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MEMORANDUM FOR:
R. L. Tedesco, Deputy Director Lessons Learned Task. Force. NRR W. R. Butler, Chief, Containment Systems Branch, OSS i
FROM:
SUBJECT:
CSB REVIEW OF CONTAIfMENT ISCLATION PROVISIONS FOR THREE MILE ISLAND, UNIT 2
Reference:
June 22, 1976 meco fram J. W. Sha;:aker thru G. C. Lainas to R. L. Tedesco titled Przoosed Position on S&W i
Containment Isolation System Per your request of July 27, 1979, the Containment Systems Branch (CSB) has examined the branch files to determine the bases for staff approval of the containment isolation provisions for THI-2 and to determine how that review relates to the enclosed memorandum, referenced above.
Our search of the branch files shows that questions concerning diversity in the parameters sensed for the initiation of containment isolation were not sent to the TNT-2 applicant during.any part of our review. The CSB review of the TMI-2 containment isolation system occurred during 1974 and 1975 with final approval given in.our draft SER dated November 17. 1975. The draft SER (with the applicable pages enclosed) did not mention diversity in the parameters sensed for centainment isolation. It simply stated that non-essential lines in the centainment would be isolated upon receipt of a containment high pressure i
signal.
i Standard Review Plan 6.2-4, Containment Isolation System, was issued on November 24, 1975. This SRP required diversity in the parameters sensed to l
initiate containment isolation. However, since the implementation of the SRP
{g was to be " front-fit" only, TMI-2 was not to be "back-fitted" to comply with the new staff requirements.
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During the NRR reorganization of January 1976, the TMI-2 reviewer, D. Shum, FB]; Qd-l was detailed out of the branch.
F. Eltawila was assigned as the new THI-2 e
reviewer. As is our policy, when a docket change hands, the new reviewer t-am only addresses the identified outstanding items. Therefore, since the p j containment isolation parameters had been previcusly approved,. the subject M ~j was never reopened.
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1 R. L. Tedesco JUL 3 01979 l
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Since the issuance of SRP 6.2-4, applications associated with plants I
(particularly OLs) designed prior to the SRP continued being submitted j
without diversity in tneir containment isolation signals. This prompted issuance of the enclosed memorandum to you which outlined our proposed implementation plans for B&W plants. Although the memorandum did not 11stinguish cps from Ols, its provisions were intended to apply to both. -
l The referenced Greene County plant did not have diversity in its isolation
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parameters and was so identified in the draft SER (February 1,1977)
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Supplement 3 to the Greene County SER (August 8,1977).. diversity was p
included in the design.
l Virtually all applications being reviewed today have diversity in their containment isolation signals. The latest plants that were approved by
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CSB without diversity are certain 'CE Ots that were designed prior to the issuance of SRP 6.2-4.
These plants are Arkansas Nuclear One, Unit 2 (ANO-2) and San Onofre Nuclear Generating Station, Units 2 & 3.
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Origi::a1 s13ned br Walter 3. Butler Walter R. Butler, Chief 1
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~ Containment Systems Branch Division of Systems Safety
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Enclosures:
As Stated
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R. Denise J. Kudrick i
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F. Eltawila D. Pickett l
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