ML20002A135
| ML20002A135 | |
| Person / Time | |
|---|---|
| Site: | 05000000 |
| Issue date: | 03/30/1981 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| References | |
| IEIN-81-11, NUDOCS 8011040266 | |
| Download: ML20002A135 (2) | |
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4 SSINS No.: 6835 L
Accession No.:
8011040266 IN 81-11 UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT i
WASHINGTON, D.C.
20555 March 30, 1981 IE Information Notice No. 81-11:
ALTERNATE R0D JNSERTION FOR BWR SCRAM
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REPRESENTS A POTENTIAL PATH FOR LOSS OF PRIMARY COOLANT Description of Circumstances:
During an engineering evaluation of the scram discharge air system in response to recently issued NRC requirements, the Boston Edison Company identified a potential path for loss of primary coolant at its Pilgrim Nuclear Power 5+ation.
The licensee found that the. installed location of an anticipated transient l
without scram (ATWS) alternate rod insertion (ARI) solenoid valve could cause i
insertion of control rods without an associated closure of the scram discharge volume vent and drain valves.
The loss of coolant could then follow an ARI actuation through the open vent and J ain valves to the reactor building equipment drain tank and then to the reactor building sump.
The rate of coolant loss through the inserted drives could be approximately 500 gpm (based t
on 3 to 4 gpm per drive for 145 control rod drives) that would be released by the open vent and drain valves.
This loss rate is well within the 4250 gpm capability of the high pressure coolant injection (HPCI) system.
However, the 400 gpm capability of the reactor core isolation cooling (RCIC) system would need the 100 gpm of the CRD pumps to maintain level.
The alternate rod insertion installation was completed at the Pilgrim BWR during the refueling outage ending in May 1980. The installation was intended to permit dumping the air header supplying the scram valves.
This function is similar to that provided by the backup scram valves, and it provides a meas:,
for inserting the control rods in the event of an ATWS that includes failure of the reactor protection system.
The testing of the ARI installation at i
Pilgrim apparently failed t) confirm vent and draic, velve function.
t Following identification of the potential path for loss of primary coolant, the licensee reviewed plant procedures to assure that until system modifi-cations could ba completed, immediate operator actions during an AiWS event
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would include closing the scram discharge vent and drain valves.
It is noted that instrumentation installed in the scram discharge header in response to Bulletin 80-17 and the instrumented volume level switches should alert the reactor operator to tne presence of reactor coolant following ARI actuation.
The licensee modified the system during a scheduled outage in February,1981 to cause the scram discharge volu.ma vent and drain valves to close in the event of ARI actuation.
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i IN 81-11 March 30, 1981 i
Page 2 of 2 Discussion with General Electric indicates that they plan to provide pertinent information to operating BWR licensees regaroing the described potential path for loss of primary coolant.
This information is provided as a notification of a possibly significant matter which is still under review by the NRC staff.
In c:se the continuing NRC review finds that specific licensee actions would be appropriate, an IE bulletin or circular may be.; sued.
In the interim, we expect that BWR licensees will review this information for applicability to their faci 1ities.
Licensee. testing of the ARI installation should also be reexamined te confirm
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that vent and drain valves close as a direct result of ARI actuation.
P No written response to this information notice is required.
If you need additional information regarding this matter, please contact the Director of the appropriate NRC Regional Office.
Attachment:
Recently issued IE Informatirn Notices 4
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~w Attachment gc IN 81-11 March 30, 1981 RECENTLY ISSUED IE INFORMATION NOTICES I
1 Information Date of Notice No.
Subject Issue Issued to 81-10
.Inadvertant Containment 3/25/81 All power reactor.
Spray Due to Personnel facilities with an s
Error:
OL or CP 81-09 Degrad'ation of Residual 3/26/61 All power reactor Heat Removal (RHR) System facilities with an OL or CP 81-08 Repetitive Failures of 3/20/81 All power reactor Limitorque Operator SNB-4 facilities with an Motor-to-Shaft Key OL or CP 81-07 Potential Proolem with 3/16/81 All power reactor Water-Soluble Purge Dam facilities with an Materials Used During OL or CP Inert Gas Welding 81-06 Failure of ITE Model 3/11/81 All power reactor K-600 Circuit Breaker facilities with an OL or CP e
81-05 Degraded DC System at 3/13/81 All power reactor Palisades facilities with an OL or CP t
81-04 Cracking in Main Steam 2/27/81 All power reactor Lines facilities with an OL h
81-03 Checklist for Licensees 2/12/81 All power reactor Making Notifications of facilities with an Significant Events in OL j
Accordance with 10 CFR 50.72 81-02 Transportatien of 1/23/81 All Radiography Radiography Devices licensees 81-01 Possible Fai'ures of 1/16/81 All power reactor General Electric Type facilities with an HFA Relays OL or CP.
i OL = Operating Licenses CP = Construction Permits j
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