Medical isotopes: the Chalk River crisis

Gordon Edwards PhD: President, Canadian Coalition for Nuclear Responsibility

I have written these notes to help activists to understand the nature of the radio-isotope

crisis currently being discussed in the news.

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 for example:

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. Because of its 6-hour half-life, Tc-99m does not pose a long-term radioactive waste problem. The Mo-99 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 they 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 that uses weapons-grade uranium (over 95% enriched!!). AECL's Maple-1 and Maple-2 reactors were designed specifically to produce Mo-99 using weapons-grade uranium as fuel. NGO's in the US went to court to stop the shipment of HEU (highly enriched uranium) to Chalk River because there is a US law which is supposed 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 use HEU; but MDS-Nordion (a private company that markets the Mo-99 that is produced by AECL) shows little sign of taking this seriously.


"Mr. 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? Everytime 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 NRY reactor, but AECL argued that they could help defray the cost be selling plutonium produced in the reactor to the USA. And that's what they did -- sold plutonium that was of course used in the American bomb program. 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 the loops without shutting down the reactor or opening up the core of the reactor so as to irradiate those materials and make them radio-active. 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, NRU

has had to be the workhorse, delivering the Mo-99 to the market.

Which raises another question: who makes the profits from this?

In 1988, the Gov't of Canada privatized the only really proftable 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 medical people are currently addicted to. I'm not saying this would be easy nor that the replacement is obvious, but I do believe that necessity if the mother of invention.

Hope all this info helps to sort out the situation somewhat.

Gordon Edwards.

On 8-Dec-07, at 11:28 AM, Mike Nickerson wrote:

Hi Gordon:

The blunders at Chalk River that have interrupted the world's supply of medical isotopes is a mixed blessing. It provides further evidence that the level of management is not up to the challenge of the dangers, but it also highlights a 'good' use of nuclear technology.

What sort of volume of isotopes are they talking about?

How much of that volume could be produced with cyclotrons, rather than fusion reactors?

I've been asked before & I would like to have a more informed answer.

Many thanks.

Yours, Mike N.


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