ML20023D218
| ML20023D218 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 05/10/1983 |
| From: | Harrell E VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| NUDOCS 8305200146 | |
| Download: ML20023D218 (2) | |
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VIRGINI A ELECTRIC AND POWER COMP ANY NORTH A NN A POWF.R ST ATION C
P.O. BOX 402 33 7 MINE R AL, VIRGINI A 23117 ee May 10, 1983
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g Nuclear Regulatory Commission, Region ll NPF-4 Office of the Executive Director for Operations Docket No: 50-338 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303 FOLLOW-UP REPORT-DECLARATION OF AN UNUSUAL EVENT-NORTH ANNA UNIT I Attached is a brief explanation of the events leading to the declaration of an Unusual Event at North Anna Unit I on May 9, 1983 at 1646. This follow-up notification constitutes the facsimile transmission required by EPIP-2.03 paragraph 15 Since there was no impact on any safety system nor on the Unit i Technical Specifications, no further reports are anticipated.
O E. Wayn Harrell Station Manager EWH/sim Attachment cc: Milton B. Shymiock NAPS Resident inspector L.JULAL 5):'
y 8305200146 830510 PDR ADOCK 05000338 j
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24 HOUR FOLLOW-UP REPORT OF AN UNUSUAL EVENT - MAY 9, 1983 EVENT:
On site release of Hydrogen (H ) Gas from the Unit 1 Main 2
Generator that had the potential to endanger station personnel or equipment.
On May 9, 1983, at 1520 hours0.0176 days <br />0.422 hours <br />0.00251 weeks <br />5.7836e-4 months <br />, with Unit 1 at 100% power, the Unit 1 Shif t Supervisor was notified of a severe hydrogen leak on the Hydrogen Inner-Cooled Turbine Generator.
(A mixture of nearly 100% pure hydrogen is utilized to cool the generator during operation with an internal generator hydrogen pressure of approximately 65 psig). Previously, several smaller leaks had been identified but those leaks were not of a serious nature and could be dealt with on a daily basis. After receiving the report of the severe hydrogen leak several operations personnel were sent to the Turbine Building to appraise the possibility of repairing the leak while operating, and to line up Turbine Building ventilation to prevent the accumulation of a potentially explosive mixture of hydrogen gas. Meanwhile, in the control Room, operators were attempting to maintain generator gas pressure by adding additional gas.
Within 15 minutes it was decided that the hydrogen leak was too large and too dangerous to attempt repair. Consequently, at 1535, a Unit rampdown of 2%/ minute was ordered.
Co-incident with the rampdown, and in accordance with operation limitations, hydrogen gas was vented to the atmosphere as the Unit was decreased in power. This measure served to reduce hydrogen pressure and minimize leakage from the main generator. At 1645 the generator was removed from service and reactor power reduced to near 3%.
During the rampdown a review of the Emergency Plan revealed that a release of toxic or flammable gas that had the potential to endanger station personnel or equipment was specifically addressed. Consequently, at 1646 an Unusual Event was declared. At this time generator gas pressure was at 35 psig (decreased from 65 psig when the rampdown began) and measures were taken to reduce the gas pressure to near 10 psig or below by venting to the atmosphere. At 1831, with hydrogen pressure less than 10 psig, operation personnel began to purge the generator of hydrogen with the addition of carbon dioxide. At 1836 the emergency was terminated and tFe pertinent governmental agencies so notified.
During the event precautions were taken to limit personnel entry to any area that could contain a dangerous concentration of hydrogen gas.
Additional measures were taken to ventilate the affected areas. At no time was there a danger of a release of radioactive material nor did a dan;er to offsite personnel exist. Therefore, the public health and safety were not affected.
This event is documented in accordance with Emergency Plan Implementing Procedure (EP1P) 1.02 requiring a written summary of the event to offsite authorities within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, and with EPIP 2.03 requiring written notification within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of the event to the NRC Director, Region II.