Sunday, March 20, 2011

Concerns for US Nuclear Power Post Fukushima

The Fukushima events have reveled a number legitimate questions about the safety of nuclear power in the United States. A thorough review of the safety here at home is warranted and has commenced. While I am a no body, here are my major concerns.

1. Pressure relief venting. The design of the GE Mark I initially allowed for venting into the exterior containment buildings. A recommended modification to reroute relief pressure in excess of the suppression pool capacity was proposed by GE which appears to not have been implemented in the Fukushima case, which caused the explosions damaging several buildings and also appears to have caused damage to one of the reactor main containment suppression pool structure.

2. Spent Fuel Storage Pool design may have cause greater than expected release of radiation. One of the primary reasons appears to be the design of the SFSP weir gate allowing more water leakage than expected or make up water loss for greater than expected duration. Make up water is a critical consideration that appears to have been compromised.

3. The design of the racks used in the SFSP and the spent fuel loading configuration needs to be verified. While considered an unlikely possibility, oxidation of the spent fuel rod cladding can occur and possibly spread if adequate dry pool passive ventilation is not available. Tests for the exact conditions at Fukushima have never been analyzed, only worst cases of totally dry pool conditions. The situation provides a unique opportunity to study mid-range situations assumed to be less critical than worst cases situations.

4. Due to tsunami destruction, offsite response equipment was greatly delayed and onsite equipment damage greater than expected. Availability of offsite equipment was reduced by the massive destruction caused by the combination earthquake and tsunami. Assigning proper priority of available equipment to the degree of risk appears to have been in question. Emergency response planning needs to be reviewed.

Those are the major considerations. "Real" risk in terms of released radiation needs to be clarified. Decisions by the plant control operators appear to have been influenced by less likely risks to the public resulting in greater overall risk. Plant designs allow for human error, but impact of human error can be reduced through better training.

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