ML17054C235
| ML17054C235 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 01/17/2017 |
| From: | Wolf Creek |
| To: | Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML17054C103 | List: |
| References | |
| ET 17-0001 | |
| Download: ML17054C235 (2) | |
Text
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UNirf.D STATU NUCLEAR REGULATORY COMMISSION WASHINOTO... 0 C. %0551 Mr. Lawrence A. Walsh, Chairman Westinghouse Owners croup March 10, 1993 North Atlantic Energy Services corporation P. 0. Sox JOO seabrook, NH OJ874 Attachment to WOG-93-066
Dear Mr. Walsh:
SUBJECT:
Westinghouse owners Croup-Steam Generator Tube
~
Uncovery Issue
References:
(l)
WCAP-13247, "Report on the methodoloqy tor th@ resolution of the steam qenerator tube uncovery iasu*." dated March 1992.
(2) letter !rom Lawrence A. Walsh to Robert c.
Jones, "Westinghousa Owners croup - Steam generator tube uncovery issue," dated March 31, l9SJ2.
(J)
Memorandum from LeMoine J. cunningham to Robert C. Jcnes, "WCAP-1J247," report on the methodoloqy !or the resolution ot the steam generator tube uncovery issue," submitted by Westinghouse Owners Croup dated Septemb~r 14, 1992.
In July 1987, North Anna Unit 1 steam generator tube rupture 1ndicated that the apex of the steam generator tubes may have been partially uncovered for 10-15 minutes.
In response to concerns expressed by the NRC staff, the Westinghouse owners Group (WOG) initiated & program in ~9e8 to de~ermine if the iodine release resulting from partial uncovery of ste~~ qenerator tubes during a steam generator tube rupture (SCTR) event or other limiting event can have a s1gnificant safety impact on Westinghouse plants.
As discussed in your letter of March 31, 1992 (Ref. 2), we understand that th~ WOG has completed its work on this matter, and that WCAP-13247 (Ref. 1) demonstrates that a significant safety issue does not ~xist for Westinghouse facilities.
Based on our review of WCAP-13247, it is our understanding that Westinghouse performed representative SGTR analyses using the LOFTTR2 computer code to characterize the thermal and hydraulic response to various SGTR scenarios for representative plants and
)
. ) to provide boundary conditions tor the mixture level model.
The represQntative plants used !or the analyses were a !our-loop plant with model ~l steam generators and a two-loop plant with model 44 tteam generators.
These plants were selected beca~**
model 51 and model 44 steam generators a~e expected to be most susceptible to tube uncovery during an event.
Westinghouse pertormed the LOFTTR2 analyaes tor the following accident scenarios:
(a) SGTR with a stuck-open PORV; (b) SGTR with a modulating PORV; and (c) SGTR with a cycling safety valve.
The stuck-open PORV case resulted in the highest steam release and consequently the greatest of!site dose consequences.
The results ot these LOFTTR2 ar.alyses were then used as boundary conditions to com~ute the st~am gen*ratvr watec level tor the duration of these events.
The results o! ~he iodine release calculation indicated th~t the SGTR analysis with a stuck-open PORV yields the highest iodine release with only about 1\\ ot the release being attributable to steam generator tube uncovery.
- Thus, Westinghouse concluded that the ettect o! tube uncovery is esaentially negligible tor the limi~inq transient, and that the curr~nt design basis SGTR analysis methodology remains valid.
Based on our review ot your submittal, we believe that the WOG program repre3ents a comprehensive e!tort to address the staff's concerns.
The assumptions and parameters used in the iodine transport quanti!icati~n are consistent with the criteria established by the staff in the Standard Review Plan (Section 15.6.3), and the Westinqhouae a~alysea demonstrate that the e!!ects of partial steam ~enerator tube uncovery on the iodine release !or SGTR and non-SGTR events is negligible.
Therefore, we agree ~ith your position on this ~atter and consider this issue to be resolved.
Thank-you tor your attention and efforts in resolving this matter.
Sincerely, C.tcfl4f.t Reactor Systems Branch Division of Systems Safety and Analysis cc:
.t~; voyt:ell:.~q\\0, A. Engel (TU Electric)
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