05000277/LER-1981-035, Forwards LER 81-035/01T-0.Detailed Event Analysis Encl

Forwards LER 81-035/01T-0.Detailed Event Analysis Encl

ML20009G210
Person / Time
Site:	Peach Bottom
Issue date:	07/06/1981
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML20009G211	List: 05000277/LER-1981-035, Forwards LER 81-035/01T-0.Detailed Event Analysis Encl 05000277/LER-1981-035-01, /01T-0:on 810622,leakage Through Several Points in Recombiner Sys Resulted in 3-h Release Through Unit 3 Reactor Bldg Vent.Caused by Loss of Negative Pressure. Leak Points Isolated by Valve Closure or Pipe Capping
References
NUDOCS 8108030430
Download: ML20009G210 (4)

LER-1981-035, Forwards LER 81-035/01T-0.Detailed Event Analysis Encl

Event date:
Report date:
2771981035R00 - NRC Website

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PHILADELPHI A ELECTRIC COMPANY p

k 23O1 M ARKET STREET P.O. BOX 8699 PHILADELPHI A. PA.19101 1881 -1981 1215)841-4000 July 6, 1981 Mr. Boyce H.

Grier, Director Office of Inspection and Enforcement Region I US Nuclear Regulatory Ccmmission 631 Park Avenue King of Prussia, PA 19406 SUBJECT: LICENSEE EVENT REPORT NARRATIVE DESCRIPTION

Dear Mr. Grier:

The following occurrence was reported to Mr. Knapp, Region I, Office of Inspection and Enforcement on June 22, 1981.

Reference:

Docket No. 50-277 Report No.:

2-81-35/1T-0 Report Date:

July 6, 1981 Occurrence Date:

June 22, 1981 Facility:

Peach Bottom Atomic Power Station RD #1, Delta, PA 17314 Technical Specification Reference:

Technical specification 3.8.C.1 states that, "The release rate of gross activity except for halogens and particulates with half lives longer than eight days shall not exceed:

Os E y

Qiv MPC( i 1

+

0.24 2.0 x 105 Where:

Os = combined units 2 and 3 off gas stack release rate in Ci/sec.

'T 6D average Y energy of release in Mev.

E

=

4

/

8108030430 810706 PDR ADOCK 05000277 S

PDR

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Qiv = combined units 2 and 3 release rate in i

Ci/sec from reactor building ventilation exhaust i

stack.

MPC'. = as defined for radionuclide i in column 1, Table II of Appendix B 10 CFR 20 assuming a 10 minute old off gas mixture."

i 1,

Description of the Event:

)

On 6/21/81 the recombiner mechanical compressors tripped due to high hydrogen gas levels downstream of the recombiner.

This resulted in the recombiner mechanical compressor suction header pressure increasing to a positive level.

When this happened, a release occurred through the Unit 3 reactor building vent, with activity levels w.ithin Tech. Spec. limits.

On 6/22/81, as previously reported in the Prompt Notification of l

this event, a second release occurred shortly after Unit 2 had shutdown automatically due to loss of a plant load bus.

The i

plant load bus which was lost also caused the trip of a recombiner mechanical compressor resulting in the compressor 1

suction line pressure again increasing to a positive value, and this again caused leakage to occur which resulted in a release which exceeded Tech. Spec. limits.

The Unit 3 roof vent monitor spiked for a seven minute period at 0930 AM on 6/22/81, releasing 12 mci /sec. peak (6.6 mci /sec.

average) for a total release of 2.8 curies during the peak period l

(182% of Tech spec limit).

The peak tailed off above background i

for three hours releasing 0.760 mci /sec. average for a total l

release of 8.6 curies over the tailing off period.

The total i

release over the entire period is calculated to be 11.4 curies.

l Four additional releases well within Tech. S.nc. limits, occurred j

between 6/2?/81 and 6/29/81 with a total ca'aalated additional j

release of 3.0 curies.

Analysis of roof vent iodine and particulate samples indicates no ii increase in the relea:!-

m.e during any of the gaseous act v ty spikes.

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Page 3 Probable Consequences of the Occurrence All of the releases identified above were of short duration.

The maximum dose at the site boundary was.08 mR on 6/22/81 and the total offsite dose for all releases during this period is calculated to be approximately.14 mR.

Cause of the Event

On 6/21/81, the recombiner mechanical compressors tripped, allowing the compressor suction line pressure to increase to a positive level.

A release occurred with an instaneous peak 45%

of Tech. Spec. limits and total activity released of 6.65 Ci.

Initially, the sole cause of this occurrence was thought to be a leaking 2B recombiner mechanical compressor suction line snubber drain valve.

Pending repairs to the valve, suction pressure was controlled negative.

However, before repairs could be made, on 6/22/81 the compressota tripped off again, and the release in excess of Tech. Spec. limits as described in " Detailed Description of Event" o'.'Irred.

Subsequent to removal of the leaking valve and capping of the line, several more losses of recombiner system negative preasure resulted in releases well within Tech. Spec. limits.

The dates of the releases and activity released are:

Release 1 6/23/81 Instantaneous Peak - 1.4% Tech Spec limit Total Calculated Release - 0.09 Ci Release 2 6/23/81 Instantaneous Peak - 4.7% Tech Spec limit Total Calculated Release - 1.63 Ci Release 3 6/28/81 Instantaneous Peak - 4.5% Tech Spec limit Total Calculated Release - 0.6 Ci Release 4 6/29/81 Instantaneous Peak - 6.4% Tech Spec limit Total Calculated Release - 0.68 Ci Investigation identified two other leakage paths; through a i

mechanical compressor common suction line loop saal isolation valve, and through a condenser conductivity element' drain valve.

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Corrective Actions

on 6/22/81 the line associated with the leaking 2B mechanical compressor suction valve was cut upstream of the valve, and a pipe cap installed to preclude further leakage.

This was accomplished as a modification, as the line is used for maintenance purposes only.

Following trip of the recombiner mechanical compressors on 6/23/81 (Releases 1 and 2) a 1ormally closed mechanical compressor common suction line loop seal isolation valve was found cracked open.

(The loop seal was drained, since several other system drains had been added to the system after initial installation and this loop seal drain was no longer required).

This valve is in a location where it could be used as a foothold and may have been accidentally cracked open by someone trying to gain access to other equipment in the area.

The valve was wired cloced.

On 6/28/81 release 3 occurred.

A hydrogen analyzer valve gas inlet valve was found cracked open, and at the ti -

4' as thoucht that this could have provided a furt.her re pa for radioactive gases.

Upon closer exaainatio determined that any gases passing through the unlve would nave gone to the main condenser.

On 6/29/81, again following loss of recombiner system negative pressure, release 4 occurred.

Recombiner equipment drain sump airborne activity levels wera found to be abnormally high, and it was determined that the reconbiner condenser conductivity element drain valve which drains to this sump was cracked open approximately one quarter turn.

The valve was closed.

Subs =guent losses of recombiner negative pressure on 6/29/81 and 7/1/81 resulted in no appreciable increase in Unit 3 reactor building vent activity levels.

Very truly yours, J

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.jp. Cooney Spperintendent Gdneration Division / Nuclear cc:

Director, NRC - Office of Inspection and Enforcement Sr. Norman M. Haller, NRC - Office of Management &

Program Analysis l