Regulatory Guide 1.119
| ML13350A277 | |
| Person / Time | |
|---|---|
| Issue date: | 06/30/1976 |
| From: | NRC/OSD |
| To: | |
| References | |
| RG-1.119 | |
| Download: ML13350A277 (7) | |
UNITED STATESOA
REGULATORY
COMMISSION
a WASHINGTON,
0. C. 20665June 23, 1977REGULATORY
GUIDE DISTRIBUTION
LIST 'DIVISION
1)Regulatory Guide 1.119, "Surveillance Program for New Fuel AssemblyDesigns,"
issued for comment in June 1976, is being withdrawn.
Inorder to broaden the scope and data base to include existing fuels,the staff now believes that fuel surveillance programs should be plantspecific and handled on a case-by-case basis rather than in a detailedgeneric manner. Therefore, the staff's need for data from fuel sur-veillance programs for both existing and new fuel designs will beincluded 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"Standard Review Plan for the Review of Safety Analysis Reports for NuclearPower Plants."Regulatory guides may be withdrawn when they are superseded by theCommission's regulations, when equivalent recommendations have beenincorporated in applicable and approved codes and standards, or whenchanging methods and techniques have made them obsolete.
Sincerely, Robert B. Mlnogue, DirectorOffice of Standards Development
.., ...-I .-..I ..... .6 -, ......
U.S. NUCLEAR REGULATORY
COMMISSION
June 1976REGULATORYGUIDE
OFFICE OF STANDARDS
DEVELOPMENT
REGULATORY
GUIDE 1.119SURVEILLANCE
PROGRAMFOR NEW FUEL ASSEMBLY
DESIGNS
A. INTRODUCTION
Paragraphs (a) and (c)(3) of §50.36, "Technical Specificatons,"
of10 CFR Part 50, "Licensing of Production and 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 thatlimiting conditions of operation will be met. Th isýZjtd4e describes asurveillance program acceptable to the NRC ,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 appliesonly to those light-water-cooled fuel asseysgs Thencorporating new designfeatures that have been deemed significa deed ea NRC staff.B. D ýCUSS ..NThe basic objective of ftl assembly designs for light-water-cooled reactors is to provide an arra of fissionable material that has highstructural integrity and is cap '"of transferring fission-generated heat to a circulating coolant while containing fission products and fuelmaterial over the des* lifetime.
Fuel assemblies of current design aremade up of fuel rod a, sting of cylindrical U02 fuel pellets stackedend to end in thin- 'bes of zircalcv.
The fundamental designbasis is that t eli sembly maintain it< structural integrity forheatup, 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 thefuel 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 theUSNRC REGULATORY
GUIDES Comments should be sent to the Secretary o' the Commistion, U.S NuclearRegulatory Ceommissiton, Was~hington, D C Attention Dockelimg andRegulatory Guides are issued to describe end make available to the public Seatrvce Sectionmethods acceptable to the NRC staff of implementing specific parts of theCommission'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 Productswith 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 Healththe Issuance or continuance of a permit or license by the Commission
4 EnvItonmental and Siting' S Antittust ReviewComments end suggestions for Improvements in these guides are encouraged S Materials end Plant Plotection
10 Generalat a.. times, and guides will be revised, as appropriate, to accommodate cornmeets and to falleta new inlormation or esprelence.
However.
commerinr ono Copies of published guides may be obtained bV written tequest indicating thethis guide. if received within about two months alter its Issuance will t- par divisrons desired to the U.S Nuclear Regulatory Commission Washington..D
Cticulartly 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 rodscan be ensured through proper design by using acceptable mechanical behavior models for fuel and cladding and thermal performance models forfuel rods and by maintaining an adequate margin between the limiting fuelrod stresses, strains, and temperatures and the values calculated forsteady-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 provedsuccessful in uncovering unpredicted behavior such as fuel densification, channel box wear, and fuel rod bowing. Therefore, verification that anew fuel assembly design can meet its design and performance criteriashould be determined through a comprehensive surveillance program whichincludes precharacterization of selected fL l assemblies.
Directed post-irradiation destructive examinations of fuel assembly components may alsohave to be performed to establish causes for unpredicted behavior ofsafety significance.
Precharacterization involves the examination and measurement ofselected fuel rods individually and in the fuel assembly.
Fuel rodmeasurements 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 ofreactor 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 locatedefects;
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 neutronradiography is an additional means to locate the ful* column. Analysesof internal gas composition and measurement of total gas volume are othermeasurements 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 inthe 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
POSITIONA surveillance program to directly observe the behavior of the actualfuel system as it performs in the reactor should be conducted in order todemonstrate the validity of the conclusions reached from the designevaluation.
The surveillance program should include visual examination of allfuel 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 toestablishing the surveillance program, documentation should be prepareddefining the functional characteristics of the new assemily design. Theanticipated performance under all expected events and conditions shouldbe-described.
The rules and procedures used for design and analysis, including safety margins, should be identified as described in Section4.2, "Fuel System Design,"
of Regulatory Guide 1.70, "Standard Format andContent of Safety Analysis Reports for Nuclear Power Plants -LWR Edition."
The surveillance program should be conducted on the initial coreloading that uses the new fuel assembly.
The initial core loading shouldcontain two precharacterized fuel assemblies in each of at least threeregions of the core. Surveillance should be conducted on approximately one-third of the initial core fuel assemblies during each of the firstthree refueling periods.The design verification program should include the following:
1. Precharacterization
.. ...... .... -...The preselected precharacterization fuel assemblies shouldundergo characterization to establish baseline data to be used to facili-tate the evaluation of fuel performance, dimensional changes, or anyanomalies 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:
1.119-3
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 andhelical 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 visualinspection of all the peripheral rods as they are discharged into thespent 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 historyshould be recorded.
Key parameters such as power, coolant temperature, coolant pressure, rapid transients, and scrams should be collated for usein evaluating fuel assembly behavior.
The visual inspection should include observations for claddingdefects, fretting, rod bowing, corrosion, crud deposition, and geometric distortion with special attention to design changes and comparison topertinent precharacterization observations.
If any anomalies are detected during normal plant operation orthe 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 gammainspections of the fuel assemblies.
In the event that these additional investigations uncover anyfuel assembly containing structural defects, fuel rod failures, or abnor-malities of such a nature or magnitude that fuel design limits could beexceeded during normal operation, this assembly should be subjected todestructive examinations.
1.119-4
3. Destructive Examinations If the detailed surveillance examinations indicate the need forfurther evaluation, destructive examinations should be performed.
Theseexaminations need not be accomplished at the plant site or within theperiod of the refueling outage.Prior to performing the destructive examinations, thq selectedassemblies should undergo whatever additional tests are necessary toestablish the types of destructive examinations to be conducted, Thesetesto 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 formicroptructural characteristiqs, corrosion or fretting behavior, oxidefilm th~ck~ies, hydride platelet orientation, and harMness, A-ea: identi-fied in the'nondestructive examinations as having clad defects should beincluded irA the ietallograph~c exam.ations, The metallographic mountingof the sections should be performed with the fuel pellet or pellet piecesmaintained in their rel4tive configuration go that the extent of anypell4et-cld chemical or mechanical tnteraqtion can be established.
Ptandar4 metallographic ezaminjtion of other fuel assemblyrwmponentp should be undertaken When 4ee~ed necessary to explain unpr@-4tcted behavior, Whe- examinatipns of the fuel pellets are indicated, theyshould 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 fueldensity ghoul4 0g 1e444red when nqeq@qpay for ev4luatiOp of the qbs@rvp4b, Maechqnical TeptingIri the event that the metallographic examinations and tests according to regulatory position C.3.
a. indicate potentially
1.1g-5 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, exceptin 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 continueto be used in the evaluation of submittals in connection with applications for operating licenses, construction permits, or amendments thereto untilthis 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 FuelElement 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. 19103,1.119-6I