We already know many facts of Chernobyl, but they are rarely publicized in the media. The UN can't seem to come up with very modest funding (~$100,000/y) to continue the excellent work of UNSCEAR. It seems they prefer the Chernobyl myths to the facts.
It's time to rerun an old letter:
9 Sandwell Crescent
Evolving Safety Analysis Technology
I enjoyed very much the excellent paper by John Luxat in the August Bulletin. As he pointed out, recent changes in the electricity market are pushing the nuclear option to be more competitive, and this is driving an evolution/revolution in safety analysis. Among the areas being examined are the specific assumptions and their conservatisms to accommodate uncertainties in supporting knowledge. To help me understand these, I looked for an explanation of requirements established more than two decades ago, and found the 1981 paper by Domaratzki et al very useful.
In addition to cost reduction, the new market requires a reduction of fear and misunderstanding. One cause is terminology. Even when there are no consequences to people, we call failures in reactor systems accidents. This invites a comparison with airplane accidents.
A particularly challenging area of analysis is a potential large-break LOCA event. Because there were no LOCAs in CANDUs by 1981, the frequency of large-pipe failures was taken to be less than one in a 1000 reactor-years, based on a 1964 survey of high pressure piping systems in non-nuclear plants. “With 25 operating CANDU reactors, the average interval (between large LOCAs) would be at least 40 years.”  It would be appropriate to reassess this frequency, based on: our use of ASME-code material; our practice of high-quality design, construction and operation; and the excellent operating experience of ~450 nuclear plants during four decades.
The defined consequences of LOCA accidents are the radiation doses which would be received by individuals at the plant boundary and those living in the vicinity. We assume no protective action is taken (evacuation, use of iodine tablets) resulting in an average thyroid dose and whole-body dose for these two groups of people. And we use the LNT model to calculate the number of fatal thyroid cancers and the number of fatal cancers (due to the whole-body dose).
At some point, we might consider revising our assumptions to fit more realistic consequences of a nuclear accident. The actual consequences of the Chernobyl disaster,[3, 4] where the intensity of the damage and lack of containment allowed a much larger release than postulated for any western reactor accident, are as follows:
· ~40% of reactor core and most of its radioactivity released to the surroundings
· population evacuated soon after the event
· average whole-body dose 1.5 cGy (rad)
· ~1800 cases of operable thyroid cancer, in children, with 3 fatalities
· no excess leukemia or other cancers observed during the following 14 years
· severe psychological stress due to fear and relocation
· severe world reaction based on fear of contamination - social, political
· severe economic stress to the nation
Evidence has been accumulating for a century, and has been presented to us repeatedly by medical doctors, especially in recent years, that the net health effect of low doses of radiation seems to be beneficial, recognizing that children are more sensitive to significant doses. We seem to be ignoring this information. In a rational world, we would be addressing only risks that involve the reasonable likelihood of acute exposures greater than 10 cGy (10 rad) or continuous exposure rates greater than the range of natural background radiation levels. So the real consequences of a severe accident are fatalities of mostly plant workers and a very strong reaction from the public and the media due to the fear of cancer (and genetic effects) leading to severe economic consequences.
This raises the question of how many more decades we will continue to use LNT ideology, and help perpetuate the fear that has been exploited for more than a century to keep nuclear technology under a cloud of cancer. Use of a scientific model for the health effects would give nuclear energy a more positive image.
1. Luxat JC. “Safety analysis technology: evolution, revolution and the drive to re-establish margins.” CNS Bulletin, Vol. 21, No. 2, pp. 32-39, Aug 2000
2. Domaratzki Z, Campbell FR and Atchison RJ. “The nature of reactor accidents.” AECB paper INFO-0053, Jan 1981
3. “Chernobyl - ten years on: radiological and health impact, an appraisal by the NEA Committee on Radiation Protection and Public Health.” Nuclear Energy Agency, Organisation for Economic Co-operation and Development, pp. 47, Nov. 1995
4. “The radiological consequences of the Chernobyl accident.” UNSCEAR 2000 report to the General Assembly, Section 1.C.18, June 6, 2000
5. Pollycove M and Feinendegen LE. “Epidemiology, molecular cellular biology and occupational radiation exposure limits.” Proceedings of World Council of Nuclear Workers (WONUC) Symposium on the Effects of Low and Very Low Doses of Ionizing Radiation on Human Health, Versailles, France, 1999 June 17-18. 2000, Elsevier Science, ISBN: 0-444-50513-x, pp. 305-316
6. Tubiana M. “Contribution of human data to the analysis of human carcinogenesis.” C.R. Acad Sci, Paris, Life Sciences 1999, 322, pp. 215-224
7. Weart SR. “Nuclear fear: a history of images.” Harvard University Press, Cambridge, MA,1988; ISBN: 0-674-62835-7