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| Entered date | Event description | |
|---|---|---|
| ENS 53892 | 22 February 2019 17:40:00 | It was discovered that the calculation which determines the periodicity for performing the IROFSC22 (Item Relied On For Safety) surveillance contains an error. IROFSC22 is a mass balance enrichment control. It is unclear if the calculation error causes the surveillance periodicity to fall outside of the minimum time to achieve a safe mass. UUSA (Urenco USA) has since changed the IROFS surveillance to a more frequent periodicity which has been determined to be sufficient. Although no event has occurred and the IROFS remain sufficient to meet the performance requirements of 10CFR70.61, as a conservative measure, UUSA is reporting this condition due to the facility being in a state that is different from that analyzed in the Integrated Safety Analysis and in accordance with 10 CFR 70 Appendix A(b)(1) The plant is in a safe condition. The licensee will notify NRC Region 2 (Lopez). |
| ENS 53869 | 12 February 2019 13:55:00 | EN Revision Text: LOSS OR DEGRADATION OF SAFETY ITEMS (On February 11, 2019 at 1519 MST,) it was discovered that the calibration certificates for Measuring and Testing Equipment (M&TE) used to perform temperature trip IROFS (Items Relied On For Safety) surveillances, only had 1 set of calibration data. The instruments have an internal temperature sensor and an external input for temperature. Previously, the IROFS surveillances for IROFS 1, 2, 4, 5, 11, 43, C15, and C16 were performed using the external input. An external vendor, that performs the calibration for this M&TE, confirmed that the calibration had only been performed on the internal temperature sensor. This issue of how ATC-1 and ATC-2 (Jofra brand dry-block temperature calibrators) were calibrated is not currently an issue, as UUSA (URENCO USA) now only uses the Jofras as a heat source and uses a separately calibrated resistance temperature detector (RTD) and display for IROFS surveillances. Further investigation findings showed that a number of UF6 stations had not had their scheduled surveillance with the new method using a separately calibrated RTD. In total, 25 stations had their required annual IROFS surveillances performed with M&TE equipment which used an input that was not properly calibrated. The plant is in a safe condition. The licensee will be contacting Region II.
Event Notification (EN) 53869, made February 11, 2019, reported a condition in accordance with Appendix A to 10 CFR 70 (b)(2). The notification described degradation of items relied on for safety (IROFS) that could potentially result in failure to meet the performance requirements of 10 CFR 70.61. This notification was prompted by improperly calibrated Measuring and Testing Equipment (M&TE) which was used to perform surveillance activities for IROFS 1, 2, 4, 5, 11, 43, C15, and C16. At the time of the report, functionality of the IROFS' Active Engineered Controls within the acceptable parameters could not be verified. Therefore, URENCO USA (UUSA) conservatively assumed a degradation of IROFS resulting in failure to meet the performance requirements of 10 CFR 70.61. Since the time of the initial report, UUSA has re-performed surveillance activities using approved methods and obtained as found tolerances of the Active Engineered Controls for all of the affected stations. With this supporting data, UUSA has concluded that the affected IROFS were, at all times, operating below the maximum IROFS trip set point. The operating events using improperly calibrated M&TE can be categorized as events with low safety significance since they would not have resulted in breached/ruptured UF6 cylinders. Cylinder integrity would not have been compromised, as the temperature sensors were found to be available and reliable to perform their safety function. This correlates with a low consequence event. Based on engineering determinations and as found trip set points, the condition reported in EN 53869 did not result in failure to meet the performance requirements of 10 CFR 70.61. Therefore, the reported condition did not exceed the criteria which would necessitate an event be reported to the NRC. URENCO USA hereby retracts EN 53869. The licensee has notified Region II. Notified R2DO (Desai) and NMSS Events Notification (email). |
| ENS 53046 | 31 October 2017 12:02:00 | 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). |