ML19338D001
| ML19338D001 | |
| Person / Time | |
|---|---|
| Site: | Dresden  |
| Issue date: | 02/20/1975 |
| From: | Stephenson B COMMONWEALTH EDISON CO. |
| To: | |
| References | |
| 105-75, NUDOCS 8009150578 | |
| Download: ML19338D001 (3) | |
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Dresden Nuclear Power Station BBS Ltr. #105-75
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February 20, 197
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James G. Keppler, Re
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Directorate of Regulatory Operations - Region III j
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SUBJECT:
REPORT OF ABNORMAL OCCURRENCE PER SECTION 6.6. A OF THE TECHNICAL SPECIFICATICRIS FAILURE OF DRAIN VALVE (363M6) PROM "lA" CONTAMINATED DEMIN TANK
References:
- 1) Regulatory Guide 1.16 Rev. 1 Appendix A
- 2) Notification of Region III of U.S. Nuclear Regulatory Connaission Telephone:
P. Johnson,1000 hrs,13 Feb 75 Telegram:
J. Keppler, 1451 hrs, 13 Feb 75 Report Number: 50-10/1975-1 Report Date:
February 20, 1975 Occurrence Date:
February 13, 1975 Facility: Dresden Nuclear Power Station, Morris, IL IDENTIFICATION OF OCCURRENCE This letter is a report of the unplanned release of liquid radioactive material from Unit 1 "A" contaminated demineralized water storage tank (T-105 A).
CONDITIONS PRIOR TO OCCURRENCE Prior to and during the occurrence Dresden Unit I was operating at steady state power, 585 MWt and 168 MWe. No testing was being performed on the unit during the period.
DESCRIPTION OF OCCURRENCE During an inspection of T-105A, it was noted that water was leaking from the drain valve (363M6) due to a crack on the bottom of the valve.
This water was draining to the storm drain. Af ter reporting the leak to the Shif t l
Engineer, operations began lowering the level of the tank by transferring water to the hotwell and pumpi.ng it to the liquid waste storage tank (T-ll4).
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i b rJruary 20, 1975 jr James G. Kapnice In addition, the scheduled laundry tank discharge to the discharge canal was secured to prevent further radioactive discharge to the river. Leakage was minimized by installing a camporary repair consisting of a 4" nipple with a pipe cap held on by two "C" clamps. At 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> the drain was plugged from the inside of the tank which stopped all leakage.
DESIWATIM OF APPAnNT CAUSE OF OCCtanur'E (Equipment Failure)
During the early part of February, up to and including the 13th of the month, the Dresden area experienced continuous sub-freezing temperatures.
It appeared that ice formed on the inside of the valve, expanded, and cracked the valve.
ANALYSIS OF OCCURRENCE At the time of discovery, the leakage rate was approximately six gallons per minute. Maintenance capped the leak at 0215 hours0.00249 days <br />0.0597 hours <br />3.554894e-4 weeks <br />8.18075e-5 months <br /> and the leakage was reduced to.16 gallon per minute. Radiation prottetion sampled and analyzed the tank water for radioactivity concentration.
This analysis indicated 5 pCi/1.
Results of a gross beta-gamma radioactivity concentration of 2.4x10 gaema isotopic analysis performed on a water sample from the Condensate Domin Storage Tanks were as follows:
Radionuclide Ci/N1 les54 3.2x10-6 CoS8 1.1x10-5 60 2.2x10-0 Co 6
1131 5.0x10 5 Cs134 5.2x10 5 Cs137 8.2x10-Unidentified 6.5x10-5 Using the measured leak rate of 6 gym, and a dilution flow of 128,000 gym, it was determined that the concentration of gross beta-gamma radioactivity in the discharge canal due to the leak was 11.3 pci/1. A review of controlled liquid waste discharges. from Unit 1 during the month of February up to and during the detection of the leak revealed the maximum gross radioactivity in the di'scharge canal to be 24 pCi/1. The contribution of 11.3pci/1 due t.o the leak, when added to the maximum controlled discharge, results in a maximum gross radioactivity concentration of ~36pCi/1. This result is less than the Technical Specification Limit of 100 picocuries per liter in the discharge canal.
Since the maximum concentration of radioactive materials in the discharge canal was well within the Technical Specification Limit there was no hazard to the public due to this occurrence.
CORRECTIVE ACTION i
The immediate corrective action taken to terminate the incident was to clamp, then plug the valve.
Further corrective action taken was to replace the cracked valve with an insulated valve which will prevent future free:ing.
4 A plant modification presently in the Engineering Evaluation Phase is in progress that will help prevent discharges to river by directing the normal crain anc over flow fro: T-105A te the 2/3 Equipment D ains.
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- James G. Kappler
--.... cbruary 20, 1975 FAII,URE DATA There had been no prior occurrence of this type on the contaminated Domineralized Water Storage Tanks.
The new valve is a,4" Walworth Gate Valve.
In light of corrective action anu the plant modification in progress we believe that sufficient action has been taken to prevent recurrence of this problem.
Sincerely, Stephenso Q B.
Superintendent Dresden Nuclear Power Station BBS:GJH: sib cc: File /AEC l