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PRELIllINARY NOTIFICATION !
September 26, 1977 d
PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-77-169 This areliminary notification constitutes EARLY notice of an event of P055I3LE safety or public interest significance. The information presented is as initially received witncut verification or evaluation and is basically all that is known by IE staff on this date.
y Facility: Comonwealth Edison Company, Dresden Unit No.1 T'
(DN 56-010), Morris, IL l
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Subject.
OFICAS EXPLOSION Commonwealth Edison Company reported to RIII (Chicago) that at 3:00 a.m.
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on September 25, 1977, a hydrogen explosion occurred in the Dresden Unit No. 1 offgas system. Upon investigation, the itcensee determined that the rupture disc ott both air ejectors had bice.
A controlled shutdown was immediately initiated.
Offgas radioactivity being discharged from the stack to the environs at the time of the incident was approximately 12,000 microcuries per second and offgas radioactivity at the air ejectors was 25,000 microcuries per second (approximately 5% of the Technical
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Specifications limit.). At the time of the incident, the offgas exhausting
,1 from the rupture disc entered the reactor turbine building and was ly exhausted to the stack through the turbine building ventilation system.
Some radioactive material was released to the atmosphere at essentially I
A' ground level through leakage from the stack access hatch. While the amount of radioactivity released to the environs is not believed to be significant, environmental samples have been taken by the licensee to confinn this evaluation.
No personnel overexposure occurred.
The State of Illinois has been notified.
The licensee does not plan to issue a press release at this time.
Region III is considering issuance of a press release.
An RIII inspector has been dispatched to the site.
RIII (Chicago) received notification of this occurrence by telephone from the Dresden Station at 8:00 a.m. on September 25, 1977.
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Contact:
GHBidinger, IE x27551 LJCunningham, IE x27551 LBHigginbotham x28098 Distribution:
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