ML19211C535
| ML19211C535 | |
| Person / Time | |
|---|---|
| Issue date: | 08/15/1979 |
| From: | Thadani A Office of Nuclear Reactor Regulation |
| To: | Hanauer S Office of Nuclear Reactor Regulation |
| References | |
| REF-GTECI-A-09, REF-GTECI-SU, TASK-A-09, TASK-A-9, TASK-OR NUDOCS 8001110645 | |
| Download: ML19211C535 (8) | |
Text
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s, v f TAP A-9 MEMORANDUM FOR:
S. H. Hanauer, Director Unresolved Safety Issues Program FROM:
A. Thadani, Task Manager, A-9
SUBJECT:
SUMMARY
The NRC staff met with B&W and B&W owners group to discuss plans for resolution of the ATWS issue.
Opening Remarks After initial staff comment on the objective of the meeting, the industry made the following opening comments:
B&W Owners Group: The owners want to work with the staff to achieve resolutic7 of ATWS but that the groundrules need to be assessed in light of TMI-2 event fcr timely resolution.
B&W:
ATWS is not a safety issue and that TMI-2 event provides further support to the B&W position that additional safety valves on pressurizer should not be required.
Impact of TMI-2 The questions (resulting from the TMI-2 event) raised by the NRC staff at the 7/25/79 meeting with the industry were discussed and summarized below.
B&W has agreed to provide some of the requested information in a report in October '79.
a) Long Term Shutdown With Stuck Open Pressurizer Safety /
Relief Valve i) The major staff concerns relate to the potential effects of the voids generated in the primary system in preventing natural circulation.
B&W stated that they intend to address this issue but did not commit to a schedule.
1736 276 8001110 [f
S. H. Hanauer AUG 151979 ii) Post TMI deliberations have shown that the tripping of RCPs imediately following a small LOCA may be the most appropriate action.
Since ATWS analyses did not consider such factors, the staff asked B&W to address this issue.
B&W has not yet committed to address this concern.
iii) The staff asked B&W owners and B&W to list the instruments and equip-ment relied on to mitigate the consequences of ATWS events and to provide assurance that the instrumentation and equipment are qualified for ATWS environment.
B&W agreed to provide the list of instruments / equipment in October but stated that the question on qualification will be addressed after " lessons learned" requirements review is complete.
b) Operator Actions The staff asked B&W to provide justification for credit for operator action ten minutes after the initiation of the postulated ATWS event.
In parti-cular B&W is to address the infomation displayed and the simplicity of operator actions.
B&W agreed to provide this information in the October report.
c)
Blocked PORV The staff has learned that some plants operate with the PORV blocked because of leakage through the PORV.
Since the PORV is relied on (for Alt #3 plants) to provide capability to limit the overpressure during ATWS events, bases for continued operation with blocked PORV must be provided.
B&W does not plan to address this issue and they suggested that individual plant owners should address this concern.
d) Larger Safety Valves B&W agreed to address in the October report the value and the impact of using larger diameter pressurizer safety valves instead of using a greater number of valves.
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S. H. Hanauer )gg e) Pressurizer Safety / Relief Valve Qualification Recent studies by the staff indicate a need for assurance that the safety / relief valves would behave as predicted in the ATWS analysis when exposed to two phase and subcooled vister coriditi ns.
Since the valves are not qualified for this environment, the staff asked that a program to verify correct valve behavior be initiated and results ob-tained early.
B&W suggested that the staff comunicate with EPRI on this issue and that the sticking open of all safety / relief valves is probably less severe than one valve sticking open.
f) Radiological Calculations B&W agreed to address all parameters in this assessment except leakage which they believe is plant specific.
However, they did not comit to any schedule on this item.
g)
Input Parameters B&W agreed to address plant specific input in their October report.
Subsequent to the above discussion, the staff made the following comments:
a) Prevention measures proposed do not provide the necessary assurance of safety from ATWS and the responsibility lies within the industry to pro-vide sufficient demonstration that Alt. #3 is adequate.
The type of rule proposed to the Commission next spring would depend on the type of in-formation provided by the industry, b)
Industry should provide by August 25, 1979 a letter which includes the scope and the schedule of the ATWS submittals.
In this regard the staff noted that consideration be given to the following:
i) Feb. 15,1979 Mattson letter to B&W ii) March 27, 1979 Mattson letter to B&W iii) TMI-2 related questions discussed iv) B&W should also address ability of the computer codes to correctly evaluate the consequences of voids in the primary system, the effect of changes in the water relief model and the role of the RCPs.Long term shutdown considerations should also address Boron precipitation.
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AUG 151979 S. H. Hanauer
,4, c) The industry should expedite valve tests, d) The industry should provide bases for the applicability of analyses to specific plant designs so that the staff can continue with the "Early Verification" approach to resolve ATWS.
The list of attendees is in Enclosure 1, and copies of the viewgraphs presented are in Enclosure 2.
ll'n/ ;,?; ; ;-
A. Thadani Task Manager, A-9
Enclosures:
As stated cc: ATWS Distribution 1736 279
ENCLOSURE 1 ATWS MEETING WITH B&W OWNERS OF B&W - 8/9/79 Attendees A. Thadani NRC/ DSS S. Hanauer NRC/USI F. Odar NRC/ DSS M. Srinivasan NRC/ DSS K. Parczewski NRC/ DOR Michael Tokar NRC/ DSS Frank C. Cherny NRC/ DSS Kulin D. Desai NRC/ DSS H. Vander Molen NRC/ DOR Jack Roberts NRC/CB James Norberg NRC/OSD M. Fleishman NRC/OSD Roy Woods NRC/ DOR F. Akstulewicz NRC/DSE F. McPhatter B&W Alan Hosler WPPSS M. J. Salerno CPCo A. J. Rushnok OEC W. B. Rodill VEPC0 Terry G. Tyler TVA P. M. Abraham Duke Power C. S. Banworth B&W S. H. Duerson B&W J. Ted Enos AP&L Ted Myers Toledo Edison Ron Clauson Florida Power Corp.
Mike White Arkansas Power & Light 1736 280
ENCLOSURE 2
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B&WB8W ATWS USERS GROUP /NRC ATWS EETING
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AUGUST 9,1979 i
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PURPOSE OF N ETItE II. B&W POSITION ON AlWS III REVIEW MARCH COMillTOfTS IV, 1Til-2 EVBIT - IMPACT ON ATWS V.
ITE4S FRGi JULY 25m EETItB VI.
EW ATWS SCEDULE
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l 1736 281
- i i
1
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lOI ATWS SCKDULE I.
SYSTEM NRYSES #0 DOCLPEiTATION II CORE #RYSES A. JUSTIFY 177 FA AS B0lF0ItG I
B. IXER FOR LDOP & 2 PCD C. PCI DURIfE RWD ADIS D. CLAD COLIAPSE E. DOCLPHfT 00DELS II. STRUCTURAL # MLYSES
-QUALITATIVEASSESS' BIT
- MEi10DS, DRAWIiES, DISTORTION #MLYSES 1736 282
4 NRC ITEMIZED CONCEMIS TMI-2IMPACTONATWS ATWS WITH SRICK OPEN RV l.ONG TERM SH M Wi EXESSIVE PRESSURE INCREASE # CF VALVES?
QUALIFY RV FOR WALER RELIEF?
PLANT SPECIFIC ATWS & ECCS ESIGFE PORVFAILS/BLOCKEDCLOSED IDRON PRECIPITATION ifMAGE OllTSIDE CONTAlttDIT OPERATORACTION 1736 283