Notes on the Isotope Shortage (written June 10 2009)


Medical Isotopes 

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
research purposes.

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.


See Molybdenum and Technetium


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

to operate.


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?


See AECL and MDS Enter Into Long-term Supply Agreement for Medical Isotopes


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 

of invention.


Gordon Edwards









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

business hours.


(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