05000237/FIN-2009004-06
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Finding | |
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| Title | Impact of Chimney Flow Monitor Degradation on Timely and Accurate EAL Classification |
| Description | The inspectors identified an Unresolved Item (URI) concerning the impact of inaccurate, non-conservative chimney flow monitor values on the licensees ability to make timely and accurate emergency action level (EAL) classifications for radiological effluent releases, as provided in procedure EP-AA-1004, Radiological Emergency Plan Annex for Dresden Nuclear Power Station. Discussion: In March 2008, the licensee identified that the chimney flow transmitter was restricted due to fouling of its flow elements. The licensees investigation disclosed that the flow transmitter had provided inaccurate indications since April 2004. The flow indicated by the transmitter was approximately 40 percent lower than the actual chimney flow. The chimney flow data provided by the transmitter is used as a parameter to quantify gaseous effluents released to the environment. Chimney flow is also used to calculate the instantaneous noble gas concentrations released to the environment from the chimney to determine EAL classifications based on radiological effluents. As a result of the flow transmitter fouling, for a four year period beginning in 2004, gaseous effluents released through the chimney were non-conservatively calculated and reported. The inspectors reviewed the licensees revised effluent calculations and determined they were accurate and technically sound. While the original offsite dose determinations for 20042007 had been underestimated by as much as 40 percent, the corrected calculations showed that the un-assessed dose for each of those years was less than 1 percent of the 10 CFR Part 50, Appendix I, design objective. Consequently, the radiological impact of the problem was of minor safety-significance. The inspectors reviewed the actions taken by the licensee to correct the flow monitor degradation, and actions planned to address deficiencies with the calibration of the flow monitoring system and with the licensees surveillance program, which contributed to the extended duration of the problem. The issue remains under review by the NRC to determine the impact of the problem on the licensees emergency preparedness program for the timely and accurate declaration of EAL classifications consistent with the licensees procedures. The issue is categorized as an URI pending further NRC review |
| Site: | Dresden  |
|---|---|
| Report | IR 05000237/2009004 Section 4OA3 |
| Date counted | Sep 30, 2009 (2009Q3) |
| Type: | URI: |
| cornerstone | Mitigating Systems |
| Identified by: | NRC identified |
| Inspection Procedure: | IP 71153 |
| Inspectors (proximate) | S Edmonds D Melendez-Colon W Slawinski C Phillips M Ring J Benjamin D Lords E Coffman C Scott |
| INPO aspect | |
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Finding - Dresden - IR 05000237/2009004 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Finding List (Dresden) @ 2009Q3
Self-Identified List (Dresden)
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