ML17138B683
| ML17138B683 | |
| Person / Time | |
|---|---|
| Site: | Susquehanna  |
| Issue date: | 12/17/1980 |
| From: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| To: | Curtis N PENNSYLVANIA POWER & LIGHT CO. |
| References | |
| NUDOCS 8101060138 | |
| Download: ML17138B683 (3) | |
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Docket Nos.
50-387 50-388 UNITED STATES NUCLEAR REGULATORY COMMISSION REGION I 631 PARK AVENUE KING OF PRUSSIA, PENNSYLVANIA19406 Dyg f7 1980 XQ gcn o(
Q7 Pennsylvania Power and Light Company ATTN:
Mr. Norman W. Curtis Vice President Engineering and Construction - Nuclear 2 Nortli Ninth Street Al 1 entown, Pennsyl vani a 18101 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, OP'oy Gr r
Di ctor
Enclosures:
1.
IE I'nformation Notice No. 80-45 2.
List of Recently Issued IE Information Notices CONTACT:
D.
L. Caphton-(215-337"5266) cc w/encls:
A.
R. Sabol,
- Manager, Nuclear guality'ssurance W.
E. Barberich, Licensing Engineer H.
W. Keiser,'uperintendent of Plant Q
81oxogo@g P
UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND'NFORCEMENT WASHINGTON, D. C.
20555 SSINS No.:
6835 Accession No.:
801216002 IN 80"45 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 facil'ities as part of a normal reactor shutdown, and for certain plant situations the Te'chnical Specifications require placing the HSS 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
~ 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 HSS is in the "Run" mode, relay K-17 is immediately deenergized and after two seconds one of two series bypass contacts in the MSS scram circuit is closed.
Upon restorati'on o'f RPS bus power, it is possible for relay K-16 to be energized before K-17 (i.e.,
a relay race).
If this occurs, the following conditions will result:
(1) the normally open K-16 contact in the HSS scram bypass circuit is closed, thereby bypassing the MSS in "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")
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 turned 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 bypassing the MSS and that General E'lectric 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.
IE Information Notice No. 80-45 December 17, 1980 RECENTLY ISSUED IE INFORMATION NOTICES Enclosure 2
Information Notice No.'ubject Date Issued Issued to 80-44 Actuation of ECCS in
- 12/14/80 the Recirculation Mode Mhile in Hot Shutdown All holders of a PMR power reactor OL or CP 80"43 Failures of the Continuous Mater Level Monitor for the Scram Discharge Volume at Dresden Unit No.
2 12/5/80 A'll holders of a, BMR power reactor OL or CP 80-29 Supplement No.
1 80-42 80-41 Broken Studs on Terry ll/26/80 Turbine Steam Inlet Flange Effects of Radiation on 11/24/80 Hydraulic Snubber Fluid Failure of Swing Check 11/10/80 Valve in the Decay Heat Removal System at Davis-Besse Unit No.
1 All holders of a power reactor OL or CP All holders of a power reactor OL or CP All holders of a power reactor OL or CP 80"40 Excessive Nitrogen Supply Pressure Activates Safety-Relief Valve Operation to Cause Reactor Depressurization 11/6/80 All holders of a power reactor OL or CP 80"39 80-38 Malfunctions of 10/31/80 Solenoid Valves Manufactured by Valcor Engineering Corporation Cracking in Charging 10/30/80 Pump Casing Cladding All holders of a power reactor OL or CP All h'olders of a
PWR power reactor OL or CP 80"37 Containment Cooler Leaks and Reactor Cavity Flooding at Indian Point Unit 2 10/24/80 All holders of a power reactor OL or CP