ML17054C235: Difference between revisions
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==References:== | ==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 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 to if the iodine release resulting from partial uncovery of 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 WOG has completed its work on this matter, and that WCAP-13247 (Ref. 1) demonstrates that a significant safety issue does not 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 | (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 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 to if the iodine release resulting from partial uncovery of 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 WOG has completed its work on this matter, and that WCAP-13247 (Ref. 1) demonstrates that a significant safety issue does not 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 steam generators and a two-loop plant with model 44 tteam generators. These plants were selected model 51 and model 44 steam generators 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 the gen*ratvr watec level tor the duration of these events. The results o! iodine release calculation indicated 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 transient, and that the 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 are consistent with the criteria established by the staff in the Standard Review Plan (Section 15.6.3), and the Westinqhouae demonstrate that the e!!ects of partial steam tube uncovery on the iodine release !or SGTR and non-SGTR events is negligible. Therefore, we agree your position on this 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: A. Engel (TU Electric) ----*-*--- | ) . ) to provide boundary conditions tor the mixture level model. The represQntative plants used !or the analyses were a !our-loop plant with model steam generators and a two-loop plant with model 44 tteam generators. These plants were selected model 51 and model 44 steam generators 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 the gen*ratvr watec level tor the duration of these events. The results o! iodine release calculation indicated 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 transient, and that the 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 are consistent with the criteria established by the staff in the Standard Review Plan (Section 15.6.3), and the Westinqhouae demonstrate that the e!!ects of partial steam tube uncovery on the iodine release !or SGTR and non-SGTR events is negligible. Therefore, we agree your position on this 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: A. Engel (TU Electric) ----*-*---}} | ||
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Revision as of 23:10, 18 May 2018
| 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
L r 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 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 to if the iodine release resulting from partial uncovery of 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 WOG has completed its work on this matter, and that WCAP-13247 (Ref. 1) demonstrates that a significant safety issue does not 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 steam generators and a two-loop plant with model 44 tteam generators. These plants were selected model 51 and model 44 steam generators 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 the gen*ratvr watec level tor the duration of these events. The results o! iodine release calculation indicated 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 transient, and that the 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 are consistent with the criteria established by the staff in the Standard Review Plan (Section 15.6.3), and the Westinqhouae demonstrate that the e!!ects of partial steam tube uncovery on the iodine release !or SGTR and non-SGTR events is negligible. Therefore, we agree your position on this 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: A. Engel (TU Electric) ----*-*---