ENS 44887
ENS Event | |
|---|---|
05:00 Mar 3, 2009 | |
| Title | Degradation of Item Relied on for Safety (Irofs) |
| Event Description | Area F is part of the solvent extraction uranium recovery process. The solvent extraction process removes usable uranium and strips out impurities from the solution. An organic solvent and nitric acid are used as part of this process. Column-0F13 is a strip column which has organic solvent flowing into the bottom and usable uranium/nitric acid entering from the top. After passing down through the solvent, the nitric acid exits Column-0F13 from the bottom, into feed Column-0G04. Column-0G04 then feeds into evaporator Column-0G05. If solvent were to enter Column-0G05 and begin reacting with the heated nitric acid while the system was closed (i.e., no vent relief) then a potential overpressurization or 'red oil' accident could occur. The scenario assumes that the reaction continues (self-heating) even though the heaters are shut off.
IROFS FAF-19 consists of flow switch FS-0F13, located in Column-0F13, which is interlocked to PUMPMT-0F19. This IROFS is in place to prevent a red oil accident by isolating organic solvent in-flow to evaporator Column 0G05 (via feed Column 0G04) upon loss of solvent-nitric acid interface in strip Column 0F13. If flow switch FS-0F13 senses loss of Column 0F13 interface, PUMPMT-0F19 shuts off which stops flow into Column 0G04 and thus into Column-0G05. The equipment associated with IROFS FAF-19 is designated as Safety Related Equipment (SRE) and is functionally tested monthly. The regularly scheduled SRE Test was performed on March 3, 2009, and the purpose of the test is to demonstrate that the flow switch will fall when interface is lost and thus will shut off PUMPMT-0F13. The test failed because the flow switch did not fall, so the pump did not stop (PIRCS Problem #17584). Though there are defense in depth factors such as procedural requirements for operators to verify that no solvent is present in feed Column-0G04 prior to operation of evaporator Column-0G05, it was determined that IROFS FAF-19 was degraded and that the performance criteria of 10CFR70.61 were not met. IROFS FAG-12 is an open vent that is credited as an additional control that is in place to prevent overpressurization due to self-heating. However IROFS FAF-19 is also required to be available in order to the performance criteria. Previous SRE testing of the flow switch in January 2009 identified a potential problem with the flow switch sticking. As follow-up to that occurrence, the area process engineer reduced the SRE testing frequency from semi-annual to its current frequency of monthly in order to provide better indication if a problem was developing. Area F is currently in a safe condition and is operating under approved compensatory measures. The licensee has notified the NRC Resident Inspector. |
| Where | |
|---|---|
| Nuclear Fuel Services Inc. Erwin, Tennessee (NRC Region 2) | |
| License number: | SNM-124 |
| Reporting | |
| Part 70 App A (B)(2) | |
| Time - Person (Reporting Time:+10.53 h0.439 days <br />0.0627 weeks <br />0.0144 months <br />) | |
| Opened: | Jennifer Wheeler 15:32 Mar 3, 2009 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Mar 3, 2009 |
| 44887 - NRC Website | |
Nuclear Fuel Services Inc. with Part 70 App A (B)(2) | |
WEEKMONTHYEARENS 561492022-10-05T19:00:0005 October 2022 19:00:00
[Table view]Part 70 App A (B)(2) Degradation of Safety Items ENS 448872009-03-03T05:00:0003 March 2009 05:00:00 Part 70 App A (B)(2) Degradation of Item Relied on for Safety (Irofs) ENS 447402008-12-23T12:49:00023 December 2008 12:49:00 Part 70 App A (B)(2) Degraded Safety Equipment ENS 445842008-10-21T17:02:00021 October 2008 17:02:00 Part 70 App A (B)(2) Irofs Failure in Area 600 ENS 441042008-03-28T14:00:00028 March 2008 14:00:00 Part 70 App A (B)(2) Filters Not Scanned Properly for Activity Prior to Packaging ENS 415232005-03-24T19:00:00024 March 2005 19:00:00 Part 70 App A (B)(2)
2022-10-05T19:00:00 | |