05000010/LER-1980-002-01, /01T-0:on 800405,while in Shutdown Mode W/Fuel Removed,Contaminated Demineralized Water Was Being Heated & Added to Primary Sys.Tube Leaks in Heat Exchanger Were Found Leaking Water Into River.Caused by Unloader Tube Failure

/01T-0:on 800405,while in Shutdown Mode W/Fuel Removed,Contaminated Demineralized Water Was Being Heated & Added to Primary Sys.Tube Leaks in Heat Exchanger Were Found Leaking Water Into River.Caused by Unloader Tube Failure

ML19309E591
Person / Time
Site:	Dresden
Issue date:	04/17/1980
From:	Gates J COMMONWEALTH EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19309E557	List: 05000010/LER-1980-002, Forwards LER 80-002/01T-0 05000010/LER-1980-002-01, /01T-0:on 800405,while in Shutdown Mode W/Fuel Removed,Contaminated Demineralized Water Was Being Heated & Added to Primary Sys.Tube Leaks in Heat Exchanger Were Found Leaking Water Into River.Caused by Unloader Tube Failure
References
LER-80-002-01T, LER-80-2-1T, NUDOCS 8004220681
Download: ML19309E591 (4)

LER-1980-002, /01T-0:on 800405,while in Shutdown Mode W/Fuel Removed,Contaminated Demineralized Water Was Being Heated & Added to Primary Sys.Tube Leaks in Heat Exchanger Were Found Leaking Water Into River.Caused by Unloader Tube Failure

Event date:
Report date:
0101980002R01 - NRC Website

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60 61 OOCXET NU.VSER 68 69 EVENT DATE 74 IS REPORT QATE dQ EVENT CESCRIPTICN AND PACBA8LE CONSECUENCES h ia}2 l While in the shutdown mode with all fuel removed, contaminated demineralized water was[

, a,3 ; l being heated and added to the primary system thru the unloader heat exchangers.

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o,, ; j taminated water was discovered leaking to the river from tube leaks in the heat ex-I i o i s ! I changer. Leakage was initially suspected to be contained in unit radvaste system.

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i i a 4 l Release was caused bv mechanical failure of unloader tubes resultine in crimar r system l 1

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o ATTACHMENT TO LICENSEE EVENT REPORT S0-002/OlT-0 COMMONWEAI.TH EDISCN COMPANY (CWE)

DRESDEN UNIT (ILDRS 1)

DOCKET 1 050-010 With the plant in the shutdown mode and with all fuel removed, a leak developed in the 3 unloader heat exchanger which resulted in a release of radioactive water from the primary system to the service water system.

This event led to a release to the environment.

From April 2 thru 5 in preparation for the 200 pound hydro on the primary system, required as a part of the pre chemical cleaning activities, contaminated danineralized water was added to the primary system through the "A" unloader heat exchanger. To maintain reactor vessel flange tempera-ture within Tech Spec limits, heating boiler steam was used to heat the makeup water. Heating boiler condensate was then returned to the service water header where it was discharged to the canal by a single service water pump rated at 4300 gpm.

Af ter the filling operations had begun, it was determined that leakage from the pri=ary system was above normal. However, it was believed that the leakage was contained and was into the newly installed chemical cleaning crossties acd the radvaste system. Consequently, opera: Ors were sent out to inspect for leakage pathways, but because of the high radia-tion fields, the inspection was severly limited to their length of :ime in radiation areas.

During this time, April i-3, several smaller fills were made to saintain level in the steam drum and efforts continued to locate the leakage.

3 oiler steam again was used to maintain temperature vi:h the s:eam supply being throttled as required. The staam supply was eventually isolated at 0053 on April 5.

Routine. daily discharge canal composi:e water samples for the period April 2-4 were within limits and were ao: significantly above reutinely observed values. However, on April 5 at 1110 Radiation ?rotection no:ified the operating Shif t Engineer that the Uni: 1 discharge canal sample seasured 1737pCisi A sixty minute isotopic crunt indica:ed that :encentra: ions in the discharge canal were 9.1" Of the MFC for the identified nuclides.

Later a 1000 minu:e count of the same sample revealed tha: the cencentrations were actually 14.3% of the MPC for':he identified nuclides.

At 1326 hours0.0153 days <br />0.368 hours <br />0.00219 weeks <br />5.04543e-4 months <br />, the 3 unloader heat exchanger was isolated and the condensate re: urn line :: the service water system was 7alved c1: sed.

Ac this time leakage fr m :he primary system fr:pped :: approximately 30 gallons / hour. At 1530 :he NRC Inergency Center was notified of the release lad an ini:ial es ima:c of :he :::21 : uria conten: was 2.93 millituries.

This was determined fr:m an estica:ed water loss of 53,000 gallons and a gr ss 10:171:7 of 1.1 x 10J pCi..&.

ni:ial vater loss estimates were made fr:m :ne steam drum level recorder anc :he ac:ivity was decernined fr:m :he :encen:ra:icn af :he : ntamina:ed de dneralized va:er ir:m "A"

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storage tank which was used to fill :he primary system.

It was apparent at this time the "B" unloader had experienced tube failure and that water from the shell side was leaking into the tube (steam) side and being released through the condensate line Lato the service water.

On April 9 it was reported to NRC personnel that the total curie release was.135 curie. This was based on the revised volume of 76,000 gallons and concentrations, believed to be more indicative of the activity released, determined from a sample which was obtained from the shell side of the "3" unloader heat exchanger. At this time only the gross activity of the water was known and later isotopic analysis revealed the total curie release : be.620 curie. Also at this time we reported that the

=aximum concentration identified occurred on April 6 when a composite sample taken from the canal yielded an isotopic concentration for the mixture of 22*,'

of the MPC for the identified nuclides.

Based on the results of our investigation, the release does not pose a health or saf ety ha:ard to the public. Corrective steps will be taken to assure that an event of this nature does not occur again. These actions include:

1) replace the existing unloader heat exchanger after chemical cleaning;

2) cut and cap the 2" condensate crosstie to the service water prior to further use of the heat exchanger; 3) begin sampling service water for activity on a routine basis; 4) develop lower reporting / action levels for canal discharge and service water activities to give the opera-

ors an earlier alert of possible unusual condi:1ons prior :o exceeding Tech Spec linics.

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0 1 30 - 5 PrRT lj T1 TLE OF OEVIATICN CCCU RRED Cnplanned and Uncontrolled Release of Radioactivity to Discharge Canal 4-5-30, 15,26 A,e IMd 3YSTEM AFFECTED PLANT CCN0lTIONS TESTING o d mary Sys tem S-D 0

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.rn e 1737.4 oci/L. (T.S. Limit 100 oci/L) with only one service water cump on (6000 gpm).

DESCRIPTION OF CAUSE Fairure of L "3"

unloading heat exchanger tube / tubes while heatinz reactor.

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