The Board observed some hesitancy on the part of NWP to initiate a PISA determination in the absence of data related to the U/G radiological release of February 14, 2014. Additionally, weaknesses were observed in USQ evaluations associated with recovery activities.
Analysis
The Board interviewed the NWP Nuclear Safety Manager and Chief Nuclear Engineer on March 6, 2014, in order to understand their roles/responsibilities related to the USQ process, actions taken in response to the radiation event on February 14, 2014, and the NWP basis for various changes made in the safety basis.
The Chief Nuclear Engineer acts in an advisory and independent review role for the NWP President. The NWP Nuclear Safety organization is responsible for DSA/TSR preparation and revision, and USQ process implementation. NWP Nuclear Safety is comprised of four nuclear safety staff and two fire protection engineers. Five of the staff within NWP Nuclear Safety are qualified as USQ evaluators. Overall, approximately 20 USQ-qualified evaluators are on-site within NWP. Qualifications for USQ personnel are established in USQ Procedure WP 02- AR3001, and are consistent with general guidelines in DOE G 424.1-1B.
Discussions with the NWP Nuclear Safety Manager and Chief Nuclear Engineer focused on the process by which NWP considers entering the USQ process through initiation of a PISA
declaration, considering one possibility that the facility may have violated an initial assumption of their DSA related to routine activities associated with the Ground Control Program, i.e., not being performed for some period of time following the event. During these discussions both NWP personnel indicated their intent to eventually enter into the PISA process. However they also noted that this would not likely occur until after the physical mechanism for the release was determined after reentry into the underground. Although the NWP procedure requires a
determination following five days of discovered information, the “clock” had not yet started on initiation of procedural steps. The concern raised by the Board was that rather than initiating the PISA process based on the “potential” inadequacy, there may have been a misconception and that the site was waiting to initiate the process only after they had confirmed any actual inadequacy.
During the course of the accident investigation, NWP made the decision to convene the NRB to initiate the formal PISA determinations for the “Underground Salt Haul Truck Fire,” PISAD Number P-14-0001, and for the “Underground Radiological Event,” PISAD Number P-14-0002. The NRB was convened March 12, 2014, and the determination that these PISAs were confirmed was made on March 13, 2014. NWP imposed operational restrictions by issuing Management
Directive 1.5 on March 12, 2014, and further actions as defined by their USQ process are planned, including performance of USQDs and “Evaluation of the Safety of the Situation.”
Observations from this NRB identified several weaknesses and inconsistencies with sound PISA practices. These included formulating responses in the draft PISA determinations that did not specifically address the question, e.g., did not identify what safety functions were previously credited and instead addressed the non-credited safety function of the U/G HEPA filtration system, which is also important. Feedback from those in attendance at the NRB resulted in adding other clarifications to the PISA determinations.
The Board also reviewed USQ documents prepared in connection with the February 14, 2014, radiological event in the WIPP underground. USQD D14-003, “ECO 13382 and Work Order 140200 for Sealing of Ventilation Dampers 413-HD 056-003A and 413-HD-056-003B,” Revision 0, was prepared to support planned high-density foaming activities of the HEPA filtration bypass to seal unfiltered leakage around dampers. NWP determined that the USQD was negative. The Board had significant concerns with the lack of details in the USQD related to the type of foaming materials and associated hazards. This is important given the hazardous constituents of the foaming product, polymeric methylene diphenyl diisocyanate, which has been evaluated at some DOE sites as having the potential for high off-site toxicological consequences. Without this information, the USQD questions are difficult to answer. Revision 1 was
subsequently issued to authorize the activity.
The Board had other concerns with the quality of the USQD Revision 1 responses related to a potential exothermic reaction due to a foaming process upset that could result in a fire and subsequent failure of contaminated HEPA filters in the U/G ventilation system due to the fire soot combined with the observed particulate loading on the Mod filters, and this event was not considered in response to Question 5 regarding creating the possibility of an accident of a different type than previously analyzed. Although the safety basis includes a fire involving the Waste Handling Building contaminated HEPA filters, which affects USQD Questions 1 and 2 on potential increase in frequency or consequences, these hazard scenarios were not addressed as bounding or representative for a fire release from the U/G HEPA filters.
An unplanned exothermic accident that could have led to a fire occurred on March 8, 2014, when “reddish-brown” vapors were observed coming from the open ports in the duct (ORPS report EM-CBFO--NWP-WIPP-2014-0003). That activity for low-density foaming of the duct between the two isolation dampers was evaluated per USQD D14-004, “Work Order 14020078,
413HD056003A Seal Duct Between 3A and 3B Dampers.” That USQD is very similar to the USQD D14-003 Revision 1, and has the same concerns related to the adequacy of responses to Questions 1, 2, and 5.
The Board also reviewed USQ Screen IS14-0062, “Work Order 1402037C, 371, SH Perform Shaft/Conveyance Habitability Phase 1 of Reentry into Underground,” which was performed to support unmanned entry via the Salt Hoist Shaft/Conveyance. This proposed activity was initially evaluated as a Categorical Exclusion established for maintenance procedures. The Board had significant concerns that this activity has never been performed at WIPP and should not be authorized as a Categorical Exclusion. Instead of completing the Categorical Exclusion,
NWP completed a USQ Screen and determined that the activity can be authorized without further USQD evaluation.