ML25140A077
| ML25140A077 | |
| Person / Time | |
|---|---|
| Site: | 07003103 |
| Issue date: | 05/19/2025 |
| From: | Padgett W Louisiana Energy Services, URENCO USA |
| To: | Office of Nuclear Material Safety and Safeguards, Document Control Desk |
| References | |
| LES-25-064-NRC, EN 57626 | |
| Download: ML25140A077 (1) | |
Text
LES-25-064-NRC May 19, 2025 ATTN: Document Control Desk Director Office of Nuclear Material Safety and Safeguards U.S. Nuclear Regulatory Commission Washington, DC 20555-0001 Louisiana Energy Services, LLC NRC Docket No. 70-3103
Subject:
60 Day Report for EN 57626 LECTS Foam Tank References
- 1) EN 57626, LECTS Foam Tank On March 26, 2025, at 10:32 MDT, Louisiana Energy Services (LES), dba Urenco USA (UUSA), made an Event Notification to the Nuclear Regulatory Commission (NRC)
Operations Center in accordance with 10 CFR 70 Appendix A (b)(1), unanalyzed condition. This notification was made due to the discovery of a non-conservative value in a calculation used to model the foam tank connected to the Liquid Effluent Collection and Transfer System (LECTS). Pursuant to 10 CFR 70 Appendix A(b), the enclosure provides the written follow-up report.
Should there be any questions concerning this submittal, please contact Steve Ward, Senior Licensing Specialist at 575.394.5152.
Respectfully, Wyatt Padgett Head of Regulatory Affairs
Enclosure:
EN 57626 60 Day Follow-up Report
LES-25-064-NRC CC:
U.S. Nuclear Regulatory Commission, Region II 245 Peachtree Center Avenue, NE.
Suite 1200 Atlanta, GA 30303-1257 RidsRgn2MailCenter@NRC.gov Jonathan Rowley, Project Manager U.S. Nuclear Regulatory Commission Jonathan.Rowley@nrc.gov Bradley Davis, Projects Branch 1, Chief U.S. Nuclear Regulatory Commission Bradley.Davis@nrc.gov Timothy Sippel, Senior Fuel Facility Inspector U.S. Nuclear Regulatory Commission Timothy.Sippel@nrc.gov
LES-25-064-NRC Enclosure EN 57626 60 Day Follow-up Report 10 CFR 70.50(c)(1)
(i) Caller's name, position title, and call-back telephone number; The individual who reported Event Notification57626 was Steve Ward, Senior Licensing Application Specialist. The call-back telephone number is 575-394-5152.
(ii) Date, time, and exact location of the event; The issue was discovered on March 25, 2025, at 1515 MDT at Urenco USA in Eunice, New Mexico (Lea County). The Liquid Effluent Collection and Transfer System (LECTS) slab tank and Foam Vessel are located in Room 156 of the Cylinder Receipt and Dispatch Building (CRDB).
(iii) Description of the event:
At 1515 MDT on March 25, 2025, a non-conservative value was found in a calculation used to model the foam tank connected to the LECTS slab tank. During preliminary Nuclear Criticality Safety (NCS) calculations for LEU+, it was identified that the outer diameter (OD) of the Foam Vessel component associated with the LECTS was not conservatively modeled.
The Foam Vessel was modeled with a maximum OD of 9 cm; however, the Safe-By-Design (SBD) criteria allowed the Foam Vessel to have a much larger OD at a maximum of 22.4 cm. This discrepancy, between the modeled dimensions and the much larger SBD criteria, brought into question the calculational results for the LECTS for present-day operations.
There was no immediate concern to criticality safety as the foam vessel was empty and additional conservatism existed in the calculation. As a conservative measure, an NCS anomalous condition was declared. The LECTS was secured, and signs were posted on the doors to prevent personnel from entering the room. Preliminary MONK8A calculations were run for current operations (less than 6 weight percent U-235). These preliminary calculations suggested the modeled LECTS would remain below the Upper Safety Limit (USL); however, the anomalous condition remained in place until a more detailed analysis with the correct (i.e.,
larger) OD could be performed.
The Headquarters Operations Officer was notified at 1032 MDT on March 26, 2025.
(A) Radiological or chemical hazards involved, including isotopes, quantities, and chemical and physical form of any material released; There were no radiological or chemical hazards involved or released.
(B) Actual or potential health and safety consequences to the workers, the public, and the environment, including relevant chemical and radiation data for actual
LES-25-064-NRC personnel exposures to radiation or radioactive materials or hazardous chemicals produced from licensed materials (e.g., level of radiation exposure, concentration of chemicals, and duration of exposure);
There were no actual or potential health and safety consequences to workers, the public, or the environment. No unexpected exposure to radioactive materials or hazardous chemicals produced from licensed materials occurred. The foam vessel very rarely has any material inside, and there was no material in the foam vessel at the time this was discovered. The calculation was revised with the correct OD for the foam vessel and showed the system remained below the USL.
(C) The sequence of occurrences leading to the event, including degradation or failure of structures, systems, equipment, components, and activities of personnel relied on to prevent potential accidents or mitigate their consequences; and Re-design of the LECTS was identified after ISA-MEM-0037 Meeting
- 1 (December 2010) and officially tracked by CR-2011-1707 (May 2011).
Vendor report LES-003-NCS-001 Revision 1 (Issued: 08/23/2011) was identified to have limitations with its NCS basis.
Limitations of the vendor report were properly identified and documented in ISA-MEM-037 Revision 1 (Issued: 06/06/2013)
Meeting #3 (August 30, September 5, and September 6 of 2012).
NCS-CSE-032 Revision 0 (Issued: 06/06/13) superseded the vendor report. It addressed the limitations of the vendor report with a non-calculational safety basis.
Two additional revisions to NCS-CSE-032 were performed (Issued:
01/30/2014 and 03/21/2014, respectively). Neither revision was calculational in nature.
NCS-CSA-037 Revision 0 (Issued: 12/04/2019) superseded NCSE.
This was the first calculational basis performed since the vendor report.
EVENT-2025-1483 (March 25, 2025) identifies non-conservatisms within NCS-CSA-037 Revision 0. An anomalous NCS condition is declared.
Event notification 57626 is made to the NRC Headquarters Operation Center on March 26, 2025, at 1032 MDT.
The anomalous NCS condition was rescinded on April 9, 2025, after new MONK8A modeling showed that the USL was not exceeded when using the correct OD for the foam vessel. The LECTS was returned to normal operating conditions.
(D) Whether the remaining structures, systems, equipment, components, and activities of personnel relied on to prevent potential accidents or mitigate their consequences are available and reliable to perform their function;
LES-25-064-NRC The structures, systems, equipment, components, and activities on site remained available and reliable to perform their function.
(iv) External conditions affecting the event; None (v) Additional actions taken by the licensee in response to the event; During the recovery phase of this event, it was also identified that the Chemical Addition Tanks associated with the LECTS had been omitted from the NCS models. The new calculation included these tanks in the model and did not exceed the USL.
(vi) Status of the event (e.g., whether the event is on-going or was terminated);
The anomalous NCS condition was rescinded on April 9, 2025.
(vii) Current and planned site status, including any declared emergency class; None (viii) Notifications, related to the event, that were made or are planned to any local, State, or other Federal agencies; None (ix) Status of any press releases, related to the event, that were made or are planned.
None 10 CFR 70.50(c)(2)
(ii) The probable cause of the event, including all factors that contributed to the event and the manufacturer and model number (if applicable) of any equipment that failed or malfunctioned; Apparent Cause - Failure to involve NCS during all design phases of the LECTS led to omissions and errors in the NCS analysis.
Contributing Cause #1 - Failure to perform a formal review or a formal Owner Acceptance Review upon immediate receipt of the vendor report limited the end users options once the limitations were identified.
Contributing Cause #2 - Failure to immediately revise or provide a new technical safety basis for an erroneous vendor performed calculational report allowed the same errors to eventually propagate in a future technical safety basis document.
(iii) Corrective actions taken or planned to prevent occurrence of similar or identical events in the future and the results of any evaluations or assessments; and Revised NCS-CSA-037 to address non-conservative Foam Vessel OD and omission of Chemical Addition Tanks.
LES-25-064-NRC Revise NCS-CSA-113 for LEU+ to address non-conservative Foam Vessel OD and omission of Chemical Addition Tanks.
Current process/procedure mandates for a formal Owner Acceptance Review (OAR) to be performed for all vendor performed reports. No Action was created for Contributing Cause #1.
Clearly define the use of a NCSE to close small gaps not covered by an NCSA or to address simple systems that can be bound by an already existing technical basis (NCSA). Furthermore, clearly define the use of a NCSA to evaluate the subcriticality of complex systems.
NCS basis documents that utilize calculations performed by the vendor of LES-003-NCS-001 will be reviewed.
(iv) For licensees subject to Subpart H of this part, whether the event was identified and evaluated in the Integrated Safety Analysis.
Nuclear criticality safety events for LECTS were identified and evaluated in the Integrated Safety Analysis Summary (ISAS). ISAS 3.5.12.5 describes the slab tanks as safe-by-design. Additionally, Loss of SBD Attribute, including for the LECTS, is an accident sequence in Table 3.7-2.