ML20002C647
| ML20002C647 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 03/23/1973 |
| From: | Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8101100651 | |
| Download: ML20002C647 (3) | |
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Mr. John F. O' Leary, Director au WM
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License No DPR-6 US Atomic Energy Commission Washington, DC 20545
Dear Mr. O' Leary:
This letter is written to infom you of the results of our investigation concerning the Big Rock Point Plant's emergency condenser tube bundle leak and is referenced to the submittal on the same cubject dated January 16, 1973 We detected a minor leak (via emergency condenser radiation vent monitor) from the primary coolant side into the emergency condenser secondcry (shell side) during plant start-up at approximately 850 psig on December 15, 1972. As the reactor precsure was increased to normal operating pressure of 13hc psig, the emergency condenser stack vent moni-tors decreased to their normal background level and remained there throughout power operation. No primary system leakage was detected during normal system power operation.
A hydrostatic test was conducted during the refueling outage on the tube side at 1685 psig. A slight weepage on the return water box Flexitallic gasket of the south tube bundle was detected. The veepage amounted to only a slight vetting of the gasket mate.ial and occurred in the 12:00 to 3:00 quadrant, facing east to vest. The return water box studs were tightened one and one half flats and a rehydro of the south tube bundle was successful. The north tube b alle was also hydroed with no leakage detected.
Following is a semy of the radiological consequence of the occurrence:
The maximum direct radiation measurement in contact with the emergency condenser vent, as recorded by the radiation vent monitor and verified with a calibrated radgun, was 30 mR/h. First increase above background was at 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> on December 16 and continued through 1600 hours0.0185 days <br />0.444 hours <br />0.00265 weeks <br />6.088e-4 months <br /> on December 17, a period of 20 hours2.314815e-4 days <br />0.00556 hours <br />3.306878e-5 weeks <br />7.61e-6 months <br />.
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Mr. John F. O' Leary 2
Docket No 50-155 License No DPR-6 March 23, 1973 In order to estimate the release, a direct radiation measurement was made at the off-gas line using the same calibrated radgun. This read-ing corresponded to a stack release rate (following 16-minute holdup) of 20,000 pCi/second.
The delay time between the reactor and off-gas line is approxi-mately the same as to the condenser vent (% 2 minutes).
Therefore, the detector energy efficiency is the same. Due to different geometry (3" diameter off-gas line vs 14" diameter vent), it is conservatively assumed that the geometric efficiency was a factor of four (4) less at the vent.
( A factor of 1 5 is more realistic. )
Based on the above assumptions, the maximum vent release rate, corresponding to 30 mR/h, for an equilibrium nuclide mixture with two (2)-
minute decay was 700 pCi/second.
From the vent monitor strip chart, the weighted average reading was determined to be 6.8 mR/h over the 20-hour period. Thus, the calculated maximum total release via the emergency condenser vent was 11.2 Ci.
This vould correspond to a site boundary radiation dose of 0.014 mrem.
Since no smearable contamination existed in the vent, it is assumed the release consisted only of noble gas and no internal or thyroid dose could have occurred.
Yours very truly, e_
i GJW/ map Gerald J. Walm Nuclear Fuels Administrator CC: BHGrier, USAEC
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