This Robust Japanese..,Japanese Nuclear Engineers are Stabilizing the Earthquake-Hit Reactors..,Ted Rockwell on Fukushima, and
Posted on March 16th By Zbigniew Jaworowski, M.D., Ph.D., D.Sc (March 15th, 2011 • 10:58 AM),Japanese Nuclear Engineers ,
This Robust Japanese Nuclear Power
Japan, perched on the so-called Pacific “Ring of Fire,” is one of the most seismically unstable countries. In the 20th Century, about 158,280 persons died there in nine major earthquakes, with Richter magnitude 6 and above. The Japanese had that in mind when building 55 nuclear reactors for 17 nuclear power plants, which supply the country with 34.5% of its electricity. They made them sturdy enough not to release any dangerous radioactivity outside the plant limits, even due to the worst earthquakes. The quake of March 11, 2011 of magnitude 9.0, the greatest in the Japan history, proved that the plants operated as expected. No dangerous radioactivity escaped from the destroyed Fukushima nuclear power plants into the environment, and nobody was seriously harmed by radiation among the public. Even though the power plants evidently withstood the 9.0 magnitude earthquake, they appeared, however, to be sensitive to the enormous tsunami, reaching up to 10 km inland, which flooded their emergency diesel power generators. The result was overheating the cores of the reactors.
In heavily affected prefectures Miyagi, Fukushima and Ibaraki, there are 11 nuclear power reactors. Those which operated during the earthquake were automatically shut down when tremors started, and the crews started standard procedures of cooling the “residual heat”, i.e. pumping the water to the pressure vessels of the reactors. However, after an hour, the emergency power generators at Fukushima Daiichi plant were destroyed by the tsunami, the high pressure emergency cooling was lost, and, before the mobile generators were supplied, the temperature of the core in the Unit 1 reactor increased to a level where zirconium cladding of the fuel rods reacted with water, producing hydrogen gas.
When the gas was released from the pressure vessel on 12 March, outside the primary containment, a hydrogen explosion occurred in the reactor building, outside the primary containment vessel, which remains intact. This technically aggravated situation injured several persons, but did not caused a large release of radioactivity to environment. Cesium-137 and iodine-131 levels increased initially after the explosion, but these levels have been observed to lessen a few hours later. On 14 March this was repeated with an explosion at the Unit 3 reactor at the Fukushima Daiichi plant. The reactor building was destroyed, but again, the primary containment vessel remained intact, keeping inside the radioactivity released from reactor fuel.
Two precautionary measures were taken by the authorities. One was evacuation of about 200,000 residents of ten towns near the affected nuclear plants, and the other the distribution of 230,000 units of stable iodine to evacuation centers from the area around Fukushima Daiichi and Fukushima Daini nuclear power plants. The iodine has not been yet administered to residents, as this measure is not necessary.
One may imagine what would happen in the case of reactor meltdowns of Fukushima Daiichi and Fukushima Daini power plants. We know what happened after reactor meltdowns in the 1979 Three Mile Island accident and the 1986 Chernobyl catastrophes. In Japan, the result would be similar as in Three Mile Island power plant, where the reactor was protected by a thick concrete containment, which efficiently retained fission products: There was almost no emission of radionuclides into the atmosphere, except innocuous radioactive noble gases, and practically zero radiation exposure of the population. There is a zero possibility of repeating the scenario from the Chernobyl nuclear power plant, which was not fitted with a containment vessel, and where for ten days, the radioactivity was freely escaping from the melted reactor, roasting in burning graphite used for its construction. But, even if by a magic miracle the containments of Japanese plants perished in the quake or tsunami, the residents around them would not be harmed by radiation. This we learned from the Chernobyl disaster in which not a single person died among the population, as according to a recent report of United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR 2011), the radiation doses from Chernobyl fallout (of about 1 mSv per year) were below the natural radiation, too small to produce any effect.
UNSCEAR. 2011. Sources and Effects of Ionizing Radiation. Vol. II. Annex D Health effects due to radiation from the Chernobyl accident, pp. 1-173. United Nations.
Zbigniew Jaworowski is a multidisciplinary scientist who has published more than 300 scientific papers, four books, and scores of popular science articles. He has been a member of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) since 1973, and served as its chairman from 1980-1982. His recent article , “Observations on Chernobyl After 25 Years of Radiophobia” is available here:
Japanese Nuclear Engineers are Stabilizing the Earthquake-Hit Reactors
A cluster of six reactors of Fukushima Daiichi (which account for 4,596 megawatts of power generating capacity) and the adjacent four reactors of Fukushima Daini (which account for 4,268 MW of generating capacity)were victims of the massive earthquake of 8.9 in the Richter scale, and waves of tsunamis that followed, were the center of attention of the engineers and technicians of Tokyo Electric and Power Company (Tepco).
Out of the six Fukushima Daiichi reactors, three were under operation, while all four of the Fukushima Daini reactors were operating when the earthquake hit. Three Daiichi reactors and 4 Daini reactors shut down automatically and the engineers commenced removal of residual heat with the help of emergency diesel generators. However, this stopped suddenly as the tsunami water flooded the area. For many hours the primary focus of work at the site was to connect enough portable power modules to fully replace the diesels and enable the full operation of cooling systems.
Without enough power for cooling systems, decay heat from the reactor cores of units 1, 2, and 3 had gradually reduced coolant water levels through evaporation. The consequent increase in pressure in the coolant circuit could be managed via pressure release valves. However, this also leads to an increase in pressure within the reactor building containment. Tepco has said that the pressure within the containment of Fukushima Daiichi 1 has reached around 840 kPa (kilopascal , unit of pressure measurement), compared to reference levels of 400 kPa.
At that point Tepco decided to lower the pressure within the reactor by means of a controlled release of air and water vapour to the atmosphere. Because this water has been through the reactor core, this would inevitably mean a certain release of radiation. Tepco has confirmed it was in the process of relieving pressure at unit 1 while preparing to do the same for units 2 and 3. Japanese Television cameras trained on the plant captured a dramatic explosion surrounding unit 1. Amid a visible pressure release and a cloud of dust it was not possible to know the extent of the damage. The external building structure does not act as the containment. The containment to the nuclear reactor is provided by the eight-inch thick special steel sealed unit, which remained wholly unharmed. Japan’s chief cabinet secretary Yukio Edano appeared on television to clarify that the explosion had damaged the walls and roof of the reactor building, but has not compromised the reactor vessel.
Monitoring of Fukushima Daiichi 1 had previously shown an increase in radiation levels detected emerging from the plant via routes such as the exhaust stack and the discharge canal. Tepco officials said that the amount of radiation at the site boundary now exceeds a regulatory limit triggering another set of emergency precautions. It also meant the incident has been rated at Level 4 on the International Nuclear Event Scale (INES) — an ‘accident with local consequences.’
To protect the public from potential health effects of radioactive isotopes of iodine that could potentially be released, authorities are preparing to distribute tablets of non-radioactive potassium-iodide. This is quickly taken up by the body and its presence prevents the take-up of iodine should people be exposed to it. Over the last several hours evacuation orders for local residents have been incrementally increased and now cover people living within 20 kilometers of the power plant.
Subsequently, the Tepco authorities have flooded the exterior containment building with seawater and boric acid, which is used to kill off nuclear reactions. Tepco had to put the operation on hold for a time when another tsunami was predicted, but work recommenced after the all-clear.
Meanwhile at adjacent Fukushima Daini, where four reactors have been shut down safely since the earthquake hit, Tepco has notified government of another emergency status and announced it has decided to prepare for controlled releases to ease pressure in the containments of all four units at Fukushima Daini.
Ted Rockwell on Fukushima: It’s Not About Radiation, It’s About Seawater
A lot of wrong lessons are being pushed on us, about the tragedy now unfolding in Japan. All the scare-talk about radiation is irrelevant. There is no radiation danger, there will be no radiation danger, regardless of how much reactor melting may occur. Life evolved on, and adapted to, a much more radioactive planet, Our current natural radiation levels—worldwide—are below optimum. Statements that there is no safe level of radiation are an affront to science and to common sense. The radiation situation should be no worse that from the Three Mile Island incident, where ten to twenty tons of the nuclear reactor melted down, slumped to the bottom of the reactor vessel, and initiated the dreaded China Syndrome. On the computers and movie screens of people who make a living “predicting” disasters, this is an unprecedented catastrophe. In the real world, the molten mass froze when it hit the colder reactor vessel, and stopped its downward journey at five-eights of an inch through the five-inch thick vessel wall. And there was no harm to people or the environment. None.
Yet here you have radiation zealots threatening to order people out of their homes, to wander, homeless and panic-stricken, through the battered countryside, to do what? All to avoid a trivial radiation level, lower than if they went skiing.
The important point for nuclear power is that some of the plants were swept with a wall of seawater that may have instantly converted a multi-billion dollar asset into a multi-billion dollar problem. That’s bad news. But suppose the money had been invested in a pharmaceutical factory, or an electronics factory, or a chemical plant or an oil refinery. Is there any reason to believe that such facilities would be any more resistant to damage from such a seawater surge? There is nothing in nuclear plants that makes them uniquely vulnerable to seawater. Moreover, the extent and nature of the damage from seawater may be less than first indicated. Rod Adams, a former nuclear submarine officer, who operated a nuclear power plant at sea for many years, says that inadvertent flooding of certain equipment with seawater was not uncommon. He includes electronics-laden missile tubes. “We flushed them out with fresh water,” he said. “Sometimes we had to replace insulation and other parts. But we could ultimately bring them back on line, working satisfactorily.” The lessons from Japan involve seawater, not radiation.
Theodore Rockwell Member, National Academy of Engineering
Dr. Rockwell’s classical 1956 handbook, The Reactor Shielding Design Manual, was recently made available on-line and as a DVD, by the U.S. Department of Energy
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