March 24, 2011
The Japanese Reactor Leaks – Without the Hype
Don Petersen, PhD, Bill Stratton, PhD
Loss of coolant events at several of Japan’s nuclear reactors are eerily similar to the Three Mile Island incident of 1979, except that four reactors and spent fuel pools are involved, and tens of thousands perished in a massive earthquake, and devastating tsunami. With all the monumental loss of life and and the unbelievable destruction, the US media still takes most of its time to report hysterically on a “Meltdown” and “Radiation”! The panic reporting is exactly the same as Three Mile Island–inflated and misinformed. It is hard to separate the facts from the assertions and the media are not helping, but with each passing day more information relevant to the outcome emerges and the hand wringing of previous days lessens. The level of severity at Fukushima Dai-Ichi has been increased to equal Three Mile Island, a desirable condition that appears to be developing–no major radiation release, no one killed, and no serious long term hazard. Even the aftermath of Chernobyl–the worst accident ever–does not reflect the exaggerated initial casualty predictions. Similar exaggerated cancer death predictions undoubtedly will be made for this accident.
The Japanese reactors, forty-year-old GE BWR Mark-1s, were shut down automatically when the earthquake, 5 times greater than the building design, struck. All containment remarkably survived the 9.0 quake intact . Loss of core cooling resulted from the tsunami interrupting offsite electrical transmission and inundating the emergency diesel generators that powered the cooling systems. Fresh water supply also was destroyed by the tsunami, leading to the use of sea water and boron in attempts to cool down the reactor cores and the spent fuel storage pools close to the reactors. The reactor cores cannot be saved but the catastrophe predicted by the frantic reporting will not happen. The spent fuel has been in the pools for a year, about half the time required for fuel to cool enough for dry cask storage. It will heat, but It is more accessible for cooling, and there will be no massive Chernobyl-style releases.
Hydrogen explosions have occurred, 137-cesium and,131-iodine have been detected around Fukushima Dai-Ichi units one through four, resulting from intentional venting to relieve strain on containment, but no major radiation releases have occurred, and the containment appears to remain intact. If cooling conditions can be maintained, most of the spent fuel melting will have been averted and the final outcome will be a huge economic loss for the power company, an engineering nightmare to decommission all four units and associated pools, but with no serious injuries, nobody killed, and little or no long term radiation-related consequences.
Recall that the reactors were shut down and that the core heat comes from the decay of fission products. The residual heat is a small fraction of what would have been present from fission. If core geometry can be cooled and preserved, the cores will not become critical (new nuclear reactions) again. It is important to distinguish between decay heat and criticality which would introduce a new temperature excursion. So far, the Japanese are dealing only with decay heat. A new and serious feature of the Japanese reactor reports is the suggestion that containment has been breached but falling radiation levels indicate that containment is intact.
Finally, in the worst case, the reactor cores will melt but remain contained without massive release of a radioactive plume. Residual heat in an uncooled but shut down reactor is enough to melt the core. The Three Mile Island core melted, the containment held, no significant radiation was released, and no one was injured or killed–not even a grasshopper. The search for cesium at Three Mile Island was intense. Finally, a pike from the Susquehanna River gave evidence of 134-, and 137-cesium but it turned out to be from a nine-month-old Chinese atmospheric weapons test, not from Three Mile Island. The story illustrates the incredible sensitivity of detection instruments. The information that “radiation” has been detected on returning commercial aircraft, dutifully reported by the distracted press, also illustrates the remarkable sensitivity of detection devices, as does reporting of 131-Iodine in local milk, and activity in leafy vegetables. Little information on amounts or identity of contributing nuclides escaping from the reactor complex is available except that measured spikes of radioactivity exceed accepted emergency annual worker exposure limits fivefold (500 millisieverts). That value suggests that relatively small amounts have been released consistent with the notion that it comes from intentional venting and not a breach.
To put the event in perspective, the four reactor cores and associated spent fuel in pools are being stabilized, iodine and cesium releases are relatively small but indicate damage to the reactor cores, exposures of recovery personnel are low, and there have been no fatalities. Thus, Fukushima Dai-Ichi is worse than Three Mile Island, but far, far less serious than Chernobyl. The event is inconsequential by comparison with the awful tragedy that has befallen the Japanese people, and eventually someone should take the melodramatic media to task for misplaced priorities that virtually ignore the genuine tragedy.
The authors are retired from LANL, write for the Los Alamos Education Group, and have credentials to comment on the nuclear situation. One (DFP) has published on human radiation injuries, biological neutron dosimetry, and has experienced working in intense radiation fields during a reactor accident recovery operation. The other (WRS) served nine years on the AEC Advisory Committee on Reactor Safeguards, was on the scientific support staff of the Kemeny Commission investigating the Three Mile Island accident, where he was instrumental in explaining the small radiation (131-iodine) release.