The Department of Energy (DOE) Office of Health, Safety and Security has published its analysis of a November 2011 accident at Idaho National Laboratory (INL), which saw an uncontrolled release of radioactivity that contaminated 16 workers and the facility. An accident investigation report lists three factors that contributed to the accident.
On 8 November 2011, workers at the INL Materials and Fuels Complex (MFC) Zero Power Physics Reactor (ZPPR) facility were packaging plutonium (Pu) reactor fuel plates. Two of the fuel storage containers had atypical labels indicating potential abnormalities with the fuel plates located inside. Upon opening one of the storage containers, the workers discovered a Pu fuel plate wrapped in plastic and tape. When the workers attempted to remove the wrapping material, an uncontrolled release of radioactive contaminants occurred, resulting in the contamination of 16 workers and the facility.
An accident investigation board, appointed at the request of the OHSS, submitted its final report on the accident on 4 January 2012.
The direct cause of the accident was the cutting and handling of the plastic wrapping around the Pu fuel plate, which released the Pu contaminants, the board noted.
It also concluded that the accident was preventable and that, over time, a number of opportunities had been missed that could have prevented the accident.
The board found, through a review of records, that the probability of encountering damaged Pu fuel plates is higher than expressed in the ZPPR safety basis. It also found that the management system lacked requirements intended to influence the decision making of the facility manager and shift supervisor, resulting in a single-point decision to cut the wrapping.
In addition, the board concluded that Pu awareness training has not been effective in giving workers a full appreciation of Pu hazards. “This lack of awareness contributed to the workers delaying their evacuation for nearly four minutes until they heard the radiation alarm, it said.” The board added that: “Not having analyzed this accident scenario also limited the effectiveness of the medical response and delayed the assessment of radioactive material intakes for use in internal dose assessments.”
The accident investigation found that three factors could have contributed to the accident:
1. The organizational transition from the Office of Science to the Office of Nuclear Energy (between 2004 and 2005), resulted in a loss of knowledge and past practices and records that indicated the conditions associated with the fuel plates.
2. Senior MFC management did not recognize the significance of information provided in a 2009 Independent Safety Review Committee (ISRC) white paper on the history of Pu fuel plate failures.
3. The process work sheet used to conduct the work did not contain directions governed by any of the referenced operating instructions, leading to the creation of work steps without an appropriate hazard analysis or accompanying means of mitigation.
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