http://www.yomiuri.co.jp/dy/national/T110407006089.htm
TEPCO entertaining no hopes of quick fix
The Yomiuri Shimbun
It has been nearly a month since the earthquake and tsunami devastated northeastern Japan, but the situation surrounding the reactors at Tokyo Electric Power Co.'s Fukushima No. 1 nuclear power plant remains perilous.
TEPCO is considering installing additional cooling systems as part of a new plan to stabilize the reactors damaged by the March 11 disaster.
According to estimates released by the utility Wednesday, 70 percent of fuel rods at the No. 1 reactor have been damaged. At the Nos. 2 and 3 reactors, 25 percent to 30 percent of fuel rods have been damaged, the utility said.
The company based the damage assessment on levels of radioactive xenon and krypton detected in gas near the reactors' containment vessels. These substances are supposed to be contained within nuclear fuel and should not be released.
TEPCO said it gauged the extent of the xenon and krypton leaks by considering factors such as radiation levels and the length of time the fuel rods had been exposed.
Damage to fuel rods could result in a hole in their zircalloy cladding, or a meltdown of the fuel rods themselves. TEPCO said details of the damage to the reactors' fuel rods remain unknown.
In the reactor cores, temperatures at the midpoints--where fuel rods are supposed to be located--are higher than at the base of the reactors. This suggests that meltdown of the fuel rods, which would see them accumulate at the bottom, has not occurred, according to TEPCO.
On March 14, radiation levels at the containment vessel of the No. 3 reactor, where a large portion of the fuel rods was believed to have been exposed, were measured at 167 sieverts per hour. This figure is roughly equivalent to radiation levels 400 meters from ground zero after the 1945 U.S. atomic bombing of Hiroshima.
Experts have expressed alarm at the current situation at the Fukushima plant.
"If fuel rods melt, they might accumulate in a shape like a soft-boiled egg about four meters in diameter and two meters thick," said Michio Ishikawa, top adviser to the Japan Nuclear Technology Institute. "It might look like steaming magma, with uranium fuel and zirconium pipes melted together."
If fuel rods melt and form a mass, the exposed surface area will be reduced. Cooling the reactors would therefore take even longer because the mass would retain more heat and pumping water on it would have less effect.
Radiation levels at the No. 1 reactor peaked at 162 sieverts per hour on March 14, and the No. 2 reactor saw radiation levels peak at 138 sieverts per hour on March 15.
Those highs were measured after those reactors lost significant volumes of cooling water around their fuel rods, leaving large parts of them exposed to the air. This has also happened at the No. 3 reactor.
Injection of water has caused radiation levels at all the three reactors to fall. Current levels are between 20 and 31 sieverts, or just 11 percent to 22 percent of their peaks.
However, the current radiation levels are still far from safe. Two workers were killed in a 1999 nuclear accident in Tokaimura, Ibaraki Prefecture, after being exposed radiation levels of between six and 18 sieverts.
TEPCO is aware that working near the reactor containment vessels is dangerous.
"Radiation levels are extremely high, so we can't do any work there right now," said one official of the utility.
Osaka University Prof. Keiji Miyazaki, an expert in nuclear engineering, said, "Radioactive substances probably leaked from damaged fuel rods and reached the reactor containment vessels through valves or some other route."
"The radiation levels are way too high for workers to get close [to the reactors]," he said. "It'll certainly take a very long time to inspect the condition of the damaged reactors."
(Apr. 8, 2011)
This is actually the first time that I read about the true maximum radiation levels at the damaged reactors in Fukushima. During the ongoing crisis TEPCO reported only values well below 1 Sv which were measured hundreds of meters away from the reactors. It sounds unlikely that anybody will be able to construct a new closed loop water cooling circuit to one of the molten core puddles there for a very long time. This implicates that millions of tons of water will be contaminated in the effort to cool down the run away reaction. TEPCO cannot continue to dump this radioactivity into the Pacific Ocean. What are they going to do with it?
It is entirely relevant to the technical debate what the damage of worst case nuclear accidents are and how often they actually occur. The true liability cost depend of those questions. Naturally there is also the follow up question if the society is really supposed to let equipment suppliers and utilities get away with fractions of the insurance premiums needed to pay for the total liability they should carry and dump the clean up cost and damage claims to the tax payers.
In that context it is very relevant to look at the question of where the accident occurred. If a plant nearer to Tokyo had been affected the impact would have been much greater. Already now we are probably looking at damages exceeding €500bn and each day the reactors are out of control and the clean up is delayed adds to the damage bill. So the likely actual cost are going to be in the €1,000bn order. The worst case with an almost direct hit of full nuclear fall out on a metropolis like Tokyo could have easily resulted in damages of €15,000bn. The mind boggles at the idea to evacuate Tokyo and clean up a metropolitan area from caesium-137 fall out with something like 1,000 Becquerel per square meter and day.
It is very relevant for the energy debate to discuss the full cost of the power generating methods including the decommissioning cost, the cost of nuclear waste disposal and the true insurance or capital risk cost. And quite obviously in that context it is very relevant whether you have your worst case accident in an area where 100 million people inhabit the fall out zone - like central Europe - or perhaps 20,000 in the case of some desert states in the USA. The proof of this point is the different political treatment the risks of nuclear accidents get in Germany and Finland. The cost of a catastrophic accident of Chernobyl or Fukushima type in Germany would be ten thousand times higher than in a desert location.
As it stand we can conclude that an accident with a €1,000bn damage statistically occurs each 25 years with 500 reactors running. And we cannot exclude that a big one with €15,000bn could happen. The logical conclusion is that the suppliers and operators have to insure between the two points of proven statistical outcome and potential maximum damage. If we settle on a collective damage fund of €6,250bn over 25 years each nuclear power plant will have to pay €500mil insurance premium per annum or €15bn over the course of a regular plant life. It means that the actual capital cost of the investment multiplies with a factor of four compared to today. Instead of €5.5bn per plant you are suddenly looking at €20.5bn.
But one can also look slightly different at the true cost scenario. It was said that the owners of the seven nuclear power plants that are now shut down in Germany can suffer a loss of profit of €1m per day and plant. We conclude that they typically earn €350m per year by the operation. If they have to pay the true insurance cost of €500m per year they would simply stop running the plants by themselves.
Everybody who looks at these figures should instantly realize why it is important for tax payers and the public debate to make sure that all hidden costs are figured into the various power generating scenarios. If you end up squandering you national wealth on costly nuclear damage repair and compensation instead of making investments into future proof power generating and distribution technology you are gambling with the future of your children. You may take the risk and get away with it but inevitably for one or the other nuclear happy nation the pay day will come like today it did for Japan and the responsible politicians will look like idiots and criminals.
