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n r - - -.ra nne A eseENtGASF UfgUTIES COesmaast December 14, 1977
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W-1-607 fer Boyce H. Grier Dienctor, Region I Office-of Inspection-and. Enforcement u, 5. Nuclear Regulatory Comadssion 531 Park Avenue King of Prussia Pennsylvania 19406 Refe nace:
Provfsfonal License Ms. DPR-21 Deckat No 50-245 Reportable Occurrence R0-77-40/1P' l
Deer-Mr. Grier-This letter is forwarded to provide prompt notification of Reportable Occurrence RO-77-40/1P as required by the Millstone Unit i Technical' Specifications.
On December 13,1977, at 0930 hours0.0108 days <br />0.258 hours <br />0.00154 weeks <br />3.53865e-4 months <br />, at approximately 8g percent power, w detonatiour in the Unit 1 Off-Gas System occurred. The detonation resulted in an indicated increase in the stack release rate and a local emergency was declared to evaluate the incident and take the necessary corrective-action.
At 1982 hours0.0229 days <br />0.551 hours <br />0.00328 weeks <br />7.54151e-4 months <br />, plant management ordered a reduction in power and subsequently, l
- e. decision was made to place the reactor in a hot shutdata condt. tion.
thering the controlled _ shutdones, a second datomation occurred at 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br />.and the reactor was. manually scrummed.
The main steam line isolation ve1wes.were closed to terminste the off gas releases and a controlled At 1308 coohtaun was established.using the Isolation Condenser System.
hours, a site emergency was declared and the Emergency Control Center was mstablished to determine the magnitude of the incident.
Immediately after the incident, it was discovered that the second detonation i
had occurred in the base of.the stack, resultim] in the force of the detonation being directed through the stack door, causing a radioactive ruleese and injury to one employee.
The injured employee was transported to a local hospital f'or treatiment.
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8301100131 821207, PDR FOIA HIATTO2-545 PDR
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M me-I - L,0 7 4.rr Bo9ce.HJGrier December 14,.1977 M
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Personnel in the F.;--J Control Center cooVdinated activities to determine the magnitude of the release and possibli spread of contaurination.
Site-access. and egress. were controlled until conditions were assessed.
Ae initial evaluation. perflovuod. by the Northeast utilities. Service Co enwiremmental group determined. that the detonations and radioactive-releases accompasqring these detonations, posed. no signi ficant. environmental threat to the public The-wind direction. at. the time of the detonations was le am offshore directioe and: calculations. revealed that the expected desa to-an individual at the South boundary of the site would have been approminately ona (1) millfrema After air evaluation of'informatioer provided by site monitoring teams, a decistorr was made to relanea personnel on site after a survey of eacfr individual was perfonned An examination of the irdured amployee revealed 1
ne significant isdurfes Pmly Unit 1 is in a cold shutdown condition.
and inspections are being performed to detensine the magnitude of the damage and corrective actions necessary.
Further inforestion and dotatis will. he provided in the 14. day report that wf11 follow.
Yours truly,
kk E. 1. Ferland Plant Superintendent Millstone Nuclear Power Station ',
GF/PJP/11 I
i Director. Office of Menegament Inforuntion and Program Control cc:.
U
- 5. Nuclear Angulatory Commission Mashingtse 0.C 20555-l t
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