The US Department of Energy (DOE) needs to do more to prevent the failure of radioactively contaminated facilities at the nuclear weapons production site at Hanford in Washington state, the US Government Accountability Office (GAO) said in a report released on 20 February.
The partial collapse in May 2017 of a tunnel containing radioactive waste on the Hanford site signalled problems with how DOE dealt with ageing infrastructure, the GAO report dated 21 January says.
In particularly, the report raised questions about the way surveillance, monitoring and inspection of existing facilities are carried out.
Nuclear facilities awaiting cleanup at the Hanford site are inspected and maintained by contractors. However, DOE has not ensured these activities fully meet requirements, the report says, noting that inspectors have not entered some parts of the site for decades.
GAO examines actions taken in response to tunnel collapse
In May 2017, there was a partial collapse of the Plutonium Uranium Extraction (PUREX) Tunnel 1.
GAO found that DOE had taken some actions to evaluate the physical causes that contributed to the tunnel partial collapse.
But it found that the DOE had not determined the "programmatic causes" that led to the collapse by completing an accident investigation or a root cause analysis.
For example, it says that, although an engineering evaluation of the tunnels was completed as requested by the State of Washington, Richland Operations Office officials told GAO that an accident investigation was not started because the event "did not meet threshold requirements in a DOE order that includes, for example, damages or costs exceeding $2.5 million."
However, the GAO analysis shows that the costs of responding to the event and stabilising the tunnel were about $10 million.
At the contractor's request, the Richland Operations Office also waived performance of a root cause analysis and agreed to a less rigorous analysis of the potential physical causes of the event.
DOE guidance states a route cause analysis is typically required for such a significant event.
The GAO review found that although the Hanford contractor is generally conducting routine surveillance inspections of contaminated excess facilities, these inspections have weaknesses.
It also found that DOE has not ensured requirements are fully met.
DOE orders require that processes be in place to ensure that inspections are conducted to detect deterioration and determine whether the structural integrity of facilities is threatened, GAO notes.
However, a December 2017 DOE report and GAO's review found that the surveillance and maintenance inspections at several facilities were not comprehensive.
It also found that there are areas of some facilities that personnel infrequently or never enter — physically or by remote means — to conduct inspections.
For example, parts of the Reduction-Oxidation Facility have not been entered in more than 50 years and structural conditions are unknown, it says.
GAO said that, without conducting comprehensive inspections, the Richland Office cannot ensure that it is meeting all of DOE's requirements, such as addressing ageing degradation and obsolescence of some facilities, and preventing potential events similar to the PUREX tunnel collapse.
GAO recommends that DOE should:
- Analyse the programmatic root causes of the tunnel collapse;
- Routinely conduct comprehensive inspections of contaminated excess facilities and take timely action as warranted; and
- Assess RL oversight of surveillance and maintenance of Hanford excess facilities.
More specifically, GAO said the Assistant Secretary of DOE's Office of Environmental Management should:
- Direct RL to conduct a root cause analysis to identify any programmatic causes that may have led to the collapse of PUREX Tunnel 1;
- Ensure that RL directs the Hanford Site clean-up contractor to explore using robotic or other means to routinely complete comprehensive surveillance inspections of contaminated excess facilities... and take timely action as warranted; and
- Ensure DOE headquarters offices responsible for the oversight of EM sites' field offices conduct an assessment of RL's management and oversight of the Hanford Site contractor's surveillance and maintenance activity for contaminated excess facilities. Based on the results, DOE headquarters offices should consider whether such assessments should be conducted on a periodic basis.
DOE agrees with GAO's recommendations and says that it is taking steps to implement all of them by December 2020.
Photo: Hanford Plutonium Uranium Extraction Plant (PUREX) and Storage Tunnels (Credit: DOE)