Semantic search
| Start date | Reporting criterion | Title | Event description | System | LER | |
|---|---|---|---|---|---|---|
| ENS 56550 | 1 June 2023 08:39:00 | 10 CFR 70.50(b)(2) | Partial Loss of Criticality Accident Alarm System | The following information was provided by the licensee via email: On June 1, 2023, during inclement weather, a Phase 2 CAAS (Criticality Accident Alarm System) detector fault was received. Troubleshooting efforts indicated two CAAS nodes are impacted and SBM1005 (Process Services Corridor) was evacuated. The affected detectors are located in the north end of the SBM1005 Process Services Corridor. Compensatory measures are implemented in the affected area to support maintenance troubleshooting efforts. UUSA is reporting this event per 10 CFR 70.50(b)(2). | ||
| ENS 55564 | 5 November 2021 18:07:00 | 10 CFR 70.50(b)(2) | Loss of High Radiation Audible Alarm | On November 5th, 2021, (1207 MDT) it was identified that a portable Area Radiation Monitor (ARM), which was performing the 10 CFR 70.24 safety function of the Criticality Accident Alarm System (CAAS) to energize clearly audible alarm signals if accidental criticality occurs, had been removed from the area in error. On July 20th, 2021, during routine CAAS maintenance, UUSA (Urenco USA) staff identified an area in which a CAAS alarm was not clearly audible. UUSA arranged the ARM as a compensatory measure which achieves an equivalent 10 CFR 70.24 safety function in the affected area. UUSA reported this event to the NRC under Event Notification 55480 in accordance with 10 CFR 70.50(b)(2) in which equipment is disabled or fails to function as designed when required by regulation. Removal of this ARM resulted in an inability for radiation detectors to energize clearly audible alarm signals if accidental criticality occurs in the affected area. UUSA hereby reports this event in accordance with 10 CFR 70.50(b)(2), in which equipment is disabled or fails to function as designed when required by regulation (10 CFR 70.24). The licensee will notify the NRC Region 2 office.
On November 5th, 2021, Louisiana Energy Services, LLC, dba Urenco USA, submitted Event Notification (EN) 55564 to the NRC Emergency Operations Center. This event notified the NRC of a 24 hour reportable event where a portable Area Radiation Monitor (ARM) performing a 10 CFR 70.24 safety function of the Criticality Accident Alarm System (CAAS) was removed from service. UUSA reported this event in accordance with 10 CFR 70.50(b)(2), in which equipment is disabled or fails to function as designed when required by regulation (10 CFR 70.24). Following this event, UUSA staff revised the calculations defining the Immediate Evacuation Zone (IEZ). The location of the ARM was near the edge of the IEZ boundary and the original calculation was completed prior to construction of the facility. The calculation was reviewed to ensure the boundary was still adequate. UUSA determined the boundary remains adequate with the area in question no longer inside the IEZ. The affected location is now outside of the IEZ. The IEZ is an area where personnel could be subject to an excessive radiation dose in the event of a criticality, required by 10 CFR 70.24(b)(1). Therefore, CAAS equipment subject to the event described in EN 55564 was not required to prevent exposures to radiation and radioactive materials exceeding regulatory limits, or to mitigate the consequences of an accident and does not meet the criteria for a reportable event UUSA herby retracts EN 55564. Details related to the revised IEZ boundary determination can be found in UUSA document CALC-S-00150, Rev 1, Immediate Evacuation Zone Calculations at UUSA. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: The licensee will notify the NRC Region 2 office. Notified the R2DO (Miller) and NMSS Events Notification (email) | ||
| ENS 55480 | 20 July 2021 20:01:00 | 10 CFR 70.50(b)(2) | CAAS Alarm Not Clearly Audible | During routine Criticality Accident Alarm System (CAAS) maintenance on July 20, 2021, UUSA ((URENCO USA)) staff identified an area in which the CAAS alarm was not clearly audible. The alarm was (and is) functioning, but not at an adequate level of sound pressure to meet the acceptance criteria. UUSA arranged compensatory measures which achieve an equivalent safety function within 24 hours in the affected area. The affected area was in the Immediate Evacuation Zone (IEZ), outside of the area in which licensed special nuclear material is handled, used, or stored. On September 16, 2021, an NRC inspector conducting an onsite inspection informed UUSA staff that given the potential that the alarm had not been clearly audible for a period of time between surveillances, this event should have been reported within 24 hours to the NRC in accordance with 10 CFR 70.50(b)(2) in which equipment is disabled or fails to function as designed when required by regulation (10 CFR 70.24). The licensee will notify the NRC Region 2.
During the Apparent Cause Evaluation related to Event Notification 55480, an extent of condition was performed. This extent of condition revealed three historical examples of inaudible CAAS alarms that were not reported under 10 CFR 70.50(b)(2) as required by regulation. These conditions occurred on April 12th, 2014, August 15th, 2014, and August 20th, 2015. Corrective actions were implemented for these deficiencies during the approximate time period in which they were identified. The affected systems are currently compliant with 10 CFR 70.24 regulations. Details of this extent of condition are documented in UUSA's Corrective Action Program, EV 148663. The licensee notified NRC Region 2 personnel. Notified R2DO (Miller) and NMSS Event Notifications via email. | ||
| ENS 53604 | 15 September 2018 06:00:00 | Information Only 10 CFR 70.50(b)(2) | Preplanned Outage of a Required Safety Monitoring System | The UUSA (URENCO USA) facility CAAS (Criticality Accident and Alarm System) exists to detect and alarm in the unlikely event of a criticality accident, as required by 10 CFR 70.24, Criticality accident requirements. This monitoring system will be temporarily disabled during planned corrective maintenance activities for approximately thirty minutes, commencing at approximately 0730 MDT, on Saturday, September 15th, 2018. This activity will affect the CAAS in the Separations Building Module (SBM) 1001/1002 and the Cylinder Receipt and Dispatch Building (CRDB). The CAAS in the remaining portions of the facility will be unaffected. Essential personnel will remain inside the controlled access area during the maintenance activities. The populated areas of the facility will be limited to the Security Alarm Station, Operations Control Room, and the Maintenance Area housing the CAAS control cabinets in the Technical Services Building (TSB) where technicians will be needed for this work evolution. CAAS coverage of these populated areas will be provided during the maintenance activity by temporary criticality detection equipment. Compensatory measures will be implemented in accordance with section 3.1.5 of the UUSA Integrated Safety Analysis (ISA) Summary. These measures including evacuation of non-essential personnel from the areas of concern and the Immediate Evacuation Zone (IEZ) before removing the equipment from service, limiting access into facility, and restricting Special Nuclear Material (SNM) movement will be implemented until CAAS coverage is verified operational. UUSA will notify the NRC when CAAS coverage is returned to normal operation. Radiation surveys will be conducted prior to re-entry to confirm acceptable conditions in the area. The licensee has notified the NRC Project Manager.
The Criticality Accident and Alarm System was returned to service at 0930 MDT after the completion of the scheduled maintenance. During the maintenance period, no abnormal radiation readings were observed. Notified R2DO (Ernstes). | ||
| ENS 53046 | 7 September 2017 06:00:00 | 10 CFR 70.50(b)(2) | Wrong Irofs Procedure Followed Prior to Filling Cylinder | The following event occurred on 9/7/17 but was not discovered until 1511 MDT on 10/30/17. Appendix A to 10 CFR 70(b)(2). While performing an extent of condition on a previous condition report in the UUSA (URENCO USA) corrective action program, UUSA discovered a product cylinder that had been introduced to the process inadvertently as a new or washed cylinder when it in fact was a heeled cylinder. The discrepancy caused the incorrect IROFS (Items Relied On For Safety) to be applied when connecting the cylinder to the process; IROFS16a for new/washed cylinders and IROFS16e/f for heeled cylinders. The IROFS applicable (16e/f), administratively limits moderator (hydrogenous) mass in heeled cylinders containing enriched uranic material to ensure sub-criticality by limiting cylinder vapor pressure and heeled 30B cylinder weight. IROFS16e was completed SAT using the IROFS16a surveillance and the Product connect procedure. IROFS16f, an independent weight check and vapor pressure check, was not completed during the cylinder connect. The IROFS performed (16a), administratively limits moderator mass (hydrocarbon oil and water) in new and cleaned 30B cylinders containing enriched uranic material to ensure sub-criticality by allowing no visible oil and by limiting cylinder vapor pressure. Both of the aforementioned IROFS prevent criticality by limiting moderator mass, however the performance is different in heeled cylinders. IROFS16e/f are implemented by independently limiting cylinder vapor pressure and weight prior to introducing product into the cylinder. Cylinder UREU103960 was connected to the process on September 7, 2017, filled with product material, heated, and liquid sampled. A criticality DID NOT occur. Existing sample results show normal for contaminants boron, technetium, and silica. Sample testing for purity showed UF6 at a temperature 24C acceptable per ASTM C996 standards of (greater than) 99.5 (percent). 10 CFR 70.50(c)(1)(iii): (A) The IROFS not performed prevent criticality. No criticality occurred, no radiological hazard, nor chemical hazards were present. (B) No exposure occurred. (C) UUSA Shift Operations inadvertently treated the cylinder with the wrong classification. The pedigree of the cylinder was misinterpreted and the IROFS16a surveillance was performed instead of the correct IROFSI6e/f surveillance. (D) IROFS remain available and reliable to perform their function. IROFS16 series are applicable during cylinder connects and are established by the performer of the cylinder connect evolution. The IROFS are not affected for future cylinder evolutions. (iv) The cylinder is currently inside the Cylinder Receipt and Dispatch Building. No external conditions affect this event. (v) UUSA immediately treated the cylinder as an anomalous condition in accordance with internal procedures and Operations Reporting Manual. The cylinder had been through the sampling process and the results are being reviewed by UUSA NCS/ISA Engineering staff. (vi) No criticality event occurred. The cylinder is in a criticality safety anomalous condition. There are currently no other cylinders immediately adjacent and the area has been roped off. (vii) No emergencies have been, nor will any be declared. (viii) No state or other federal agencies will be notified. (ix) No press releases are planned. SAFETY SIGNIFICANCE OF EVENTS: No Event Occurred SAFETY EQUIPMENT STATUS: The cylinder is in a criticality safety anomalous condition. Existing sample results from cylinder contents are being reviewed. STATUS OF CORRECTIVE ACTIONS: Condition has been entered into facility's Corrective Action Program The licensee will inform NRC Region 2 (Sykes).
11/2/2017 1429 MST Update: Based on existing liquid sample results, conservatively assuming a moderator concentration of 0.5 percent, the filled cylinder's heel meets the acceptance criteria. This demonstrates a criticality event to be highly unlikely and therefore, the anomalous condition was exited at 1242 MST. Notified the R2DO (Ehrhardt), NMSS (via email) and Fuels Group (via email). | ||
| ENS 51593 | 7 December 2015 23:00:00 | 10 CFR 70.50(b)(2) | Crane Item Relied Upon for Safety Never Installed | During unrelated maintenance, it was discovered that the UUSA UBC crane was missing components that are within the IROFS27e, QL1 boundary. These components have been missing since the crane went into operation in early 2015. The IROFS (Item relied upon for safety) has been declared degraded and is currently inoperable, and in a location where it cannot impact licensed material. This IROFS is designed to mitigate the consequences of UF6 release, to meet 10 CFR 70.61 performance requirements. No accident occurred, no release occurred. During the period in which the crane was operating in a degraded state, no design basis accidents occurred, thus there are no actual consequences. The crane had been moved to a safe position in order to perform other repairs (away from licensed material), and it locked in a place, thereby removing applicability of the IROFS. Thus, there is currently no potential for consequences. During unrelated repair activities, it was discovered that the URENCO USA UBC Crane has been in operations since March of 2015 while in a degraded condition. A component within the IROFS QL1 boundary was never installed. This is a sole IROFS to mitigate consequences. There are no other IROFS in place to support this function. Currently there is no analysis available to support the ability of the degraded IROFS to perform its safety function. There were no design basis external events during operation of the crane, nor do any currently exist. The UBC Crane was already locked out for ongoing corrective maintenance, The lockout remains active, and the IROFS is now declared inoperable. The condition was entered into the USA's Correcting Action Program for Evaluation and Corrective Actions. The degraded IROFS has been declared inoperable. No accident sequences occurred. The plant did not enter an emergency classification, nor is one planned. There are no planned notifications other that this event notification to the NRC Operations Center. The NRC Regional Inspector (Munson) was notified. |