Page 7 - 2011 - The 'X' Chronicles Newspaper - March 2011

Fukushima Dai-ichi Nuclear Disaster The Fukushima Dai-ichi experienced a complete blackout — no electric tsunami may have created a leak in the cooling Nuclear Power Station power at all. pool, and could have damaged the containment There was no way to cool the reactors’ dome of the number 4 reactor. The last report Disaster cores or replace lost cooling water until more received indicated no fire was visible. generators arrived. The water level dropped and A steam plume will quickly cool and the Continued From Page 6 the clad fuel rods were exposed to the air, radioactive heavy metals will drop to earth, thus generating steam and hydrogen. Batteries and limiting the downwind contamination zone. The When “spent” fuel rods are removed new generators were delivered to the site and graphite fire at Chernobyl produces a hot ash from a reactor, they are placed into a cooling cooling water was introduced into the reactor plume that reached higher altitudes and thus pool to cool until it is safe to dispose of them or cores. was carried for greater distances. This is the re-process them. Useable fuel rods may also be Damage caused by the super earthquake, main difference between Fukushima and placed in the cooling pool if maintenance super tsunami, and the exposure of fuel rods to Chernobyl. The main threat from the requires their removal from the reactor core. air combined to create extreme conditions. It Fukushima accident appears to be a cooling Fuel rods that have been in an operating reactor was necessary to employ the installed seawater pool event, rather than a reactor melt down. must be cooled. If exposed to the air, they will cooling option to flood the reactors with Radiation terminology is confusing. melt and appear to be burning. The cladding seawater. There as been no mention of damage Radiation absorbed in measured in RADs metal will react with moisture and release to or clogging of seawater intakes by debris (radiation absorbed dose) or the newer System hydrogen gas. caused by the tsunami. Internationale (SI), using the term Gy (gray). A Cooling pools are usually not located When fuel rods are exposed to the air more important measurement is radiation inside the reactor containment vessel. The (cooling water level drops) the fuel rod’s hot damage measured in REM (radiation equivalent location of the cooling pools at the Fukushima metal cladding reacts with moisture and mammal) or the new term Sv (sievert). My reactor facility is unclear. If they are located produces hydrogen gas. Hydrogen gas had to be training and experience was under the old outside the containment vessel, they pose a very vented from the containment dome into the system, REMs and RADs, and I am still serious threat if cooling water is cut off. building enclosing the dome where it exploded. learning to cope with sieverts and grays, the Water is circulated through the reactor Hydrogen (H) combines with oxygen (O) to terms encountered in news reports. Some core by pumps. Electrically actuated valves produce water (H2O) and a large amount of guidelines: direct the flow of water. In addition to several energy. This same reaction propels the space backup systems, a method to flood the reactor shuttle. Igniters designed to burn off hydrogen 1 sievert = 100 REM = a very serious dose with seawater was included into the Fukushima were damaged and did not work, allowing .01 (cinti)sievert = 1 REM = not a serious nuclear power facility design. Regular coolant enough gas to accumulate for a detonation. dose, but should be avoided water is superheated in the reactor core, and The Fukushima reactor accident is .001 (milli)sievert = 0.1 REM = not a serious then passed through a heat exchanger to comparable to the U.S. Three Mile Island dose produce the steam that drives the electric accident, but it may NOT be comparable to the .000001 (micro)sievert = 0.0001 REM = not a generator’s turbines. Cooled core cooling water Soviet Chernobyl reactor melt down for two threat is condensed and circulated back into the core important reasons. 400 milisieverts = 40 REM = a dangerous but — a closed loop system. First, Chernobyl was a graphite- not lethal dose Each Fukushima nuclear reactor had a moderated reactor. Graphite will burn, and it primary and secondary cooling system. One did, producing radioactive smoke that rose into Short term readings have reached 400 system required AC power, and the other one the atmosphere and was spread by the wind. millisievert, and then dropped. So far no depended upon onsite generators. Valves had Japanese and American power reactors are not radiation in the sievert range has been battery powered backup systems. A seawater graphite moderated. measured. Radiation damage potential is a injection system was included in the design as a Second, the Chernobyl reactors had no function of intensity and time. final backup system. containment domes. There are three basic types of radiation, Now, let’s examine what happened at Another reason is that safety procedures gamma (and X-rays), beta and alpha. Isotopes the Fukushima Daiichi Nuclear Power Station. and worker training are much better in Japan that emit beta and alpha particles can only harm Reactors 4, 5 and 6 were shut down for and the U.S. than they were in Russia. On the you if the isotopes themselves enter your body. maintenance. All of the fuel rods in reactor 4 other hand, the bravery and sacrifices made by You skin will shield you from them as long as had been removed and placed in its cooling the Soviet responders was amazing. Men died in they are external. Only dense metal can protect pool. Approximately one third of the fuel rods order to seal the core. you from gamma and X-rays, however. in reactors 5 and 6 had been removed and Contrary to news reports, the number 4 Iodine (I) pills provide some protection placed in their cooling pools. Cooling water was reactor is not on fire. Its fuel rods had been from radioactive iodine-131, and no protection being circulated through the reactor cores of removed and placed in its cooling pool. The from other radioactive daughter products: reactors 5 and 6 to remove residual heat (heat location of the cooling pool has not been cesium-137 or strontium-90 for example. I-131 generated by the decay of fission products). identified, and it could be inside the main damages the thyroid, and has a half live of 8 Reactors 1 - 3 scrammed, and cooling reactor building. This is important, as you will days. I-131 dissolves in water and is absorbed water was pumped through them to remove soon see. by plants that are eaten by animals, fish, and residual heat. The reactors were designed to Cooling pools usually do not have humans. Inhalation is also possible if a person is withstand a 7.9 earthquake, and they survived containment domes, thus a drop in water level is close to the release point. Human I-131 the 9.0 earthquake that occurred. Without the very serious. At Fukushima, the building contamination usually occurs by drinking milk super tsunami, there would not have been any constructed over the pool accumulated produced from contaminated cows, or by eating notable problems — an incredible feat of hydrogen gas and exploded. If cooling pools contaminated vegetables, fish and meat. engineering. were inside the main reactor building, then the In summary, the six nuclear reactors The tsunami was another matter. All hydrogen would be a serious threat and may survived an event a full order of magnitude external power to the station was lost when the have been the cause of the explosions in the more severe than their design criteria. Instead of seawater swept away power lines. Six diesel reactor buildings. listening to Chicken Little, we should pay backup generators ceased functioning after The number 4 reactor cooling pool is tribute to Japanese and American engineering approximately one hour, due to tsunami induced now the major threat. News reports indicate that and safety procedures. Can we do better? Yes. damage, reportedly to their fuel supply. Reactor the fuel rods are exposed to the air, and are so Lessons learned will be reflected in future Core Isolation Cooling (RCIC) pumps, which hot they appear to be burning. If so, the cooling nuclear reactor designs. The concurrent super operate on steam from the reactor, were used to water will boil. Protective metal cladding has tsunami and 9.0 earthquake exceeded any replace reactor core water inventory; however, melted and radioactive isotopes, daughter previously anticipated catastrophes. That is no the battery supplied control valves lost DC products, will be released and carried upward longer true. [] power in approximately eight hours when the by the steam plume. A combination of damage batteries were used up. At that point, the plant from the hydrogen explosion, earthquake and www.leeboylandbooks.com