ML19210A125

Event Rept 76-26/3L:on 760622,reactor Bldg Exhaust Monitor RM-49 Failed to Close Purge Exhaust Valves AH-V1A & B.High Radiation Test Signal Showed Degradation of Radioactive Matl Control Sys.Caused by Personnel Error During Maint

ML19210A125
Person / Time
Site:	Three Mile Island
Issue date:	07/19/1976
From:	Arnold R METROPOLITAN EDISON CO.
To:
References
NUDOCS 7910240842
Download: ML19210A125 (4)

Text

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. FILE NUM 01R NRC DISTRIBUTION FOR PART 50 DOCKET MATERIAL INCIDENT REPORT TO: ,Q.P.0'Reilly FROM: Metropolitan Edison C,. D^TE eo CUuENT Reading, Pa. 7-19-76 R.C. Arnold DATE RECE E QLETTER O NOTO RIZ E D PROP INPUT FORM NUMBER OF COPIES RECEIVED GORIGINAL Q UNC LASSIFIE D OCOev 1 DESCRIPTION ENCLOSU RE Ltr. providing Reportable Occurrence # 76-26/3L on 6-22-76 concerning Inoperable High Radiation Actuation Mode of a Reactor Building Purge Exhaust Monitor.......

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Mr. J. P. O'Reilly, Director Office of Inspection & Enforcement, Regicn I U.S. IIuclear Regulatory Cc==issicn 631 Park Avenue King of Prussia, PA 19hc6

Dear Sir:

Docket :Io. 50-289 Operating License No. DPR-50 In accordance with the Technical Specifications of our Three Mile Island Nuclear Station Unit 1 (TMI-1), we are reporting the following reiortable occurrence:

(1) Repcrt Ilumber: ER 76-26/3L (2a) Required Report Date: July 22, 1976 (2b) Date of Occurrence: June 22, 1976 (3) Facility: Three Mile Island Nuclear Station - Unit 1

(*) Identification of Occurrence:

Title:

Inoperable High Radiation Actuation Mode of a Reactor Building Purge Exhaust Mcnitor.

Type: A reportable occurrence as defined by Technical Specification 6.9.2.B(4) in that failure of Reactor Building purFe exhaust monitor RM-A9 to close purge exhaust valvs.s AH-VlA and AH-V1B upon receipt of a high radiation test signal showed abnormal degradation of a system designed to contain radioactive material resulting frca the fission process.

(5) Conditions Prior to Occurrence:

Pcver: Core: 2531 MWt

." ?c: 83h !"Je (Gross)

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,U # 1dQO RC Flev: lh0 x 106 lbs/hr.

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RC Pressure: 2155 psig RC Temp.: 579 F PRZR Level: 225 inches FRZR Temp.: 650 F (6) Description of Occurrence:

On June 22, 1976, while performing Surveillance Procedure 1303-h.15, Radiation Monitoring System (RMS) Monthly Test, Reactor Building purge exhaust monitor RM-A9 failed to close purge exhaust valves AH-V1A and AH-71B upcn receipt of a high radiation test signal. Upon recognition of this condition both valves were irmediately closed. Investigation results showed that the plug-in interlock and alarm relays for RM-A9 had been removed. The relays were returned to their correct location and tested. The test results were satisfactory.

(7) Designation of Apparent Cause of Occurrence:

The cause of this occurrence has been determined to be personnel in that +he interlock and alarm relays , which were apparently removed during calibration to prevent spurious alarms on the RMS alarm panel, were not returncl to the RM-A9 module on completion of the maintenance.

(8) Analysis of Occurrence:

From June 11, 1976, the date on which the alarm and interlock relays were not returned to their proper location following maintenance on RM-A9, to June 22, 1976, when the relays were reinstalled, three (3) Reactor Building purges were performed. However, it has been determined that this occurrence did not constitute a threat to the health and safety of the public in that:

a. Review of the release data showed that no technical specification release limits were exceeded during the purges.

b. Even though the alarm and interlock relays of RM-A9 vere missing, RM-A9 still monitored the radiation level of the purges with read out and local alarm available in the Control Rocm.

c. The Reactor Building purge valves could have been closed ~

manually if a high radiation condition existed.

(9) Corrective Actica:

In addition to the immediate corrective action described above, the instrument maintenance personnel have been counseled regarding restoring equipment to service and assuring that adequate procedures are used.

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(10) Failure Data: II/A Similar Occurrences: None Sincerely,

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I R. C. Arnold Vice President RCA:JMC:cas V

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