ENS 57472

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v t e ENS Event
15:30 Dec 12, 2024
Title	Degradation of Safety Item
Event Description	The following information was provided by the licensee via phone and email: At approximately 1030 EST, on 12/12/2024, Nuclear Criticality Safety (NCS) staff were notified that the polyvinyl chloride (PVC) piping of a passive overflow item relied on for safety (IROFS, SGD-147) for Uranium Recovery and Recycle Services (URRS) vessel V-756A was in a deformed condition. V-756A and V-756B are interconnected URRS dissolver product hold tanks. The V-756B redundant passive IROFS overflow (SGD-130) is constructed of steel. NCS staff reviewed the condition of the PVC overflow piping and determined the overflow was deformed into a position that would restrict flow to the point that it could not provide its intended safety function. The safety function of the IROFS is to prevent backflow of uranium bearing material into water and nitric acid systems by providing an overflow path below the height of the water and nitric acid inputs into V-756A/B. The SGD-130 passive overflow was available to perform its intended safety function. The issue was entered as a red-book item in the corrective action program (CAP) as IR-2024-13041. Per criticality safety evaluation, CSE-4A, and supporting calculation note, CN-SB-11-031, with the passive overflow IROFS SGD-147 in a failed condition, the overall likelihood index (OLI) for the fault tree scenario increased from -6 to -3 which does not meet the OLI of -4 necessary to meet 10 CFR 70.61 performance requirements. The result is reportable per 10 CFR Part 70 Appendix A(b)(2), 'Loss or degradation of items relied on for safety that results in failure to meet the performance requirements of 10 CFR 70.61.' Operations for the dirty dissolver process are down pending further investigation and development of compensatory actions. A causal analysis will be performed and corrective actions to prevent recurrence will be documented in the CAP. Further investigation determined that on 12/12/2024, during third shift URRS, while dirty dissolver operations were down, a centrifuge malfunction occurred that necessitated spill clean up of the centrifuge platform area in the ground floor level below the platform. Based on interviews of URRS personnel, it was determined that to clean up the two spill locations, two separate steam-driven eductors with suction wands were utilized to transfer spill solutions to V-756A in roughly the same timeframe. The apparent cause of the PVC overflow piping deformation is excessive steam vapor influx into V-756A from the simultaneous spill cleanup activities. A review of the site maintenance database identified one completed maintenance work order for the replacement of V-756A overflow piping for PVC pipe deformation. Additional review of previous maintenance activities for the V-756A will be performed to determine if there were other instances of deformation of the overflow piping for V-756A. This occurrence in September 2024 was not brought to the attention of management or engineering staff to ensure comprehensive follow-up and corrective actions. The occurrence was not captured as red-book CAP item for a degraded or failed IROFS." Number and types of controls necessary under normal operating conditions: For scenario 4.3 of CSE-4-A supporting Calculation Note, CN-SB-11-031, two passive overflow IROFS controls (SGD-130 and SGD-147) are necessary under normal operating conditions to prevent a backflow condition into the nitric acid supply. Number and types of controls which functioned properly under upset conditions: Passive overflow IROFS (SGD-130) on V-756B is constructed of metal and will not deform when exposed to steam. Criticality safety staff reviewed the SGD-130 overflow for V-756 A/B and determined it could perform its safety function. Number and types of controls necessary to restore a safe situation: The PVC overflow IROFS SGD-147 for vessel V-756A was replaced on 12/12/2024. An extent of condition review for process vessels with PVC/plastic pipe passive overflows with potential exposure to excess heat has been initiated. Safety significance of events: Passive overflow IROFS SGD-130 remained available and a review of tank level data logging confirmed there was no overflow of V-756 A/B and there was no backflow condition into the deionized water and nitric acid systems. Safety equipment status: The passive overflow IROFS control SGD-147 for V-756A/B was replaced on 12/12/2024. The IROFS controls necessary to meet 10 CFR 70.61 performance requirements are in place. Status of corrective actions: Operations for the dirty dissolver are down pending further investigation and development of compensatory actions. A causal analysis will be performed and corrective actions to prevent recurrence will be documented in the corrective action program. * * RETRACTION ON 01/16/2025 AT 1228 EST FROM STEVE SUBOSITS TO JORDAN WINGATE * * * The following information was provided by the licensee via phone and email: Following review of pertinent integrated safety analysis risk assessment information, Westinghouse reevaluated the nuclear criticality safety scenario utilized as the basis for reporting event notification57472 on December 13, 2024. The scenario for a backflow condition into the nitric acid header did not consider initiating and enabling conditions in the accident sequence for a potential backflow of uranyl nitrate solution into Uranium Recovery and Recycle Services (URRS) vessels V-756 A/B. The reevaluation determined the overall likelihood index of the scenario with a failure of the SGD-147 passive overflow meets the performance requirements of 10 CFR 70.61. Westinghouse is retracting EN 57472 based on the reevaluation of the scenario. 10 CFR 70.61 performance requirements were met to ensure a nuclear criticality remained highly unlikely for the backflow scenario. Notified R2DO (Suggs), and NMSS Events Notification (email).

ENS 57472 +/- *RETRACTED*
Where
Westinghouse Electric Corporation Hopkins, South Carolina (NRC Region 2)
License number:	SNM-1107
Reporting

Part 70 App A (B)(2)
Time - Person (Reporting Time:+18.88 h0.787 days <br />0.112 weeks <br />0.0259 months <br />)
Opened:	Stephen Subosits 10:23 Dec 13, 2024
NRC Officer:	Adam Koziol
Last Updated:	Jan 16, 2025
57472 - NRC Website
v • d • e

v t e Emergency Notification System
Westinghouse Electric Corporation with Part 70 App A (B)(2)
WEEKMONTHYEAR2024-12-12T15:30:00 [Table view]
[ENS list for Westinghouse Electric Corporation]

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