Safety board has concerns about WIPP’s new ventilation system

May 21, 2024, 12:04PMRadwaste Solutions
A 125-foot-tall exhaust stack towers over the Safety Significant Confinement Ventilation System’s filter building at the Waste Isolation Pilot Plant. (Photo: DOE)

The Defense Nuclear Facilities Safety Board (DNFSB), an independent government organization responsible for overseeing public health and safety issues at Department of Energy defense nuclear facilities, has alerted the DOE because of safety concerns it has regarding the use of continuous air monitors (CAM) at the Waste Isolation Pilot Plant in New Mexico.

Part of WIPP’s new Safety Significant Confinement Ventilation System (SSCVS), the CAM system is intended to detect a radiological release in the repository and automatically close vent dampers to prevent the escape of radioactive particles to the outside environment. The SSCVS, which began commissioning in November 2023, is intended to increase airflow to the underground to allow for simultaneous underground waste emplacement, mining, and ground control work.

The concerns: In a May 15 letter to energy secretary Jennifer Granholm, DNFSB chair Joyce Connery noted that the WIPP CAM system must be capable of performing in the presence of airborne salt particles generated from mining activities, as well as smoke and ash from accidental fires. “However, the current WIPP management and operating contractor, Salado Isolation Mining Contractors, LLC [SIMCO], has not demonstrated that the CAM system will perform its safety function in this environment,” Connery wrote.

Connery also noted that, in one area of the WIPP underground, only administrative (procedural) controls are used to reduce the risk of accidents, but not the engineered controls offered by the CAMs and SSCVS. “In the Department of Energy’s published hierarchy, engineered controls are preferred over administrative controls due to the susceptibility to human errors inherent in administrative controls,” Connery wrote.

The details: In a report dated March 21 that accompanied Connery’s letter, the DNFSB staff noted that while the CAMs used by SIMCO are robust and fitted with titanium-clad detectors to better withstand the salt dust environment, it is possible that salt dust and combustion products from a potential fire could build up on the detector. The dust and ash could shield the detector from alpha and beta radiation, preventing the system from automatically closing the SSCVS dampers and possibly allowing a radiological release.

“SIMCO has maintained that the operating environment is not considered as part of the [safety integrity level] analysis. This amounts to an assertion that the operating environment has no effect on component reliability. However, the environment in which the safety-significant CAMs operate could have a significant impact on their performance, as recognized in ANSI/ISA-84.00.01-2004,” the report states.

The report further notes that additional CAMs could be placed at the waste shaft station in the WIPP underground, which lacks engineered safety controls to mitigate accidents. When being disposed of in the WIPP underground, transuranic waste passes through the waste shaft station after being lowered through the waste shaft. It then proceeds through the repository’s waste transport path before being emplaced in the waste panel.

DNFSB staff note that to reduce the risk of accidents, SIMCO uses both administrative and engineered controls both along the transport path and at the waste panels but uses only administrative controls at the waste shaft station. “DOE Standard 3009-2014 establishes that due to the inherent uncertainty of human performance, engineered controls are preferred over administrative controls,” the report states.

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