ML20052F737
| ML20052F737 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 05/04/1982 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20052F734 | List: |
| References | |
| NUDOCS 8205130543 | |
| Download: ML20052F737 (5) | |
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1 SAFETY EVALUATI0tl BY THE OFFICE OF HUCLEAR REACTOR REGULATION RELATED TO AMD!DMENT NO.13 TO FACILITY OPERATING LICENSE DPR-77 i
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AHD AMEND?iEHT N0. 4 TO FACILITY OPERATItir. LICENSE DPR-79 i
i TDmESSEE VALLEY AUTHORITY 1
INTRODUCTION This SER covers the following TVA requests for amendeents to the Technical Specifi-cations:
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A.
Proposed changes dated 12/10/81 on Fire Hose Hydrostatic Test Pressure, ice Red Determination and Surveillance, Maximum Isolation Yalve Tic.es, J
j Vital Battery Surveillance; B.
Proposed changes, dated 12/10/81 on a table correction, OA Monitoring of Plant Effluents, Land Use Census, and System Flushing;
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C.
Proposed changes, dated 3/9/82, on Downscale Failure Alarns; D.
Proposed changes, dated 4/7/82, on Visual Inspection Schedule on Snubbers; and E.
Proposed changes, dated 3/1/82, on Maxinun Enrichnent for Reload Fuel.
1 EVALUATION ITEM A The proposed changes related to vital battery surveillance and the fire hose test pressure requirements were mac.a in Amendment 12 to the Technical I
Specifications of Unit 1.
The original Technical Specifications of Unit 2 i
incorporated the proposed changes.
The alternate reasurenent for the determination of ice bed temperature (if the control room monitor fails) was considered acceptable since the use of j
a digital voltreter is more accurate than the Control Room nonitor.
The proposed change fren 10 seconds to 30 seconds for the eight glycol valves l
i to close is acceptable because the response time conforms with the safety analysis on isolating the contain ent reported in the SER, HUREG-0011. The j
glycol valves are part of the refrigeration system for the ice bed, and they do not provide a direct leakage path to the environs. For such valves, closure times of less than 60 seconds are acceptable (See SRP section 6.2.4 HUREG-Ot00).
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. ITEft B Tabic 3.6-2 for both units is revised to add a containment isolation valve to the list which was inadvertently lef t off by the Itcensee. This valve for the units has been tested even though it was not On the table in the Technical Specifications.
The change clarifies the responsibilities for irplementing the OA progran for effluent monitoring at the site. This is an administrative change.
The Technical Soecifications are revised to define more specifically the survey of land use census that is performed. This revision is for clarifi-cation purposes. !!o actual changes are being made in the perfornance of the census.
The change provides creater coordination between the surveillance require-ments for the fire suppression water system flush with the chlorination of the raw service water and the fire suppression systens. Chlorination is a seasonal process and coordinating this with the fire suppression system flush pronotes greater ef ficiency without degradation of the systems.
ITEM C Dounscale failure alarms are nmv installed for units 1 & 2.
This change is cade to Tables 4.3-8 and 4.3-9 to reflect that such an installation has occurred. This revision is adminstrative in nature.
ITEM D In order to preclude a forced outage of Unit 1, the requirement for visual inspection of the snubbers was changed to state that such an inspection would be performed at an outage of sufficient duration (approxinately 72 j
hours in Mode 5) but no later than 18 nonths 225% from the first inspection.
l The completian of the second inspection period is changed fron 12 nonths to l
18 nonths wi.sch is judged to be acceptable by the staff because the majority I
of the snubbers have been inspected and only a few retain to be inspected in Mode 5.
These are in areas that are impossible to inspect during oper-ations.
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ITEM E l
Tennessee Valley Authority has sub"itted a proposed arendrent requesting changes in the maximum fuel enrichment for reload fuel fron 3.5 to 4.0 w/o U-235 and changes in the maxirun fuel enrichnent for fuel in tbc new fuel pit storage racks fran 3.5 to 4.5 w/o U-235 (Letter from L.11. Mills to it. R. Denton, TVA-StP-TS-26, dated !iarch 1,1982) for the Sequoyah Units 1 and 2.
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. The criticality aspects of the new and spent fuel storage racks have been analyzed by TVA using the KEMO-IV Ponte Carlo code with cross sections generated by the AMPX code. These codes have been benchnarked against a set of 27 critical experirents ranging from water roderated, oxide fuel arrays separated by various naterials (Boral, steel and water) to dry, harder spectrum uraniu, metal cylinder arrays with various interspersed naterials (Plexiglass, steel and air). The average V-effective calculated for these benchnarks is 0.9993 uhich de mnstrates that there is no bias associated with the analytical rethod over the wide rance of experirental conditions analyzed.
Hew ruel Criticality of fuel assemblies in the new fuel storage rack is prevented by restrictinq tha minirma separation between asserblies to 21 inches center-to-center. Tho analysis by TVA assu1ed the highest alloweble enrichrent (4.5 w/o U-235) without any control rods or any noncontained burnable poison at its rost reactiva point in life (no depletion or fission product buildup).
The fuel racks are assumed to be infinite in lateral and axial extent. Althouoh the new fuel storace pit is designed to he dry, the maximtm K-effective must be detemined by considering credible accidents. The nost liniting credible accident has been found to be the introduction of moderator into the new fuel storage pit. The nptinir achievable poderation occurs with full den-sity water (1.0 g/cc) and the calculations were perfomed at this condition.
Under these assumptions the nominal K-ef fective for the new fuel storage racks in their design confic,uration is 0.9189 as deternined by the KENO-IV code. A rechanical bias of 0.001 is added to this value to account for the fact that rechanical tolerances can result in spacings between assenblies less than noninal. A total uncertainty at a 95/95 probability / confidence leval which includes the statistical uncertainty associated with the nominal case VI.?>0 V-ef fective and tha statistical uncertainty due to the method is i
also applied. The resultino K-effective, including all of these biases and uncertainties, is 0.9343, vell below the acceptance criterion of 0.93 for new fuel with optimun myteration, and tha acceptance criterion of 0.95 for l
new fuel fully flooded with nonborated water.
I De conclude that the nodification to the Sequoyah Technical Specification 5.6.1.2 increasing the raxinum fuel enrichnent for fuel in the new fuel pit storane racks for Units 1 and I fron 3.5 w/o U-235 to 4.5 w/o U-235 is acceptable. The maxinu, enrichrent of fuel allowed in the core is, however, j
4.0 u/o U-235.
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Criticality of fuel assemblies in the spent fuel storage rack is prevented j
by restricting the ninimen separation between assenblies to 10.375 inches i
center-to-center and inserting neutron poison (Boral) between assemblies.
The analysis assuned that highest allowable enrichrent (4.0 w/o U-235) without any control rods or any noncontained burnable poison at its most j
reactive point in life (no depletion or fission product buildup). The i
fuel racks are assuned to be infinite in lateral and axial extent. The l
noderator is pure water at a density of 1.0 g/cc. Ho dissolved boron is i
included in the water. Credit is taken for the neutron absorption in full length structural raterials and in solid mterials added specifica11g is for neutron absorption. The mininun boron loading of 0.0232 gm (D10)/cm i
assuned in the poison plates.
Under these assumptions the nominal K-effective for the spent fuel storage racks in their design configuration is 0.9230% as determined by KEND-IV.
Un mechanical bias was included since studies indicated that the noninal case assumptions result in the worse case. A bias of 0.0025 to account for B C particle self-shielding is included. A total uncertainty at a 4
95/95 probability / confidence level which includes the statistical uncer-tainty associated with mechanical tolerances, uncertainty in the nominal case K-effective, and uncertainty in the nethod bias, is also applied.
The resulting K-effective, including all of these biases and uncertainties, is 0.9397, below the acceptance criterion of 0.95.
J The effect of credible accidents has been considered and the most con-saquential one is dropping of a single fuel assembly outside the rack i
between the periphery of the storage racks and the side walls of the pool.
For accident conditions, TVA has applied the double contingency principle of AUS N16.1-1975 which states that it shall require two unlikely, indepen-dent, concurrent events to produce a criticality accident. This has been accepted by the staff. Therefore, the presence of soluble boron in the storage pool water can be assumed for accioent conditions such as the fuel assettly dron. Since 2000 ppn of boron in the pool uater will decrease 1
reactivity by more than 30%, any postulated accidental reactivity increase i
will be mch less than the negative worth of the dissolved boron.
In a phone conversation on March 12, 1932, between TVA and NRC, a nodifica-i tion to Technical Specification S.6.1.1 was agreed upon. The reference to the double contingency erinciple was remved fron the Technical Specifica-tion itself and inserted as a footnote.
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, We conclude that the rodification to Technical Specification 5.6.1.1, allowing the assunption of the double contingency principle (as a foot-note) in deternining the criticality of spent fuel storage racks is accept-able.
Our evaluation and apnroval of these Technical Specification modifications is based on PWR fuel pins and fuel asser.blies similar in design to the Westinghouse 17x17 fuel presently installed in the Sequoyah Units 1 and 2.
Fuel designs differing from this may require a reevaluation even though the U-235 enrichment and fuel assembly spacing specifications remain the same.
ENVIR0HMENTAL CONSIDERATION Ve have determined that the anendnent does not authorize a change in effluent types or total annunts nor an increase in power level and will not result in any signifi-cant environrental inpact. Having made this determination, we have further con-cluded that the amendment involves an action which is insignificant fro 1 the stand-point of environmental inpact and, pursuant to 10 CFR 51.S(d)(4), that an environ-rental impact statement or negative declaration and environnental irpact appraisal need not be prepared in connection with the issuance of this amendment.
COL'CLUSIGH We have concludod, based on the considerations discussed above, that:
(1) because the amenorent does not involve a significant increase in the probability or con-sequences of accidents previously considered and does not involve a significant decrease in a safety margin, the amendnent does not involve a significant hazards consideration, (2) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed nanner, and (3) such activities will be conducted in compliance with the Commission's reculations and the issuance of this anendaent will not be ininical to the comon defense and security or to the health and safety of the public.
Dated:
May 4, 1982 Principal Contributors: Carl Stahle, Licensing Branch Ho. 4, DOL Laurence Kopp, Core performance Branch, DSI l
Nor,an Wagner, Auxiliary Systens Branch, DSI OFFICE )
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