Regulatory Guide 1.119
| ML13350A277 | |
| Person / Time | |
|---|---|
| Issue date: | 06/30/1976 |
| From: | NRC/OSD |
| To: | |
| References | |
| RG-1.119 | |
| Download: ML13350A277 (7) | |
UNITED STATES
OA
- NUCLEAR
REGULATORY COMMISSION
a WASHINGTON, 0. C. 20665 June 23, 1977 REGULATORY GUIDE DISTRIBUTION LIST 'DIVISION 1)
Regulatory Guide 1.119, "Surveillance Program for New Fuel Assembly Designs," issued for comment in June 1976, is being withdrawn.
In order to broaden the scope and data base to include existing fuels, the staff now believes that fuel surveillance programs should be plant specific and handled on a case-by-case basis rather than in a detailed generic manner.
Therefore, the staff's need for data from fuel sur- veillance programs for both existing and new fuel designs will be included in the planned update of Regulatory Guide 1.70, "Standard Format and Content of Safety Analysis Reports for Nuclear Power Plants,"
and reflected in the planned revision to NUREG-75/087,
"Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants."
Regulatory guides may be withdrawn when they are superseded by the Commission's regulations, when equivalent recommendations have been incorporated in applicable and approved codes and standards, or when changing methods and techniques have made them obsolete.
Sincerely, Robert B. Mlnogue, Director Office of Standards Development
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U.S. NUCLEAR REGULATORY COMMISSION
June 1976 REGULATORYGUIDE
OFFICE OF STANDARDS DEVELOPMENT
REGULATORY GUIDE 1.119 SURVEILLANCE PROGRAM
FOR NEW FUEL ASSEMBLY DESIGNS
A.
INTRODUCTION
Paragraphs (a) and (c)(3) of §50.36, "Technical Specificatons," of
10 CFR Part 50, "Licensing of Production and Utilization*Facilites, prescribe a surveillance program consisting of inspecti.6ns and,.Ytests nec- essary to ensure that the quality of systems and compo"n.'
is" main- tained, that facility operation will be within safet*ýliiftte and that limiting conditions of operation will be met.
Th isýZjtd4e describes a surveillance program acceptable to the NRC staf*'
,r etýrmining the per- formance of new fuel assembly designs.* The pr m
include postirra- diation destructive examination if deemed ni-'tia r This guide applies only to those light-water-cooled fuel asseysgs Thencorporating new design features that have been deemed significa deed ea NRC staff.
B. D ýCUSS ..N
The basic objective of ftl assembly designs for light-water-cooled reactors is to provide an arra of fissionable material that has high structural integrity and is cap
'"of transferring fission-generated heat to a circulating coolant while containing fission products and fuel material over the des*
lifetime.
Fuel assemblies of current design are made up of fuel rod a, sting of cylindrical U02 fuel pellets stacked end to end in thin-
'bes of zircalcv.
The fundamental design basis is that t eli sembly maintain it< structural integrity for heatup, cooldo
, s down, and power operat.!.onb including the most
.adverse seto era ng conditions expected throughout its lifetime.
Some e phenomena that may possibly affect the integrity of the fuel rod are0
rmal cycling, fission gas release to rod plenums, densi- fication, cracking and ratcheting of the fuel pellet, pellet-clad mechan- ical interaction, and corrosion- or radiation-induced changes in the USNRC REGULATORY GUIDES
Comments should be sent to the Secretary o' the Commistion, U.S Nuclear Regulatory Ceommissiton, Was~hington, D C
M56*. Attention Dockelimg and Regulatory Guides are issued to describe end make available to the public Seatrvce Section methods acceptable to the NRC staff of implementing specific parts of the Commission's regulations, to delineate techniques used by the stiff in evatu The guldes are issued in the following tn broad divisions sting specific problems or postulated acctdents. or to provide guidance to appht
&ntsi. Regulatory Guides ate not substltutes fot regulations, and compliance
1. Power Reactors S Products with them It not required. Methods and solutions different fone those Sto out in
2. Research and Test Reactors
7 Transportation the guides will be acceptable if they provide a basis fto th, findings requisite to
3 F u si and Materials Facilities S Occupatliont Health the Issuance or continuance of a permit or license by the Commission
4 EnvItonmental and Siting'
S Antittust Review Comments end suggestions for Improvements in these guides are encouraged S Materials end Plant Plotection
10 General at a.. times, and guides will be revised, as appropriate, to accommodate corn meets and to falleta new inlormation or esprelence. However. commerinr ono Copies of published guides may be obtained bV written tequest indicating the this guide. if received within about two months alter its Issuance will t- par divisrons desired to the U.S Nuclear Regulatory Commission Washington..D C
ticulartly useful in evaluating the need for an early revision Z056. Attention. ODiector. Office of Standards Development
mechanical properties of the cladding.
The integrity of the fuel rods can be ensured through proper design by using acceptable mechanical behavior models for fuel and cladding and thermal performance models for fuel rods and by maintaining an adequate margin between the limiting fuel rod stresses, strains, and temperatures and the values calculated for steady-state and transient conditions.
Among other things, designers should consider limits on fuel rod bowing, linear power, internal pres- sure, rate of power increase, coolant temperature, and coolant pressure.
Surveillance of fuel assemblies in operating reactors has proved successful in uncovering unpredicted behavior such as fuel densification, channel box wear, and fuel rod bowing.
Therefore, verification that a new fuel assembly design can meet its design and performance criteria should be determined through a comprehensive surveillance program which includes precharacterization of selected fL l assemblies.
Directed post- irradiation destructive examinations of fuel assembly components may also have to be performed to establish causes for unpredicted behavior of safety significance.
Precharacterization involves the examination and measurement of selected fuel rods individually and in the fuel assembly.
Fuel rod measurements should include diameter and length, and assembly measure- ments may include rod-to-rod spacing and spacer perpendicularity.
Surveillance of fuel rod performance may include the monitoring of reactor offgas and coolant activity; wet or dry "sipping" of fuel assem- blies to identify leakers; visual observations of structural integrity with various optical aids (i.e.,
borescope, periscope, etc.) or closed- circuit underwater TV; and remote dimensional measurements of length, diameter, and degree of bowing.
Postirradiation examinations may involve visual inspections, dimen- sional measurements, and both nondestructive and destructive examinations of the fuel rod, cladding, and fuel pellet.
.. Nondestructive examinations of the fuel rod are used to locate defects; these can include profilometry, pulse eddy current, ultrasonic, and leak tests.
Ganma scanning is used to determine axial distributioz of fission product activity, fuel column length, and gaps, and neutron radiography is an additional means to locate the ful*
column.
Analyses of internal gas composition and measurement of total gas volume are other measurements important in design verification.
.Cladding examinations and tests are designed to determine physical, chemical, and mechanical changes that have occurred as a result of ther- mal, mechanical, and environmental exposure in the reactor.
Metallo- graphic examinations determine microstructural changes, corrosion
1.119-2
behavior, and, for zircaloy cladding, hydride platelet orientation.
Density and hardness measurements supplement the metallographic examina- tion for determining the type of physical changes that have occurred in the cladding.
Chemical analyses of the cladding are useful in correlating the physical, mechanical, and corrosion behavior of the cladding.
Mechan- ical property testing can include the complete spectrum of tensile tests, burst tests, bend tests, and creep and fatigue tests.
Fuel pellet exami- nations can include density and dimensional determinations plus micro- structural observations.
C.
REGULATORY POSITION
A surveillance program to directly observe the behavior of the actual fuel system as it performs in the reactor should be conducted in order to demonstrate the validity of the conclusions reached from the design evaluation.
The surveillance program should include visual examination of all fuel assemblies upon discharge into the spent fuel pit and precharacteri- zation of selected fuel assemblies, with nondestructive and destructive postirradiation examinations conducted when deemed necessary.
Prior to establishing the surveillance program, documentation should be prepared defining the functional characteristics of the new assemily design.
The anticipated performance under all expected events and conditions should be-described.
The rules and procedures used for design and analysis, including safety margins, should be identified as described in Section
4.2, "Fuel System Design," of Regulatory Guide 1.70, "Standard Format and Content of Safety Analysis Reports for Nuclear Power Plants -
LWR Edition."
The surveillance program should be conducted on the initial core loading that uses the new fuel assembly.
The initial core loading should contain two precharacterized fuel assemblies in each of at least three regions of the core.
Surveillance should be conducted on approximately one-third of the initial core fuel assemblies during each of the first three refueling periods.
The design verification program should include the following:
1.
Precharacterization
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The preselected precharacterization fuel assemblies should undergo characterization to establish baseline data to be used to facili- tate the evaluation of fuel performance, dimensional changes, or any anomalies that might be evident from the subsequent surveillance program.
Precharacterization should be directed at the specific parameters under- going redesign and may include the following or other applicable k
examinations:
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a.
Assemblies
(1) Measurement of the distance between spacers.
(2)
Measurement of spacing between rods.
(3)
Measurement of spacer-to-fuel-rod perpendicularity.
b.
Fuel Rods
(1)
Overall visual examination.
(2)
Measurement of length and diameter, both axial and helical profiles using profilometry.
(3)
Eddy current or ultrasonic tests.
(4)
X-ray or neutron radiography.
2.
Surveillance The surveillance program should consist of a general visual inspection of all the peripheral rods as they are discharged into the spent fuel pool.
Approximately one-third of the initial core fuel assem- blies should be inapected during each of the first three refueling periods.
All pertinent data on the nuclear environment and plant operating history should be recorded.
Key parameters such as power, coolant temperature, coolant pressure, rapid transients, and scrams should be collated for use in evaluating fuel assembly behavior.
The visual inspection should include observations for cladding defects, fretting, rod bowing, corrosion, crud deposition, and geometric distortion with special attention to design changes and comparison to pertinent precharacterization observations.
If any anomalies are detected during normal plant operation or the visual examinations, further investigation should be performed.
Depending on the nature of the observed condition, the additional examina- tion could include appropriate surface, dimensional, leak-test, or gamma inspections of the fuel assemblies.
In the event that these additional investigations uncover any fuel assembly containing structural defects, fuel rod failures, or abnor- malities of such a nature or magnitude that fuel design limits could be exceeded during normal operation, this assembly should be subjected to destructive examinations.
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3.
Destructive Examinations If the detailed surveillance examinations indicate the need for further evaluation, destructive examinations should be performed.
These examinations need not be accomplished at the plant site or within the period of the refueling outage.
Prior to performing the destructive examinations, thq selected assemblies should undergo whatever additional tests are necessary to establish the types of destructive examinations to be conducted, These testo ran include leak tests, dye penetrant, eddy current, profilometry gamma scanning, or neutron radiography, Again depending on the nature of the observed condition, metal- lographic examinations and mechanical testing may be undertaken.
a, Metallography When examination of the fuel aqgdding is indicated, sections of tubing should be m*unted for examination of the cladding for microptructural characteristiqs, corrosion or fretting behavior, oxide film th~ck~ies, hydride platelet orientation, and harMness, A-ea: identi- fied in the'nondestructive examinations as having clad defects should be included irA the ietallograph~c exam.ations, The metallographic mounting of the sections should be performed with the fuel pellet or pellet pieces maintained in their rel4tive configuration go that the extent of any pell4et-cld chemical or mechanical tnteraqtion can be established.
Ptandar4 metallographic ezaminjtion of other fuel assembly rwmponentp should be undertaken When 4ee~ed necessary to explain unpr@-
4tcted behavior, Whe- examinatipns of the fuel pellets are indicated, they should be Mad@ using th metaliqaraphic specqmeps prqp&;ed for fuel clad- ding oxatmnationa.
Qbservation pf fr@pture, pore sige 4A4 porosity dtatribu- tignt Ogailp ae,
@tp., shou~ld be pqted wheq pqrtinient: tg eptablishing the gagg@ of unpredicted bphv4.or, Fuel-!lad gap size should be dAtermiq@d, gnd fi#al fuel density ghoul4
0g 1e444red when nqeq@qpay for ev4luatiOp of the qbs@rvp4 b,
Maechqnical Tepting Iri the event that the metallographic examinations and tests prf*ormed according to regulatory position C.3.
a. indicate potentially
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serious- mechanical degradation of the fuel rod cladding, tensile, bend, or burst tests should be performed according to ASTM E 453-72* to quanti- tatively confirm the degree of damage.
D,
IMPLEMENTATION
The purpose of this section is to provide information to applicants and lict-nsees regarding the NRC staff's plans for using this regulatory guide.
This guide reflects current NRC staff practice, Therefore, except in those cases in which the applicant or licensee proposes an acceptable alternative method for complying with specified portions of the Commis- sion's regulations, the method described herein is being and will continue to be used in the evaluation of submittals in connection with applications for operating licenses, construction permits, or amendments thereto until this guide is revised as a result of suggestions from the public or addi- tional staff review, ASTM E 453-72, "Standard Recommended Practice for Examination of Fuel Element Cladding Including the Determination of Mechanical Properties."
Copies may be obtained from the American Society for Testing and Mate- rials, 1916 Race Streeat Philadelphia, Pa. 19103,
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