05000245/LER-1981-024, Forwards LER 81-024/03L-0.Detailed Event Analysis Encl

Forwards LER 81-024/03L-0.Detailed Event Analysis Encl

ML20031A905
Person / Time
Site:	Millstone
Issue date:	09/17/1981
From:	Mroczka E NORTHEAST NUCLEAR ENERGY CO.
To:	Haynes R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20031A906	List: 05000245/LER-1981-024, Forwards LER 81-024/03L-0.Detailed Event Analysis Encl 05000245/LER-1981-024-03, /03L-0:on 810817,trip Settings for 3 of 4 Monitors Found Out of Tech Spec Setpoint Limit During Reactor Bldg Exhaust Duct & Refuel Floor High Radiation Monitor Surveillance.Caused by Setpoint Drift.Monitors Recalibr
References
MP-1-1884, NUDOCS 8109280377
Download: ML20031A905 (3)

LER-1981-024, Forwards LER 81-024/03L-0.Detailed Event Analysis Encl

Event date:
Report date:
2451981024R00 - NRC Website

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September U, 1981 MP-1-1884 MI Mr. Ronald C. Haynes f)

Director, Region I Office of Inspection and Enforcement E

SEP 2 51981 '

U. S. Nuclear Regulatory Commission 5

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631 Park Avenue O'

King of Prussia, Pennsylvania 19406

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Reference:

Facility Operating License No. DPR-21

' MsTN Docket No. 50-245 Reportable Occurrence R0-81-24/3L

Dear Mr. Haynes:

This letter is forwarded to provide prompt notification of Reportable Occurrence R0-81-24/3L as required by Millstone Unit 1 Technical Specifications Section 6.9.1.8. b.

On August 17, 1981, at 1325 hours0.0153 days <br />0.368 hours <br />0.00219 weeks <br />5.041625e-4 months <br />, during Reactor Building Exhaust Duct and Refuel Floor High Radiation Surveillance, the trip settings for the Reactor Building Ventilation (channel 1 and channel 2) and the Refuel Floor (channel

1) were found to be above Technical Specifications.

The plant incident report was originally classified as a 30 day reportable.

However, after further investigation into the incident it was determined that the Technical Specification limiting condition of operation was violated.

Yours truly, NORTHEAST NUCLEAR ENERGY COMPANY l

$gp E. J. Mroczka l

Station Superintendent Millstone Nuclear Power Station f

EJM/TST:jf

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Attachment:

LER R0-81-24/3L cc:

Director, Office of Inspection and Enforcement, Washington, D.C. (30)

Director, Office of Management Information and Program Control, Washington, D. C. (3)

U. S. Nuclear Regulatory Commission, c/o Document Management Branch, Washington, D. C.

20555 h9280377e10937 S

ADOCK 05000245 PDR

ATTACHMENT TO LER 81-24/3L NORTHEAST NUCLEAR ENERGY COMPAN'.

MILLSTONE NUCLEAR POWER M ATION - LNIT 1 PPOVISIONAL LICENSE NUMBER DPR-21 DOCKET NUMBER 245 Identification of Occurrence Secondary containment isolation instrument settings were found to be less conservative than those established by Technical Specification.

Conditions Prior to Uccurrence The plant was operating at a steady state power level of 100 percent.

Description of Occurrence On August 17, 1981, at 1325 hours0.0153 days <br />0.368 hours <br />0.00219 weeks <br />5.041625e-4 months <br />, while performing Reactor Building Exhaust Duct and Refuel Floor High Radiation Monitor Surveillance, the trip settings for the Reactor Building Ventilation (channel 1 and channel 2) and the Refuel Floor (channel 1) were found to be above Technical Specification limit.

Technical Specification 3.2.E.3 requires the ventilation duct radiation monitor to trip at 11 Mr/hr and the refuel floor radiation monitor to trip'at 100 Mr/hr.

Apparent Cause On August 10, 1981, at 1410 hours0.0163 days <br />0.392 hours <br />0.00233 weeks <br />5.36505e-4 months <br />, during the ARM Power Supply Calibration Surveillance, the ARM power supplies were checked and adjusted.

The adjustment of t.he power supply voltage caused tne reactor building ventilation radiation monitor and the refuel floor radiation monitor set points to drift.

Analysis of Occurrence Reactor building ventilation duct radiation monitor and the refuel floor radiation monitor detect airborne radioactive release into the reactor building. When this airborne radioactivity increases above technical specification setpoint limit, reactor building ventilation isolation signal and standby gas treatment initiation signal are generatei.

The isolation signal cc cains the airborne activity to the reactor builditu and the standby gas tre;tment fans maintain the reactor building pressure to the design negative pressure so that all leakage should be in-leakage.

Additionally the standby gas treatment system is designed to filter and exhaJst the reactor building atmosphere to the stack during' secondary containment isolation conditions.

Failure of the refuel floor radiation monitor to trip at its desired setpoint did not result in a condition that had not been previously analyzed. The remaining channel on the refuel floor radiation monitor was found to be within its desired setpoint range and would have initiated the required action if a high radiation condition had existed on the refuel floor.

Even though both channels on the ventilation duct radiation monitors did not fall within the technical specification limit, the as found setpoints would not have caused an increase in. the site beundary radiological limits.

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Currective Action i -

The radiation monitors were recalibrated and tested satisfactorily within the 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Technical Specification time frame.

To prevent a reoccurrence, ARM Power Supply Calibration Procedure (IC 403F) has been changed to' check radiation cionitor setpoints after adjusting the ARM power supplies.

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