ML20046B865
| ML20046B865 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 07/30/1993 |
| From: | Stetz J CONNECTICUT YANKEE ATOMIC POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9308060337 | |
| Download: ML20046B865 (3) | |
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CONNECTICUT YANKEE ATOMIC POWER COMPANY HADDAM NECK PLANT 362 INJUN HOLLOW ROAD e EAST HAMPTON. CT 06424-3099 July 30,1993 Re: Technical Specification 6.9.2 Docket 50-213 F
U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555
Dear Sir:
Attached is a Special Report, submitted in accordance with the Haddam Neck Plant Technical Specification 3.3.3.5, Action 37 and Specification 6.9.2.
On July 15,1993, the Wide Range Noble Gas Stack Monitor, RMS-14B was isolated to accommodate higher steam generator blowdown rates during stanup, as allowed by l
Technical Specification 3.3.3.5 (Table 3.3-7). This Technical Spfication also requires that "... the monitor must be retumed to service for at least 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> at the end of each six day period to demonstrate operability". Connecticut Yankee Atomic Power Company (CYAPCO) has interpreted this requirement to mean that between the end of the sixth day and prior to the end of the seventh day of the monitor being isolated, the monitor will be 3
restored to service for three hours to demonstrate operability. Depending on the demand for high steam generator blowdown, the monitor may then be re-isolated and a new seven day clock started. On July 22,1993, when attempting to return the monitor to service for three hours prior to the end of the seventh day of the monitor being isolated, the monitor failed. Due to this failure, the demonstration of the operability of this monitor prior to the end of seven days could not be accomplished. As a result of the monitor failure, and pursuant ta Technical Specifications 3.3.3.5 and 6.9.2, this report is required to be filed within ten days of the end of the seven day action statement.
Should you have any questions or require additional information, please contact us.
Very truly yours, kf John P. Stetz Vice President Haddam Neck Plant 1
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Mr. Thomas T. Martin Regional Administrator, Region I D. Allendale Road
. King of Prussia, PA 19406 Mr. William J. Raymond Sr. Resident Inspector Haddam Neck l
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Special Report Main Stack Wide Range Noble Gas Monitor Failure Intmduction The Wide Range Noble Gas Stack Monitor, RMS-14B is a TMI backfit that is intended to be used during accident nicases. It is designed to measure radioactive gas concentrations in the range of 1.0E-07 to 1.0E+05 microcuries/cc of Xenon-133. This range is significantly larger than the capabilities of the original stack monitor, RMS-14A.
During periods of high blowdown, the steam generator blowdown vent condensers need to be bypassed and the moistum from the blowdown tank is rerouted to the stack. This moistum would damage RMS-14B, thus the Wide Range Noble Gas Stack Monitor is removed from service during periods of high blowdown. During these periods of increased blowdown, RMS-14B is placed back into service for at least 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> at the end of each six day period to demonstrate operability.
Discussion On July 15,1993 at 2150, with the plant in Mode 2, the Wide Range Noble Gas Stack Monitor, RMS-14B, was isolated to allow for increased steam generator blowdown at stanup. On July 22 at 1430, the monitor failed when an attempt was made to place the monitor back into service in accordance with Technical Specification 3.3.3.5. Repair effons failed to correct the problem prior to exceeding the seven day action statement.
Tmub!cshooting has revealed that the root cause of the failum was a failed power isolation board, which caused a cascading failure of a power supply and diode on the power supply board. The monitor was repaired, operationally tested and retumed to service on July 27,1993 at 1258.
I During the time period that the Wide Range Noble Gas Stack Monitor is out of service, routine gaseous effluents am adequately monitored with the backup stack monitor, R-14A. Should an event have occurred that resulted in the radioactive effluent release rate increasing beyond the range of the back-up stack monitor, back up pmcedures (Emergency Plan Implementation Procedures) am in place for radiation dose assessment, including the use of radiological field teams. These procedums provide adequate means to determine effluent release rates based upon calculations using field data.
On the basis that adequate alternate capabilities using the backup stack monitor and Emergency Plan pmcedures were in place, the inoperability of RMS-14B imposed a low safety significance on our ability to assess the dose consequence of a major gaseous release,
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