ML20037B240
| ML20037B240 | |
| Person / Time | |
|---|---|
| Site: | Dresden, Byron, Braidwood, Quad Cities, Zion, LaSalle  |
| Issue date: | 07/18/1977 |
| From: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | Brian Lee COMMONWEALTH EDISON CO. |
| References | |
| NUDOCS 8009090883 | |
| Download: ML20037B240 (1) | |
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C:~.. ~ i FILES Docket i:on.50-010. 50-237, so.,.w. 50-2 %, Se.w,, 50-295,53-304, 50-373, 50-374, 50-454, d,'"_1 81977 50-455, 50-456, 50-457 Co=tontrealth 11dison Company ATT;:
Mr. Lyron Lee, Jr.
Vice President P.O. Lox 767 Chicago, IL 60690 Genticr.cn:
The caelesed Circular lic. 77-10 is foruarded to you for information.
If there are nny questions rclated to your undcr-standing of the actions required, plence contact this office.
Sincerely, James G. 1:eppler Director
Enclosure:
IE Circular
!!o. 77-10 cc u/ encl:
Iir. R. Cosaro, Project
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Superintendent Mr. Gunnar Sorenson, Site Project Superintendent lir. B. B. Stephenson, Station Superintendent Mr. L. J. Durke, Site Project Superintendent Mr. '!!. J. l'alivianakis,
Plant Superintendent i:r. J. S. Eitel, Plant Superinteniicat Central Files "eproduction Unit Hnc 20b PDR Local PDR 1; SIC TIC
/D**D D'3 Anthony Roisman, Esq., Attorney A
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IE Circular No. 77-10 i
VACUU:: COUDITIONS RESULTING 1: Did! AGE TO LIQUID PROCESS T/J:F.S 1
Description'of Circumstances On January 31, 1977, at the Portland General Electric Company's Trojan l
Nuclear Station, a vacuum uns pulled on a Chemical and Voluac Control l
System holdup tank which caused the tank to buckle inwardly and crack i
at the junction of two buc.kled areas.
(LER 50-344/77-02)
Radioactive cover gas escaped from the tank to the fuel building exhaust l
ventilation and ultimately through the auniliary building ventilation-l stack to the environment.
During the period of January 31 through l
February 7,1977, (date of discovery) approximately 62.5 curies of nobic l
gases ucre released.to the environment. The occurrence vas caused by malfunctions of both the primary (waste gas decay tank collection header) l and the backup (nitrogen pressurization system) cover gas supply pressurc l
regulators during pumpout of the tank contents.
The malfunction of the prir.ary regulator uns due to moisture accumulation uhich led to the forma-tion of a water column on the discharge side of the pressure regulatcr.
The regulator in the backup nitrogen supply system malfunctioned at the l
came time, but the cause has not been determincd. There verc no alarms or remote indication for the holdup tank or the gas control header to indicate abnormal pressure or to indicate the operating status of the nitrogen supply system.
A similar event occurred at the Sacramento Municipal Utility District's Rancho Seco nuclear station uhcrcin the Reactor Coolant System Drain Tank partially collapsed under vacuum conditions and in doing so cracked an inlet line attached to the tank (LER 50-312/77-03). The first indica-tion of the condition was detceted by the radiction monitor that. samples the ventilation c::haust in an area adjacent to the room in which the damaged tank uns located.
Radioactive gases ucre relcased through the failed line between January 12 and February 16, 1977.
During this period, approninately 9 curies of radioactive gas vere released.
The cause of this occurrence was attributed to the tanh not being properly vented by the operator during discharge of its liquid contents.
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l IE Circular No. 77-10 2-July 18, 1977
- It is recommended that you examine the systems of your reactor j
facility (ics) that contain low pressure process or holdup tanks and assure that adequate measures have been taken to protect against vacuum conditions that could result'in tank inward buckling and failure with subsequent release of radioactive material or cause other detrimental effects with regard to the overall safety of planc operations.
It is also recommended-that you examine your capability to dewect and locate possible leaks of radioactive material from such tanks.
No uritten response to this Circular is required.
If you desire additional information regardin;; this matter, contact the Director of the' appropriate NRC Regional Office.
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