Nuclear Power Plant Safety Following Fukushima
The secondary battery backup (19) was of no use either because it was drastically undersized. It provided only about eight hours worth of electricity, while about ten times that would have been needed to supply the electricity needed for a safe shutdown. (It should be noted here that of the 104 American reactors, 93 are provided with only four-hour battery backups). Another problem in the Fukushima plant was the lack of automatic battery recharging. This could have been provided because the plant was still generating steam at a rate of about 5% of full capacity and, therefore, some of the turbine-generators could have been kept in operation.
No other backup was provided at the Fukushima plant. This is unfortunate, because electricity itself is not essential to cool the reactors. For example, if emergency cooling water tanks were provided on the roof, would have made it possible to charge water just by gravity, and if those tanks were properly sized, the accident could have been prevented.
Similarly, in any plant where excess energy is present, that excess energy can be used directly to run the plant and its cooling systems. This could have been done by providing backup pumps with steam or Stirling type heat drives. The design of the Fukushima plant did not provide for any of these options.
Other Design Defects
Probably the worst design defect was the under-sizing of the spent fuel rod storage pool. This was a universal practice 40 years ago, because everybody assumed that means for permanent storage would shortly be available, but that never occurred. Therefore, at the Fukushima plant 1760 tons of spent fuel rods were in the temporary storage pool (10 times the amount the pools were designed for), requiring continuous cooling to protect against a meltdown. The melting of these spent fuel rods outside the primary containment (3) also caused hydrogen explosions and release of radioactivity. The running out of space in the temporary storage pools is a common problem all over the world because permanent and earthquake proof storage facilities are still not available anywhere.
Some improved storage technology did evolve over the years, such as storing the spent fuel rods in dry casks and/or underground, but these storages are also only temporarily. What is even worse is that, while the temporary storage facilities are getting full, governments are not concentrating on building permanent ones. For example, in President Obama's 2011 budget proposal, all funding for nuclear waste disposal was eliminated. So as of today, nearly 500 nuclear power plants around the world operate without permanent means of storing the waste they produce.
This article originally appeared in our sister publication ControlGlobal.com