05000000/LER-1977-043, Forwards LER 77-043/03L-0.Detailed Event Analysis Encl
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, a ecx m hi NORTHEAST NUCLEAR ENERGY COMPANY L3 666 A NCRTHEAST UTILITIES COMPANY Mr. Boyce H. Grier January 18, 1978 Director, Region I MP-1-652 Office of Inspection and Enforceme'nt U. S. tiuclear Regulatory Cccmission 631 Park Avenue King of Prussia, Pennsylvania 19406
Reference:
Provisional License DPR-21 Occket No. 50-245 Reportable Occurrence R0-77-43/3L
Dear Mr. Grier:
As previously discussed with your office this letter foraards the Licensee Event Report for Reportable Occurrence R0-77-43/3L required to be submitted within 30 days pursuant to the requirements of the Millstone Unit 1 Technical
. Specifications, Section 6.9.1.
An additional three copies of the report are enclosed.
Yours truly, l', J:
y.,.
s~. J.' Ferland Plant Superintendent
~
Millstone fluclear Pcwer Station EJF/PJP:lla
Attachment:
(LER R0-77-43/3L )
Director, Office of Inspection and Enforcement, Washington, D. C. (30) cc:
Director, Office Of Management Information and Program Control, Washington, D. C. (3)
J 8301100175 821207 PDR FOIA HIATT82-545 PDR
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Report Number: R0-77-43/3L Report Date:
January 18, 1978 Occurrence Date:
December 19, 1977 Facility: Millstone Nuclear Power Station, Unit 1, Waterford, Ct.
06385 Identification of Occurrence:
Degradation of a system used to measure gaseous effluents was discovered during a special inspection.
Condition Prior to Occurrence:
The plant was shutdown on December 13, 1977 as a result of hydrogen detonations
,, occurring in the Off Gas System and stack base.
Inspections, repairs and tests, necessitated by the hydrogen detonations, were being performed at this time.
Description of Occurrence:
- - On December 19,1977 at 1735 hours0.0201 days <br />0.482 hours <br />0.00287 weeks <br />6.601675e-4 months <br />, an inspection of the stack gas monitor
- - sample probes was initiated. The Stack Gas Monitor System was removed from service at this time for performance of the inspection.
At 1900 hours0.022 days <br />0.528 hours <br />0.00314 weeks <br />7.2295e-4 months <br /> on December 19, 1977, it became appdrent that the sEack gas monitor probes and mounting beam, located at the stack 265 foot elevation, were damaged and would require some repairs.
Temporary sample probes were connected to the existing monitoring system so that the permanent system could be repaired.
Desianation into Apparent Cause of Occurrence:
Further investigation into the incident revealed that the stack gas monitor sample probe mounting beam was dislocated as a result of the hydrogen detonation occurring in the stack base on December 13, 1977.
The sample probes lacking the support of the mounting beam were deflected downward.
i 3
. Report Number: R0-77-43/3L Report Date:
January 18, 1978 Occurrence Date:
December 19, 1977 Facility: Millstone Nuclear Power Station, Unit 1, Waterford, Ct.
06385 Analysis of Occurrence:
The Stack Gas Monitor System provides a continuously recorded indication of stack releases so that pre-established limits are not exceeded. A review of probe condition and taking into account the relatively uniform flow of effluents up the stack, it is felt that the stack gas sample probes were still functional and would have provided monitoring and indication of any abnormal conditions that would have been a health or safety concern.
Corrective Action
The stack gas monitor probes and support beam were replaced in accordance with the original design.
The permanent installation was performed and system operation restored on December 23, 1977.
Corrective actions to prevent hydrogen detonations, which could result in stack gas monitor damage, was described ir Reportable Occurrence:
R0-77-40/,,1T da ted December 27, 1977.