The letter from Willson Bloch concerning the risks of nuclear power raises important questions about the current plans to build several new nuclear plants. His letter, however, contains some questionable assertions.
It is not yet clear to what extent the radiation from the Fukushima disaster is a result of partial meltdown of the reactor core or from tsunami damage to the spent fuel containers, nor have the Japanese identified which isotopes, other than tritium (t½, 12.3 years), iodine 131 (t½. 8.1 days) and cesium 137 (t½, 30.2 years) have been released into the environment (t½ = radioactive half-life). While these isotopes are of concern, they must be compared to the transuranium elements in the spent fuel rods, e.g. plutonium 239 (t½, 24,400 years). Furthermore, to equate the radiation levels received from the Hiroshim and Nagasaki bombs with those at Fukushima is not credible, nor is it likely that Japans existence is threatened. (The Ukraine is still with us 25 years after Chernobyl.)
Having said this, however, I am opposed to the construction of new thermal (slow neutron) reactors for three good reasons:
They are extremely inefficient. Less than 1 percent of the uranium in the ore mined is consumed (0.7 percent fissionable U235, and 99.3 percent U238, which does not undergo fission with slow neutrons).
These reactors produce large quantities of highly radioactive waste, currently stored on site (63,000+ metric tons), with no permanent storage planned.
In the anti-regulation climate of the Tea Party/Republicans, it is likely most of the NRC regulations, which are primarily responsible for the good safety record of US nuclear reactors, will be repealed. Leaving the safety of the U.S. population to the tender mercies of the free market is a nightmare indeed.