ML20244C129

Proposed Tech Spec Page 5-5,allowing Util to Conduct Demonstration Program Re Rod Control Cluster Assemblies

ML20244C129
Person / Time
Site:	Catawba
Issue date:	04/06/1989
From:	DUKE POWER CO.
To:
Shared Package
ML20244C118	List: ML20244C116 ML20244C129
References
TAC-72886, TAC-72887, NUDOCS 8904200058
Download: ML20244C129 (10)

Text

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DESIGN FEATURES O'ESIGN PRESSURE AND TEMPERATURE

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5.2.2 The reactor containtnent vessel is designed and shall be maintained for a maximum internal pressure of 15 psig and a temperature of 328 F.

5.3 REACTOR CORE FUEL ASSEMBLIES 5.3.1 The core shall contain 193 fuel assemblies with each fuel assembly nominally containing 264 fuel rods clad with Zircaloy-4, except that substitu- l tions of fuel rods by filler rods consisting of Zircaloy-4 or stainless steel, or by vacancies, may be made in fuel assemblies if justified by cycle-specific reload analyses using NRC-approved methodology. Should more than 30 rods in the core, or 10 rods in any assembly, be replaced per refueling, a special report describing the number of rods replaced will be submitted to the commis-

. sion pursuant to Specification 6.9.2 within 30 days after cycle startup. Each fuel rod shall have a nominal active fuel length of 144 inches. Reload fuel

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shall be similar in physical design to the initial core loading and snall have

. a maximum enrichment of 4.0 weight percent U-235 with a maximum' enrichment tolerance of i 0.05 weight percent U-235.

CONTROL ROD ASSEMBLIES 5.3.2 The core shall contain 53 full-length control rcd assemblies. The full-length control rod assemblies shall contain a nominal 142 inches of absorber material of which 102 inches shall be 1007. boron carbide and remaining 40-inch tip shall be 80% silver, 15% indium, and 5% cadmium.

For Unit 1, all contrnl rods shall be clad with stainless steel tubing.

For Unit 2, all control rods, except for the control rods in one Rod Cluster Control Assembly (RCCA), shall be clad with stainless steel tubing. The remaining Rod Cluster Control Assembly control rods shall be clad with Inconel.

5' . 4 REACTOR COOLANT SYSTEM DESIGN PRESSURE AND TEMPERATURE 5.4.1 The Reactor Coolant System is designed and shall be maintained:

a. In accordance with the Code requirements specified in > tion 5.2 of the FSAR, with allowance for normal degradation pursuant to the, applicable Surveillance Requirements, )

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b. For a pressure a 2485 psig, and j

c. For a temperature of 650*F, except for the pressurizer which is 680 F.

VOLUME l l

5.4.2 The total water and steam volur e of .be Reactor Coolant Sn ten is 12,040 100 cubic feet at a nominal ],, c' 525 F.

5. 5 METEOROLOGICAL TOWER LOCATION 5.5.1 The meteorological tower shall be 1)cated as shown in Fi JrE 5. l' 1.

CATAVEA - UNITS 1 & 2 5-5 8904200058 DR 890406 ADOCK 05000413 PNU

Attachment 2 Discussion, No Significant Hazards Analysis and  ;

Environmental Irapact Statement l 1

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,. DIS (iUSSION , NO SIGNIFICANT HAZARDS ANALYSIS AND ENVIRONMENTAL IMPACT STATEMFNr

'The proposed amendment would:

• Allow a demonstration program to be conducted at Catawba. This L

demonstration program will demonstrate the interface compatibility and successful operating experience with BWFC supplied 17x17 RCCA's and define and compare the operational wear characteristics of. wear resistant ,

'RCCA coatings and conventional RCCA clad materials. 1

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. This change will slightly modify the description of the Control Rod Assemblies in section 5.3.2 of the-Technical Specifications.  !

Babcock & Wilcox Fuel Company (BWFC) and-Duke Power have entered into a joint agreement to conduct a RCCA demonstration program at the Catawba Unit 2,.

starting with Cycle 3. The objectives of the program are:

o Demonstration of interface compatibility and successful operating experi-ence with BWFC supplied 17x17 RCCA's.

o Definition and comparison of the operational wear characteristics =Uf wear I resistant RCCA coatings and conventional RCCA clad materials.

The program includes a detailed wear measurement campaign of the demonstration

.RCCA's to verify the performance of the wear resistant coatings for mitigating clad wear and to quantify the effect of coatings on the wear of the upper guide structure.

The demonstration program requires the supply of three W type 17x17 RCCA's by

-the BWFC. Two of the demonstration assemblies are comprised of control rods fabricated with Armaloy plated 304 stainless steel cladding. The Armaloy plating is a patented, wear resistant, electrolytic chrome plating supplied by Armoloy of Illinois. The third assembly is comprised of control rods fabri-cated with chromium carbide coated Inconel 625 cladding. The chromium carbide  !

coating is supplied by Union Carbide and is applied by their patented D-Gun l process.

In-reactor experience with the chromium carbide coating has shown that the coating performs extremely well. A full core of BWFC designed control rod assemblies, which were coated full length, has successfully operated for one i cycle of operation in a 17x17 205 fuel assembly reactor. Post irradiation ultrasonic wear measurements showed no indicated of clad wear or spalling of the coating. Kraft Work Utility (KWU) has also successfully used the same ,

chromium carbide coating for its control rods for 8 cycles of operation. l

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DISC'USSION , NO SIGNIFICANT HAZARDS ANALYSIS AND ENVIRONMENTAL IMPACT STATEMENT The Armaloy plating is presently in use on 14x14 W RCCA's at several domestic reactors. Armoloy plated RCCA's have also been supplied for use in a 15x15 reactor. BWFC's experience is limited to out of core testing. Tests have shown that the Armaloy plating has good corrosion resistance in a reactor environment, is not subject to spalling or flaking, and improves the clad wear resistance considerably.

The base W 17x17 RCCA design features are maintained for the three BWFC supplied RCCA's with few exceptions. All of the primary interface features have been verified by on-site dimensional measurement inspections made at McGuire Units 1 and 2.

In addition, a dummy RCCA was fabricated and shipped to Catawba Unit 2 for interface and handling checkout. The. site checkout was performed success-fully. Interface and handling verification was made with the following:

1) New RCCA Handling Tool

2) RCCA Changeout Tool

3) Dummy Fuel Assembly in the Fuel Handling Mast

4) One Cycle Fuel Assembly in the Fuel Handling Mast

5) Third Cycle Fuel Assembly in the Fuel Handling Mast

6) CRDM Gripper Mockup Tool The demonstration RCCA's are the hybrid B 4 r d design where the lower 40 inches of the absorber stack is comprised of silver-indium-cadmium with the remaining 102 inches comprised of 4B C pellets. Table 1.1 provides general design information for the demonstration RCCA's supplied by BWFC.

Primary design differences between the base W 17x17 RCCA design and that provided by BWFC are as follows:

1) The lower 12 inches of the Ag-In-Cd absorber stack has a reduced diameter compared to that of the base W design (0.294 inch vs. 0.300 inch). The reduced diameter increases the cladding / absorber gap at the highest flux region thereby increasing the margin for clad strain due to absorber swelling. The net impact on shutdown margin due to the absorber diameter reduction is less than 0.0047. delta rho assuming all control rods in the core were of this design. Considering that only the three demo RCCA's reflect this change, the effect on shutdown margin is negligible. In addition, measurements are performed during each cycles initial startup to verify the acceptability of the rod worths.

, DISC'USSION , NO SIGNIFICANT HAZARDS ANALYSIS AND ENVIRONMENTAL IMPACT STATEMENT

2) BWFC coupling-spider is a machined casting as opposed to a brazement.

The casting is designed to accept the required 4500 lb. load due to RCCA scram.

3) Due to the spider casting design, the rodlet is attached to the spider by means of a threaded upper end plug and nut. However, the rodlet con-tinues to be pinned to the spider as in the base W design to prevent rod rotation. In addition, the upper end plug is designed to maintain the flexibility features as in the base W design, which accommodate small misalignments.

4) The starting (before coating) cladding diameter for the chromium carbide coated RCCA is 0.3785 inch compared to 0.381 inch for the base design.

The reduced clad diameter is to account for the coating thickness. The maximum clad diameter after Armaloy plating or chromium carbide coating is 0.383 inch. Nominal thickness of the Armoloy plating is 0.0005 inch.

The nominal thickness of the chromium carbide coating is 0.002 inch. 'Ihe lower 30 inches of the control rod remains uncoated such that the coating / plating and guide thimble do not contact for both safety and regulating RCCA duty. Therefore , the coated RCCAs'will not create a concern for increased wear in the fuel assembly guide tubes during normal operation. The coated RCCAs will remain in Shutdown Bank Locations for the duration of the demonstration program. Although the maximum rodlet OD for the demonstration RCCAs, including coatings, is 2.0 mils greater than the nominal clad OD of the (Westinghouse) W RCCAs, the impact on trip times is expected to be insignificant. B&W trip time tests performed on the MK-C fuel assembly / control rod combination indicates insignificant changes in trip times as a result of small variations in control rod OD. Note that the .3785 inch diameter will increase the safety margin for trip time. There is sufficient RCCA spring energy absorption capability to accommodate the higher velocity and continue to meet both spring stress and solid height requirements. However, the BWFC supplied 17 x 17 RCCAs are slightly lighter than the Westinghouse base RCCA design. The armoloy plated /304 SS and chromium carbide coated /Inconel 625 RCCAs weigh 91 and 93 lbs. respectively versus 94 lbs.

for the Westinghouse RCCAs. The slight decrease in weight will result in a correspondingly small and insignificant increase in drop times and decrease in RCCA impact velocity. Overall, the size and weight differences should have no impact on the ability of the rods to perform their intended safety function. In addition, tests are performed prior to each cycle startup at hot, full flow conditions to ensure that control rod drop times are within Technical Specification requirements.

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. DISC'USSION , NO SIGNIFICANT HAZARDS ANALYSIS AND ENVIRONMENTAL IMPACT STATEMENT  !

5) The Inconel 625 clad (as opposed to 304 stainless steel) is used for the third RCCA in conjunction with the chromium carbide coating. The Inconel 625 is used primarily for two reasons: 1) Recent developments have shown under particular reactor applications (pump seals) that 304 stain-less steel coated with the chromium carbide is susceptible to crevice a corrosion cracking. Although none of the out-of-core or incore RCCA coating experience has shown this phenomena, the Inconel 625 clad mate-rial was chosen as a precaution. Inconel in general is not susceptible to crevice corrosion cracking in the coating application. 2) The Inconel 625 clad material is used'for the BWFC MK-B Ag-In-Cd and the C-E B C control rods due to its improved irradiation ductility. The clad 4

material and absorber tip diameter change combined improve rod lifetime and reduce the possibility of clad cracking due to absorber swelling induced strain. The use of Inconel 625 as an RCCA clad material is not expected to substantially change the absorption properties of the control rods at Catawba Unit 2. The intent of control rod cladding is to maintain the integrity of the absorber material.

The BWFC 17x17 E RCCA consists of 24 rods attached at the top end to a common spider assembly. Each rod is comprised of sealed absorber materials of boron carbide and Ag-In-Cd solid rods in either 304 stainless steel or inconel 625 clad. Sufficient diametral and end clearance is maintained to accommodate 4 relative thermal expansions and irradiation swelling. Absorber material thernal stability and gas release from the B C4 are considered also. The absorber material composition, length, and diameter are the same as those of j the base E design with the exception of the noted Ag-In-Cd diameter reduction in the lower 12 inches. Sufficient shutdown margin and rod worth is maintained.

Each rod is coated with chromium carbide coating or Armaloy chrome plating.

The lower 30 inches of the clad remains uncoated. The uncoated diameter is

.3785 inch for the chromium carbide coated rod to account for the coating thickness. The unplated diameter of the Armoloy plated rod is .381 inch. The maximum coated / plated clad diameter is .383 inch. The nominal Armoloy plating thickness is .0005 inch. The nominal chromium carbide coating thickness is

.002 inch.

The lower end plugs are bullet nosed with the same geometry as the base design to reduce hydraulic drag during reactor trip and to guide smoothly into the dashpot region of the fuel assembly guide thimbles.

The spider assembly is of the same form as the base design, i.e., radial vanes protrude from a central hub from which the rods are supported. The spider is designed to accept the required 4500 lb load attributed to RCCA scram. The pitch pattern and the dimensions of the spider vanes are the same as the base j design. Coupling detents are machined into the upper end of the spider hub for connection to the handling equipment and drive rod assembly. This

DISC'USSION , NO SIGNIFICANT HAZARDS ANALYSIS AND ENVIRONMENTAL IMPACT STATEMENT interface has been verified by site checkouts with the appropriate interfaces as noted earlier. A helical spring inside the spider hub absorbs the impact energy at the end of the RCCA trip. The spring rate and preload are set to the same values measured on actual RCCA's of the base design. The spring is restrained in the spider hub with a tension bolt and spring retainer of the same dimensions as in the base design. The spider is a one piece casting as noted earlier which eliminates the need for piece part brazing. The spider casting is made of 316 stainless steel. The spring tension bolt, spring retainer, and spring are made of 304 stainless steel,17-4PH stair.less steel, and Inconel 718, respectively.

The absorber rods are securely fastened to the spider. The rods are inserted into the mating holes of the spider. A lockpin which is welded in place secures the rod as in the base design. A nut is then threaded to the top of the upper end plug, pretorqued, and welded in place. The nut serves as a redundant rod attachment in addition to providing lead-in for the top of the rods. The four innermost locations with the taller spider boss and nut serve as the guidance for the RCCA as it is being withdrawn from the fuel assembly through the upper guide structure /or handling equipment as with the base design. The upper end plug below the pin position is designed with a reduced  ;

section to permit flexing of the rods to correct for small misalignments.  !

The overall length of the assembly is such that for full withdrawal the tips of the absorber rods remain engaged in the guide thimbles so that alignment between rods and guide thimbles is maintained. All critical interface dimen-sions are maintained to ensure compatibility with handling and operational hardware. A site checkout of a dummy RCCA was made to ensure interface compatibility.

Thermal Hydraulic Compatibility The RCCAs were analyzed and shown to meet all thermal hydraulic design require-ments. The absorber centerline temperature does not exceed the material melting temperature. The rod internal pressure as a result of gas release due to B SuffY,C depletion cient RCCA todoes guidenotthimble exceed the system clearance pressure exists for the to prevent bulkdesign boilinglifetime.

within the guide thimble.

RCCA To Dashpot Clearance There is no change in the RCCA to dashpot clearance for the Armoloy/304 SS RCCA. The lower 30 inches remains uncoated. A diametral increase of .003" occurs for the Cr,C9/Inconel 625 RCCA, which results in slightly increased safety margin in RCCA drop time.

DISC'USSION , NO SIGNIFICANT HAZARDS ANALYSIS AND ENVIRONMENTAL IMPACT STATEMENT l

l Impact on Fuel Assembly Guide Tubes The B&W RCCAs are to operate in shutdown bank locations through the duration of the demonstration program. The Catawba Unit 2 shutdown bank RCCAs operate at a constant elevation. This constant can be set to any value between 225 and 230 steps withdrawn during each refueling outage. The operating elevation l of the shutdown bank RCCAs does not chanBe as a function of reactor power.

Since the bottom 30 inches of RCCAs are uncoated and 9.96 inches of the RCCA tips are overlapped by the fuel assembly guide tubes at 225 steps withdrawn, the coated region of the RCCAs will never be overlapped by the fuel assembly guide during normal operation. In addition, the coated region of the rodlets will not overlap the fuel assembly guide tubes when the Catawba reactor operators perform monthly routine RCCA bank exercises. The shutdown bank RCCAs can be inserted to the 215 step elevation during monthly routine RCCA bank exercises. Overlap between the coated region of the RCCAs and the fuel assembly guide tubes will only occur during shutdowns and startups. Since the  ;

l occurrence of these events relative to the total cycle operating time is very low, the impact of the coating materials on the fuel assembly guide tubes is expected to be negligible.

10 CFR 50.92 states that a proposed amendment involves no significant hazards considerations if operation in accordance with the proposed amendment would nott l (1) Involve a significant increase in the probability or consequences of an accident previously evaluated; or (2) Create the possibility of a new or different kind of accident from any accident previously evaluated; or (3) Involve a significant reduction in a margin of safety, i This change, which would allow the demonstration of the interface compatibility and successful operating experience with BWFC supplied 17x17 RCCA's and define and compare the operational wear characteristics of wear  ;

resistant RCCA coatings and conventional RCCA clad materials will not involve a significant increase in the probability or consequences of an accident previously evaluated. As shown above the effect of the change on the operation and design of the RCCA's does not increase the probability or consequences of any accidents.

This change will not create the possibility of a new or different kind of accident because the RCCA's will continue to function as before. No new mode of operation is introduced by this change.

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DISCUSSION , NO SIGNIFICANT HAZARDS ANALYSIS AND ENVIRONMENTAL IMPACT STATEMENT l l

This amendment does not involve any reduction in a margin of safety. The drop times of the control rods will be verified within the Technical Specification limits before unit operation is begun following the current refueling outage.

No other margins of safety are affected by this change.

Environmental Impact The proposed Technical Specification change has been reviewed against the criteria of'10 CFR 51.22 for the environmental considerations. As shown above, the proposed change does not involve a significant hazards consideration, nor increase the types and amounts of effluents that may be released offsite, nor increase individual or cumulative occupational radiation exposures. Based on this, the proposed Technical Specification change meets the criteria given in 10 CFR 51.22(c)(9) for a categorical exclusion from the requirement for an Environmental Impact Statement.

r Table 1.1 17 x 17 Uybrid B C4 RCCA Dimensional Information B&W Chromium B&W Armaloy Carbide Coated Westinghouse Description Plated RCCA RCCA RCCA Overall Assembly Length 161.07 in. .161.07 in. 160.95 in.

Rod Length - Tip of Bottom 150.68 in. 150.68 in. 150.58 in, of Spring Retainer Cladding Material 304 SS 'Inconel 625 304 SS Cladding 0.D. .381 in. .3785 in. .381 in.

Cladding I.D. .304 in. .304 in. .304 in.

Absorber Stack Length 142.0 in. 142 in. 142 in.

B C Pellet Stack Length 102.0 in. 102 in. 102 in.

4 Ag-In-Cd 40.0 in. 40.0 in. 40.0 in.

Absorber Diamoter B C Pellet .294 in. .294 in. .294 in.

4 Ag-In-Cd .300 in. .300 in. .301 in.

(28 in. length) (28 in. length) (40 in. length)

.294 in. .294 in.

(12 in. length) (12 in. length)

Coating or Plating Thickness .0005 in. .002 in. N/A RCCA Weight (Calculated) 91 lbs. 93 lbs. 94 lbs.

Spring Retainer Travel .880 in. .880 in. .880 in.

1 Spring Preload 340 lbs. 340 lbs. 352 lbs.

RCCA Spring Rate 706 lbs./in. 706 lbs./in. 706 lbs./in.

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