applications.

The in-service performance of BORALTM has been good.In this section the composition, physical properties and mechanical properties of bothmaterials are compared and the industry experience with the BORALTM neutronabsorber reviewed.

4.1 Comparison of the Alcan Composite with BORALtmComposition Both of these neutron absorber materials utilize AA1 100 as the base alloy for the metal5matrix that retains the boron carbide.

The compositions of the alloy matrices arecompared in Table 4-1. With the exception of the addition of Ti to the Alcan composite, as noted previously, the compositions are almost identical.

In fact, the Alcanrequirement for other elements is somewhat more stringent than the BORALTMrequirement.

4-1 NET-259-03 Rev 5Table 4-1Comparison of Aluminum Alloy MatricesBORAL ALCAN ALCAN ALCANAA1100 Metal Matrix Composite Composite Composite Property UNS A91100 Material Metal Matrix Vol 16% B4C Vol 17% B4CTemper 0 Materl Matetal Max Typical TypicalSpec Material Spec Properties Properties Al 99.00% min 99.00% min 99.00% min 82.7% 82.0%Si & Fe 0.95% max 1.00% max 0.45% max 0.38% 0.39%Cu 0.05-0.20%

0.05-0.20%

0.11% 0.11%Mn 0.05% max 0.05% max 0.05% max < 0.01% < 0.01%Zn 0.10% max 0.10% max 0.10% max <0.01% 0.01%Mg --- 0.05% max < 0.01% <0.01%Ti --.--- 1.00% -2.50%* 1.85% 2%B4C ---.-----

15.3% 15.9%Other 0.15% total 0.15% max 0.15% total 0.08%Elements each 0.05% max eacheach11 ksito 10 ksi Not Specified 17 ksi 17 ksiTensile 15.5 ksiYield 3.5 ksi min --- Not Specified 10 ksi 10 ksiElongation 30% min 0.1 Not Specified 5% -8% 5% -8%*Titanium is added during mixing of the B4C and not part of the matrix materialspecification.

54-2 NET-259-03 Rev 5The boron carbide specifications are compared in Table 4-2. The Alcan specification issomewhat tighter in terms of allowable impurities and requires a much smaller particlesize. With respect to the latter, the smaller particle size results in a more homogeneous

absorber, less potential for neutron streaming and a more effective neutron absorbermaterial.

Table 4-2Comparison of Boron CarbideBORALTM Constituent Alcan Composite 70.0 min Total Boron 76 w/o min3.0 max Boric Oxide 0.03 % Typ.2.0 max Iron 0.075% Typ.94.0 min Total Boron & 99.6% Typ.940min Carbon 99.6%_Typ.

75 -250 pm Particle Size 17.5 +/- 2 pmManufacturing Process Physical FormThe manufacturing processes for BORALTM and the Alcan composite are compared inFigure 4-1. The manufacture of BORALTM starts with the complete blending of atomizedAA1 100 powder and boron carbide.

An AA1 100 rectangular box -12 to 15 inches on aside and a few inches high depending on the thickness of the finished product is filledwith the blended powder. The walls of the box are -1 inch thick. After a top is weldedon the box, the billet is ready for hot rolling to final gage.The production process for the Alcan material differs from the BORALTM process in thatthe boron carbide powder is blended into molten aluminum and a rectangular billetformed by direct chill casting.

Hot rolling is used to produce the final sheet.54-3 NET-259-03 Rev 5BORALTMALCAN COMPOSITE Figure 4-1: Comparison of Manufacturing Processes In its finished form, BORALTM consists of 1) a core of uniformly mixed and distributed boron carbide and alloy AA1 100 aluminum particles; and 2) an AA1 100 surfacecladding on both sides of the core, serving as a solid barrier.

Figure 4-2 is a microphotograph of the edge of a BORALTM sample showing the core and clad region.BORALTM has been produced with the core containing anywhere between 35 w% and65 w% boron carbide.

For most cores produced

recently, the core contains about 50w% boron carbide.

In addition, the core is not fully dense and contains as much as 5%open and interconnected porosity.

The Alcan composite, on the other hand, in its final form is a fully dense homogeneous mixture of fine boron carbide particles embedded in the matrix aluminum alloy. As suchit contains no porosity that can allow water intrusion and potential problems associated with internal moisture.

54-4 NET-259-03 Rev 5Figure 4-2: Micro Photograph of BORALTMMechanical Properties The mechanical properties of BORALTM and the Alcan composite are compared in Table4-3.Table 4-3Room Temperature Mechanical Properties of BORALTM and the Alcan Composite BORALTM Alcan Composite 10 Tensile Strength, ksi 10Ultimate

Strength, ksi 170.1 Elongation,

% 7.0This comparison shows that the tensile properties of the two materials are similar butthe Alcan composite has improved ductility.

4-5 NET-259-03 Rev 5Stress Relaxation During installation, the absorber inserts are compressed from an initial bend anglegreater than 900 to the square dimensions of the rack cell interior.

Once installed, theinserts maintain a fixed strain within the rack storage cell that may be susceptible torelaxation over time. An analysis of stress relaxation in aluminum alloys has beenperformed to establish the expected performance of the inserts in this regard.As shown above, the Rio Tinto Alcan W11OON.16 B alloy had similar mechanical characteristics to 6061 aluminum alloy based Boral material.

Reference 4-1 detailsstress relaxation performance of 6060-T6 alloy after 1000 hours0.0116 days 0.278 hours 0.00165 weeks 3.805e-4 months at varioustemperatures.

The data shows approximately 15% stress relaxation after 1000 hours0.0116 days 0.278 hours 0.00165 weeks 3.805e-4 months at1000 C.[41]Average bulk pool temperatures within the LaSalle spent fuel pool are approximately 850 F. Stress relaxation at this temperature is expected to be significantly lower than15% over 1000 hours0.0116 days 0.278 hours 0.00165 weeks 3.805e-4 months . As an upper limit, however, data for AA 100-HI 12 seriesaluminum[

42] was analyzed to estimate total stress relaxation after 20 years of service.The results of that analysis showed that the AA 100 series aluminum was, based uponextrapolated data, expected to have experienced an approximate stress reduction of50% over 20 years. Given the reduced elongation of the Rio-Tinto Alcan composite incomparison with AA1 100 series aluminum, this stress relaxation is likely an upper limitfor the performance of the W11 OON series material.

Typical breakaway withdrawal forces were measured and are typically several hundredpounds. At the 15% relaxation predicted for the 6061-T6 alloy, a reduction in retention force between 45 and 90 lbf after 1000 hours0.0116 days 0.278 hours 0.00165 weeks 3.805e-4 months at 1000 C would be expected.

At thelimiting case of a 50% reduction in retention force over 20 years, the inserts would stillmaintain greater than 150 lbf of retention within the cell if there were no other mitigating factors.

These values are adequate to maintain the inserts in their configuration duringfuel movement operations provided the fuel bundles are qualified for use in those4-6 NET-259-03 Rev 5locations (i.e. they fit within the specified dimensions).

However, the following factorswould tend to mitigate the stress relaxation effects:1. Stress relaxation in boron carbide reinforced aluminum will be less thanfor the pure alloy; 42. The formation of an oxide film on the surface of the inserts will increasethe stress (by increasing the spacing between the rack wall and the insert)as well as the coefficient of friction between the insert and the cell wall.Neutronic Properties It has been previously noted that the average particle size of boron carbide in BORALTMis 85 microns and individual particles can range up to 250 microns.

Particles of thesedimensions introduce self shielding effects that can diminish the neutron absorption effectiveness.

NETCO has measured the neutron attenuation characteristics ofBORALTrM and the Alcan composite, the latter material with average boron carbideparticle size of 17.5 microns.Figure 4-3 compares the neutron attenuation characteristics of BORALTM and the Alcancomposite.

The neutron attenuation characteristics are measured using a collimated thermal energy neutron beam. A sample of a neutron absorber is placed in this neutronbeam and the intensity of the beam incident on the absorber, Ii, is measured.

Theintensity of the beam transmitted through the material, It, is also measured and theneutron attenuation characteristic, NA, is calculated as:NA = 1 -It/liFigure 4-3 shows that for the same areal density BORALTM absorbs fewer neutrons thanthe Alcan absorber.

This illustrates the importance of neutron channeling effects inabsorbers with relatively large particles when a normal mono-directional neutron beamis incident on the absorber.

4-7 NET-259-03 Rev 50.990.960170.960.950.930.920.910.890,89c 0840.830821 /= 0.80 0.790.780.770.760.7 /0.760.740.73 /0,72 / -Boral0.710.7 Alcan Fit0.690.680.007 o.009 0.011 0.013 0.015 0.017 0.019 001 0.023 0.025 0.027 o.029 0.031 0.033 0.035 0.037 0.0 0.041 0.043 0.045Areal Density, gm/cm^2Figure 4-3: Neutron Attenuation Comparison:

BORALTM vs. Alcan Aluminum Matrix Absorber4-8 NET-259-03 Rev 54.2 In-Service Performance of Aluminum Matrix Neutron AbsorberMaterialBORALTM has been used for nuclear applications for almost 45 years starting in 1964when it was used for reactivity control in the Yankee Rowe spent fuel racks. Nuclearapplications include control elements for test reactors, fuel storage racks for spentnuclear fuel and in dry fuel storage and transportation casks. Table 4-4 contains apartial listing of research reactors where BORALTM has been used. Table 4-5 containsa partial list of LWR plants where BORALTM has been used in spent fuel storage racks.It is noted that LaSalle Unit 2 sister unit currently has some 43,000 lbs of BORALTM in itsracks. Table 4-6 is a partial list of plants where BORALTM has been used for reactivity control in dry storage casks.For dry storage applications, it is noted that the Alcan composite is now approved foruse in the NUHOMS dry storage system as well as the Transnuclear metal cask storagesystem. The Alcan composite is being used at Peach Bottom, Limerick and St. Lucie aswell as in Europe.Table 4-4Partial Listing of Research and Test Reactors Where BORALTM Has Been UsedResearch and Test ReactorsAE-6 (USAEC)BORAX-5 (USAEC)Brookhaven Medical Research ReactorJEN-1 (Spain)Philippine Research-1 Rhode Island ReactorTriga Mark II (Italy, Austria, etc.)University of Kansas ReactorUniversity of Wisconsin ReactorVenezuela-1 Washington State University Reactor4-9 NET-259-03 Rev 5Table 4-5Partial List of LWRs Where BORALTM Has Been Used in Spent Fuel Storage RacksPool Plant Type Manufacturer Storage CountryLocations BEAVER VALLEY 1 PWR Holtec 1621 USABELLEFONTE I PWR Westinghouse 1058 USABRAIDWOOD 1&2 PWR Holtec 2984 USABROWNS FERRY 1 BWR GE 3471 USABROWNS FERRY 2 BWR GE 3471 USABROWNS FERRY 3 BWR GE 3471 USABRUNSWICK 1 BWR Holtec 1839 USABYRON 1&2 PWR Holtec 2984 USACALLAWAY PWR Holtec 1302 USACOMANCHE PEAK 1 PWR Holtec 222 USACOMANCHE PEAK 2 PWR Holtec 219 USACONN YANKEE PWR Holtec USACOOK 1&2 PWR Holtec 3613 USACOOPER BWR NES USACRYSTAL RIVER 3 PWR Westinghouse 932 USADAVIS BESSE 1 PWR Holtec 1624 USADRESDEN 1 BWR CECO 3537 USADRESDEN 2 BWR CECO 3537 USADRESDEN 3 BWR CECO 3537 USADUANE ARNOLD BWR PAR 1898 USADUANE ARNOLD BWR Holtec 1254 USAFERMI 2 BWR Holtec 559 USAFITZPATRICK BWR PAR 2797 USAFITZPATRICK BWR Holtec USAFT. CALHOUN PWR Holtec 160 USAHARRIS 1 PWR Holtec 484 USAHATCH 1 BWR GE 5830 USAHATCH 2 BWR GE 2765 USAHOPE CREEK BWR Holtec 3998 USAHUMBOLDT BAY 3 BWR Unknown USAINDIAN POINT 3 PWR UST&D 1340 USA4-10 NET-259-03 Rev 5Table 4-5 (con't.)Partial List of LWRs Where BORALTMHas Been Usedin Spent Fuel Storage RacksKEWAUNEE PWR Holtec 215 USAKOEBERG 1 PWR Holtec South AfricaKOEBERG 2 PWR Holtec South AfricaKORI-4 PWR Holtec South KoreaKUOSHENG 1 BWR ENSA 1578 TaiwanKUOSHENG 2 BWR ENSA 1578 TaiwanLAGUNA VERDE 1 BWR Holtec MexicoLAGUNA VERDE 2 BWR Holtec MexicoLASALLE 1 BWR UST&D 4029 USALIMERICK 1 BWR Holtec 2500 USALIMERICK 2 BWR Holtec 2766 USAMAINE YANKEE PWR PAR 1464 USAMCGUIRE 1 PWR Holtec 286 USAMCGUIRE 2 PWR Holtec 286 USAMILLSTONE 3 PWR Holtec 1104 USAMONTICELLO BWR GE 2229 USANINE MILE POINT 1 BWR Holtec 3496 USAOYSTER CREEK BWR Holtec 390 USAPERRY 1 BWR PAR 2400 USAPERRY 2 BWR PAR 1620 USAPILGRIM BWR Holtec 1539 USASALEM 1 PWR ENC 1117 USASALEM 1 PWR Holtec 1117 USASALEM 2 PWR ENC 1139 USASALEM 2 PWR Holtec 1139 USASEABROOK 1 PWR Westinghouse 576 USASEQUOYAH 1 PWR Westinghouse 2091 USASEQUOYAH 2 PWR Holtec USASEQUOYAH 2 PWR PAR 2091 USASIZEWELL B PWR Holtec 1901 UnitedKingdomSUMMER 1 PWR Holtec 1712 USASUSQUEHANNA 1 BWR PAR 2840 USASUSQUEHANNA 2 BWR PAR 2840 USA4-11 NET-259-03 Rev 5Table 4-5 (con't.)Partial List of LWRs Where BORALTM Has Been Used in Spent Fuel Storage RacksTHREE MILE ISLAND 1 PWR Holtec 1284 USATURKEY POINT 3 PWR Holtec 131 USATURKEY POINT 4 PWR Holtec 131 USAULCHIN 1 PWR Holtec 1000 South KoreaVERMONT YANKEE BWR UST&D 2860 USAVOGTLE 1 PWR Unknown 1476 USAWATERFORD 3 PWR Holtec 2232 USAWATTS BAR 1 PWR Holtec 1610 USAWATTS BAR 2 PWR Holtec 1610 USAYANKEE ROWE PWR PAR 721 USAYONGGWANG 1 PWR Holtec 1152 South KoreaYONGGWANG 2 PWR Holtec 1152 South KoreaZION 1 PWR Holtec 3012 USAZION 2 PWR Holtec 3012 USAANGRA 1 PWR Holtec 1252 BrazilCATTENOM-1 PWR Framatome 2520 FranceCATTENOM-2 PWR Framatome 2520 FranceCATTENOM-3 PWR Framatome 2520 FranceCATTENOM-4 PWR Framatome 2520 FranceBELLEVILLE-1 PWR Framatome 1260 FranceBELLEVILLE-2 PWR Framatome 1260 FranceNOGENT-1 PWR Framatome 1260 FranceNOGENT-2 PWR Framatome 1260 FrancePENLY-1 PWR Framatome 1260 FrancePENLY-2 PWR Framatome 1260 FranceGOLFECH-1 PWR Framatome 1260 FranceGOLFECH-2 PWR Framatome 1260 France4-12 NET-259-03 Rev 5Table 4-6Partial Listing of LWRs Where BORALTM Has Been Used in Dry Storage CasksCurrent Module AbsorberPlant Type Supplier Inventory Capacity TypeARKANSAS 2 Hi-Storm 100(MPC-32)

Holtec 416 32 BORALCATAWBA 1 UMS-24 NAC 24 BORALDIABLO CANYON 1 Hi-Storm 100(MPC-32)

Holtec BORALDIABLO CANYON 2 Hi-Storm 100(MPC-24)

Holtec BORALDRESDEN 2 Hi-Storm 100(MPC-68)

Holtec 1632 68 BORALDUANE ARNOLD NUHOMS-61BT Transnuclear 610 61 BORALFITZPATRICK Hi-Storm 100(MPC-68)

Holtec 204 68 BORALHADDAM NECK MPC-24 NAC 651 24 BORALHATCH 2 Hi-Storm 100(MPC-68)

Holtec 1496 68 BORALMAINE YANKEE UMS-24 NAC 1440 24 BORALPALO VERDE 1 UMS-24 NAC 624 24 BORALPEACH BOTTOM 2 TN-68 Transnuclear 1632 68 BORALPRAIRIE ISLAND 1 TN-40 Transnuclear 680 40 BORALSEQUOYAH 2 Hi-Storm 100(MPC-32)

Holtec 96 32 BORALTROJAN MPC(24)-Only Holtec 816 24 BORALSUSQUEHANNA I NUHOMS-61BT Transnuclear 183 61 BORAL* as of mid 2005In-Service Experience BORALTM Plate and Sheet in Wet StorageIt has been noted that in conventional storage racks, once BORALTM is installed in fuelracks, it is not accessible for inspection to determine its in-service performance.

Accordingly, the NRC has, in the past, required utilities to initiate a coupon surveillance program when new racks were installed.

A coupon surveillance program consists of aseries of small coupons either in a shroud (simulating the manner in which theBORALTM is encapsulated) or bare. The coupons are generally attached to asurveillance

assembly, which is placed in a spent fuel rack storage cell.4-13 NET-259-03 Rev 5The surveillance assembly is generally surrounded by recently discharged fuelassemblies to accelerate the rate at which the coupons accumulate gamma exposure.

Prior to placing the assembly in service, the coupons are generally characterized withrespect to:" visual appearance

" dry weight* dimensions

" specific gravity and density" boron-10 areal densityPeriodically, coupons are removed from the surveillance assembly and sent to anindependent laboratory for testing.

The post-irradiation test results generally mirror thepre-irradiation test results.

As the surveillance coupons are prepared from BORALTMcoupons cut from panels taken from the same production lot(s) used in the racks, theperformance of the coupons should be indicative of the performance of the material inthe racks.NETCO maintains laboratory facilities and offers inspection and testing services ofneutron absorber surveillance coupons.

In that capacity, NETCO has inspected hundreds of aluminum matrix surveillance

coupons, many of them BORALTM, from spentfuel pools around the world. It has been observed during testing that some surveillance coupons can be subject to a generalized corrosion, that includes the development of auniform oxide film. This film, once it forms, tends to be self passivating and preventsfurther corrosion.

Depending on pool conditions, other coupons can be susceptible tolocalized pitting corrosion.

It should be noted that while these corrosion effects canoccur in aluminum matrix neutron absorbers, to date this in-service corrosion has notresulted in any detectable decrease in the boron-10 areal density.

It is therefore concluded that the aluminum alloy matrix serves as suitable matrix to retain the boroncarbide in spent fuel storage racks. Additional qualification testing has been performed 5to further demonstrate the corrosion resistance of the Alcan W1 100.XYB material in4-14 NET-259-03 Rev 5BWR and PWR spent fuel pool applications.

This testing is described in Section 5.0 ofthis report.4.3 NETCO Credentials NETCO has been evaluating, specifying and qualifying neutron absorber material forstorage systems and transportation packaging for more than a quarter of a century.

Inthis capacity, NETCO has become an internationally recognized expert in assessing thein-service performance of this class of materials.

In 1987, the Electric Power Research Institute (EPRI) retained NETCO to evaluate theinstances of unanticipated performance of one neutron absorber,

Boraflex, at twoMidwest plants. NETCO's first report on this phenomenon concluded the observedshrinkage of the sheets of absorber would be expected when cross linking polymer wasexposed to gamma radiation.

NETCO notified EPRI that the BISCO materials qualification program did not adequately test the synergistic effects of gamma radiation and long term exposure to the pool water.These projections subsequently proved to be remarkably accurate and formed thebases for NETCO's development of BADGER and RACKLIFE.

BADGER (Boron-10 Areal Density Gage for Evaluating Racks) is a non-destructive test method thatmeasures the residual boron-10 in spent fuel racks. BADGER has now been used insome 35 test campaigns to assess the reactivity hold down capability of both Boraflexracks and racks with other neutron absorbers.

RACKLIFE is a comprehensive computer program that tracks the performance of eachand every Boraflex panel (as many as 4,000) in a typical rack installation.

RACKLIFE isbased on first principles and on the mass balance of soluble silica as it dissolves fromthe degraded Boraflex matrix and gradually migrates to the bulk pool volume. NETCOtested samples of irradiated Boraflex and measured the rate of dissolution as a functionof both absorbed dose and temperature in its laboratory.

This experimental data servesas the basis for the RACKLIFE dissolution model. This model and the RACKLIFE4-15 NET-259-03 Rev 5software upon which it is based as verified by BADGER measurements, serve to assurethat spent fuel pool criticality limits are met.At the Penn State Breazeale Research Reactor laboratory, NETCO routinely testsneutron absorber surveillance coupons.

These tests include Alcan composite

material, BORALTM, Boraflex, borated stainless steel, METAMIC, Talbor, Carborundum and ESKborated graphite and nano steel.NETCO was selected by Reynolds Metals Company to conduct qualification testing ofits new neutron absorber

material, METAMIC.

In this test sequence, NETCO conducted accelerated radiation

testing, accelerated corrosion testing and elevated temperature testing to qualify this material for use in spent fuel racks and storage and transportation casks. The resulting test report has been accepted by the NRC for both wet and dryapplications.

A second qualification test sequence for another new neutron absorberBorTecTM was completed by NETCO for DWA Technologies, the manufacturer ofBorTecTM.As such NETCO is the only organization to have successfully qualified newneutron absorber materials for wet storage applications since BORALTM was qualified some 40 years ago.NETCO was retained by EPRI, ENRESA and AAR (former BORALTM manufacturer) toevaluate clad blister formation under cask drying conditions.

Laboratory testing byNETCO simulating cask drying condition lead to recommended changes in the AARrolling schedule and lead to an improved BORALTM product that is largely blisterresistant.

4-16 NET-259-03 Rev 5References Section 4:4-1 K. Farrell, "ORNL/TM-13049 Assessment of Aluminum Structural Materials for 4Service Within the ANS Reflector Vessel,"

Oak Ridge National Laboratory, August 19954-2 John Gilbert Kaufman, Properties of Aluminum Alloys, ASM International, 19994-17 NET-259-03 Rev 55.0 Accelerated Corrosion Testing5.1 Test Description The accelerated corrosion test program has been designed to determine thesusceptibility of the Rio Tinto Alcan composite to general (uniform) and localized (pitting) corrosion in PWR and BWR spent fuel pools. Two sets of coupons have beentested at the NETCO laboratory; one set in deionized water, simulating BWR poolconditions and one set in deionized water containing 2500 ppm boron as boric acid,simulating PWR pool conditions.

Both tests were conducted at 195°F (90.5*C) toaccelerate any corrosion

effects, which might occur after the 8000 hour0.0926 days 2.222 hours 0.0132 weeks 0.00304 months (- 1 year) testperiod. The tests are accelerated by testing at elevated temperatures relative to typicaltemperatures in the actual service environment.

Typically, spent fuel pools areoperated in the temperature range of 80 to 1 00°F (27 to 380C) with short term 4excursions to 130'F (5400) during refueling outages.Coupons from each environment were removed after approximately 2000, 4000, 6000and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months and subjected to testing.

Prior to testing the coupons wereprecharacterized with respect to thickness, weight and boron-10 areal density.

Aftertesting, the coupons were subjected to post-test characterization of these sameattributes.

The testing after 2000, 4000, 6000 and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months has been completed.

This document represents the final report for this accelerated corrosion test.5.2 Test Matrices and Coupon Description The coupon test matrix for the accelerated corrosion test is shown in Table 5-1. A totalof 168 coupons have been tested; 84 in deionized water and 84 in 2500 ppm boron as 4boric acid. As shown in Table 5-1, coupons with two levels of boron carbide loadingswere tested. The coupons with an intermediate loading contain 16 vol% boron carbide.The coupons with the maximum boron carbide loading contain 25 vol% boron carbide.5-1 NET-259-03 Rev 5Table 5-1Coupon Test Matrix for Accelerated Corrosion TestingNumber of CouponsType of Coupon16 vol % B4C 25 vol % B4CGeneral 12 12Bend 12 12Galvanic (bi-metallic)*

18 18Subtotal 42 42Total 84*Note: For the galvanic bi-metallic

coupons, there are 3 subtypes.

These are SS-304L, Zircaloy and Inconel 718, eachseparately in combination with the Alcan composite.

At each of the scheduled test campaigns specific coupons were removed from the bathsand subjected to testing.

The number and type of coupons tested at 2000 and 6000hours is summarized in Table 5-2. The number and type of coupons tested at 4000 and8000 hours is summarized in Table 5-3. Three types of coupons at two boron carbideloadings have been tested as described in Tables 5-2 and 5-3.Table 5-2Number and Type of Coupons per Bath Tested After 2000 and 6000 HoursBoron Carbide LoadingeofCoupon 16vol % 25 vol %General (G) 3 3Bend (B) 3 3Total 1245-2 NET-259-03 Rev 5Table 5-3Number and Type of Coupons per Bath Tested After 4000 and 8000 HoursBoron Carbide LoadingType of Coupon l6vol % 25 vol %General (G) 3 3Bend (B) 3 3Bi-Metallic (BSS) 3 3Bi-Metallic (BZ) 3 3Bi-Metallic (BI) 3 3Total 30Since the NETCO-SNAP-INs are to be used with a mill finish absorber

material, that isthe finish of the coupons tested. For each coupon type the corrosion rates aredetermined.

The three coupon types are described below.General 4General coupons are rectangular (nominally 4 in. x 2 in. in length and width). A testobjective of the general coupons is to determine the rate at which a uniform oxide filmforms. The rate of oxide build-up is determined by changes in the coupon weight andthickness.

Post test exposure, the coupons are subject to precision weighing prior totesting and after a sequence of nitric acid washes and drying after testing.BendCoupons with press brake formed bends are included in the test matrix. These couponshave been deformed to the same bend angle and bend radius used for the NETCO-SNAP-IN.

The test objective of the bend coupons is to determine whether or not benddeformation and stress adversely affect the corrosion susceptibility of the Alcanmaterial.

These will be subject to the same pre and post testing as the generalcoupons.

In addition the inner and outer bend radius will be subject to microscopy before and after acid cleaning.

5-3 NET-259-03 Rev 5Galvanic (Bi-Metallic)

CouponsIn conventional spent fuel racks the neutron absorber material is enclosed in 304Lstainless steel wrapper plate, thus the potential for aluminum/stainless steel galvaniccorrosion exists. In the NETCO-SNAP-IN application this material is used unsheathed so that is could be in contact with LWR fuel assemblies.

Of the materials in LWR fuelassemblies supplied by U.S. fuel manufacturers, only stainless steel, Inconel andZircaloy could contact the surface of fuel racks. Accordingly bi-metallic coupons havebeen prepared with Alcan composite and: 4304L stainless steelInconel 718ZircaloyThe test objective of the galvanic coupon is to evaluate the potential for galvaniccorrosion.

The above alloy coupons are nominally 2 in. x 4 in. x 0.065 in. thick. A pieceof 2 in. x 4 in. Alcan composite forms the other piece of each couple. The two metalscomprising each couple are fastened to each other mechanically with AA1 100 wire.Inspection of the galvanic coupons is via optical microscopy, thickness and dry weightmeasurements.

Post test acid cleaning is used depending on the depth of any oxidefilms.5.3 Water Chemistry The laboratory tap water was processed by first passing it through two universal ionexchange columns and then through two research grade ion exchange columns.

The 4typical quality of the deionized water used for both the BWR and PWR corrosion bathsand make up water is shown in Table 5-4.5-4 NET-259-03 Rev 5Table 5-4Water Specification for Corrosion BathspH 5.75 @ 20°CConductivity,

ps/cm 0.5Resistivity,

f/cm 2.0Aluminum

< 0.010 ppmSiO2 < 0.100 ppmCl < 0.010 ppmNa < 0.030 ppmTo the PWR bath, sufficient reagent grade boric acid was added to bring the boronconcentration to -2500 ppm. This increased the initial conductivity from < 1.0 ps/cm to-40 ps/cm @ 20.0°C and decreased the initial pH from 5.75 @ 20.0°C to -4.76 at20.00C.The conductivity and pH of each of the baths was measured at an approximate frequency of once per week. Figures 5-1 and 5-2 are plots of the measured pH andconductivity of the BWR bath versus time. The plots of the measured pH andconductivity versus time of the PWR bath are shown in Figures 5-3 and 5-4,respectively.

45-5 11NET-259-03 Rev 5.210864-2 -- ----- --------------40.CL0 1000 2000 3000 4000 5000Hourse 5-1: pH versus Time: BWR Accelerated Corrosion Test600070008000Figur10.009.008.00E 7.00.6.00U5.00o 4.003.002.001.000.00I4vv0 1000 2000 3000 4000 5000 6000 7000Figure 5-2: Water Conductivity versus Time: BWR Accelerated Corrosion Test80005-6 NET-259-03 Rev 5121108"r.6,+/-.041000 ..000 .3000.4000.5000.6000 2 --- --40 1000 2000 3000 4000 5000 6000HoursFigure 5-3: pH versus Time: PWR Accelerated Corrosion Test7000800050.045.010.0E35.0U_.. 0 .0P25.0820.0I415.010.05.00.00 1000 2000 3000 4000 5000 6000 7000HoursFigure 5-4: Water Conductivity versus Time: PWR Accelerated Corrosion Test80005-7 NET-259-03 Rev 55.4 Corrosion Test ResultsVisual Inspection and Microscopy All coupons removed from the BWR and PWR accelerated corrosion tests after 2000,4000, 6000 and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months were subjected to visual inspection.

Some of the couponswere subjected to optional microscopy.

In addition, high resolution macro photographs were taken both upon removal from the test solutions and after air drying. Opticalmicroscopy was also performed to verify that the oxide films were substantially removedprior to determining coupon weight loss and prior to inspecting for any anomalies alongthe outer bend radii of the bend coupons.

The coupons and the digital data files of allmacro photographs, microphotographs and photo micrographs are in permanent storage.A sampling of photographs and photomicrographs are included in this report to illustrate the pre and post test appearance of the coupons.

Photographs and photomicrographs from the 4000 hour0.0463 days 1.111 hours 0.00661 weeks 0.00152 months and 8000 hour0.0926 days 2.222 hours 0.0132 weeks 0.00304 months inspections are compared to illustrate little change incoupon surface appearance once an initial oxide film forms. This suggests that theinitial oxide film is largely self-passivating, limiting the rate of subsequent oxidation ofthe base metal. 4Figure 5-5 is a macrophotograph that compares the appearance of the 16 vol %coupons exposed to the BWR and PWR test conditions for 4000 hours0.0463 days 1.111 hours 0.00661 weeks 0.00152 months with an as-fabricated archive coupon. The archive coupon is a somewhat darker grey color thanpure AA1 100 aluminum.

This appearance is characteristic of mill finish aluminum that isdarkened somewhat by numerous small black boron carbide particles embedded in itssurface.

Figure 5-6 contains a similar macrophotograph for coupons inspected after8000 hours.The coupons exposed to the BWR environment have a more or less uniform white oxidecoating with some larger black areas where the boron carbide areas have beenexposed.

The areas of exposed boron carbide are larger than on the archive material.

This may be due to boron carbide that was near the surface but covered by a thin layer5-8 NET-259-03 Rev 5of aluminum in the as-produced material.

Once oxidized, the thin oxide layer hasinsufficient strength to adhere to the underlying boron carbide and is loosened by thecirculating bath water.The coupons exposed to the PWR environment appear somewhat different.

Thebackground color is a light grey with smaller areas of exposed boron carbide on thesurface.

Examination of the surface under a microscope revealed the surface iscovered with a uniform translucent film showing some of the color of aluminum throughthe film. Randomly interspersed are smaller dark areas of exposed boron carbideparticles.

The surface appearance is similar after 4000 hours0.0463 days 1.111 hours 0.00661 weeks 0.00152 months and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months .Figures 5-7 and 5-8 compare the post test coupons with archive material for thecomposite with 25 vol % boron carbide loading after 4000 and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months , respectively.

It is noted that the archive material has a darker appearance than the archive materialwith 16 vol % due to the higher B4C loading.

Similarly, the post test coupons aresomewhat darker for the same reason. The oxidized surfaces of these post test4coupons are similar to the surfaces of the 16 vol % post test coupons and theappearances maintain their similarity after 4000 and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months exposure.

Figures 5-9 and 5-10 are microphotographs that compare the appearance of the 16 vol% post test coupons after 4000 and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months , respectively, with archive material at8X magnification.

Figures 5-11 and 5-12 are microphotographs of 25 vol % couponsexposed to demineralized water and boric acid after 4000 hours0.0463 days 1.111 hours 0.00661 weeks 0.00152 months and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months ,respectively.

Figures 5-13 and 5-14 are photomicrographs of the surfaces of 16 vol % and 25 vol %boron carbide composite, respectively, in the as-fabricated condition.

These can serveas a reference when evaluating the surface condition of the composites after 8000hours exposure to demineralized water and boric acid.5-9 NET-259-03 Rev 5Figures 5-15 and 5-16 are photomicrographs of the 16 vol % B4C composite after 8000hours in demineralized water and boric acid, respectively.

The surface appearance inFigure 5-15 is characteristic of areas of between locally heavy surface boron carbide(see e.g. Figure 5-10).Figures 5-17 and 5-18 are photomicrographs of the 25 vol % B4C composite after 8000hours in demineralized water and boric acid, respectively.

The photograph and microphotographs contained in Figures 5-5 through 5-18 serve toillustrate that all coupons develop a more or less uniform oxide film on all surfaces.

Theappearance of the coupons after 4000 hours0.0463 days 1.111 hours 0.00661 weeks 0.00152 months exposure compared to their appearance after 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months exposure show that they are essentially identical.

This suggests thatthe oxide film, once formed, is self-passivating and retards subsequent corrosion of the 4base metal. This conclusion is further supported by the quantitative corrosion ratemeasurements described subsequently.

The difference in appearance of the coupons exposed to demineralized water and boricacid suggests the different pHs of the baths result in different forms of the oxide.Subsequent acid cleaning of the oxide to measure weight loss further supports thishypothesis.

For the coupons exposed to demineralized water, the oxided layer isreadily removed by one short soak in nitric acid. For the coupons exposed to the boricacid solution, it required several longer soak periods in order for oxide removal and thecoupons to achieve constant weight. It is postulated that at lower pH in the boric acidcondition, oc -alumina (A1203) forms, which is less soluble in nitric acid than the oxideformed at a higher pH in demineralized water. The latter form of the oxide formed at thehigher pH in demineralized water is thought to be a hydrated form or Gibbsite (Al203"3H20). Optical microscopy of the inside and outside radius of the bend coupons beforeand after acid cleaning revealed no cracks or other anomalistic corrosion behavior.

5-10 NET-259-03 Rev 54Figure 5-5: Comparison of Post-Test Coupon Appearance with16 vol % Boron Carbide Loading after 4000 HoursArchive Material:

13WjgARCHIVSPWRFigure 5-6: Comparison of Post-Test Coupon Appearance with Archive Material:

16 vol % Boron Carbide Loading after 8000 Hours5-11 NET-259-03 Rev 525voi%ARCHIVEBWRPWRFigure 5-7: Comparison of Post-Test Coupon Appearance with Archive Material:

25 vol % Boron Carbide Loading after 4000 Hours4BWR ARCHIVE PWRFigure 5-8: Comparison of Post-Test Coupon Appearance with Archive Material:

25 vol % Boron Carbide Loading after 8000 Hours5-12 NET-259-03 Rev 5FiQure 5-9: Comparison of Post-Test Coupon Appearance with Archive Material:

16 vol % Boron Carbide Loading at 8X Magnification after 4000 Hours 4ARCHIVEFigure 5-10: Comparison of Post-Test Coupon Appearance with Archive Material:

16 vol % Boron Carbide Loading at 8X Magnification after 8000 Hours5-13 NET-259-03 Rev 5Figure 5-11: Comparison of Post-Test Coupon Appearance with Archive Material:

25 vol % Boron Carbide Loading at 8X Magnification after 4000 Hours4Figure 5-12: Comparison of Post-Test Coupon Appearance with Archive Material:

25 vol % Boron Carbide Loading at 8X Magnification after 8000 Hours5-14 NET-259-03 Rev 5Figure 5-13: Photomicrograph of 16 vol % B4C Composite As-Fabricated (45X)4B4C Composite As-Fabricated (45X)Figure 5-14: Photomicrograph of 25 vol %5-15 NET-259-03 Rev 5-1 a MLI L, f ol a 1 0/ D r% 4 Onnn UrlyUlu -i. I-IlU0 LUIIIL.,

I dJII UI lV VUl /O 4 .,,U IIJ,,JU ILV dILtI 4UVVV rlUUl; III 4Demineralized Water (45X)Figure 5-16: Photomicrograph of 16 vol % B4C Composite after 8000 Hours inBoric Acid (45X)5-16 NET-259-03 Rev 5Figure 5-17: Photomicrograph of 25 vol % B4C Composite after 8000 Hours inDemineralized Water (45X)4Figure 5-18: Photomicrograph of 25 vol % B4C Composite after 8000 Hours inBoric Acid (45X)5-17 NET-259-03 Rev 5Quantitative Corrosion Measurements The change in coupon thickness can provide a semi-quantitative measure of the extentand progression of corrosion.

The change in coupon weight, on the other hand, canprovide a more accurate measure of the extent and progression of corrosion.

As thealuminum base metal on the surface of the coupons is converted to the oxide (eitherA1203 or A1203" n H20), the volume of the oxide exceeds the volume of the original basemetal consumed.

Concurrent with this conversion is an increase in thickness andincrease in weight.The pre-test thickness of each general coupon was measured at nine locations.

Thepre-test thickness of each bend coupon was measured at six locations.

The post-test thickness was measured at the same nine and six locations on the general and bendcoupons, respectively.

The values reported are the average of either nine or sixmeasurements for each coupon. The pre and post test coupons' weights weremeasured for each coupon after a one hour drying at 11 0°C to remove surfacemoisture.

4Figures 5-19 and 5-20 contain the results of the average coupon thickness changesversus exposure times for the BWR and PWR coupons, respectively.

The data showthat, with one exception, the coupons show a measurable increase in thickness.

Thescatter in the data is likely attributable to measuring small changes in thickness inrelatively thin samples.

To place this data in perspective, a 5% increase in thickness ona coupon of initial thickness of 0.080 inches is 0.004 inches or 4 mils. If it is assumedthat both sides of the coupon contribute equally then the increase is 0.002 inches perside. After 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months , the average change in the thickness of the coupons exposed toaccelerated BWR conditions is 4.2%; the corresponding value for the PWR coupons is4.1 %. Figures 5-21 and 5-22 contain plots of coupon weight change versus exposuretime.At the 4000 hour0.0463 days 1.111 hours 0.00661 weeks 0.00152 months and 8000 hour0.0926 days 2.222 hours 0.0132 weeks 0.00304 months tests, eighteen of the galvanic corrosion couples wereremoved from each test bath and were subjected to testing.

These included three 304Lstainless steel couples, three Inconel 718 couples and three Zircaloy coupons at each5-18 NET-259-03 Rev 5B4C loading.

No couples were tested at 2000 hours0.0231 days 0.556 hours 0.00331 weeks 7.61e-4 months and 6000 hours0.0694 days 1.667 hours 0.00992 weeks 0.00228 months . Figures 5-23 and5-24 show the weight change of the BWR and PWR couple samples after coupondrying.In accordance with ASTM G-31-72[1] and ASTM G-1-03[2], the coupons were cleaned in1.42 sp.gr. nitric acid to remove the corrosion products.

The intent of cleaning is toremove all of the corrosion products but none of the base metal so that the weight of thecorrosion products can be determined.

This weight change can subsequently be usedto determine the corrosion rate in mils/year.

As noted previously, the oxide on coupons in the BWR test was easily removed by oneor two ten-minute soaks in nitric acid at room temperature.

For the PWR coupons itrequired several successive soak periods.

After each cleaning cycle, the coupons weredried and reweighed.

The cleaning proceeded until the coupons achieved constantweight or visual and/or microscopic examination indicated the oxide film had beenremoved.

4Figures 5-25 and 5-26 show the average change in coupon thickness after acidcleaning for the BWR and PWR general and bend coupons, respectively.

Figures 5-27and 5-28 show the change in coupon thickness after acid cleaning for the BWR andPWR galvanic

coupons, respectively, after 4000 hours0.0463 days 1.111 hours 0.00661 weeks 0.00152 months and 8000 hours0.0926 days 2.222 hours 0.0132 weeks 0.00304 months . These valuesrepresent the thickness of oxide removed by acid cleaning.

The average change inthickness by coupon type are summarized in Table 5-5. The data in Table 5-5 illustrate the difficulty in obtaining accurate changes in coupon thickness when the specimens are very thin. This is further evidenced by the variability in the coupon thickness data.The coupon weight changes as a result of acid cleaning are shown in Figures 5-29 and5-30 for the BWR and PWR general and bend coupons, respectively.

The couponweight changes as a result of acid cleaning are shown in Figures 5-31 and 5-32 for theBWR and PWR galvanic

coupons, respectively.

The average change in coupon weightby coupon type are summarized in Table 5-6. This table shows the weight changes5-19 NET-259-03 Rev 5exhibit far less variability than the thickness changes in Table 5-5. Accordingly, theweight change data are used subsequently to compute corrosion rates.Table 5-5Summary of Coupon Thickness Changes by Coupon TypeThir~knA~

ChlnaA %Coupon Types 2153 Hours 4019 Hours 5871 Hours 8119 HoursBWR General and Bend16 vol % B4C -1.14% +/- 0.59% -3.08% +/- 0.64% -1.40% + 1.07% -0.55% +/- 0.88%25 vol % B4C -0.72% + 0.89% -2.09% +/- 1.40% 0.08% +/- 0.44% -0.94% +/- 0.79%BWR Galvanic16 vol % B4C -0.07% +/- 0.68% -0.91% +/- 0.35%25 vol % B4C -1.05% +/- 0.35% -0.98% +/- 0.81%PWR General and Bend16 vol % B4C -0.03% +/- 0.51% -2.73% +/- 1.14% -0.70% +/- 0.92% -3.32% +/- 4.64%25 vol % B4C -0.55% +/- 0.46% -1.24% +/- 1.05% 0.44% +/- 1.10% -0.13% +/- 0.82%PWR Galvanic16 vol % B4C -1.04% + 0.81% 1-2.55% +/- 3.25%25 vol % B4C -1.24% +/- 0.27% -0.40% +/- 0.88%Table 5-6Summary of Coupon Weight Changes by Coupon TypeWeiaht Chanae. %Coupon Types 2153 Hours 4019 Hours 5871 Hours 8119 HoursBWR General and Bend16 vol % B4C -0.15% +/- 0.12% -0.28% +/- 0.22% -0.68% +/- 0.19% -0.50% +/- 0.17%25 vol % B4C -0.29% +/- 0.27% -0.36% +/- 0.38% -0.68% +/- 0.25% -0.69% +/- 0.75%BWR Galvanic16 vol % B4C 0.05% +/- 0.2% -0.34% +/- 0.19%25 vol % B4C -0.24% +/- 0.27% -0.81% +/- 0.28%PWR General and Bend16 vol % B4C -0.12% +/- 0.04% -0.07% +/- 0.09% -0.10% +/- 0.12% -0.26% +/- 0.37%25 vol % B4C -0.04% +/- 0.07% -0.02% +/- 0.05% -0.17% +/- 0.12% -0.16% +/- 0.09%PWR Galvanic16 vol % B4C -0.64% +/- 0.77% -0.89% +/- 0.46%25 vol % B4C 1-0.79% +/- 0.98% -0.66% +/- 0.46%45-20 NET-259-03 Rev 5Boron-10 Areal DensityThe boron-1 0 areal density of the general coupons was measured using neutronattenuation testing.

The results of the post-test measurements were compared withsimilar testing of archive coupons.

Figures 5-33 and 5-34 contain plots of the change inboron-1 0 areal density versus exposure time for the BWR and PWR coupons, 4respectively.

To place these measurements in perspective, the average areal density ofthe 16 vol % coupons is 0.010 gms B-1 0/cm2; the corresponding areal density of the 25vol % coupons is 0.0176 gms B-10/cm2.The variation in areal density changes arewithin +/- 1.0 to 2.0% of zero change, which is within the absolute uncertainty of the arealdensity measurements.

5-21 NET-259-03 Rev 58%6%o40/OkUC2o%F--4%/o-6%0Z1 6Vol % B4C025Vol % B4C0 1000 2000 3000 4000 5000Time, hrs6000 7000 8000Figure 5-19: BWR Thickness Change (Pre-Test vs. Post-Test) 48%/6%/Oe 4 /oCUOU.C4%/_6--80/0 1000 2000 3000 4000 5000Time, hrs6000 7000 8000Figure 5-20: PWR Thickness Change (Pre-Test vs. Post-Test) 5-22 NET-259-03 Rev 54.00%316Vol % B4C3. 000/O25Vol % B4C2.00%1.00%(0.000% II IU*1- 1.oo0/o0-2.00%-3.00%-4.00%0 1000 2000 3000 4000 5000 60Time, hrsFigure 5-21: BWR Weight Change (Pre-Test vs. Post-Test) 4.00%016Vot % B4C3.00%30-25Vol

% B4C2.00%e 1.00%c 0.00% , IIUAw -1.00%-2.00%-3.00%-4.00%00 7000 80004'p0 1000 2000 3000 4000 5000Time, hrs6000 7000 8000Figure 5-22: PWR Weight Change (Pre-Test vs. Post-Test) 5-23 NET-259-03 Rev 54.00%016Vol % B4C3.00% 0 25VoI % B4C2.000/00~. 1.00%2o.00/U2 1.00%'02.00%/o

-3.00%0/-4.00%0 1000 2000 3000 4000 5000Time, hrs6000 7000 8000Figure 5-23: BWR Coupon Weight Change versus Time: Galvanic Couple Coupons44.00%3.00%2.00%C1.00%00.00%U-1.00%2.00%-3.00%-4.00%0 1000 2000 3000 4000 5000 6000 7000 8000Time, hrsFigure 5-24: PWR Coupon Weight Change versus Time: Galvanic Couple Coupons5-24 NET-259-03 Rev 58%6%Oe4%too/Uz 4%U:O/I-o16Vol % B4C025Vol % B4CE30 1000 2000 3000 4000 5000 6000 7000 8000Time, hrs-8%Figure 5-25: BWR Thickness Change (Pre-Test vs. Post-Test)

After Acid Cleaning:

General and Bend Coupons48%6%4%02O/oUOO/ow -2%-4%*16Vol % B4C025Vol % B4C0<-8%0 1000 2000 3000 4000 5000Time, hrs6000 7000 8000Figure 5-26: PWR Thickness Change (Pre-Test vs. Post-Test)

After Acid Cleaning:

General and Bend Coupons5-25 NET-259-03 Rev 58%6%0%2'OoU2 0%U2-240/oI--6%O16Vol % B4CIJ25Vol % B4C!30 1000 2000 3000 4000 5000Time, hrs6000 7000 8000Figure 5-27: BWR Galvanic Coupons After Acid Cleaning:

Coupon Thickness Change4.0Q;C8%6%4%2%0%-2%-4%-6%-8%0 1000 2000 3000 4000 5000Time, hrs6000 7000 8000Figure 5-28: PWR Galvanic Coupons After Acid Cleaning:

Coupon Thickness Change5-26 NET-259-03 Rev 54.00%0 16VoI % B4C3.000/025Vol % B4C2.00%1.00%0.00% 'U*-2.00%-3.00%-4.00%0 1000 2000 3000 1000 5000Time, hrs6000 7000 8000Figure 5-29: BWR Coupon Weight Change (Pre-Test vs. Post-Test)

After AcidCleaning:

General and Bend Coupons Only4.00%016Vol % B4C3.00%3 25Vol % B4C2.00%q 1.00%/o50.00% ,.CU-1.00%/o-2.00%-3.00%-4.00%40 1000 2000 3000 4000 5000Time, hrs6000 7000 8000Figure 5-30: PWR Coupon Weight Change (Pre-Test vs. Post-Test)

After AcidCleaning:

General and Bend Coupons Only5-27 NET-259-03 Rev 510. 000%8.00%/6.00%/$4.00%/4P2.00%/*0.00%/ý:6.00%/-8.00%/-M1O000/0*16Vo0 % B4CO25Vol % B4C0 1000 2000 3000 4000 5000Time, hrs6000 7000 8000Figure 5-31: BWR Galvanic Coupon Weight Change versus Time10.00%0/8.00% o 16Vo % B4C6% 25Vol % B4C6.00%/o 4.00% /V 2.000/o60.00%t.w-2.00%.0-4.00%-6.00%-8.00%-10.00%40 1000 2000 3000 4000 5000Time, hrs6000 7000 8000Figure 5-32: PWR Galvanic Coupon Weight Change versus Time5-28 NET-259-03 Rev 5016Vol % B4CO25Vol % B4CE(Uo 0Uncertainty I0B0RM0.00200.00150.00100.00050.0000-0.0005-0.0010-0.0015-0.00206000I20004000Time, hrs80004Figure 5-33: BWR Coupon Areal Density Change versus TimeS1 6VoI % B4C025VoI % B4CE0-IMUncertainty I0]U].A0.00200.00150.00100.00050.0000-0.0005-0.0010-0.0015-0.0020020004000Time. hrs60008000Figure 5-34: PWR Coupon Areal Density Change versus Time5-29 NET-259-03 Rev 55.5 Discussion of Test Results and Conclusions Following the guidance provided in Reference 1, the post-test coupon weights after acidcleaning can be compared with pre-test weights to compute the test environment corrosion rate (mils/year) of the various coupon types. Using corrosion data inReference 3 for AA1200 series aluminum in water at 1220 F and 3920 F, it is possible tocompute the corresponding in-service corrosion rates at typical spent fuel poolconditions and water temperature (typically 800 F). These calculations are contained inthe Appendix and the so calculated in-service corrosion rates are summarized in Table5-7. Table 5-8 contains the equivalent in-service exposure times for each of the fourtest intervals.

Table 5-7: Average Corrosion RatesIn..Qarvii-a (fnrrnainn P~faa miI@IlIo2r 2153-Hour 4019-Hour 5871-Hour 8119-Hour Coupon Types Test Test Test TestBWR General andBend16 vol % B4C -0.01 -0.01 -0.02 -0.0125 vol % B4C -0.02 -0.02 -0.02 -0.02BWR Galvanic16 vol % B4C 0.01 -0.0125 vol % B4C -0.01 -0.02PWR General andBend16 vol % B4C -0.01 -0.01 -0.03 -0.0125 vol % B4C -0.01 -0.02 -0.01 -0.01PWR Galvanic16 vol % B4C -0.02 -0.0225 vol % B4C -0.04 -0.014Table 5-8: Equivalent Exposure TimeTest Hours ) 1950 F In-Service Hours (& 800 F2153 390504019 729115871 1074478119 1486055-30 NET-259-03 Rev 5The computed in-service corrosion rates shown in Table 5-7 are extremely low and ineach instance are based on the average weight loss of several coupons.

A corrosion rate of -0.02 mils/year can be interpreted to mean that after 100 years an oxide film 2mils thick would be expected on all surfaces.

The reason for this extremely lowcorrosion rate is that once an oxide film forms on all surfaces, the film tends to be self-passivating; that is, it tends to retard further corrosion.

This property of the oxide filmformation leads to the excellent corrosion resistance of AA1 100 aluminum alloy and theperformance of the Rio-Tinto Alcan material shows similar performance.

This has been 5observed in other aluminum boron carbide composites tested by NETCO.J41It is further noted that for both the 16 vol % and the 25 vol % coupons, there has beenno measurable change in the B-10 areal density, nor has any local corrosion (pitting) orcracking been detected.

Optical microscopy of inside and outside radius of bendcoupons revealed no cracks or anomalistic corrosion behavior.

These observations 4apply to both the BWR and the PWR test environments.

Once installed, the inserts assume a constant strain condition within the rack cell. Thiscompression leads to internal

stresses, especially at the bend, that might make theinserts susceptible to stress corrosion cracking.

An examination of the literature on thissubject[5" 5]'[5"6], indicates that "In general, high-purity aluminum and low-strength 5aluminum alloys are not susceptible to SCC."t[5-5 However, surveillance bend couponsto be placed in the pool prior to the installation of the inserts will be maintained underthe same strain conditions to provide indication of any unexpected crack phenomena.

Not withstanding the low measured corrosion rates, corrosion itself does not result inany loss of boron carbide.

After the corrosion film forms, the boron carbide remainstightly bound in the corrosion layer. This was confirmed by the neutron attenuation measurements for boron-10 areal density, which were performed prior to acid cleaningto remove corrosion products.

5-31 NET-259-03 Rev 5As determined by the testing sequences described herein, the low measured corrosion rates under accelerated corrosion test conditions as well as the constancy of boron-1 0areal density, recommends that the AA1 100/boron carbide composite produced by RioTinto Alcan is a highly suitable neutron absorber material for use in spent fuel storageracks.References Section 5:5-1 ASTM G-31-72 (Reapproved 2004), Standard Practice for Laboratory Corrosion Testing of Metals.5-2 ASTM G-1-03, Standard Practice for Preparing,

Cleaning, and Evaluating Corrosion Test Specimens.

5-3 Godard, Epson, Bothwell and Kane, The Corrosion of Light Metals, John Wiley &Sons, Inc., New York, 1967.5-4 Qualification of METAMIC for Spent-Fuel Storage Applications, Electric PowerResearch Institute Report 1003137 by Northeast Technology Corp., Kingston, NY. October 2001.5-5 Davis, J.R. Corrosion of Aluminum and Aluminum Alloys. ASM International.

November 2000. Pg. 108 45-6 Bauccio, Michael.

ASM Metals Reference Book, Third Edition.

ASM International.

April 2003. Pg. 4085-32 NET-259-03 Rev 56.0 Fast Start Coupon Surveillance Program Description The fast start coupon surveillance program consists of a series of 24 coupons cut fromextra Alcan composite produced for the LaSalle demonstration.

These coupons are 2 x4 inches in width and length and have two 0.25 inch diameter holes along the top andbottom edge as shown in Figure 6-1. Their thickness is nominally 0.065 inch and eachcoupon contains 16 vol% boron carbide.

The purpose of the fast start program is toprovide early performance data on the Alcan composite in the LaSalle Unit 2 poolenvironment.

Each of the coupons will be connected to the next coupon with a stainless steel link clip.The string of 24 coupons will be attached to a short piece of stainless steel chain, whichin turn will be attached to a head assembly (See Figure 6-2). The head assemblycontains a hook so that it can be remotely lowered into a rack storage cell in the LaSalleUnit 2 pool. When in place the head piece will rest on top of a storage cell with thestring of coupons suspended in the cell below. The length of the connecting chainbetween the head piece and the string of coupons was adjusted so that all 24 couponsare within the active fuel region of the eight surrounding fuel assemblies.

At each refueling outage the fast start coupons will be in a cell surrounded in all eightlocations with freshly discharged fuel. In this manner the gamma energy disposition and temperatures of the coupons will be maximized.

Two coupons will be removedevery six months from the string and sent to a qualified laboratory for testing andinspection.

The coupons have been subjected to pre characterization and will be posttest characterized.

Table 6-1 contains the pre and post test inspections andmeasurements.

6-1 NET-259-03 Rev 5r- 2.00' 1.5'TYPLaSalle Unit 2 Fast Start CouponFigure 6-1: Fast Start Surveillance CouponFigure 6-2: Fast Start Coupons String6-2 NET-259-03 Rev 5Table 6-1Pre and Post Test Coupon Characterization Test Pre PostCharacterization Characterization Visual (Hi resolution digital photo)Dimension

/1Dry Weight _/_ _ _Density __ _ __Areal Density __+___Acid Cleaning

'1Weight LossCorrosion RateMicroscopy

+ On select coupons*as-required A prime objective of this fast start program is to provide some early data as to the actualcorrosion rates anticipated under actual LaSalle spent fuel pool conditions.

6-3 NET-259-03 Rev 57.0 Long-Term Surveillance ProgramThe long-term surveillance program will consist of a specially designed surveillance treeto which a series of surveillance coupons are attached.

The long-term surveillance treewill be placed within the pool as part of the first installation campaign of NETCO-SNAP-INs and will reside there as long as the fuel racks continue to be used. Periodically, coupons will be removed and sent to a qualified laboratory for testing.7.1 Tree and Coupon Description The surveillance tree will be a four-sided structure with 18 -2" x 4" coupons attached toeach side and 12 -2" bend coupons abutting adjacent faces. The bend coupons will be 34maintained under a fixed strain in the fixture.

They will be manufactured at the sameinitial angle as the inserts and bent to the square angle of the rack cells. All couponswill contain 17 vol% boron carbide.

The types and numbers of coupons included in theprogram are shown in Table 7-1.Table 7-1Long-Term Surveillance CouponsCoupon Type Number Objective General 48 Quantify long-term corrosion Track effects along bend radiiBend 24 including stress relaxation andstress corrosion crackingTrend galvanic corrosion withGalvanic (bi-metallic) 24In and Zirc coupons47.2 Coupon Inspection and TestingSpecific coupons will be removed from tree on a frequency schedule as described subsequently.

The general coupons will be subject to pre and post examination according to Table 7-2.7-1 NET-259-03 Rev 5Table 7-2Long-Term Surveillance General Coupon Characterization Test Pre PostCharacterization Characterization Visual (Hi resolution digital photo)Dimension

/ 4Dry Weight 4 4Areal Density /+ 4Acid Cleaning 4Weight Loss 4Corrosion Rate 4Microscopy 4*4+ On select coupons*as-required The bend and galvanic coupons will be subject to the tests in Table 7-3.Table 7-3Long-Term Surveillance Bend and Galvanic Coupon Characterization Test Pre PostCharacterization Characterization Visual (High 4Resolution Digital 4Photo)Thickness 4 4Dry Weight / /Bending Stress (Bend 4 4Coupons Only)Acid Cleaning 4Weight Loss and 4Corrosion RateMicroscopy 4**as-required 47-2 NET-259-03 Rev 57.3 Frequency for Coupon Inspection The frequency for coupon inspection will depend on the coupon type and results ofprevious inspections.

The frequency for inspection is shown in Table 7-4.Table 7-4Frequency for Coupon TestingAfter 10 Years withCoupon Type First Ten Years Acceptable Performance General 2 coupons every 2 years 2 coupons every 4 yearsBend 1 coupon every 2 years 1 coupon every 4 yearsGalvanic Couples304 Stainless 1 couple every 6 yearsZ irc "In27-3 ATTACHMENT 9Summary of Regulatory Commitments Page 1 of 1The following table identifies commitments made in this document.

(Any other actions discussed inthe submittal represent intended or planned actions.

They are described for the NRC's information and are not regulatory commitments.)

COMMITMENT COMMITTED COMMITMENT TYPEDATE OR ONE-TIME PROGRAMMATIC "OUTAGE" ACTION (Yes/No)(Yes/No)EGC will update the UFSAR Upon Yes Noto describe the Rio-Tinto implementation ofAlcan Composite the proposedSurveillance Program as changedescribed in Section 3.9of Attachment 1.The k-infinity limitations will Upon No Yesbe incorporated into reload implementation ofdesign documents and SFP the proposedcriticality compliance changeprocedures.

The k-infinity limitations will Upon Yes Nobe reflected in Section 9.1.2 implementation ofof the UFSAR. the proposedchangeEGC will submit the data and Within 60 days Yes Noanalysis associated with the following first 10-year surveillance of completion of thethe NETCO-SNAP-IN rack analysisinserts to the U.S. NuclearRegulatory Commission.

ML13199A039

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