SECTION 2
By Gordon Edwards, Ph.D., President
Canadian Coalition for Nuclear Responsibility on behalf of the International
Fact-Finding Mission on Cernavoda 2
(January 2003)
The present paper has been submitted to Dipl. Eng. Manoela Georgieva, Deputy
Minister of Environment and Water of Bulgaria on March 10th, 2003, as requested
by her office during a meeting with representatives of Campagna per la riforma
della Banca mondiale in Sofia on January 18th, 2003. The submission to the
Bulgarian government meant to contribute to its evaluation of the environmental
information about the controversial Cernavoda-2 NPP project made available to it
upon explicit request by Romanian authorities under the provisions of the UN/ECE
Espoo Convention on EIA in a Transboundary Context. The paper has been
transmitted, along with other NGO submissions, to Romanian authorities in April
2003.
First and foremost, it is important to note that CANDU
reactors are by no means immune from the threat of catastrophic accidents. In
what follows, we call your attention to several official Canadian documents
dealing precisely with this point. In the event of such an accident, large
quantities of radioactive materials can be released into the atmosphere and can
travel for many hundreds of kilometers, contaminating land, buildings, food, and
water supplies through radioactive fallout.
Since 1978, when the first of these official documents was published in Canada
(A Race Against Time, the report of the Ontario Royal Commission on Electric
Power Planning dealing specifically with Ontario's nuclear reactors), there have
been no new orders for nuclear reactors anywhere in Canada, nor are there any
plans for building more CANDU reactors by any public utility in any of the
provinces or territories of Canada.
Members of the International Fact-Finding Mission on
Cernavoda-2, which visited Romania in January 2003, were stunned when told by
officials of the Environmental Protection Agency that they considered
transboundary impacts from the Cernavoda-2 reactor to be impossible. At the
same meeting, the head of the Romanian nuclear regulatory agency insisted that
transboundary effects are not relevant because, he said, "we have a containment
structure; we have a one-kilometer exclusion zone."
The naiveté of these comments is chilling. Contrast them with the published
findings of the Ontario Royal Commission of Inquiry Into Electric Power
Planning: "All operating nuclear reactors accumulate in their cores, as we have
indicated, a large quantity of radioactive material. For the most part this is
made up of fission products, many of which are short lived and usually very
radioactive, and the actinides (e.g. plutonium-239) which are very long lived
and highly toxic substances.
"By definition, 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 major health and environmental threat would be due to the escape of the
fission products to the atmosphere. The most important of these are caesium,
ruthenium, tellurium and the fission gases, iodine, krypton and xenon.
"... If a substantial quantity of radioactivity were to be released to the
atmosphere, the radioactivity would collect in a "cloud" and would be carried
down wind.
"... 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. In consequence, both prompt and latent cancers would be produced.
"... When we talk about the safety of a nuclear reactor, we are referring
essentially to how effectively the fantastic amount of radioactivity contained
in the reactor core can be prevented from escaping into the ground and
atmosphere in the event of major malfunctions.
"Clearly, if a major release of this accumulated radioactivity occurred, as
discussed in the previous section, the consequences would be extremely serious
and could involve several thousand immediate fatalities and many more delayed
fatalities."
A Race Against Time, pp. 73-76
Ontario Royal Commission on Electric Power Planning, 1978
Evidently, severe accidents in CANDU reactors -- which by definition are
fuel-melting accidents -- do carry with them a potential for serious
transboundary effects.
In answer to direct questioning from members of the Fact-Finding Mission,
Romanian officials confirmed that the six cases of "severe accidents" listed on
page 133 of the ICIM EIA Summary do involve fuel melting. Nevertheless, there
is no acknowledgment or discussion of transboundary effects -- nor, for that
matter, even of local environmental contamination resulting from such accidents.
Following the Three Mile Island (TMI) accident, the Select
Committee on Ontario Hydro Affairs -- an all-party committee of the Ontario
Legislature -- held public hearings on the hazards of CANDU reactors. From its
1980 Report on this matter:
"It is not right to say that a catastrophic accident 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 large land areas for future habitation
or cultivation."
The Safety of Ontario's Nuclear Reactors, pp. 9-10, Select Committee on
Ontario Hydro Affairs, 1980.
None of the Romanian officials we met recognized these threats as credible in
the context of the Cernavoda 2 NPP. Indeed, they seemed bewildered that we
would even raise such questions. In effect, they were telling us that
catastrophic accidents are impossible. Such an attitude of denial, based on
ignorance or not, is dangerous.
Following the Three-Mile-Island (TMI) accident in 1979, US President Jimmy
Carter ordered a special Presidential Inquiry into the causes of the TMI
accident. The Commission found that attitudes of denial on the part of the
regulators and operators of nuclear power plants, preventing them from
appreciating the danger, was one of the most important factors contributing to
the severity of the accident.
"In announcing the formation of the Commission, the President
of the United States said that the Commission 'will make recommendations to
enable us to prevent any future nuclear accidents.' After a six-month
investigation of all the factors surrounding the accident and contributing to
it, the Commission has concluded that:
"to prevent nuclear accidents as serious as Three Mile Island, fundamental
changes will be necessary in the organization, procedures, and practices -- and
above all -- in the attitudes of the Nuclear Regulatory Commissi on and,
to the extent that the institutions we investigated are typical, of the nuclear
industry." [emphasis in original]\
"... the belief that nuclear power plants are sufficiently safe ... must be
changed to one that says nuclear power is by its very nature inherently
dangerous, and, therefore, one must continually question whether the safeguards
already in place are sufficient to prevent major accidents."
The Need For Change - The Legacy of TMI, pp. 7 and 9,
Report of the President's Commission on the Accident at Three Mile Island,
1979.
There is one outstanding feature of the Cernavoda 2 design
that makes it particularly vulnerable to serious accidents, including meltdowns.
Instead of containing all the nuclear fuel in one large vessel, CANDU reactors
house the fuel in hundreds of separate "fuel channels" each enclosed in its own
individual "pressure tube". In this regard, CANDU is similar to the Chernobyl
reactor design.
It is well known that such "pressure tube" reactors all share a dangerous
characteristic known as "positive void coefficient of reactivity". In plain
English, the positive void coefficient means that whenever there is a loss of
coolant in one or more channels of the reactor core, there is an immediate power
surge. This compounds the accident, for if the power surge is not immediately
dealt with -- within seconds -- the core could self-destruct quite violently,
and the resulting energy release could breach the containment, providing a
pathway for radioactivity.
The world's first severe nuclear accident took place in Chalk River Ontario in
1952, when the Canadian NRX research reactor (a precursor of the CANDU )
suffered a loss-of-coolant. It was accompanied by a power surge, due to the
positive void coefficient, and the control rods were unable to stop the fission
reaction. This precipitated a series of explosions (either steam explosions or
hydrogen gas explosions, no one is certain) powerful enough to fling the
four-ton gasholder dome through the air and destroy the core of the reactor.
The damaged NRX reactor core is buried somewhere on the Chalk River site.
In 1969, in Switzerland, the Lucens reactor -- another pressure tube design --
exploded inside a rocky cavern when a loss-of-coolant accident (LOCA) provoked
an uncontainable power surge; the reactor was totally destroyed.
The pressure-tube design of the ill-fated Chernobyl reactor was an important
factor contributing to the sudden surge in power and heat -- brought on by the
positive void coefficient -- that led to the melting of the core and the
explosive penetration of containment in the accident of 1986.
The positive void coefficient of reactivity is a generic design flaw of all
pressure tube reactors; it is one of the worrisome characteristics of the
Cernavoda 2 reactor.
On page 133 of the ICIM Cernavoda 2 NPP Environmental Impact
Summary, one reads of "severe accidents that are not considered in the design
because their probability is lower than 10-7 events per year." Thus ICIM claims
that severe accidents in CANDUs would occur less than once in 10 million reactor
years!
These probability estimates are simply not credible.
In 1974, the US NRC (Nuclear Regulatory Commission) published its 12-volume
Reactor Safety Study (commonly known as "The Rasmussen Report") . The report
concluded that the probability of a complete core meltdown is about 1 in
20,000 per reactor per year. That is already 500 times greater than the ICIM
estimate for the probability of a "severe accident" at Cernavoda 2 with
(according to ICIM) no serious environmental consequences worth mentioning.
One of the major findings of the Rasmussen Report was that small pipe breaks,
rather than large pipe breaks, are the most significant contributors to the
probability of a core meltdown in a nuclear reactor. Because of its "pressure
tube" design, the CANDU reactor has a great deal more small piping -- even in
the primary cooling system -- than other reactor types. Thus the probability of
a small pipe break in a CANDU reactor is significantly higher (one or two orders
of magnitude more) than the probability of a small pipe break in an American
light-water reactor.
Thus the probability of a core meltdown in a CANDU reactor such as Cernavoda 2
may well be higher than the probability of such an accident in an American Light
Water reactor. Indeed, that was one of the conclusions reached by the Ontario
Royal Commission on Electric Power Planning in its 1978 Report about Nuclear
Power in Ontario, as seen in the following excerpt:
"During normal operation, not only is a great deal of radioactivity created in
the reactor core but also a great deal of thermal energy. If the shutdown
system fails to operate in response to a fuel temperature rise, caused by a
major rupture in the primary coolant circuit, a rapid escalation of heat and
temperature would occur. The purpose of the ECCS [Emergency Core Cooling
System] is to remove the heat from the core as rapidly as possible.
"If, however, both primary coolant and emergency coolant fail there would
probably be partial or complete melting of the reactor core. An uncontained
complete core meltdown would almost certainly give rise to a large release of
radioactivity, the consequences of which were discussed previously....
"Assuming absolute independence of the process and safety systems, the
probability of a core meltdown per reactor at Pickering is said to be in the
order of 1 in 1,000,000 years....
"However, two well-informed nuclear critics who participated in the hearings,
Dr. Gordon Edwards and Ralph Torrie, have argued that the probability of a dual
failure could be about 100 times higher than the theoretical levels. This
estimate is based on failure rates in the high pressure piping of the primary
heat transport system being 10 times higher than has been assumed, and also on
the fact that the availability of the Pickering ECCS has been demonstrated to
be 10 times lower than postulated by the designers.
"We believe that the Edwards/Torrie estimate [of 1 in 10,000 per reactor
per year] is more realistic than the theoretical probability, not least because
the Rasmussen Report has concluded that the probability of an uncontained
meltdown in a light water (U.S.) reactor is 1 in 20,000 per reactor per
year. It has been suggested, moreover, that this figure could be out by a
factor of five either way.
"Assuming, for the sake of argument, that within the next forty years Canada
will have 100 operating reactors, the probability of a core meltdown might be
in the order of 1 in 40 years, if the most pessimistic estimate of
probability is assumed...."
A Race Against Time - Nuclear Power in Ontario, pp. 78-79,
Report of the Royal Commission on Electric Power Planning, 1978.
Thus in Canada, independent assessment of the CANDU industry's probability
figures by a credible and responsible body has shown those estimates to be
highly suspect. The same can be said of the unsupported probability figures for
"severe accidents" at Cernavoda 2 quoted by ICIM. Hence the industry's low
probability estimates do not constitute a valid reason for refusing to address
the transboundary health and environmental consequences of severe accidents at
Cernavoda 2 NPP.
Reactor designers have provided special safety features to
deal with
anticipated emergencies: containment systems, emergency core cooling
systems, fast shut-down systems, emergency electrical supply systems,
and so on. Unlike most other reactor types, each CANDU reactor has two
fully independent fast shut-down systems. This redundancy was prompted
by the need to cope with the sudden surge in power following a
loss-of-coolant, due to the positive void coefficient. The cost of
adding a second fast shut-down system was justified by the fact that
"loss-of-regulation" accidents -- those which may require the use of a
fast shut-down system -- were occurring about a hundred times more
frequently in Ontario's CANDU reactors than predicted by the industry's
probability calculations.
In operational situations, however, CANDU safety systems are often
partially or completely unavailable. In some cases, CANDU emergency
cooling systems have been unavailable for months at a time. CANDU fast
shut-down systems are also unavailable at times. Just recently in
Canada, for example, CANDU workers mistakenly installed a neutron
detector backwards, so that the second fast shutdown system would have
been unavailable during an emergency.
Such unavailability episodes are usually not discovered by plant
operators or regulators until long after the fact -- possibly during a
maintenance shutdown, and sometimes not even then.
Likewise, CANDU containment systems have suffered impairments for long
periods. The kind of problem outlined below is not an isolated
instance:
" . . . a leak was discovered in the wall of the Pickering unit 2
reactor building in June, 1974, and may have existed for 1 and 1/2
years -- this leak 'would have reduced the ability of the containment
system to limit radioactive release after any unit 2 accident since the
beginning of 1973'. . . . As Ralph Torrie has pointed out, the
'Pickering unit 2 containment would have to operate within target
levels for 500 years before the average annual availability would be
back within the bounds of the annual regulatory limit'.
"In assessing the legitimacy of the above limits it should be stressed
that no study similar to the Rasmussen study has been undertaken in
Canada to assess the reliability of the reactor system as a whole and
the consequences of major CANDU reactor accidents."
A Race Against Time - Nuclear Power in Ontario, p. 79,
Report of the Royal Commission on Electric Power Planning, 1978.
The Cernavoda 2 reactor will be subject to similar problems of
unavailability. On page 133 of the ICIM Report, for example, five of
the six accident scenarios involve "impairment of the pre-existing
containment envelope", while the remaining scenario involves "late
containment failure due to steam over-pressurization". Given the
hypotheses of impaired containment at Cernavoda 2, it is a mystery why
ICIM believes that radiation releases will not continue beyond 24 hours.
In the event of a pipe break in the primary cooling system at Cernavoda
2, the superheated cooling water will flash into steam, instantly
pressurizing the interior of the containment building and driving
radioactive gases and vapors into the outer atmosphere if there is any
impairment of the containment envelope. Such impairment of containment
can occur in many different ways -- for example, by failure of
ventilation dampers to close properly, by failure of personnel air-lock
doors to seal correctly, or by means of undetected leaks around any of
the hundreds of penetrations through the containment wall. As long as
steam is being generated by the heat of the crippled core, radiation
releases would be expected to continue.
Compared with the CANDU reactors in Ontario, leaks in the containment
wall of Cernavoda 2 could have more serious health and environmental
consequences in the event of a major reactor accident. This is because,
at Cernavoda, there is no "Vacuum Building" as there is at every
operating CANDU reactor in Ontario.
A "Vacuum Building" is a separate large structure connected to the
reactor, designed to "suck up" all the radioactive steam and vapors
released from the reactor core during a major accident. CANDU export
models, like Cernavoda 2, have been re-designed without a Vacuum
Building in order to reduce over-all costs.
In 1989, the Atomic Energy Control Board (AECB) -- the Canadian nuclear
regulatory agency -- submitted a report to the Treasury Board of
Canada. This report echoed the conclusion of the Ontario Royal
Commission on Electric Power Planning cited earlier by re-asserting that
there is no basis for believing that CANDU reactors are safer than any
other type of reactor. It also added the important perception that
safety problems seem to multiply as time goes by and the plants get
older:
"When modern nuclear power plants were being designed in Canada two
decades ago, their complexity and potential for catastrophic
consequences were recognized. The plants were designed to high
standards, and special safety systems were incorporated to prevent or
reduce the consequences of malfunctions. Reactor designers and owners
adopted a relatively simple process for evaluating plant safety. 'Worst
credible' accident scenarios were investigated to ensure that their
consequences would be acceptably low. It was then assumed that the
consequences of less severe but more likely accidents would be
acceptable.
"Since that time, experience in Canada and the rest of the world has
demonstrated that this approach to safety is too simplistic. It is
recognized now that, through the combination of a series of
comparatively common failures which, on their own, are of little
consequence, accidents can develop in a myriad of ways (as demonstrated
most vividly at Three Mile Island and Chernobyl). This makes the
calculation of consequences of potential accidents very difficult,
research to simulate accident consequences is often incomplete, and,
perhaps most significant, human errors are an unquantifiable element.
"As a result, there is a legacy of unresolved safety issues that should
be addressed further. This issue is particularly important as twelve of
Canada's largest reactors are close to Toronto.
"AECB's review of safety has also been too simplistic. Spot checks of a
fairly small number of the key areas were thought to be sufficient.
These spot checks have uncovered enough safety problems to demonstrate
that more thorough review is essential, since the risk posed by nuclear
power plants may be higher than once believed.
"The size and complexity of the task of ensuring and demonstrating the
safety of nuclear power plants has not increased suddenly -- it has been
building up for the last decade. It has led reactor designers, operators
and regulators around the world to demand far more thorough analyses
which are far more complex, and a far more detailed understanding of how
a plant can malfunction, than was required in the past.
"The task is overwhelming the AECB. It does not have the resources to
analyze and understand this increased level of knowledge and
information. Three examples will illustrate the problem....
"The consequences of a severe accident can be very high. The accident at
Chernobyl has cost the Soviet economy about $ 16 billion including
replacement power costs. The accident has generated anti-nuclear
sentiment in the USSR and throughout the world. Three Mile Island has
cost the USA $ 4.8 billion even though the Three Mile Island accident
had essentially no radiation impact on the public. The accident was a
major contributor to the public distrust of nuclear power in the USA.
"The years of successful accident-free operation which are a hallmark of
the Canadian nuclear program are not, by themselves, proof of adequate
safety. Canada has amassed about 170 years of operation of large
reactors, compared with 480 years in the US and 270 years in the
USSR at the time of Three Mile Island (1979) and Chernobyl (1986)
respectively. The likelihood of serious accidents cannot be judged from
statistics such as these, and CANDU plants cannot be said to be either
more or less safe than other types....
"Given the potential consequences of severe accidents everything
possible should be done in order to increase the confidence in the
AECB's judgment by improving the depth and breadth of its technical
evaluations and inspections. The AECB considers that the scope and depth
of the reviews on which it makes its judgments currently is
insufficient. The resources needed to ensure that licensees are taking
all possible measures to prevent accidents and for the AECB to take
enforcement action when they do not are also currently insufficient."
Report to the Treasury Board of Canada, Atomic Energy Control Board, 1989.
In 1997, seven of Ontario's CANDU reactors were voluntarily shut down by
the owner. Ontario Hydro, because of an inability on the part of Hydro
management to cope with the huge backlog of safety-related maintenance
issues:
"Long standing management, process and equipment problems in Ontario
Hydro Nuclear (OHN) plants are well known but have not been aggressively
resolved. . . . Immediate attention is needed to improve performance. .
. .
"OHN staff at every level are reluctant to ask difficult questions of
themselves and others. Failure to establish a questioning attitude is
a primary cause of the reduction in the "defense-in-depth" concept.
There is no real independent evaluation of proposed operations by
people not directly involved in formulating the planned actions (e.g. is
this the safest way to accomplish an operation? Are the operators
challenged unnecessarily by the proposed change? Will all required
structures, systems and components remain capable of performing their
intended functions for their day-to-day mission and all credible
accident scenarios?)"
Executive Summary, Findings and Recommendations of the IIPA/SSFI
Evaluation ,
A Report to Ontario Hydro Management, June 1997.
Those seven Ontario reactors are still shut down today, six years
later. Although plans are underway to restart some of them, the
combined cost of doing so -- currently estimated at about three billion
dollars -- may prove prohibitive.
If Ontario Hydro, despite its wealth of experience with CANDU technology
and its stable of well-paid professionals, cannot manage to keep CANDU
reactors operating safely, it is not unreasonable to ask how Societata
Nationala Nuclearelectrica (SNN) will manage to do so with Cernavoda 2.
Yet SNN officials seem completely unfazed by the challenge, perhaps
because they do not yet grasp the complexities of the problems.
Cernavoda 2 -- like all large nuclear power reactors -- will contain an
enormous inventory of radioactive materials. About 300 different kinds
of radionuclides will be created inside the reactor as an inevitable
result of the nuclear fission process. They all generate heat as a
result of radioactive decay. Most of the heat is produced by the
"fission products" -- the broken bits of uranium and plutonium atoms
that have been "split". In addition to the fission products are the
"activation products" -- previously non-radioactive materials that have
become radioactive as a result of nuclear transmutation -- and the very
long-lived and highly toxic "transuranic elements" (the so-called
"actinides") such as americium, plutonium, and curium -- heavy man-made
elements, created when uranium atoms in the fuel absorb one or more
neutrons without splitting.
As previously noted, large releases of radioactivity into the
environment may occur whenever the reactor fuel is severely damaged and
the containment of the reactor building is impaired. Moreover, fuel
melting can occur in the absence of nuclear fission. The irradiated
fuel will melt spontaneously even though the reactor is completely shut
down, if there is inadequate cooling of the core. During the TMI
accident, for example, the reactor was shut down almost immediately, yet
fuel melting took place over the next two or three days.
The Cernavoda-2 reactor operating at full power will generate about 2100
megawatts of heat (only one-third is transformed into electricity).
Immediately after shutdown, due to radioactive decay, the core will
continue to generate about 7 percent of full power heat -- that is,
about 147 megawatts of heat. One hour after shutdown, residual heat
generation will still be about 4 percent of full power heat -- that is,
84 million watts of heat. That is more than enough heat to melt the
core of the reactor. Unless the "decay heat" is removed promptly and
continuously, the core will melt.
Moreover, even in the absence of a pre-existing impairment of
containment, the course of the accident itself could unleash forces that
would end up breaching the containment envelope through
over-pressurization, explosions, or melt-through.
The Canadian Department of Energy Mines and Resources published a report
on nuclear issues in Canada in 1981; here's some of what they wrote
about meltdowns:
"In the absence of relevant Canadian information, the work done by N. C.
Rasmussen, as described in the Reactor Safety Study (WASH-1400) issued
in 1975 by the U.S. Nuclear Regulatory Commission is used. The
following information borrows extensively from that document and
although not strictly applicable to CANDU reactors, does give useful
illustrative information on very serious potential accidents.
"The Reactor Safety Study defined two broad types of situation that
might potentially lead to melting of the reactor core: a LOCA [Loss Of
Coolant Accident] , and transients.
. "In the event of a LOCA , the normal cooling water would be lost from
the main cooling system but core melting would normally be prevented by
the action of the ECCS [Emergency Core Cooling System] .
"However, if the ECCS failed to act, melting of metallic components of
the core and eventually of the uranium oxide fuel itself would probably
occur.
. "The term 'transient' refers to those situations where there is an
uncontrolled increase in reactor power or a loss of normal cooling flow,
both of which require the reactor to be shut down. Following shutdown,
the decay heat removal systems act to keep the core from overheating.
However, if the reactor fails to shut down or the decay heat removal
systems fail, melting of the core would ensue.
"The Rasmussen study conservatively assumed that if any melting
occurred, then complete core melting would occur. It was then predicted
that the molten core, consisting of a mixture of molten uranium oxide,
stainless steel, zirconium, and other core structural materials, could
melt through the bottom of the 20 cm thick steel reactor vessel and
through the 3.69 meter thick concrete base slab of the containment
structure.
"The study estimated the time for going through the reactor vessel to
be 1 to 1 1/2 hours and through the base slab to be an additional
13 to 28 hours. The molten mass was then predicted to sink into the
ground an additional 3 to 15 meters before coming to rest.
"Much larger consequences could be associated with core meltdowns which
also cause failures in the containment structure above ground. If the
containment sprays malfunction or are damaged by flying debris
(generated by a LOCA or transient) the steam being released from the
reactor core would not be condensed.
"This steam, along with various vapors and noncondensible gases, could
cause failure of the containment structure due to over-pressurization.
Hot zircaloy from the fuel sheaths and steel would also react with water
to produce large volumes of hydrogen. Detonation of this hydrogen
(reacting with oxygen) might damage the containment or, if not, the heat
of combustion combined with high steam pressure would at least add to
the pressure loads on the structure.
"A further contributor to containment pressurization would be the large
quantities of carbon dioxide generated as the molten core melts through
the concrete base slabs. Another possibility is one in which the molten
fuel falls into the pool of water in the bottom of the reactor vessel
with the formation of flying debris which could, in turn, damage the
containment structure. All post-meltdown occurrences which threaten to
damage or breach the containment structure can result in the release of
substantial amounts of radioactive material to the environment."
Nuclear Policy Review Background Papers, pp. 210-211,
Department of Energy Mines and Resources (Canada), 1981.
As already noted, ICIM lists six accident scenarios involving fuel
melting on page 133 of the EIA Summary (although nothing is said about
fuel melting in the text). In all of these scenarios, the Cernavoda 2
containment is assumed to be impaired (or breached) and "large" (or
"significant") radioactive releases are assumed to take place, at least
for the first 6 (or 24) hours. Yet each scenario is allotted only one
sentence, and there is not even a definition of terms such as "large"
and "significant". Nor is there any discussion of environmental impacts
associated with these scenarios.
The ICIM EIA Summary makes no mention of how much radioactive iodine,
cesium, strontium, or plutonium is expected to be released in each of
the six cases of severe accidents listed on page 133. There is no
description of the behavior of the radioactive plume, no discussion of
the degree of long-term environmental contamination remaining once the
emergency is over, and no mention of possible transboundary effects.
The ICIM document simply refuses to deal with such unpleasant realities.
According to the Rasmussen Report, under the worst conditions, a major
nuclear accident could result in:
. about 45,000 cases of radiation sickness requiring
hospitalization, of which about 3300 would die;
. about 45,000 fatal radiation-induced cancers in the thirty-year
period following the accident;
. about 250,000 non-fatal radiation-induced cancers in the
thirty-year period following the accident:
. about 170 genetically defective children born each year to the
population surviving the accident;
. about $14 billion dollars (1974 dollars) in property damage,
mainly due to radioactive contamination of food, water, land,
and buildings.
According to the ICIM EIA Summary, the consequences of severe nuclear
accidents at Cernavoda 2 are not even worth mentioning.
There are evacuation plans in the event of a nuclear accident at
Cernavoda 2, and officials of the Environmental Protection Agency told
the members of the Fact-Finding Mission about an actual rehearsal that
was carried out last year.
However, those same officials revealed that they had never questioned
the proponents of the project about possible residual radioactive
contamination of the environment after the emergency was over.
If such matters were not raised in the report, members of the
Fact-Finding Mission were told, then they were of no concern to the
Environmental Protection Agency. They did not seem to think it
appropriate that the Environmental Protection Agency should question the
adequacy of the Environmental Impact Assessment presented to them by the
proponent.
Romania is an earthquake-prone region, Because of the great depth from
which some of these quakes originate, the so-called "sub-crustal" quakes
are often less attenuated and more destructive than quakes of comparable
magnitude originating in other regions of the world. These sub-crustal
quakes have in the past killed thousands and caused great damage. In
some cases they have been felt as far away as Moscow. Earthquakes
originating closer to the surface ("crustal quakes") are also common in
the region, some with epicenters much closer to the Cernavoda site --
including some just across the border in Bulgaria.
Because Cernavoda 2 uses natural uranium rather than enriched uranium,
it is a larger and bulkier structure than reactors of different design
but comparable power. Other things being equal, large structures are
often more vulnerable to earthquake damage than smaller ones.
Even if the overall structural integrity of the reactor is not
challenged, internal damage may occur, possibly affecting the integrity
of the containment envelope (e.g. the ventilation dampers) or the
special safety systems of the reactor.
As previously mentioned, the Cernavoda 2 reactor will contain
proportionately more small piping than most other reactors. During an
earthquake, vibrations may precipitate some pipe breakage inside the
reactor building, thereby causing a loss of coolant and a power surge.
Electrical supply problems could also become manifest.
If a severe earthquake occurred during on-line refuelling -- an activity
which is carried out every day in a CANDU reactor -- it is conceivable
that mechanical interaction between the fuelling machine and the
pressure tubes could cause breakage of pipes at both ends of the
horizontal core. This would be a particularly serious situation;
emergency coolant could not be expected to flow through the core in such
a case, due to a lack of the necessary pressure differential.
This safety concern involving a "double-ended pipe break" was identified
many years ago by the US Argonne National Laboratory in a short paper on
CANDU reactors. To the best of our knowledge, this concern has never
been fully addressed.
In response to direct questions from the Fact-Finding Mission,
representatives of the SNN admitted that such accident scenarios,
involving the simultaneous breakage of pipes on both sides of the
Cernavoda 2 reactor core, have never been analyzed.
Experience in Canada has shown that as the years go by, CANDU reactors
undergo a process of accelerated aging. In particular, the pressure
tubes in the core of the reactor become increasingly brittle, and
therefore increasingly likely to crack or split without warning, thus
causing a loss-of-coolant accident. Moreover, the sudden influx of cold
emergency cooling water into the hot pressure tubes could cause further
breakage because of the embrittlement of the tubes. At a certain point,
the pressure tubes must be replaced for safety reasons.
Retubing the core of a CANDU reactor is a major operation. The plant
has to be shut down completely for one to four years. The reactor has
to be "de-fuelled", the heavy water moderator has to be drained out of
the core, and the intensely radio-active pressure tubes must be removed
and replaced with new ones. The materials in the pressure tube walls
have become radioactive through "neutron activation", and must now be
treated as highly radioactive waste materials.
Currently, in Canada, there are two reactors operating which are based
on the same design as the Cernavoda 2 reactor; these are the Point
Lepreau reactor in New Brunswick and the Gentilly-2 reactor in Quebec.
Both of them have been operating for less than 20 years. Both of them
must be re-tubed if they are to continue operating safely. The
estimated cost of refurbishing the reactors, in both cases, is estimated
to be $845 million Canadian (approximately $550 million US).
This is a very large price tag. So large, in fact, that the Public
Utilities Commission (PUC) in New Brunswick last year, after hearings,
unanimously recommended against refurbishing the Point Lepreau reactor.
In their report, the PUC expressed skepticism that the price of
refurbishment would be kept to within the $845 million estimate, since
the nuclear industry in Canada has an extensive track record of
underestimating the costs of nuclear engineering projects by factors of
2 to 4.
Given Romania's credit situation, it may prove difficult to borrow the
$1690 million Canadian ($1100 million US) that may be needed to
refurbish both Cernavoda 1 and Cernavoda 2 when the time comes. Yet we
were informed by the SNN authorities that they have not established a
fund to finance such refurbishment projects.
But there are serious safety implications involved in not refurbishing
the reactors. The older the plants get, and the more embrittled the
pressure tubes become, the greater the likelihood of a severe accident
having transboundary impacts.
The most obvious difference between CANDU reactors and other power
reactors is the use of "heavy water" or "deuterium oxide" (chemical
symbol D2O ) instead or "light water" or "hydrogen oxide" (chemical
symbol H2O ) as a coolant/moderator. Indeed, the word "CANDU" stands
for "Canadian Deuterium Uranium".
Heavy water is chemically identical to light water, but it is slightly
heavier and very expensive. Although deuterium (D) is a naturally
occurring form of hydrogen, much time and energy is needed to produce
concentrated D2O. Up to 20 percent of the capital cost of a CANDU
reactor is due to its large heavy water inventory.
The nucleus of an ordinary hydrogen atom (H) consists of a single
proton. A deuterium atom (D) is twice as heavy; its nucleus consists of
a proton and a neutron bound together. Because deuterium atoms already
contain one neutron, they are less likely than hydrogen atoms are to
absorb other neutrons -- neutrons that are needed to keep the nuclear
fission chain reaction going inside the nuclear reactor.
For that reason, heavy water is far more "neutron-efficient" than
ordinary light water. By using heavy water instead of light water,
CANDU technology allows for the use of "natural uranium" instead of
"enriched uranium" as a fuel. Thus the extra cost of the heavy water is
offset by the lower cost of the fuel in a CANDU plant.
But there is an environmental price to pay for this technological
efficiency. When a deuterium atom does absorb a neutron, which happens
all the time during fission, it becomes a tritium atom (T). A tritium
atom is three times as heavy as a normal hydrogen atom; it consists of
one proton and two neutrons bound together.
But tritium is a radioactive form of hydrogen, hence dangerous. It is a
weak beta-emitter with a half-life of 12.3 years. It is released into
the environment in large quantities by every operating CANDU reactor;
tritium emissions are at least one or two orders of magnitude greater
from CANDUs than from light-water reactors.
Tritium appears most often in the form HTO or DTO ("tritiated water") ,
both of which are chemically identical to ordinary water. Consequently
tritium is very difficult to control; it cannot be filtered out, for
example. It is given off into the air and the water on a routine
basis. From time to time large spills occur in which tens of thousands
of curies of tritium may be released into the environment all at once.
Moreover, tritium is constantly being produced in the "heavy water" that
is used as both primary coolant and as moderator in the CANDU reactor
design. Every year, the inventory of tritium in this large volume of
heavy water increases, and so the amount released to the environment
also generally increases year after year.
For example, in the ICIM EIA Summary, the following figures are given
for releases of tritium into the atmosphere from Cernavoda-1 (Table
III.2.5-1) :
1997 25.57 terabecquerels
1998 50.67 terabecquerels
1999 84.89 terabecquerels
2000 208.03 terabecquerels
[These figures are obtained by multiplying the reported emissions in the
last four columns of the table by one percent of the annual derived
emission limit given in column 1. Note that one TBq = 1 terabecquerel
= 1 million million becquerels]
Notice that the atmospheric tritium emissions in the table are roughly
doubling each year. Annual tritium emissions to the atmosphere would be
expected to continue to increase throughout the lifetime of the plant,
unless an expensive tritium-removal plant is built to remove the
tritium from the heavy water moderator and coolant of the reactor.
Such a tritium removal plant was built in Ontario, Canada, for precisely
this purpose.
Although tritium is a very weak beta emitter and therefore difficult to
detect, laboratory studies have shown that it is more effective in
causing cancer, per unit dose, than gamma rays or x-rays. The "quality
factor" (QF) is between 2 and 3. Tritiated water enters easily into
animals, plants and soil just as ordinary water does. Also, tritium
enters readily into all organic molecules including DNA. In Canada
there has been much controversy over rising levels of tritium in
drinking water of communities near CANDU nuclear plants. There has also
been inter-national concern voiced -- by the International Commission on
the Great Lakes, for example -- over the rising levels of tritium in the
Great Lakes. This phenomenon is almost entirely due to the CANDU
nuclear plants operating on the Canadian side.
Like all radioactive materials, tritium is a cancer-causing agent.
However, tritium has also been implicated directly in the production of
genetic and teratogenic damage. Here is a small excerpt from the 1980
BEIR-3 Report (BEIR = Biological Effects of Ionizing Radiation) by the
US National Academy of Sciences:
"Because tritium (hydrogen-3) is a potential pollutant from
nuclear-energy production, its effect on development [of unborn
babies] has been the subject of a number of studies.
"Tritiated water (HTO) is a common chemical state of tritium, and it has
easy and rapid access to living cells, including those of the embryo or
foetus.
"HTO administered in the drinking water to rats throughout pregnancy
produced significant decreases in relative weights of brain, testes, and
probably ovaries, and increases in norepinephrine concentration, at
doses of 10 microcuries per millilitre (estimated at 3 rads per day),
and produced weight decreases in a number of organs at higher doses.
"Because the length of the critical period for various organs is not
known, the total damaging dose cannot yet be estimated. Relative brain
weight was found to be reduced at only 0.3 rads per day (one microcurie
per millilitre of drinking water) when exposure began at the time of the
mother's conception.
"Even lower exposures (0.003 rads per day and 0.03 rads per day) have
been implicated in the induction of behavioral damage, such as delayed
development of the righting reflex and depressed spontaneous activity.
However, because the data fail to show a clear dose dependence, there is
some doubt about the validity of this suggestion.
Effects on Populations of Exposure to Low Levels of Ionizing Radiation,
pp. 485-486,
U.S. National Academy of Sciences' BEIR-III Committee, 1980
Gneetic effects of tritium were discussed in the 1977 Report of the
United Nations Scientific Committee on the Effects of Atomic Radiation
(UNSCEAR):
[Paragraph 374. ]
"Cumming et al. (128) have completed the first series of experiments on
tritium-induced specific locus mutations in mice, providing the only
data available on such gene mutations in any mammal.
''In view of possible levels of tritium release, not only from existing
nuclear installations but also from contemplated controlled
thermo-nuclear reactors, these data are of great relevance. [emphasis
added]
". . . The results demonstrate that beta radiation from the decay of
tritium can induce specific-locus mutations in spermatogonia as well as
in post-meiotic stages: 16 mutations have been recovered among a total
of 20,626 offspring derived from germ cells irradiated as spermato-gonia
and 11 in 7,943 offspring from irradiated post-meiotic stages...
[Paragraph 375.]
"Hori and Nakai (233) and Bocian et al. (39) have reported on the
induction of chromosome aberrations in human lymphocytes exposed to
tritiated water in vitro. Exposures were carried out by the addition of
whole blood to the culture medium containing tritiated water...
[Paragraph 376.]
"The results indicate that with protracted exposures (48 or 53 hours)
the [chromosome] aberrations produced were mostly of the chromatid
type, such as gaps, deletions and fragments, and there were relatively
few chromatid exchanges.
"In the concentration range used by Hori and Nakai, the dose-effect
curve for the number of [chromosome] breaks induced was quite complex
at low concentrations. In the work of Bocian et al. and with the range
of concentrations they used, the frequency of chromatid aberrations
increased linearly with dose...
[Paragraph 378.]
''Summary and conclusions: During the past few years, there has been a
growing interest in the study of the biological effects of
radioisotopes, particularly of plutonium-239 and tritium.
"A number of genetic and cytogenetic studies that have so far been
carried out in mice demonstrate that these isotopes are capable of
inducing dominant lethals [i.e. lethal mutations] , chromosome
aberrations and point mutations (for the last category, only the
effects of tritium have been studied) .
Sources and Effects of Ionizing Radiation,
Annex H, Genetic Effects of Radiation, Topic 2: Tritium; UNSCEAR Report
to the U.N. General Assembly, 1977.
For all these reasons, contamination of the North American environment
by tritium and carbon-14 (another weak beta emitter produced in
particularly large amounts in CANDU reactors) has become a major
transbounday concern:
"Carbon-14 and tritium are of comparable and special concern for similar
reasons.
"First, they each have long half-lives: 5 730 years for carbon-14 and
12.3 years for tritium. Long half-lives allow them to accumulate in the
environment around a reactor and in the global biosphere.
"Second, they are easily incorporated into human tissue. Carbon-14 is
incorporated into the carbon that comprises about 18 percent of total
body weight, including the fatty tissue, proteins and DNA [molecules].
Tritium is incorporated into all parts of the body that contain water.
"Thus the radiological significance of both elements is not related to
their inherent toxicity, as each is a very low energy form of radiation,
but to their easy incorporation in the body."
The Safety of Ontario's Nuclear Reactors,
Select Committee on Ontario Hydro Affairs, 1980.
The ICIM EIA Summary gives no useful information on health and
environmental effects of tritium emissions from Cernavoda 2. There is
no discussion of the gradual buildup of tritium in the environment or
the possibility of transbounday impacts. There is no discussion of
carcinogenic, teratogenic or mutagenic aspects of tritium exposure -- or
of exposure to ionizing radiation in general.
Atomic Energy Control Board. Submission to the Treasury Board of
Canada. Ottawa 1989.
BEIR III. The Effects on Populations of Exposure to Low Levels of
Ionizing Radiation. Committee on the Biological Effects of lonizing
Radiation.
National Academy Press. Washington, D.C., 1980.
Energy, Mines and Resources (EMR), Department of. Nuclear Policy Review
Background Papers. Government of Canada. Ottawa 1981.
National Institute of Research and Development for Environmental
Protection (ICIM). Cernavoda 2 NPP Environmental Impact Summary.
Bucharest 2002.
Nuclear Performance Advisory Group (NPAG). The IIPA/SSFI Evaluation ~
Findings and Recommendations. A Report to Ontario Hydro Management.
Toronto 1997.
[IIPA = Independent Integrated Performance Assessment]
[SSFI = Safety System Functional Inspections]
Nuclear Regulatory Commission. Reactor Safety Study (the "Rasmussen
Report"). WASH-1400. Washington DC 1974.
President's Commission on the Accident at Three Mile Island.
The Need For Change : The Legacy of TMI. Washington DC 1979.
Royal Commission on Electric Power Planning. A Race Against Time:
Interim Report on Nuclear Power. Toronto 1978.
Select Committee on Ontario Hydro Affairs. Safety of Ontario's Nuclear
Reactors: Final Report. Ontario Legislature. Toronto 1980.
United Nations Scientific Committee on the Effects of Atomic Radiation
(UNSCEAR). Sources and Effects of Ionizing Radiation. New York 1977.
[Annex H: Genetic Effects of Radiation.]
[Annex J: Developmental Effects of Radiation.]