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Panel Reporter: John Mathieson
Introduction
The session was attended by some 160 people.
John Mathieson introduced the panel, noting that one of the original invitees Prof. Vladimir
Tokarevsky, Ministry of Ukraine of Emergencies and Affairs of Population Protection from Consequences of Chornobyl Catastrophe (Ukraine), was unable to obtain a visa in time for the
conference. Didier Louvat is head of the Waste Safety Section of the Department of Nuclear Safety and Security, and looks after the section responsible for the Chornobyl Forum.
Bill Dornsife is currently with Waste Control Specialists, Texas, but at the time of the TMI accident
he was in the Pennsylvania Bureau of Radiation Protection. Lake Barrett is currently a consultant in the energy field but held the position of Acting Director of OCRWM within his time at
USDOE between 1993 and 2003. With relevance to the session, he was site director for the NRC stationed at TMI after the Unit 2 accident and was responsible for regulatory programmes
during the stabilisation and clean up of the damaged reactor.
Chornobyl
Given Prof. Tokarevsky's absence, John Mathieson gave some background to the accident. It occurred on
26 April 1986 to Chornobyl Unit 4 which was a RBMK 1000, 925MW(e) graphite moderated, water cooled reactor with no secondary containment building. An experiment was being carried out
relating to the loss of external power and the ability of the turbo-generator to continue cooling the reactor. However, engineers had bypassed emergency systems, demonstrating a lack of
safety culture, which together with a flawed reactor design led to the accident following the course it did. A power surge and steam explosion resulted in a graphite fire which was
eventually extinguished after 10 days. The explosion resulted in the dispersion of 8te out of 140te of fuel. Ultimately a sarcophagus was constructed to contain the damage.
Didier Louvat reported on the outcome of the recently completed Chornobyl Forum. This ran between
2003 and 2005 and comprised representatives from a number of UN affiliated organisations, and from Belarus, Russia and Ukraine. Its aim was to provide authoritative statements on the
accident relating to radiation health effects, environmental consequences, provide advice on remediation and health care programmes, and continued research.
He said the most significant health effects were the severe social and economic depression of the
affected regions leading to serious psychological problems: trauma caused by relocation of some 340,000 people, breakdown in social contacts, fear and elevated anxiety about unknown
health effects, and unexplained physical symptoms. The economic impact had been exacerbated by compensating people for exposure to risk rather than actual injury to health or economy
("victims" v. "survivors" attitudes) and difficulties in implementing expensive investment programmes, particularly in market conditions.
The majority of recovery operation workers and 5 million members of the public received relatively
minor radiation doses which did not result in any observable radiation-induced health effects. In total about 4000 deaths would be attributable to the accident among some 600,000
emergency workers, evacuees and residents of the most contaminated areas. Several hundred emergency workers received very high radiation doses of which 50 died from radiation sickness and
subsequent disease. About 4000 thyroid cancers had been detected in children and adolescents who drank contaminated milk; more than 99% were treated successfully but 9 persons died (by
2004). The remainder of the 4000 deaths would be from radiation induced cancers among the affected populations. He noted there was no prevalence of birth malformations observed.
Radiation levels in the environment had reduced by a factor of several hundred due to natural
processes and the introduction of countermeasures. The majority of land originally contaminated was now deemed safe, but in the Exclusion Zone, and some other limited areas, land-use
restrictions would be in place for decades. Although there had been an initial increase in mortality and a loss of reproductive capacity in plants and animals living up to 10-30 km, this
had recovered after only a few years. He added that, paradoxically, the Exclusion Zone had become a unique sanctuary for biodiversity due to the absence of human activity.
The priority now for Ukraine is the decommissioning of the destroyed Chornobyl Unit 4 and the safe
management of radioactive waste in the Exclusion Zone, as well as its gradual remediation.
In going forward, the Forum recommends that targeted research on long-term environmental, health and
social consequences should continue. This would include annual examinations of the highly exposed emergency workers and continued screening for thyroid cancer in children and adolescents.
There should be continued effort to bring down the incidence of infant mortality and cardiovascular disease. and improve people's mental health status; dependence on alcohol and tobacco
was also too high.
M. Louvat concluded by reporting that the 60th Session of the UN General Assembly had been positive about the Forum's findings, noting that it had reached the highest international consensus in the assessment of the accident and recommendations for future actions.
Three Mile Island
Bill Dornsife described the causes of the TMI accident and its impacts, indicating the response from
the State's perspective, recalling some personal anecdotes and highlighting waste management issues during cleanup. The accident stared on Wednesday, 28 March 1979 with the failure of
main feed water pump. This led to an increase in pressure of the primary circuit which in turn led to the pressure relief valve (PRV) opening, as intended. However, the PRV failed to
close with the consequence that cooling water poured out of the reactor exposing fuel. The operators failed to understand what the actual reactor coolant level was, not believing their
instruments, and a partial meltdown resulted. The containment system prevented major releases of radioactivity to the environment. He described the progress of events including his
appearance at the first press conference with the State's Lieutenant Governor.
The day following the initiating events had been relatively quiet but on what was later referred to
as "Black Friday", the Governor ordered the evacuation of pregnant women and children. Rumours had circulated that there had been an uncontrolled release of radioactive gas but it was
actually a controlled release to help relieve pressure. Over the weekend a hydrogen bubble appeared within the containment; this had caused some unfounded anxiety for fear of an explosion
which could not occur due to lack of oxygen.
It was estimated that some 14 million curies of noble gases (~500 PBq) and 14 curies (~500 GBq)
of I-131 were released during the course of the accident. About 50,000 curies (~2 PBq) of Kr-85 were vented from the containment and 2 million curies (~75 PBq) of tritium was released.
Within the first week following the accident it was estimated the maximum dose to someone situated near to the plant was be about 50 millirem (500 microsievert) this fell to 10 millirem
(100 microsievert) at about 5 miles and 1 millirem (10 microsievert) at about 10 miles and 0.1 millirem (1 microsievert) at 20 miles. It was estimated the maximum dose received as a
result of the accident was 83 millirem (830 microsieverts), noting that this was about half the annual dose received from natural background
radiation. The collective dose was estimated at about 3300 man-rem (~33 man-sieverts).
The accident gave rise to a number of waste management challenges. The EPICOR resins and waste from
the from the Submerged Demineralizer System were shipped to the Hanford LLW site. Damaged reactor fuel and core debris was shipped to INEEL.
In terms of impact, Mr Dornsife said "We scared the hell out of about 1 million people" due to poor
coordination of decision-making and communication. However, the lessons learned greatly improved light water reactor safety. TMI was an accident waiting to happen and the biggest untold
story he said was the rapid mobilisation of the nuclear industry to assist in response efforts. Ultimately, TMI was a big factor in no new plant orders. He showed a newspaper headline
which indicated that Catholics living near to the plant were given general absolution.
Lake Barrett added that while the actual problem ended within a relatively short time, it was
prolonged unnecessarily due to poor communication and lack of trust in the community.
Q&A
The question was asked whether examination of Chornobyl exposure data had triggered any new interest
in investigating the linear–no–threshold (LNT) dose-response debate. M. Louvat said that even with 5 million exposed individuals this would not provide enough statistical evidence to be
able to see any effects and justify such a study. Mr Dornsife added that some health studies following TMI had implied a link between cancer incidence and perceived risk. Lake Barrett
indicated that as the presentations had indicated, it was the socio-psychological effects that were a significant issue.
A further question related to the acceptability of a next generation of nuclear, given Chornobyl and
TMI. Mr Barrett thought there was significant worldwide momentum and that with the new reactor designs, accidents of the kind leading to Chornobyl and TMI could not happen. M. Louvat
indicated the importance of having proper organisational infrastructures in place, as required by the Nuclear Safety convention. This was later commented upon by one questioner who
indicated the necessity to have an independent nuclear regulator. Mr Dornsife added that TMI had indicated that small utilities should not be in the nuclear field. In comparing the
consequences of TMI and Chornobyl, it had to be remembered that the releases from Chornobyl were a factor of 3 million greater (for I-131) than TMI.
The suggestion was made by one commentator that a major cause of the Chornobyl accident was due to
the political system in place at the time. He believed the accident had been a major reason for the collapse of the Soviet system leading to opening up of the nuclear community in the
former Eastern Bloc. He praised the role of WANO in helping to introduce new safety systems to these reactors.
In response to a question on what specific plant design changes had taken place as a result of TMI,
Mr Dornsife and Mr Barrett pointed out a number including better plant shutdown safety systems, better control room layout and staff training and enhancement of emergency preparedness. Mr
Mathieson added that the last point was most significant in the UK, resulting in a wholesale review of emergency arrangements at nuclear power stations.
Referring to the psychological impact of accidents and how the population could be better prepared,
Mr Dornsife was of the view that not much could be done before the event, but a single voice for communicating with the public was a necessity. Mr Barrett agreed.
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2006 Waste Management Symposium