In April of 2011, a consortium of industrial and governmental organizations established to provide advice to Japan in its efforts to stabilize the conditions at the Fukushima Daiichi nuclear power plant, authored an analysis of Tokyo Electric’s roadmap to restore stability at the crippled facility. The consortium was made up of representatives from General Electric, Hitachi, Institute of Nuclear Power Operations (INPO), Naval Reactors, United States Department of Energy / Nuclear Energy, and the United States Nuclear Regulatory Commission.
The roadmap which had been released by TEPCO gave examples of the near-term actions that TEPCO deemed necessary to minimize radiation releases and reestablish safety.
The consortium established five essential functions necessary for achieving the near term goal for improving plant conditions.
The five essential functions are as follows:
- Remove decay and chemical heat from reactors, containment, and spent fuel pools.
- Maintain reactors and spent fuel pools subcritical and adequately shielded.
- Ensure structural integrity for all units (e.g. containment and spent fuel pools).
- Provide reliable indication of essential parameters.
- Terminate (or render insignificant) uncontrolled radioactive releases.
The consortium was also very concerned about the spent fuel pools in nearly all of the units. The consortium largely dismissed the thermographic work that TEPCO had carried out, because it only indicated the surface temperature of the first obstacle encountered, and did not indicate the actual spent fuel pool temperature.
At Unit 1, the consortium was concerned that water being sprayed on the spent fuel pool was not actually reaching the pool. They advised that TEPCO investigate and confirm that the spent fuel in the spent fuel pool was being cooled.
In Unit 1, Unit 2, and Unit 4, the consortium felt that TEPCO should install independent redundant backup systems for cooling.
While the consortium expressed concern about the Unit 4 spent fuel pool, experts were also concerned about the structural integrity of the Unit 3 building after being ripped apart by the explosions.
The consortium analysis pointed out that TEPCO’s roadmap was glaringly silent on maintaining the fuel sub-critical. Further, the experts even questioned TEPCO’s ability to detect and monitor inadvertent criticality.
After using sea water for emergency cooling in the reactors, experts felt that consideration should be given to biological growth which may occur in the reactor vessels, containments, and spent fuel pools. This had been witnessed at Three Mile Island, where it had been learned that the growth of such life forms could reduce visibility in the waters at best, or even worse could affect coolability of the fuel by reducing flows or heat transfer coefficients from surfaces.
To view the TEPCO Roadmap follow the link below: