05000277/LER-1979-048, Forwards LER 79-048/03L-0

Forwards LER 79-048/03L-0

ML19253C915
Person / Time
Site:	Peach Bottom
Issue date:	11/29/1979
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19253C916	List: 05000277/LER-1979-048, Forwards LER 79-048/03L-0 05000277/LER-1979-048-03, /03L-0:on 791030,during Relamping of Main Off Gas Stack,Personnel Discovered Broken Isokinetic Sample Line. Caused by Crimp at U Clamp Support Bracket & Fatigue from Expansion,Contraction & Wind Loading
References
NUDOCS 7912120343
Download: ML19253C915 (4)

LER-1979-048, Forwards LER 79-048/03L-0

Event date:
Report date:
2771979048R00 - NRC Website

text

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PHILADELPHI A ELECTRIC COM PANY 2301 M ARKET STREET P.O. BOX 8699 PHILADELPHI A. PA.19101 (215)8414000 November 29, 1979 Mr. Boyce H.

Grier, Director Office of Inspection and Enf orcement Region I United States Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA 19406

Dear Mr. Grier:

SUBJECT:

License Event Report Narrative Description

Reference:

Docket No. 50-277 Report No:

LER 2-79-48/3L Report Date:

November 29, 1979 Occurrence Date:

October 30, 1979 Facility:

Peach Bottom Atomic Power Station RD.

1, Delta, PA 17314 Technical Specification Reference:

This occurrence is rep ortable under Technical Specifications 3.8.C.7.a and 3.8.C.8.

Technical Specification 3.8.C.7.a states "During release of gaseous wastes the following conditions shall be met: monitors for gross gas activity, iodine and particulate sampler shall be op e r a b le.

Technical Specification 3.8.C.8 states "One reactor building exhaust vent and one plant stack monitoring system shall be operable and the off-gas radiation monitors shall be operable or operating whenever s team p ressure is available to the air ejectors.

If these requirements are not satisfied, a normal orderly shutdown shall be initiated within one h ou r, and the reactor shall be in the hot shutdown condition within 10 hourk in the case of the stack monitor or 10 days in the case of the building vent monitor."

Description of the Event:

With Unit 2 at power and Unit 3 off for refueling, at approximately 4:45 pm on 10/30/79 during relamping of the main 1542 158 7 912120j3eF[$

Mr. Boyce H.

Grier Page 2 off-gas stack observation li gh t s, it was discovered that the main stack isokinetic sample line was broken.

The defective sample line was removed from scrvice and a temporary isokinetic probe and samp le line was placed in service within 35 minutes after the

~

discovery.

The damaged sample line was t e mp o ra rily repaired and returned to service within two h ou rs after the event and permanent repairs were performed the next day (10/31/79).

No unit power reduction was required per Tech. Spec. 3 8.c.8 because the temporary sample line was in service in less than one hour after the event.

Before returning to service, the permanent sample line was velocity cleaned using compressed air.

When the system was placed in service, a significant decrease in sample vacuum was noted which indicates a partial restriction had existed.

It is believed that the restriction reduced the indicated release rate of short lived particulate.

Consequences of Event After permanent repairs were made to the s a mp le line, the indicated nobic gas release rate increased by a factor of approximately 2.1.

Based on a review of the is ot op ic gamma analysis done on the holdup pipe samples during the past six months which showed normally lower readings than the calculated release rate from the noble gas radiation monitors, and based on the conservatism in the noble gas radiation monitor calculation, it is believed that a correction factor need not be applied to ca lcu la t e d noble gas releases during the period between the estimated f ailu re date and the date of repair.

The iodine (131) and particulate (h a lf lives less than eight days) indicated release rate increased by a factor of about six after repairs were made.

It is believed that a portion of the increase resulted from the cleaning of the sample line.

However, since the release rates before and after the repair were so very low (a b ou t 0.00055 % of Tech Spec.

instantaneous limit), it is extremely difficult to determine whether the change in release rate was due to sample line problems or to fluctuations in the release rate.

Using a correction factor of six, the h i gh es t instantaneous release rate during the last six months would have been only 0.02 % of Tech spec limit.

Applying the factor of six results in an insignificant ch an ge in the quarterly Tech Spec release limit.

Cause o _f_

Ev e n t Upon inspection of the s a mp le line failure it appeared that the line had been crimped at a "U" clamp support bracket.

It is believed that the failure resulted from subsequent fatigue from expansion, contraction, and wind loading.

In retrospect, after reviewing the main stack radiation recorder t ra ces, it appears that the f ailure may have occurred on 1542 159

Mr. Boyce II. Grier Page 3 September 14, 1979, during a violent thunderstorm.

After the storm, the monitor experienced low s amp le flow.

After the correct flow was established, monitor readings dropped by a factor of two.

An investigation revealed no apparent problems and the monitor continued to respond to varying plant conditions, therefore it was believed to be operating correctly.

Even with a broken sample line, the monitor received a diluted but representative sample of stack gas which was contained by the insulation and heating tracing.

Corrective Action

Within 35 minutes of the discovery of the failure, a t emp ora ry isokinetic probe and sample line was placed into service in accordance with Special Procedure No. 298 which permitted normal operation of main stack radiation monitors with t e mp ora ry lodine and particulate sampling.

T e mp o ra ry repairs were c omp le t e d and normal operation resumed on the main stack radiation monitoring system within two h ours of the event.

The next day, 10/31/79, the s a mp le line was permanently repaired.

Before returning to service, the permanent sample line was velocity cleaned using compressed air.

After the system was placed int o s ervice, a significant decrease in sample vacuum was noted which indicates there had been a partial restriction in the line.

An air test at 40 psig was successfully performed to prove the integrity of the sample line.

The sample line was checked at each of the support brackets for crimping and breakage and no evidence of damage was found.

In addition, once a week during the normal filter change, a dif f erential p ressure test is now performed to prove the integrity of the sample line.

Philadelphia Electric Company's Engineering Department is reviewing the f ailu re to determine if additional corrective action is required.

1542 160

Mr. B oy ce H.

Grier Page 4 The iodine and particulate release rates will be increased by a factor of six f rom Sep tembe r 14, 1979 to October 30, 1979 in the s e mi -a n n u a l report to c on s e r va t ive ly account for releases during this period.

Because of"the c on s e r va t i ve calculation method used f or noble gas releases no correction is anticipated.

Very truly yours,

' fl( ( <

M.

J.

Cooney SIfperintendent Generation Division - Nuclear At ta ch me n t cc:

Director, NRC - Office of Inspection and Enforcement Mr. Norman M.

Haller, NRC Office of Management &

Program Analysis 1542 161