Canadian Coalition
for Nuclear

Regroupement pour
la surveillance
du nucléaire

A Chernobyl in Canada?
It could happen . . .

Globe and Mail Op-Ed Article,
August 22, 1986.

by Dr. Gordon Edwards

Gordon Edwards is president of the
Canadian Coalition for Nuclear Responsibility.

Table of Contents

  • Disastrous Nuclear Accidents

  • Heat and Radioactivity

  • Facing the Facts

  • Possible Containment Failures

  • Limited Protection

  • Lack of Independent Review

  • Disastrous Nuclear Accidents

    Following the Chernobyl disaster, Canadian nuclear advocates were quick to assure us that "it can't happen here." Now, with Wednesday's announcement [August 20, 1986] that Ontario plans to go ahead with its $11-billion Darlington nuclear plant, the assurances are certain to be renewed. They will tell us the  CANDU  is such a superior reactor that it can't possibly melt down and, even if it did, the elaborate  CANDU  containment systems are so well-designed that the public would not be in danger.

    The official record shows otherwise. Three organizations have undertaken independent examinations of the dangers of  CANDU  reactors: the Ontario Royal Commission on Electric Power Planning, the Select Committee on Ontario Hydro Affairs and the Atomic Energy Control Board (AECB). All concluded that meltdowns are possible in  CANDU  reactors and that the  CANDU  containment system can fail.

    Heat and Radioactivity

    The fundamental problems are the same in all large nuclear power plants. All contain an enormous inventory of radioactive poisons, created inside the reactor as a result of the fission process. Because of this intense radioactivity, it is impossible to completely stop the heat generation in the event of an emergency. Even after shutdown, heat continues to be produced at about seven per cent of the full-power rate.

    Unless the residual heat is removed from the reactor core as fast as it is produced, the temperature will rise, and there is no theoretical limit as to how high it can get. Consequently, if all cooling systems fail, massive melting of the uranium fuel, the zirconium cladding and the stainless steel of the reactor vessel will occur, at temperatures in excess of  5,000  degrees Fahrenheit. Vast quantities of radioactive poisons will be driven off in the form of toxic vapors, ashes and gases. It is exceedingly difficult to contain all this material, particularly since there is a strong likelihood of steam explosions, hydrogen gas explosions and other chemical explosions with the meltdown.

    Facing the Facts

    In its  1978  report on nuclear power in Ontario, titled A Race Against Time, the Ontario Royal Commission wrote:

    A major reactor accident would lead to the severe overheating, and subsequent melting, of the nuclear fuel, which would give rise to a substantial quantity of radioactive material escaping, after breaching several formidable barriers, into the environment ...

    The radioactivity would collect in a 'cloud' and would be carried downwind. At distances of two or three kilometres, depending on wind velocity, the cloud would begin to disperse (the dispersal zone could extend to distances of several hundred kilometres) and radioactive materials would be deposited on the ground.

    The Royal Commission Report discredited claims by  CANDU  designers that the probability of a complete meltdown at Pickering is as low as one in a million (per reactor per year). Nuclear critics have made a "more realistic" estimate, says the report, which is about  100  times higher -- one in  10,000  per reactor per year. The Soviets used the same figure -- one in  10,000  per reactor per year -- as the probability of an uncontained core meltdown at Chernobyl.

    In its  1980  report, The Safety Of Ontario's Nuclear Reactors, the Select Committee on Ontario Hydro Affairs (an all-party committee of the Ontario Legislature) warned:

    It is not right to say that a catastrophic accident (in a  CANDU  reactor) is impossible ... The worst possible accident could involve the spread of radioactive poisons over large areas, killing thousands immediately, killing others through increasing susceptibility to cancer, risking genetic defects that could affect future generations, and possibly contaminating, for further habitation, large land areas...

    Accidents, mistakes and malfunctions do occur in [CANDU] nuclear plants: equipment fails; instrumentation gives improper readings; operators and maintainers make errors and fail to follow instructions; designs are inadequate; events that are considered `incredible' matter how careful we are, we must anticipate the unexpected.

    Possible Containment Failures

    Following the Chernobyl accident, Zygmund Domaratsky of the Atomic Energy Control Board -- the man in charge of licensing for all nuclear reactors in Canada -- said no  CANDU  reactor is designed to contain a meltdown, because it is such an improbable event.

     CANDU  containment systems are all elaborate, some more than others. Besides its own thick-walled containment structure, each power reactor in Ontario is also connected to a large vacuum building -- a separate structure designed to suck up the radioactive gases in an accident.  CANDUs in Quebec and New Brunswick -- as well as those in Korea, Argentina, India and Pakistan -- do not share this feature.

    But the  CANDU  containment system is not foolproof. It might be incapacitated by explosions like those that blew the roof off the Chernobyl plant or those that threw a four-ton gas-holder dome four feet through the air during a devastating nuclear accident at Chalk River, Ontario, in  1952. The  CANDU  containment system also relies on ventilation dampers automatically closing in the event of an accident. During an accident in  1958  at Chalk River, the ventilation system of the  NRU  reactor was accidentally jammed open, allowing significant amounts of radioactivity to escape from the plant.

     CANDU  containment systems may be impaired even before an accident occurs. The  1978  royal commission report cited one example where a significant leak (20  square inches) was discovered in the wall of the Pickering Unit 2 reactor building; it had gone unnoticed for about  1 1/2  years. On numerous other occasions, personnel airlock doors were found improperly closed, establishing a sizeable pathway to the atmosphere. In  1979, the containment structure of Ontario Hydro's Douglas Point reactor was found to be so leaky that the plant was forced to operate at reduced power until it was finally mothballed in  1984. In  1980, the select committee report warned that almost none of the  CANDU  containment systems was meeting the criteria.

    Limited Protection

    In the event of a meltdown, even if the ventilation dampers close, the vacuum building works perfectly, the containment has no leaks and the explosions are not too violent, the  CANDU  system still only partially protects the public. As an Ontario Hydro spokesman recently indicated on national television, radioactivity would eventually have to be released to the environment -- likely after about  24  hours -- because the vacuum building could no longer retain it.

    Canadians have taken much comfort in the fact that a  CANDU  reactor cannot experience a graphite fire like the one that raged in the Chernobyl reactor, because the  CANDU  uses heavy water rather than graphite as a moderator. But a fierce fire is nevertheless possible. Some  U.S.  nuclear experts have said that a  CANDU  reactor will probably burn up before it will melt down. This is because every  CANDU  contains zirconium metal in its core, which burns with a very intense heat. The cladding of the  CANDU  fuel, the metallic structure of the fuel bundles and the hundreds of pressure tubes inside the core are all made of zirconium. Being separated from the heavy-water moderator by zirconium alloy calandria tubes, these components are in a perfect position to sustain a raging zirconium fire that could release enormous quantities of radioactive smoke.

    If a catastrophic accident occurs in a  CANDU  reactor and the containment fails, what protection does the public have? Very little. All property insurance policies in Canada contain a "nuclear exclusion clause" that voids coverage in the event of radioactive contamination. The liability of the owner of a  CANDU  nuclear plant is limited to  $75-million by an act of Parliament. (At Pickering, this works out to about  $25  for every man, woman and child in the Toronto area.) By the same act, no compensation can be sought for cancers or other health effects occurring more than  10  years after the accident. Extraordinary precautions for an accident considered so improbable that it isn't worth spending money on engineered safeguards!

    Lack of Independent Review

    In its  1980  report, the Select Committee on Ontario Hydro Affairs made several recommendations regarding  CANDU  safety which have been largely ignored by all levels of government in Canada. The most important of these is Recommendation  VII :

    The  AECB  should commission a study to analyze the likelihood and consequences of a catastrophic accident in a  CANDU  reactor. The study should be conducted by recognized experts outside the  AECB  [Atomic Energy Conrol Board],  AECL  [Atomic Energy of Canada Limited] and Ontario Hydro...
    This recommendation was resurrected in the July 1986 Report of the Select Committee.

    When the Darlington go-ahead was announced Wednesday, Ontario's Liberal Government promised it would launch a special study of  CANDU  safety by "internationally recognized experts." How independent these experts are, and whether this study will meet the recommendations, remains to be seen.

    However, one thing is certain -- if Canadians do not wish to repeat the ghastly experience of the people of Ukraine, they must insist that their governments do the necessary studies, take the necessary measures and resist being lulled by a powerful technological lobby group -- the Canadian nuclear establishment.

    [ Accident Possibilities at Gentilly-2 and other CANDUs ]

    [ Findings on CANDU Safety ] [ All About Meltdowns ]

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