ENS 51757
ENS Event | |
|---|---|
19:45 Feb 25, 2016 | |
| Title | Potential Common Mode Failure of Item Relied on for Safety |
| Event Description | While processing liquid effluent, process operators noticed that a set of uranium monitors, IROFS [Item Relied On For Safety] for the process system, registered a negative value. The process operators shut down process flows and contacted maintenance to come and check the uranium monitors. The uranium monitors checked out to be functioning correctly. The process was resumed until the condition repeated. The process operator then contacted maintenance again and shut the process down at 0300 [PST] pending further evaluation.
It appears that an interference material (likely copper or nickel) is masking some of the uranium present in the effluent causing the uranium monitors, which are based on colorimetry, to read low. At 1145 PST on 2/25/16, AREVA Richland Reliability Engineering and EHS[and]L staff confirmed that this condition had not been anticipated in the ISA [Integrated Safety Analysis] and had the potential to cause a common mode failure of two IROFS. The waste tank that contains the process effluent is a 30,000 gallon tank and currently contains about 3,000 gallons and based on laboratory analysis of a sample of the tank contents contains about 136 grams of low enriched (<5 wt. [percent] U235) uranium. A total of 2 kg has been processed through the tank since the last NCS [Nuclear Criticality Safety] required emptying and clean out of the tank. Although the IROFS were degraded, it was determined that the IROFS were available and reliable to perform their function. However, this event meets the criteria in 10CFR70 Appendix A 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> reporting item 1, in that this condition had not been anticipated in the ISA and had the potential to cause a common mode failure of IROFS. The NRC Regional Office will be notified. |
| Where | |
|---|---|
| Areva Np Inc Richland Richland, Washington (NRC Region 2) | |
| License number: | SNM-1227 |
| Reporting | |
| Part 70 App A (B)(1) | |
| Time - Person (Reporting Time:+16.78 h0.699 days <br />0.0999 weeks <br />0.023 months <br />) | |
| Opened: | Calvin Manning 12:32 Feb 26, 2016 |
| NRC Officer: | Jeff Herrera |
| Last Updated: | Feb 26, 2016 |
| 51757 - NRC Website | |
Areva Np Inc Richland with Part 70 App A (B)(1) | |
WEEKMONTHYEARENS 517572016-02-25T19:45:00025 February 2016 19:45:00
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