ML20125D526

Safety Evaluation Supporting Change 5 to License DPR-11, Authorizing Increase of Max Reactivity Addition Rate During R&D Testing Program

ML20125D526
Person / Time
Site:	05000130
Issue date:	05/27/1965
From:	Boyd R US ATOMIC ENERGY COMMISSION (AEC)
To:
Shared Package
ML20125A538	List: ML20125D123 ML20125D151 ML20125D175 ML20125D208 ML20125D224 ML20125D241 ML20125D271 ML20125D310 ML20125D324 ML20125D333 ML20125D352 ML20125D364 ML20125D385 ML20125D404 ML20125D418 ML20125D526 ML20125D534 ML20125D541 ML20125D545 ML20125D551 ML20125D554 ML20125D559 ML20125D561 ML20125D563 ML20125D567 ML20125D571 ML20125D582 ML20125D587 ML20125D595 ML20125D618 ML20125D671 ML20125D691 ML20125D706 ML20125D718 ML20125D736 ML20125D760 ML20125D771 ML20125D787 ML20125D800
References
FOIA-85-54 NUDOCS 8506120391
Download: ML20125D526 (2)

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LICL A AUTHORITY pq COPY SAFETY EVALUATION BY TiiE RESEAROI AND POWER REACTOR SAFETY BRANul

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D VISTON OF REACTOR LICENSIMO IN Tile MATTER OF NORT1 TERN STATES POWER COMPANY PATilFINDER ATOMIC POWER PLANT DOCKET No. 50-130 ,

INCREASE IN REACTIVITY INSERTION RATE LIMIT-DURIN0 TESTING , l CIANOE No. 5 -

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Introduction By application dated May 24, 1965, the Northern States power Company (NSP) requested a change in Technical Specifications to increase the maximum reactivity addition rate '

during the research and development testing program. The revised limit would apply l during Phase I and Phase II testing programs which are restricted to maximum power ,

( cvels of 1 IM(c) and 5 FM(t) respectively. This change has been requested because c: sting has indicated that certain control rod configurations could result in re ctivity insertions in excess of those presently authorized.

Evaluation

'The present Technical Specifications, which are applicable to the research and develop- ,

ment testing program, require that the maximum possible reactivity insertion rate shall c:t exceed 40 cents per second when testing slab arrays in the core, and shall not '

cxceed 10 cents per second during boiler only testing. The requested change would per-cit reactivity insertions of as high as 25 cents per second for both boiler only and full core testing. 4 The applicant has analyzed various reactor transients with the increased reactivity insertion rates. To demonstrate that the proposed limit of 25 cents per second would cot pose any safety problems, the evaluations were made with a reactivity insertion r ta of 50 cents per second. The results of the analyses from an initial power level cf 1 PM(t) with a drained superheater were reported in the request. Transients initiated at lower power levels would result in lower peak fuel temperatures before the transient were terminated by scram, and transients initiated from higher power 1:vels would roquire higher range settings than would be permitted during Phase 11 t: sting. The applicant therefore believes that the transient as analyzed represents th] most severe accident possible as a consequence of the increased reactivity inser-tion rate. The transient as reported resulted in peak fuel temperatures of about 1000*F in the boiler region and about 1100'F in the superheater region.

. The Staf f has evaluated the analyses of the applicant and agrees that no detrimental

.ffects should occur as a consequence of this transient, provided that a reactor scram signal is initiated at or before 23 PM(t). In this regard, to insure that a scram 0506120391 030214 PDH FOIA PAY 05-54 PDH

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signal'is generated at or before this power level, we believe that either instrument l Channel 5 or 6 should by itself be capable of scramming the reactor. We therefore i believe that the present logic change which automatically occurs at a preset power 1 vel on Channel 7 should be reset at some power level in excess of 23 MW(t) during these tests to ensuru that either channel has scram capability during the operations proposed.

Con clus ions dased upon our review of the information submitted, we have concluded that the operation of the Pathfinder reactor in accordance with the proposed change during research and development tests does not present significant hazards considerations cot described or implicit in the hazards summary report, and there is reasonable assurance that the health and safety of the public will not be endangered.

Accordingly, we believe that the third paragraph of Section 8.0 may be amended to read as follows:

"During the experiments with the slab array, the maximum possible reactivity addition rate shall be no greater than 40 cents per second. During Phase I and Phase II experiments (othtr than slab array), the maximum reactivity insertion rate may be as high as 25 cents per second provided that either channel 5 or 6, by itself, is capable of scramming the reactor." i Original signed by,t  !

( noger S.Bo)d  !

Roger S. Boyd, Chief Research & Power Reactor Safety Branch l' Division of Reactor Licensing Dico: May 2 71935 i

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