ML20197H937
| ML20197H937 | |
| Person / Time | |
|---|---|
| Issue date: | 08/02/1984 |
| From: | Thadani A Office of Nuclear Reactor Regulation |
| To: | Sheron B Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML19292D914 | List: |
| References | |
| NUDOCS 8408090089 | |
| Download: ML20197H937 (2) | |
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UNITED STATES 8'
NUCLEAR REGULATORY COMMISSION n
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MEMORANDUM FOR:
Brian Sheron, Chief Reactor Systems Branch, DSI FROM:
Ashok C. Thadani, Chief Reliability and Risk Assessment Branch, DST t
SUBJECT:
REACTOR VESSEL LEVEL INSTRUMENTATION IN BWR's I
(GENERIC ISSUE 50) i
Reference:
CRGR Submittal for Resolution of Generic Issue 50 i
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RRAB has completed a brief review of the CRGR submittal and has made
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recommendations to Mr. Denton under separate memorandum (Enclosure 1).
w The purpose of this memorandum is to transmit the analysis (Enclosure 2)
'I of the "Michelson Concern" which has been performed to support the recommendations made to Mr. Denton.
,i It is noted that not all transmitter single failures together with the reference leg break will result in core uncovery and subsequent damage.
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Only when the single failure occurs in the ECCS transmitter in such a way that all automatic initiation of the ECCS is lost in combination with the reference leg break could there be a core damage event if manual f^
corrective action is not taken.
For a typical BWR plant, it is estimated that the core melt frequency may be reduced by a factor of about 5 from
~1 x 10 5 per reactor year following modifications for the "Michelson Concern".
F Based on a simplified value-impact analysis using the RSS source term, the
'I risk reduction resulting from modification to fix the "Michelson Concern" is about $1,000 per man-rem.
Although this would place the recommended modifications on the borderline of being cost beneficial, it is still better 2
by orders of magnitude than that estimated by the BWR Owners.
- However, because there are large differences due to plant specific variations in water level measurement systems, the "Michelson Concern" may be of more j
significance in some plants than the others.
The elements considered in in Enclosure 2 can, in conjunction with better understanding of each plant to plant variations, be considered in performing regulatory analyses in support of any future decisions related to this issue.
RRAB continues to believe that the need exists for training the operator to
" trend" an accident progression with all available instrumentation, specifically if the water level measure instrumentation is failed.
Recommendations on this subject were made in the memorandum from F. Rowsome to L. Rubenstein dated October 27, 1984.
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.. 2 2-AUG 2 gy If you have any questions, please contact D. Yue, RRA8 (X28129).
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f YW" Ashok : lhadani, Chief Reliab lity and Risk Assessment Branch, DST
Enclosures:
- 1. Memorandum, T. Speis to H. Denton on the same subject
- 2. Analysis of the "Michelson Concern" cc:
T. Speis F. Rowsome D. Muller L Rubenstein W. Houston W. Hodges
- v. 3 W. G. Kennedy 3
W. Minners
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