ML18046A268
| ML18046A268 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 12/16/1980 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Dewitt R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| References | |
| NUDOCS 8101070100 | |
| Download: ML18046A268 (5) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION REGION Ill Those on Attached List:
799 ROOSEVELT ROAD GLEN ELLYN, ILLINOIS 60137 December 16, 1980 The enclosed IE Information Notice No. 80-44 provides early notification of an event that may have safety significance.
Accordingly, you should review the Information Notice for possible applicability to your facility.
No specific action or response is requested at this time; however, contingent upon the results of further staff evaluation, a Bulletin or Circular recom-mending or requesting specific licensee actions may be issued.
If you have any questions regarding this matter, please contact this office.
Enclosure:
IE Information Notice No. 80-44
\\00 Sincerely,
Docket No. 50-255 Consumers Power Company ATTN:
Mr. R. B. DeWitt Vice President Nuclear Operations 212 West Michigan Avenue Jackson, MI 49201 cc w/encl:
D. P. Hoffman, Nuclear Licensing Administrator R. W. Montross, Manager Central Files AD/Licensing AD/Operating Reactors AEOD
~ent Inspector, Local PDR NSIC TIC RIII Ronald Callen, Michigan Public Service Commission Myron M. Cherry I'--
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UNITED STATES NUCLEAR REGULATORY COMMISSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D.C.
20555 December 15, 1980 SS INS No. :
6835 Accession No.:
8012160001 IN 80-44 IE INFORMATION NOTICE NO. 80-44:
ACTUATION OF ECCS IN THE RECIRCULATION MODE WHILE IN HOT SHUTDOWN PURPOSE:
The intent of this Information Notice is to alert PWR licensees and holders of construction permits of a potentially generic problem involving inadvertent actuation of the emergency core cooling system (ECCS) in the "Recirculation Mode".
Such an event occurred at the Davis-Besse Nuclear Power Station (Docket No. 50-346) on December 5, 1980.
The plant was in a hot shutdown mode of opera-tion at the time of the event and was undergoing certain maintenance activities as described below.
DISCUSSION:
Just prior to the inadvertent actuation of the ECCS, the licensee was attempt-ing to isolate electrical shorts and/or grounds in the Safety Features Actua-tion System (SFAS).
Towards this end, A-C power had been removed from Channel 3 of the SFAS.
Upon reenergizing Channel 3 it was noted that an indicating lamp was out; therefore, an attempt was made to replace the failed lamp with a spare unit.
While removing a lamp from a spare output slot in a Channel 3 chassis, an arc was drawn between the lamp and the module chassis.
This arcing was apparent-ly due to a combination of shorts or grounds in the SFAS, which coupled with the "common 11 connection between Channe 1 1 and 3 resulted in the loss of a power supply in Channel 1.
Since all the bistable trips in Channel 3 had not been completely reset, and since a power supply to Channel 1 was lost, SFAS Levels 1, 2, 3 and 5 were actuated by the two-out-of four actuation logic.
Since SFAS Level 5 indicates that the Borated Water Storage Tank (BWST) is at a low level, the ECCS was placed in a recirculation mode (i.e., the ECCS suction was aligned to the emergency containment sump.)
In order to place the ECCS system in the recirculation mode, the supply valves leading to the Decay Heat Removal (OHR) pumps from the BWST start closing after those in the ECCS line and from the containment emergency sump fully open.
Thus, during this valve transition period, a flow path existed to the reactor coolant system (RCS) via the BWST and the ECCS pumping system (i.e., the OHR pumps); however, since the RCS pressure was higher than that of the pumping system (2100 vs. 1600 psig) no BWST water was pumped into the RCS.
- Rather, during the valve transition time of about 1-1/2 minutes, approximately 15,000 gallons of borated water was drained from the BWST to the containment emergency sump.
IN 80-44 December 16, 1980 Page 2 of 2 The Davis-Besse Nuclear Power Station has experienced several events during the past three and one-half years which have either degraded the OHR system or caused a temporary interruption of OHR operation.
Of these, the one most closely paralleling the event described above occurred on April 19, 1980.
(See IE Infor-mation Notice 80-20, 11 Loss of Decay Heat Removal Operability at Davis Besse Unit 1 While in A Refueling Mode 11 dated May 8, 1980 and IE Bulletin No. 80-12, 11 Decay Heat Removal System Operability 11 dated May 9, 1980.) During the Decem-ber 5, 1980 event, the plant was in a hot shutdown mode with RCS pressure at approximately 2100 psig; therefore, the operator was able to promptly trip the OHR pumps, thereby precluding air entrapment in the system or pump damage.
In contrast, the April 19, 1980 event occurred while the plant was in a quasi refueling mode (i.e., the reactor head was in place but detensioned, RCS water level was below the steam generator's bottom plate, the RCS was vented to the atmosphere by an open manhole at the top of the steam generator, and decay heat was being removed by one OHR system).
Since the OHR pump was being used to remove decay heat during the April 19 event, it was left running for approxi-mately two minutes after the pump had been aligned to the recirculation mode of operation, and tripped when water was discharged from a temporary tygon line.
Since the OHR system was the only system available for decay heat removal, the OHR pump was restarted approximately forty minutes later; however, it was tripped shortly thereafter when it was determined that there was air in the suction line of the system.
In all, the April 19, 1980 event required approx-imately two and one-half hours to vent the OHR system and reestablish OHR flow.
As a consequence of the relatively long recovery time, the temperature limit specified in the Technical Specification for the refueling mode of opera-tion was exceeded during the April 19, 1980 event.
The above events illustrate means whereby the integrity of a* major ECCS system can be jeopardized by inadvertently or prematurely aligning the ECCS to the recirculation mode of operation.
The major concern in such cases is that the OHR pumps could become air bound if their suction lines are aligned to a dry sump.
At best, with the pumps air bound, the pump motor would trip automatically or could be tripped manually before any damage occurred, in which case flow could be established after the system is vented; at worst, the pumps could be damaged and become inoperable, in which case the active portion of the ECCS would not be available, if needed at that time.
This Information Notice is provided as an early notification of a possibly signi-ficant matter that is still under review by the NRC staff.
Recipients should re-view 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.
Information Notice No. 80-43 80-42 80-41 80-40 80-39 80-38 80-37 80-36 80-35 80-34 RECENTLY ISSUED IE INFORMATION NOTICES Date of Subject Issue Failures of the Continuous 12/5/80 Water Level Monitor for the Scram Discharge Volume at Dresden Unit No. 2 Effect 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 Excessive Nitrogen Supply 11/10/80 Pressure Actuates Safety-Rel i ef Valve Operation to Cause Reactor Depressur-i zat ion Malfunctions of Solenoid 10/31/80 Valves Manufactured By Valcor Engineering Corporation Cracking in Charging Pump 10/30/80 Casing Cladding Containment Cooler Leaks and Reactor Cavity Flooding at Indian Point Unit 2 Failure of Steam Generator Support Bolting Leaking and Dislodged Iodine-124 Implant Seeds Boron Dilution of Reactor Coolant During Steam Generator Decontamination 10/24/80 10/10/80 10/10/80 9/26/80 OL =Operating Licenses CP = Construction Permits IN 80-44 December 16, 1980 Issued to All power reactor facilities with OL or CP All power reactor facilities with OL or CP All power reactor facilities with an OL or CP All power reactor facilities with OL or CP All light water reactor facilities with OLs or CPs All PWR facilities with an OL or CP All power reactor facilities with OLs or CPs All power reactor facilities with OLs or CPs All categories G and Gl medical licensees All PWR facilities with OLs