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| Entered date | Event description | |
|---|---|---|
| ENS 48522 | 20 November 2012 11:02:00 | At 1625 CST on 11-19-12, Electrical Maintenance and Power Operations were in the process of changing a circuit breaker in the C-409 facility which supplies power to the C-409 Criticality Accident Alarm System (CAAS) Uninterruptable Power Supply (UPS). This UPS supplies power to the C-409 CAAS horns. Procedure CP2-CO-ON3031 was being utilized and the CAAS Horn Power UPS was being monitored continuously to maintain the CAAS operable. As soon as the breaker was opened it was identified that the UPS failed to throw over to battery power. At that point the breaker was re-closed and AC power restored to the CAAS horns. The time that AC power was off the CAAS horns was approximately 3-5 seconds. There were no fissile material operations in progress in the C-409 facility. This event is reportable as a 24 hour event in accordance with 10CFR76.120(c)(2)(i). This is an event in which equipment is disabled or fails to function as designed when: a.) the equipment is required by a TSR (Technical Safety Requirements) to prevent releases, prevent exposures to radiation and radioactive materials exceeding specified limits, mitigate the consequences of an accident, or restore this facility to a pre-established safe condition after an accident; b.) the equipment is required by a TSR to be available and operable and either should have been operating or should have operated on demand, and c.) no redundant equipment is available and operable to perform the required safety function. The NRC Senior Resident Inspector has been notified of this event. |
| ENS 47176 | 19 August 2011 16:26:00 | At 0815 CDT on 08-19-11, a Chemical Operations First Line Manager discovered that during disassembly of a single Seal Exhaust/Wet Air (SX/WA) pump, pump housing subcomponents (i.e. two piston slides and a cam) were placed within 2 feet of the internal oil separators. Nuclear Criticality Safety Approval (NCSA) GEN-011 requires a minimum 2-foot edge-to-edge spacing between pump housing subcomponents and internal oil separators. The purpose of this control is to ensure interaction between grossly contaminated fissile items is minimized during movement and storage. The Plant Shift Superintendent and the NCS group were notified and access to the area was controlled. Since one leg of double contingency was lost, this is being reported to the NRC as a 24-hour Event Report in accordance with NRC BL 91-01, Supplement 1. The NRC Senior Resident Inspector has been notified of this event. PGDP Problem Report No. ATRC-11-2161 PGDP Event Report No. PAD-2011-13 POTENTIAL CRITICALITY PATHWAYS INVOLVED: In order for a criticality to be possible, the components would have to be grossly contaminated and brought together in a geometry capable of supporting a criticality and an additional spacing violation would have to occur before a criticality is possible. CONTROLLED PARAMETERS: Double contingency is maintained by implementing controls on geometry and interaction. ESTIMATED AMOUNT, ENRICHMENT, FORM OF LICENSED MATERIAL : Uranium contaminated oil. Product withdrawal assay at the time of the event was less than 4.95 wt% U235. The pump components were not grossly contaminated. NUCLEAR CRITICALITY SAFETY CONTROL(S) OR CONTROL SYSTEM(S) AND DESCRIPTION OF THE FAILURES OR DEFICIENCIES: The first leg of double contingency relies on the geometry of the seal exhaust/wet air pump components. The pump components are controlled as safety related items. This control was not violated. Therefore, this leg of double contingency was maintained. The second leg of double contingency relies on minimizing interaction between internal oil separators and pump housing subcomponents. Interaction is controlled by maintaining a minimum 2-foot edge-to-edge spacing between pump internal oil separators and pump housing subcomponents. The pump housing subcomponents were placed within 2 feet of the internal oil separators in violation of this control. The interaction parameter was not maintained; therefore this leg of double contingency was not maintained. Double contingency was not maintained because the interaction parameter was not maintained. CORRECTIVE ACTIONS TO RESTORE SAFETY SYSTEMS AND WHEN EACH WAS IMPLEMENTED: 1. Control Access to the area. This was completed at 0845 CDT on 08/19/11. 2. Move one item at a time such that the spacing between the pump housing subcomponents and the internal oil separators is always increasing until a minimum 2-foot edge-to-edge spacing has been established. This was completed at 1445 CDT on 08/19/11. 3. Upon establishing the proper spacing between the pump housing subcomponents and the internal oil separators, the exclusion zone may be removed. This was accomplished at 1450 CDT on 08/19/11. |
| ENS 46592 | 4 February 2011 09:05:00 | At 0930 CST on 02-03-11, the Plant Shift Superintendent (PSS) was notified that a steam condensate line broke above the C-310 withdrawal room and water leaked through the ceiling into the withdrawal room on the ground floor. Water accumulated greater than 0.5 inch in depth in the diked area above the withdrawal room in violation of NCSA (Nuclear Criticality Safety Approval) 310-004. NCSA 310-004 requires that open containers with volumes greater than 5.5 gallons shall not contain pre-existing moderator greater than 0.5 inches in depth. During the walk down, it was discovered that the sprinkler heads currently installed above the withdrawal room are rated at 160F in violation of the NCS (Nuclear Criticality Safety) limit. NCSE (Nuclear Criticality Safety Evaluation) 032 requires the minimum activation temperature to be no lower than 200F. The sprinkler system was taken out of service and drained at 2131 CST on 02-03-11 and the level of water accumulated in the diked area was verified to be less than 0.5 inches at 0426 CST on 02-04-11. Since one leg of double contingency was lost, this is being reported to the NRC as a 24-hour Event Report in accordance with NRC BL 91-01 Supplement 1. The NRC Senior Resident Inspector has been notified of this event. SAFETY SIGNIFICANCE OF EVENTS The first leg of double contingency is based on preventing a release of fissile material greater than the safe mass of uranium. This event did not release fissile material greater than the safe mass of uranium. POTENTIAL CRITICALITY PATHWAYS (BRIEF SCENARIO(S) OF HOW CRITICALITY COULD OCCUR) In order for a criticality to be possible, a large UF6 release containing greater than a critical mass of uranium would have to occur and accumulate greater than the critical configuration. CONTROLLED PARAMETERS (MASS, MODERATION, GEOMETRY, CONCENTRATION, ETC.) The two process conditions relied upon for double contingency are mass and geometry. ESTIMATED AMOUNT, ENRICHMENT, FORM OF MATERIAL (INCLUDE PROCESS LIMIT AND % WORST CASE CRITICAL MASS) Product withdrawal assay at the time of the event was less than 4.95 wt% U235. However, no UF6 release occurred. NUCLEAR CRITICALITY SAFETY CONTROL(S) OR CONTROL SYSTEM(S) AND DESCRIPTION OF THE FAILURES OR DEFICIENCIES The first leg of double contingency is based on preventing a release of fissile material greater than the safe mass of uranium. Since a UF6 release containing greater than the safe mass has not occurred, the mass parameter has maintained. The second leg of double contingency limiting moderating liquids in open containers to less than 0.5 inches and requiring the sprinkler head activation temperature to greater than 200F. Since the diked area above the withdrawal room did accumulate water level greater than 0.5 inches, the control was violated. Additionally, since the installed sprinkler heads activation temperature is less than 200F, a design feature of NCSE 032 was violated. Therefore, double contingency was not maintained. CORRECTIVE ACTIONS TO RESTORE SAFETY SYSTEMS AND WHEN EACH WAS IMPLEMENTED Shiftly checks of the diked area above the withdrawal have been initiated to ensure water level is not accumulating. The condensate leak above the withdrawal room was repaired and solution level verified to be less than 0.5 inches (0426 (CST) on 2/4/11). The sprinkler systems associated with the sprinkler heads above the withdrawal room have been isolated until the sprinkler heads can be replaced with heads that comply with NCSE 032 (Systems isolated at 2131 (CST) on 2/3/11). |
| ENS 46487 | 17 December 2010 14:12:00 | At 0937 CST, 12/17/2010, the Kentucky Emergency Response Team (Report Number 2321984), the Kentucky Department for Environmental Protection, and the National Response Center (Report Number 962502) were notified of the following issue: a diesel fuel oil leak occurred from a pressure indicating line from storage tank located at (Bldg) C-600. The amount of diesel fuel that leaked from the storage tank is greater than the reportable quantity of 75 gallons. The secondary containment drain valve leaked which allowed the diesel fuel to reach the oil containment underflow dam at outfall 008. The diesel fuel is currently contained in the oil containment underflow dam. The effluent from outfall 008 has been tested and does not contain any detectable diesel fuel. Additionally, no visible sheen was observed from the effluent from outfall 008. Cleanup of the diesel fuel is in progress. This event is reportable as 'USEC shall notify NRC of any event or situation, related to the health and safety of the public or on-site personnel, or protection of the environment, for which a news release is planned or notification to other government agencies has been or will be made. Such an event may include an on-site fatality or inadvertent release of radioactively contaminated materials.' The NRC Resident Inspector has been notified of this event. PGDP Event Report No. PAD-2010-13. |
| ENS 45527 | 29 November 2009 13:01:00 | At 1850 CST, on 11/28/09 the Plant Shift Superintendent (PSS) was notified that the C-333 Unit 6 Cell 5 UF6 Release Detection (PGLD) System was inoperable due to loss of power to the Area Control Room (ACR) alarm for this system. The purpose of the PGLD System is to detect a UF6 release and alert operators in the ACR by sounding an alarm. At the time this was discovered, G-333 Unit 6 Cell 5 was operating above atmospheric pressure. TSR 2.4.4.1 requires that at least the minimum number of detector heads in the cell are operable during steady state operations above atmospheric pressure. With the Unit 6 Cell 5 PGLD system inoperable, none of the required heads were operable. This PGLD System was declared inoperable, TSR LCO 2.4.4.1.B.1 was entered and a continuous smoke watch was put in place within one hour. Troubleshooting was initiated, a ground was discovered on the alarm circuit, the ground was isolated, and the system was tested and declared operable at 2305 (CST). This event is reportable as a 24 hour event in accordance with 10CFR76.120(c)(2)(i). This is an event in which equipment is disabled or fails to function as designed when: a) the equipment is required by a TSR to prevent releases, prevent exposures to radiation and radioactive materials exceeding specified limits, mitigate the consequences of an accident, or restore this facility to a pre-established safe condition after an accident; b) the equipment is required by a TSR to be available and operable and either should have been operating or should have operated on demand, and c) no redundant equipment is available and operable to perform the required safety function. The NRC Resident Inspector has been notified of this event. |
| ENS 45413 | 5 October 2009 15:55:00 | On 10/04/2009 at 1500 C-331 unit 2 cell 2 was being charged and placed on stream and had just gone above atmospheric pressure when a Maintenance Mechanic observed smoke coming from the cell instrument cubicle and determined it to be UF6 outleakage from cell process instrumentation. To stop the release the cell was immediately taken back below atmospheric pressure. Investigation revealed that a UF6 release had occurred inside the instrument cubicle. The amount of material released has not yet been determined. Decontamination is underway but has not been completed inside the cabinet. The area outside the cabinet has been decontaminated. No injuries or personnel exposure occurred as a result of this event. This is being reported based on 10 CFR 76.120(c)(1)(i) (unplanned contamination event). PGDP Problem Report Nos. ATRC-09-2435; PGDP Event Report No. PAD-2009-016. Responsible Division: Operations PGDP Assessment and Tracking Report No. ATR-09-2435; PGDP Event Report No. PAD-2009-16; Worksheet No. Responsible Division: Operations The NRC Senior Resident Inspector has been notified of this event. Decontamination is expected to be completed on 10/6/2009.
After further review, it was determined that the amount of contamination was significantly less than five times the lowest annual limit on intake specified in Appendix B to Section 20.1001-20.2402 of 10CFR20 for the material. The licensee notified the NRC Resident Inspector. Notified the R2DO (Guthrie) and NMSS (Whaley). |
| ENS 44820 | 31 January 2009 13:22:00 | At 0150 CST, on 01-31-09 the Plant Shift Superintendent (PSS) was notified that a Criticality Accident Alarm System (CAAS) trouble alarm had actuated for the C-409 (Stabilization Building). The PSS dispatched personnel to investigate and discovered that a circuit breaker had tripped causing a loss of power to the CAAS horn uninterruptible power supply (UPS). Further investigation revealed that the output of the UPS was off. This caused loss of CAAS audibility for C-409 and TSR LCO 2.6.4.1b was immediately entered. There were no fissile material operations in progress and all personnel in the affected area had a radio in constant communication with the Central Communications Facility satisfying the required actions of TSR 2.6.4.1 b. The circuit breaker that tripped was closed, the UPS was turned back on, and TSR 2.6.4.1b was exited at 0317 hours. This event is reportable as a 24 hour event in accordance with 10CFR 76.120(c)(2)(i). This is an event in which equipment is disabled or fails to function as designed when: a.) the equipment is required by a TSR to prevent releases, prevent exposures to radiation and radioactive materials exceeding specified limits, mitigate the consequences of an accident, or restore this facility to a pre-established safe condition after an accident; b.) the equipment is required by a TSR to be available and operable and either should have been operating or should have operated on demand, and c.) no redundant equipment is available and operable to perform the required safety function. The NRC Senior Resident Inspector has been notified of this event. PGDP Assessment and Tracking Report No. ATR-09-0203; PGDP Event Report No. PAD-2009-02 |
| ENS 44515 | 23 September 2008 15:22:00 | At 0937 CDST, on 09/23/08 the Plant Shift Superintendent (PSS) was notified that C-315 (tails withdrawal facility) had lost power due to a fault on a 14 KV feeder. As a result of the power loss, the C-315 High Voltage Process Gas Leak Detection (PGLD) System was rendered inoperable. This PGLD System contains detectors that cover the C-315 UF6 condensers, accumulators, and piping heated housing. At the time of this loss of power, these areas were operating above atmospheric pressure. TSR 2.3.4.4 requires that all of detector heads in this system be operable during operations above atmospheric pressure. This PGLD System was declared inoperable. TSR LCO 2.3.4.4.A.1 was entered and a continuous smoke watch was put in place within one hour. This event is reportable as a 24 hour event in accordance with 10CFR 76.120(c)(2)(i). This is an event in which equipment is disabled or fails to function as designed when: a.) the equipment is required by a TSR to prevent releases, prevent exposures to radiation and radioactive materials exceeding specified limits, mitigate the consequences of an accident, or restore this facility to a pre-established safe condition after an accident; b.) the equipment is required by a TSR to be available and operable and either should have been operating or should have operated on demand; and, c.) no redundant equipment is available and operable to perform the required safety function. Once the source of the fault was identified, power was restored to the C-315 facility. The High Voltage PGLD system was tested, and the system was declared operable. Power was restored at 1039 hours and the High Voltage PGLD System was declared operable at 1118 hours. The NRC Resident Inspector has been notified of this event. PGDP Assessment and Tracking Report No. ATR-08-2371; PGDP Event Report No. PAD-2008-29; Responsible Division: Operations. |
| ENS 44223 | 19 May 2008 17:20:00 | At 1721 hours on 5-18-08 the Plant Shift Superintendent was notified that violation of a nuclear criticality safety approval (NCSA) had occurred. At 1720 hours on 5-17-08, the coolant system for (DELETED) was evacuated using an R-114 evacuation pump. The recirculating cooling water (RCW) condenser for that cell had not been disconnected or vented before evacuation of coolant system vapor or air, in violation of NCSA CAS-21 Rev. 01, 'Operation and Shutdown of the Diffusion Cascade,' Control 3.2.3. That control states: 'The RCW condenser shall be disconnected or vented before coolant vapor is evacuated.' This control minimizes the amount of water that is available to moderate fissile material that might be present in the UF6 region of the process gas cooler. Coolant system leak rate testing results were logged as of 2100 hours on 5-18-08 showing the coolant system to be evacuated to 30" vacuum and holding. At that pressure the system would be below the vapor pressure of water. Therefore, the coolant system being evacuated to that level and holding would indicate that no liquid water was present in the coolant system. The system being evacuated and holding proves that not only was the condenser free of any significant RCW to coolant leaks, but the process gas cooler was also essentially leak-tight. The NRC Senior Resident Inspector has been notified of this event. PGDP Problem Report No. ATRC-08-1471: PGDP Event Report No. PAD-2008-18; NRC Worksheet No. 44223 This violation represents a significant breach of NCS administrative controls for this operation: however, the safety significance of the as-found condition was quite low. The worst case enrichment (DELETED) at this location was just above the minimum fissile enrichment, so that a very large mass of optimally moderated uranium (more than (DELETED)) would have been needed for a criticality to be possible. Moderation would have required excessive water intrusion into the coolant system through condenser tube leaks, and subsequent water intrusion into the process gas region of the cooler/converter through a concurrent process gas cooler lube leak. Even though NCS Control 3.2.3 was violated, no significant water intrusion occurred. Although the as-found condition of the coolant system did not contain water, the parameter is considered lost since the typical condition of condenser tubes would be expect to result in water intrusion and would not represent a reliable barrier to in-leakage. Double contingency was re-established within four hours of discovery by confirming the coolant system was drained of any possible liquid. At 1615 hours on 5-18-08 the air evacuation pumps were isolated from (DELETED) coolant system, which is the last point at which any potential liquid would have been drained from the coolant system. The condenser venting was completed at 2050 hours on 5-18-08. Coolant system leak rate completed at 2100 hours on 5-18-08 confirmed 30" vacuum and holding to show the condenser and process cooler were leak-tight. |
| ENS 44202 | 12 May 2008 15:34:00 | At 1230 CDST, on 05-12-08 the Plant Shift Superintendent (PSS) was notified that an alarm was received for the C-331 Unit 3 Cell 5 UF6 Release Detection (PGLD) System. Operators responded and found that the READY and MANUAL lights for this system were not illuminated. This PGLD System contains detectors that cover C-331 Unit 3 Cell 5 and Sections 2 and 3 of the cell bypass piping. At the time of this alarm, unit 3 Cell 5 and some areas of Sections 2 and 3 of the cell bypass were operating above atmospheric pressure. TSR 2.4.4.1 requires that at least the minimum number of detector heads in the cell and in each defined section of the cell bypass are operable during steady state operations above atmospheric pressure. With the Unit 3 Cell 5 PGLD system inoperable, none of the required cell heads and only 2 of the required 3 heads in Sections 2 and 3 of the cell bypass were operable. This PGLD System was declared inoperable, TSR LCO 2.4.4.1.A.1 and 2.4.4.1.C.1 were entered and a continuous smoke watch was put in place within one hour. Engineering has determined that the system would not have been able to perform its intended safety function when this alarm came in. This event is reportable as a 24 hour event in accordance with 10 CFR 76.120(c)(2)(i). This is an event in which equipment is disabled or fails to function as designed when: a.) the equipment is required by a TSR to prevent releases, prevent exposures to radiation and radioactive materials exceeding specified limits, mitigate the consequences of an accident, or restore this facility to a pre-established safe condition after an accident; b.) the equipment is required by a TSR to be available and operable and either should have been operating or should have operated on demand, and c.) no redundant equipment is available and operable to perform the required safety function. The NRC Senior Resident Inspector has been notified of this event. PGDP Assessment and Tracking Report No. ATR-08-1412; PGDP Event Report No. PAD-2008-14; Worksheet No. Responsible Division: Operations |
| ENS 44056 | 12 March 2008 13:44:00 | Between 1979 and 1985, approximately 960 thin-walled cylinders were obtained by Paducah Gaseous Diffusion Plant (PGDP), transferred to Allied Chemical, and filled with near-normal assay material as part of a strategic feed reserve. These cylinders were transferred to Oak Ridge Gaseous Diffusion Plant (ORGDP) for storage. They were shipped back to PGDP beginning in the early 1990s. All but three of these cylinders have been fed. In early 2003, the Nuclear Criticality Safety Evaluation (NCSE) was revised to evaluate the washing of the heeled cylinders. At 1457 hours on 3/11/2008, the Plant Shift Superintendent was notified that two non-fissile cylinders were identified in the ORGDP strategic reserve category that had a weight change while stored at ORGDP in violation of the NCSE for the C-400 cylinder wash operation. One leg of double contingency is based on it being unlikely that cylinders in this category would be introduced into the process while stored at ORGDP. The weight change indicated that these cylinders were introduced into the process at ORGDP. The other leg of double contingency is based on two individuals independently verifying that the cylinder had no weight change while it was stored at ORGDP. This control was not violated. The NCSE concern associated with these cylinders entering the process is the potential to introduce fissile material into the cylinder while stored at ORGDP and subsequent washing at the non-fissile C-400 cylinder wash. Even though one leg of double contingency was lost, these cylinders were not washed. The cylinder heel of one cylinder is approximately 11 lbs. at 0.711 wt% U-235 in solid form and the other cylinder is approximately 39 lbs. at 0.7 wt% U-235 in solid form. The NRC Senior Resident Inspector has been notified of this event. PGDP Problem Report No. ATRC-08-0730; PGDP Event Report No. PAD-2008-06. |
| ENS 43801 | 21 November 2007 17:42:00 | At 2028 CDST, on 11-20-07 the Plant Shift Superintendent (PSS) was notified that the C-333 Unit 6 Cell 7 UF6 Release Detection (PGLD) System failed to function when performing the twice per shift test firing. The test firing of the PGLD detector heads is required per TSR-SR 2.4.4.1-1. This PGLD System contains detectors that cover C-333 Unit 6 Cell 7, Section 3, and Section 4 of the cell bypass piping. At the time of this failure, unit 6 cell 7 and some areas of Section 3 and Section 4 of the cell bypass were operating above atmospheric pressure. TSR 2.4.4.1 requires that at least the minimum number of detector heads in the cell and in each defined section of the cell bypass are operable during steady state operations above atmospheric pressure. With the Unit 6 Cell 7 PGLD system inoperable, none of the required cell heads and only 2 of the required 3 heads in Section 3 and Section 4 of the cell bypass were operable. This PGLD System was declared inoperable, TSR LCO 2.4.4.1.B.1 and 2.4.4.1.C.1 was entered and a continuous smoke watch was put in place within one hour. Troubleshooting indicated the failure was not similar to writing failures recently experienced on other PGLD systems. The two components most susceptible to failure have been replaced and investigations continue into root cause. The system had functioned correctly when the previous test firing was performed at 1430 hours on 11-20-07. However, since the failure potentially occurred prior to the test firing at 2028 hours the event is being reported as a 24 hour event in accordance with 10 CFR 76.120(c)(2)(i). This is an event in which equipment is disabled or fails to function as designed when (a) the equipment is required by a TSR to prevent releases, prevent exposures to radiation and radioactive materials exceeding specified limits, mitigate the consequences of an accident, or restore this facility to a pre-established safe condition after an accident; (b) the equipment is required by a TSR to be available and operable and either should have been operating or should have operated on demand, and (c) no redundant equipment is available and operable to perform the required safety function." The NRC Resident Inspector has been notified of this event. |
| ENS 41465 | 7 March 2005 08:50:00 | The following information was obtained from the Paducah Gaseous Diffusion Plant via facsimile (text in quotes); At 1140, on 03-6-05, the Plant Shift Superintendent was notified that the C-360 Toll and Transfer Facility Zone 1 PGLD (Process Gas Leak Detection) system (Q Safety System) on # 4 Sample Cabinet actuated. The operators evacuated to the proper assembly point. The emergency Squad entered the building and sampled for Hydrogen Fluoride and sample results were positive. The autoclave and sample cabinet UF6 lines were evacuated and purged. Operators gave bioassay sample and the results indicated an uptake of Uranium. Event investigation is ongoing. This event is reportable as a 24 hour event in accordance with the plant procedure UE2-RA-RE1030, Nuclear Regulatory Event Reporting (no 10 CFR section is referenced). An automatic or manual actuation of a Q safety system that results from an event or condition that has the potential for significant impact on the health or safety of personnel. Event having the potential for significant impact are those events where actual plant conditions existed that the system was designed to protect against. The NRC Senior Resident Inspector has been notified of this event. PGDP Problem Report No. ATRC-05-0892; PGDP Event Report No. PAD-2005-07; Worksheet Responsible Division: Operations Atmospheric leak was on line between the autoclave and the sample cabinet. C-360 Toll and Transfer Facility is a stand alone facility. Operations were secured and two individuals had uptakes (Minimal risk): One had an uptake of 7.3 mg/ liter uranium and the other individual had an uptake level of 5.2 mg/ liter uranium. The limit is 5.0 mg/ liter uranium. There was no smoke (very small leak) and a slight smell of Hydrogen Fluoride caused by the leak.
This report is being retracted based on the following information received from the regulatee via fax: This report is being retracted. Subsequent analysis of the actuation determined that the PGLD head actuation occurred from a minor incidental release of UF6 from a valve packing that is not considered a breach of the pressure boundary. Reporting is required if the safety system actuates in response to a condition that the system is designed against and that could result in significant impact on the safety and health of personnel. The PGLD systems safety function, described in the PGDP accident analysis, is to mitigate pigtail/line failures outside of the autoclave that could cause offsite consequences. This incidental UF6 leak did not have the potential for significant impact on personnel or offsite consequences and is not what the safety system is designed to protect against. Thus, the reporting criteria were not met in this case. (The) resident inspector has been notified of this retraction. Notified R2DO (Ayres) and NMSS (Essig). |
| ENS 41223 | 24 November 2004 13:39:00 | At 1325 (CST) on 11-23-04, the Plant Shift Superintendent (PSS) was notified of a failure of the C-310 High Voltage UF6 Release Detection System. The High Voltage UF6 detection system was disabled due to loss of power. Power was lost when a circuit breaker was tripped to de-energize an auxiliary substation that faulted and caused a fire. This High Voltage UF6 Release System is designed to activate alarms to alert operators in the event of a UF6 release. The PSS declared the system inoperable and TSR LCO 2.3.4.4.A actions were implemented to post a continuous smoke watch in the affected area. The event is reportable as a 24 hour event, as required by 10 CFR 76.120(c)(2)(i); An event in which equipment is disabled or fails to function as designed when the equipment is required by a TSR to prevent releases, prevent exposures to radiation and radioactive materials exceeding specified limits, mitigate the consequences of an accident, or restore this facility to a preestablished safe condition after an accident. The equipment was required by TSR to be available and operable and no redundant equipment was available to perform the required safety function. In addition, the loss of power caused the Low Voltage UF6 Detection System to isolate the C-310 withdrawal positions as designed. The substation fault and subsequent fire did not result in a release of radioactive material. The Senior NRC Resident Inspector has been notified of this event. |
| ENS 40805 | 10 June 2004 16:37:00 | At 1550 on 6-09-04, the Plant Shift Superintendent was notified of a failure of a Safety Related Item (SRI) relied upon in Nuclear Criticality Safety Evaluation (NCSE) 052 'Enrichment Cascade During Normal Operations at the Paducah Gaseous Diffusion Plant.' At 0553 hours on 4-23-04, when responding to alarms on Cell 6 in Building C-310, the second bank of motors could not be shut down using the manual motor trip system. Operators opened the Transformer Secondary Breaker (TSB) as an alternate means to shut down the motors. The manual motor trip system is credited to mitigate/minimize the consequences or extent of a Hot Metal Reaction (HMR). PGDP Problem Report No, ATRC-04-2299; PGDP Event Report No. PAD-2004-17; Event Worksheet (NRC Event Number): # 40805, Responsible Division: Operations. SAFETY SIGNIFICANCE OF EVENTS: Minimal. There are multiple methods capable of shutting down equipment suspected of undergoing a HMR. The compressor motors were shut down using one of these methods. The shutdown was accomplished within 2 minutes. POTENTIAL CRITICALITY PATHWAYS INVOLVED (BRIEF SCENARIOS) OF HOW CRITICALITY COULD OCCUR: In order for a criticality to occur, the equipment would have had to be involved In the initiating event of a HMR. There were no indications of a HMR. Additionally, the HMR event would need to have occurred with a significant inventory of UF6 present. The event was in the purge cascade having UF6 concentrations in the ppm range. Therefore, there is no credible pathway to criticality for this incident. CONTROLLED PARAMETERS (MASS, MODERATION. GEOMETRY, CONCENTRATION, ETC): This scenario is singly contingent based on moderation control. ESTIMATED AMOUNT, ENRICHMENT, FORM OF LICENSED MATERIAL (INCLUDE PROCESS LIMIT AND % WORST CASE CRITICAL MASS): The event was in the purge cascade having UF6 concentrations in the ppm range at an enrichment of less than (DELETED) wt % 235U. NUCLEAR CRITICALITY SAFETY CONTROL(S) OR CONTROL SYSTEM(S) AND DESCRIPTION OF THE FAILURES OR DEFICIENCIES: This scenario is singly contingent based on moderation control. The scenario indicates that it is unlikely for a significant HMR to occur resulting in a cooler/cascade breach with subsequent sprinkler activation based on historical operations. The manual motor trip system is credited to mitigate/minimize the consequences or extent of a HMR. The credited trip failed to perform its intended function. Although the credited trip failed, alternative methods were used to shutdown the cell, thereby satisfying the intent of the administrative portion of the control. Also, no HMR, cell breach, or sprinkler activation occurred. Although the SRI failed, the moderation parameter was maintained. CORRECTIVE ACTIONS TO RESTORE SAFETY SYSTEMS AND WHEN EACH WAS IMPLEMENTED: The cell was shut down using alternate means within 2 minutes. The manual motor trip system was declared inoperable at 0700 on 4-23-04 and repaired. The NRC Resident Inspector has been notified of this event. |
| ENS 40438 | 12 January 2004 14:17:00 | At 1810 (CST) on 01-11-04 the Plant Shift Superintendent (PSS) was notified of a failure of the C-360 #4 Autoclave High Pressure Isolation System. Water was observed leaking from the autoclave head-to-shell interface near the six o'clock position shortly after initiating a cylinder heat cycle. At the time of discovery, the autoclave was in TSR mode 5 and the High Pressure Isolation System was required to be operable while in this mode. This system is designed to provide containment of the autoclave and prevent an external release of UF6 during a system breach while heating a UF6 cylinder. The PSS declared the system inoperable and TSR LCO 2.1.3.1 .C1 actions were implemented to remove the autoclave from service and place it in Mode 2, 'Out of Service.' The event is reportable as a 24 hour event, as required by 10 CFR 76.120 (c)(2)(i); An event in which equipment is disabled or fails to function as designed when the equipment is required by a TSR to prevent releases, prevent exposures to radiation and radioactive materials exceeding specified limits, mitigate the consequences of an accident, or restore this facility to a preestablished safe condition after an accident. The equipment was required by TSR to be available and operable and no redundant equipment was available to perform the required safety function. PGDP Problem Report No. ATR-04-0095; PGDP Event Report No. PAD-2004-02; Event Worksheet Responsible Division; Operations Operations has notified the Senior NRC Resident Inspector.
This event has been retracted and the following update information provided: Subsequent to the report, plant engineers inspected the autoclave sealing surfaces and O-ring. The O-ring and autoclave sealing surfaces were found to be in good condition with no problems noted that would cause the water leak observed by the operators. The autoclave was subjected to a head-to-shell alignment (pinch) test. The test determined that the autoclave sealing surfaces were within acceptable alignment tolerances and no adjustments were made. To determine the autoclave's ability to perform its containment function, the TSR surveillance (pressure decay test) was performed with the autoclave In the as-found condition, i.e., without any maintenance or changes in the autoclave condition. The autoclave passed this test with approximately half the maximum allowable leak rate. The successful performance of the autoclave pressure decay test indicates that the autoclave HPIS (High Pressure Isolation System) would have been able to perform its designed containment function on January 11, 2004, had it been necessary. Thus, the 10CFR76.120 reporting criteria were not met. The NRC Resident Inspector has been notified of this retraction. PGDP Problem Report No. ATR-04-0095; PGDP Event Report No. PAP-2004-02; Event Worksheet 40438 Responsible Division: Operations Notified R2DO (Robert Haag), NMSS (Tom Essig), DIRO (Richard Wessman). |