05000369/LER-1981-020, Forwards LER 81-020/03L-0.Detailed Event Analysis Encl

Forwards LER 81-020/03L-0.Detailed Event Analysis Encl

ML20032B343
Person / Time
Site:	McGuire
Issue date:	03/20/1981
From:	Parker W DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML20032B344	List: 05000369/LER-1981-020, Forwards LER 81-020/03L-0.Detailed Event Analysis Encl 05000369/LER-1981-020-03, /03L-0:on 810219,spurious High Radiation Alarm & Loss of Flow Alarm Sounded in Control Room on EMF-49. Personnel Cleared Radiation Alarm But Overlooked Closed Valve,Causing Loss of Flow Alarm.Monitor Repaired
References
NUDOCS 8111050452
Download: ML20032B343 (3)

LER-1981-020, Forwards LER 81-020/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
3691981020R00 - NRC Website

text

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March 20, 1981 V cc PetsiotNT T E L E PMO h t :ARE A 704 Strane Pmooverion 373-4083 8/-D M - U b [h[4 Mr. James P. O'Reilly, Directcr h

U. S. Nuclear Regulato.y Commission

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101 Marietta Street, Suite 3100 U

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Re: McGuire Nuclear Station Unit 1

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Docket No. 50-369 g6p

Dear Mr. O'Reilly:

Please find attached Reportable Occurrence Report R0-369/81-20. This report concerns a spurious high radiation alarm and a subsequent loss of sample riow alarm on the WL system. This incident was considered to be of no signi-ficance with respect to the health and safety of the public.

~' ry truly yours, (1 w O

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William O. Parker, Jr RWO:scs cc: Director Mr. Bill Lavallee Office of Management and Program Analysis Nuclear Safety Analysis Center U. S. Nuclear Regulatory Commission P. O. Box 10412 Washington, D. C.

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'a DUKE POWER COMPANY MCGUIRE NUCLEAR STATION Report Number: R0-369/81-20 Report Date: March 10, 1981 Occurrence Date: February 19, 1981, 1830 Hours Facility: McGuire Unit 1, Corr.elius, North Carolina Identification of Occurrence:

The radiation monitor (D4F-49) on the Waste Liquid (WL) af fluent line annunciated a high radiation alarm and a subsequent loss of sample flow alarm during a release.

Condition Prior to Occurrence: Mode 6, Initial Fuel Loading Description of Occurrence:

During a routine release of liquid waste from a Waste Monitor Tank (WMT), into the Condenser Cooling Water (RC) Discharge, a spurious high radiation alarm and a loss of flow alarm sounded in the control room on EMF-49.

Operations personnel were able to clear the high radiation alarm, but overlooked a closed valve in the system which caused the loss of flow alarm. The system was, there-fore, declared inoperable. This constituted a degraded mode of operations and required going to the action statement stipulated by Technical Specification 3.3.3.8.

Apparent Cause of Incident:

The radiation monitor for EMF-49 is a gross-gamma sodium-iodide detector. Like a number of other detectors of this type, it is temperature sensitive.

There-fore, it is not uncommon for a spurious high radiation alarm to occur when cold water is first passed through such a detector. Such was the case, apparently, with EMF-49 on February 19, 1981. Upon receipt of a high radiation signal from EMF-49, 1-WM-46 automatically closed to stop the discharge.

This, in turn, caused the loss of flow alarm.

WM-46 is an air-operated valve which is operated in the control room. Valve position indicators for WM-46 are located in the control room and on the waste system processing canal. However, when it closed during the aforementioned release, it apparently went unnoticed.

Analysis of Occurrence:

Hours before the event, on February 19, 1981, Chemistry-Radwaste and Health Physics technicians were making preparations in accordance with the appropriate procedure to release Waste Monitor Tank "B" via the WL System, into the condenser cooling water discharge.

~,

w The tank contents had been recirculated, sampled, and analyzed per applicable procedure (s).

The analysis revealed that, as expected at this point in time of the plant's operation, no radior.ctivity was present above normal background and that all other parameters were satisfied to safely release this tank to the environment.

At 1830 hours0.0212 days <br />0.508 hours <br />0.00303 weeks <br />6.96315e-4 months <br />, Operations was notified and the discharge was initiated. Following this, t'ae high radiation annunciator for EMF-49 alarmed in the control rc om.

This signal caused 1-WM-46 (Rad Monitor outlet high rad shutcff) to close. Within momentc, the annunciator for loss of sample flow through EMF-49 alarmed on the panel.

At 1846 hours0.0214 days <br />0.513 hours <br />0.00305 weeks <br />7.02403e-4 months <br />, the shift supervisor contacted Health Physics shift technicians and requested that a radiation survey be performed on WMT "B" and EMF-49.

No radiation, above background, was found and this was reported to the shift supervisor.

The shift supervisor, working with an I&E representative, managed to clear the high radiation alarm and an attempt to release the tank was made again at 2020 hours0.0234 days <br />0.561 hours <br />0.00334 weeks <br />7.6861e-4 months <br />, but there was no flow. Another attempt was made at 2040 hours0.0236 days <br />0.567 hours <br />0.00337 weeks <br />7.7622e-4 months <br />, but still no flow could be obtained. No further attempts were made that night.

The att emp t to release was terminated by the shift supervisor. The release could have been completed if Operations or Chemistry personnel had been aware that WM-46 was closed and had opened it.

On February 20, 1981, preparations were made to release WMT "A", utilizing action statement No. 28 of Table 3.3-13 in the Technical Specifications.

The discharge began at 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br />, and was completed without incident.

I&E technicians checked out this system (EMF-49), and reported that it functioned as intended; no repair work was required. The system was declared operable on February 21, 1981 at 0910 hours0.0105 days <br />0.253 hours <br />0.0015 weeks <br />3.46255e-4 months <br />.

Corrective Action

The immediate corrective action was to issue two (2) work request to:

a.

repair the high radiation alarm (later voided); and b.

repair the low-flow alarm on EMF-49.

Additionally, the cppropriate technical specification action statement was put into effect.

Since the occurrence, Operations has provided a nuclear equipment operator to devote his full attention to each liquid waste release. This was actually a requirement of the approved procedure, but was not being adhered to at the time of the incident.

As plant system temperatures increase in the future, the possibility for spurious alarms, resulting from a cold thermal shock, should diminish.