ML19340D997
| ML19340D997 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 12/17/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Kemper J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC |
| References | |
| NUDOCS 8101060123 | |
| Download: ML19340D997 (1) | |
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Docket Nos. 50-352 DEC 17 gge, u:
50-353 Philadelphia Electric Company ATTN:
Mr. John S. Kemper Vice President Engineering and Research 2301 Market Street Philadelphia, Pennsylvania 19101 Gentlemen:
The enclosed IE Information Notice No. 80-45, " Potential Failure of BWR Backup Manual Scram Capability," is forwarded to you for information.
No written response is required.
If you desire additional information regarding this matter, please contact this office.
Sin rely,
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. G rf r Di ctor
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Enclosures:
1.
IE Information Notice No. 80-45 2.
List of Recently Issued IE Information Notices CONTACT:
D. L. Caphton d.
(215-337-5266) cc w/encis:
V. S. Boyer, Senior Vice President, Nuclear Power q
8101060ll3
SSINS Ns.:
6835 Accession No.:
801216002 IN 80-45 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 December 17, 1980 IE Information Notice No. 80-45:
POTENTIAL FAILURE OF BWR BACKUP MANUAL SCRAM CAPABILITY The primary purpose of this Notice is to advise BWR licensees that a mechanism exists which could defeat one of the backup manual scram (reactor trip) features normally available to the reactor operator.
In some GE-designed reactors, placing the Mode Selector Switch (MSS) in " Shutdown" should actuate a scram.
This feature is used at some facilities as part of a normal reactor shutdown, and for certain plant situations the Technical Specifications require placing the MSS in the " Shutdown" position as a means of attaining immediate shutdown.
As described below, a situation may arise that blocks this scram.
The Pilgrim Nuclear Power Station has reported that following the loss of power from a vital M-G set and manual transfer to the alternate power source, the annunciator " Shutdown Scram Reset Permissive" came on and stayed on.
Since
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such an annunciator may not be provided for all BWRs, some facilities may not be able to detect this condition.
Subsequent investigation revealed that when one RPS bus power supply is lost and the MSS is in the "Run" mode, relay K-17 l
is immediately deenergized and after two seconds one of two series bypass contacts in the MSS scram circuit is closed.
Upon restoration of RPS bus power, it is possible for relay K-16 to be energized before K-17 (i.e., a relay race).
If l
this occurs, the following conditions will result: (1) the normally open K-16 l
contact in the MSS scram bypass circuit is closed, thereby bypassing the MSS in
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" Shutdown" Scram; and (2) relay K-17 will be kept deenergized.
Even with this condition (i.e., the bypass circuit made up and the MSS in "Run")
i a Scram should occur if the MSS is turned in a deliberate manner to " Shutdown" with a pause in either the "Startup" or " Refuel" mode; however, if the MSS is, tur,ned to " Shutdown" quickly such that relay K-17 is not energized, a Scram due to MSS manipulation may not occur.
We understand that General Electric has been informed of this potential for l
bypassing the MSS and that General Electric is preparing a Service Information Letter (SIL) containing recommendations for preventing such bypassing.
This Information Notice is provided as an early notification of a possibly significant matter that is still under review by the NRC staff.
Recipients should review the information for possible applicability to their facilities.
No specific action or response is requested at this time; however, if NRC evaluations so indicate, further licensee actions may be requested or required.
If you have any question regarding this matter, please contact the director of the appropriate NRC Regional Office.
v--
l IE Information Notice No. 80-45 December 17, 1980 RECENTLY ISSUED IE INFORMATION NOTICES Information Subject Date Issued to Notice No.
Issued 80-44 Actuation of ECCS in 12/14/80 All holders of a t.5 Recirculation Mode PWR power reactor OL While in Hot Shutdown or CP 80-43 Failures of the 12/5/80 All holders of a Continuous Water Level BWR power reactor Monitor for the Scram OL or CP Discharge Volume at Dresden Unit No. 2 80-29 Broken Studs on Terry 11/26/80 All holders of a Supplement Turbine Steam Inlet power reactor No. 1 Flange OL or CP l
80-42 Effects of Radiation on 11/24/80 All holders of a Hydraulic Snubber Fluid power reactor OL or CP
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80-41 Failure of Swing Check 11/10/80 All holders of Valve in the Decay Heat a power reactor Removal System at OL or CP Davis-Besse Unit No. 1 80-40 Excessive Nitrogen 11/6/80 All holders of Supply Pressure a power reactor OL Activates Safety-Relief or CP
.e Valve Operation to Cause Reactor Depressurization 80-39 Malfunctions of 10/31/80 All holders of a Solenoid Velves power reactoi OL or CP Manufactured by Valcor Engineering Corporation 80-38 Cracking in Charging 10/30/80 All holders of Pump Casing Cladding a PWR power reactor OL or CP 80-37 Containment Cooler 10/24/80 All holders of a Leaks and Reactor power reactor OL Cavity Flooding at or CP Indian Point Unit 2
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