The Chalk River crisis
Notes by Gordon Edwards (2007)
The isotope question is a complicated one.
It is important to realize that isotopes were being used
for diagnosis and therapy long before the discovery of
nuclear fission -- and that even after the discovery of fission,
cyclotrons and other types of particle accelerators were
widely used to produce isotopes for medical and scientific
See Nuclear Medicine, Radioisotopes and Nuclear Reactors
But AECL has deliberately worked over the years to
create a market for specialized isotopes that are
produced in nuclear reactors, chiefly cobalt-60 and
molybdenum-99. Cobalt-60 is a “hard” gamma emitter
and is used outside the body to irradiate tumours and
to sterilize medical instruments, for example. It has a
half-life of 5.3 years and so loses about 13% of its
inventory in one year through radioactive decay.
Molybdenum-99 has a half-life of 66 hours, and it decays
into a metastable (short half-life) isotope called
technetium-99m (the “m” has to be included) which has
a half-life of only 6 hours. The technetium-99m is used
internally for many many diagnostic purposes. Tc-99m
can easily be attached to various molecules which can
then be injected into patients. The gamma rays given off
by Tc-99m are a lot “softer” than those from cobalt-60 so
they give a good “picture” without giving too high a dose
to the patient. It's like having little x-ray machines inside
the patient rather than having one big x-ray machine outside
the patient. This allows doctors to see details of the soft
organs which can be helpful in diagnosing cancer and other
The Mo-99 isotope is used as a “cow” which can be
“milked” to give Tc-99m over a period of many days. Just
a few micrograms of Mo-99 is enough to produce enough
Tc-99m to be used to diagnose 10,000 patients. However,
the supply of Mo-99 has to be uninterrupted or hospitals
will run out of Tc-99m in a short time.
The downside to this is that Mo-99 (called “moly” for short)
is only produced, now, in a very high-intensity neutron field,
which means a nuclear reactor, and at Chalk River they use
"targets" which are made of weapons-grade uranium (over
95% enriched!!) in order to get the Mo-99. The 50-year old
NRU reactor is used to produce the M0-99. That very old
reactor was supposed to have been permanently retired in
2000 and replaced by the two Maple reactors. But AECL’s
Maple-1 and Maple-2 reactors were designed to produce
Mo-99 using weapons-grade uranium targets also.
In the USA, the Nuclear Control Institute (NCI) went to court
to stop the shipment of HEU (highly enriched uranium) to
Chalk River because there is a US law (the Schumer
amendment) which is meant to halt all shipments of
weapons-grade materials to other countries. AECL has been
told by US authorities that they must develop technologies
to produce Mo-99 that do not require HEU; but
MDS-Nordion (a private company that markets the Mo-99
that is produced by AECL) shows little sign of taking this
Vice-President Malkoske said Nordion never agreed to convert
to low-enriched uranium at any cost. “It is not written in stone,"
he says. ‘Technically, it seems feasible to me, but what’s it
going to cost to do this? Every time you add costs you pass
that on to the health-care community, you increase the cost
of nuclear medicine."
“What we said we would do . . . is do a technical and
economic feasibility (study) and if it was economically
feasible then we would convert. We didn't say we were
going to convert at any cost. That could kill our business.”
Another problem: in the past, HEU irradiated fuel has been
returned to the USA (Savannah River) from Chalk River where
it has been recycled into the bomb program (which uses HEU
as “driver rods” in plutonium-production reactors to produce
the plutonium needed for warheads). So in this sense, Mo-99
is like a piece of candy that is produced as a byproduct of the
nuclear weapons business. Without nuclear weapons it would
be too expensive to produce the HEU in the first place, and
without the cash credit obtained by returning the HEU to the
USA the costs become prohibitive also. I am not sure whether
this practice of returning the irradiated HEU is still going on.
Yet another problem is that the Maple reactors cannot be operated
safely and so they are at least 6 years behind schedule. The
reactors do not operate as the AECL designers said they should,
and the difference is a matter of safety — instead of being “self-
braking” when the power of the reactor is increased, the Maple
reactors accelerate in power when any attempt is made to just
increase the power a little bit. This makes the reactors too unsafe
The NRU (National Research Universal) reactor started up in
1957. It was about 10 times more powerful than the earlier NRX
(National Research eXperimental) reactor that started up in 1946.
The Gov’t of Canada was reluctant to spend the money to build
the NRU reactor, but AECL argued that the NRU reactor could help
defray its own cost by producing plutonium in the reactor and selling
it to the US military. And that’s what they did — sold plutonium
produced at NRU that was of course used in the American bomb
But the main purpose of the NRU was to produce isotopes of
various kinds by using ingenious “loops” that would allow you to
insert non-radioactive materials into those loops without shutting
down the reactor or opening up the core of the reactor, so as to
irradiate those “target” materials and make them radioactive.
The NRU was also used to test various fuels and components
of CANDU reactors. But it is 50 years old now and should have been
retired years ago. Since the Maple reactors are not running, the
geriatric NRU reactor has had to be the workhorse, delivering the
Mo-99 to the market.
Two years ago, the Canadian Nuclear Safety Commission (CNSC)
required that emergency pumps be connected to a backup electricity
supply at the NRU reactor, in order to prevent a core meltdown in case
of loss of normal electrical supply as a result of an earthquake or some
equivalent event. AECL did not carry out this work however, and now
the chickens have come home to roost. The CNSC is furious that their
licensing requirements have not been met, AECL is scrambling to find the
necessary parts from around the world to finally bring the NRU reactor
into compliance, and the medical community is aghast that they were
never informed of the problems with the much-ballyhooed Maple
reactors and the fact that the supply of Molybdenum-99 was so fragile,
depending as it does on the operation of an aging and improperly
equipped NRU reactor.
Which raises another question: who makes the profits from all this?
In 1988, the Gov’t of Canada privatized the only really profitable
part of AECL’s operations, which was the radio-isotope production.
AECL sold Nordion International Inc. (formerly the AECL division
known as the Radiochemical Company) to the Canada Development
Investment Corporation (CDIC) for eventual privatization. In 1991,
CDIC sold Nordion to MDS Health Group Ltd. for $165 million, and
it was reported that AECL received $150.5 million from CDIC, and
that this “together with interest earned thereon between the dates
of receipt and disbursement, has been distributed to the shareholder
(i.e. gov’t of Canada) by way of dividends”.
So AECL is responsible for designing and building and operating the
reactors to produce the isotopes that MDS-Nordion sells for a profit.
This also means that the radwaste and the decommissioning of the
reactors is a public responsibility through AECL whereas the profits
are a private matter for MDS-Nordion.
As of now, it would be difficult to replace the Mo-99/Tc-99m isotope
business with something else, but I believe that if nuclear weapons
were phased out the entire isotope business as currently practiced
would be unaffordable. In that case I have little doubt that some other
more cost-effective isotope production scheme would be found to
replace the Mo-99/Tc-99m that the "nuclear medicine" practitioners
are currently addicted to. I’m not saying this would be easy nor that
the replacement is obvious, but I do believe that necessity is the mother
Notes on the Isotope Shortage
by Gordon Edwards, Ph.D.
(written June 10 2009)
(1) The vast majority of uses of radioisotopes in nuclear medicine
is for diagnosis, not for cancer treatment. Thus a shortage of these
isotopes may cause a lot of difficulties, and a lot of distress, but it is
not in itself a "life-threatening" medical emergency.
(2) The fact that these diagnoses using medical isotopes are not life-
threatening is supported by the fact that the tests are never given after
regular hospital hours or on the weekends, but only during regular
(3) McGill University used to produce all of its medical isotopes using a
cyclotron located right on the university campus in downtown Montreal.
A cyclotron is not a nuclear reactor but a "particle Accelerator". It does
not use uranium at all, nor does it produce high-level radioactive waste.
(4) The most frequently used procedure in nuclear medicine is using a
radioactive isotope called technetium-99m to get a picture of the internal
soft organs of a patient. When the radioactive material is taken internally
by the patient, his or her insides light up like a Christmas tree because
of radioactive emissions for a period of a few hours.
(5) Two alternatives to Technetium-99m are (a) using thallium-206, a radioactive
isotope that is produced in a cyclotron (no uranium use) (b) PET-scans, which require
a short-lived radioactive isotope called fluorine-18, which is also produced in a
cyclotron (no uranium use). PET scans often give better pictures than technetium-99m.
(6) PET scan machines are expensive, about 2-3 million dollars each, but remembering
that Ottawa has poured 1.7 billion dollars into Chalk River since 2006, you
could buy 500-600 PET machines with this amount of money. Even the money wasted
on the MAPLE reactors (about 530 million) would buy over 170 PET scan machines.
(7) The main use of radioactive isotopes for treatment is iodine-131, used to treat thyroid
cancer. This isotope is produced in a nuclear reactor, not in a cyclotron. There are very
few other therapeutic uses of isotopes, but there are some. Iodine-131 has a half-life of
8 days, so a given hospital supply can remain useful for some weeks. The availability
of iodine-131 will be reduced because of the isotope shortage. But alternative treatments
are available, and thyroid cancer is not generally life-threatening, though it sometimes is.
(8) The amount of uranium used for medical isotopes is an extremely small fraction of the
uranium used by nuclear power reactors. Even if no new uranium mines were opened up
there would be plenty of uranium to produce medical isotopes for a very long time to come.
Gordon Edwards, Ph.D., President,
Canadian Coalition for Nuclear Responsibility