ML19329B633
| ML19329B633 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 03/01/1977 |
| From: | Mazetis G Office of Nuclear Reactor Regulation |
| To: | Ross D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8002050747 | |
| Download: ML19329B633 (3) | |
Text
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MAR 1 1977 9
PEMORANDUM FOR:
D. F. Ross, Jr., Assistant Of rector for Reactor Safety, DSS THRU: Thomas M. Novak, Chief, Reactor Systers Branch, DSS FROM: Gerald Ma:etts, Section Leader, Reactor Systers Branch, DSS
SUBJECT:
2/17/77 APPEALS uEETING WITM TOLE 00 EDISON CO9PANY ON DHR ISOLATION VALVES A staff position oreviously transmitted to TECO stated that lockino out newer to the DHR isolation valves during shutdown was not acceptable. The basis for this decision was:
i 1.
Our judgement that the autceatic feature pmvides desired addi-tional assurance that both isolation valves would be closed during power operation.
2.
Recent staff acreement (DeYoung/Ipnolito/Baer/Novak/Fazetis/
Berlincer, et al) that the automatic closure feature durinc shutdown oceration should be retained It is my ooinion that we hcwd little at the TECO acceal meeting to chance our minds.
The two major points brought uo by TECO were:
1.
Both CH oun s, as well as the reactor coolant oressure orotection are subject to the inadvertent closure of the CHR valves which would cause a loss of all decay heat ramoval capabilitie_s_.
-RESPONSE: Acree; however, there are other ways around this oroblem.
For the present, it looks like raising the auto isolation setpoint of the DHR valves and not allowino both trains to be operating during shutdown cooling (one train on standby) would be a feasible interim solution to get the olant on the line.
2.
The chance would not afford any additional oressure orotection (double valve isolatiu) durino startno since a sincle active failura could orevent one of the two valves from closino as the system is designed at this tim or if a change were made.
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nwo a G. Mazetis, NRR o 'c=127591-
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Foran MC 318 (Rev. 9-$3) MCSE 0240 W u. e. novsanusar ramesmo orricas tev4.sas.see 800205099g747
D. B. Vassallo MAR 1 1977
' RESPONSE: Disagree. As shown in the attached diagran, by dis-connecting the power to these valves, an additional failure mode is introduced which is not orasent when oower is available. This additional failure mode (circled) is the operator forgetting to restore oower on one, or both, valves.
It should be noted that the complete spectrum of /ailure modes was not included in the diagram, such as connon mode failures and valve disc secarations; however, the coint is that the diauram shows that an additional failure mode is introduced in the overall schere. More work would have to be cerfomd before a ricerous assessment could be made of exactly what this additional failure.wde would introduce in terns of its finite contribution ce the overall orobability estimate of a LOCA outside containment.
odstaal signed by:
G. R. Fazetis, Section Leader Reactor Systems Branch Division of Systems Safety
Enclosure:
Diagram cc:
T. Novak S. Israel G. Mazetis b
Central File RSB Reading Mazetis Chron suomam >
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