Medical isotopes do not depend on electricity-producing nuclear power reactors
Dr. Gordon Edwards, President, Canadian Coalition for Nuclear Responsibility,
http://www.ccnr.org - March 8, 2024 -
A few notes about medical isotopes:
(1) Until very recently, medical isotopes were always produced in cyclotrons (or other particle accelerators) or in relatively small research reactors, that are not used to generate electricity.
Even when new radio-isotopes that have an important application in medicine are discovered or developed, it is generally anticipated that these will all be produced in accelerators or in small research reactors rather than large power plants.
For example, in 2023 the CEO of Canadian Nuclear Laboratories told visitors at Chalk River that they (CNL) will be producing an exciting new radioactive isotope, a “targeted cancer therapy” radionuclide called Actinium-225. I asked him exactly how it is created. He said using an accelerator to fire protons at a radium-226 target. Note that radium-226 is a naturally occurring radioactive material and so this new isotope has nothing whatsoever to do with nuclear reactors of any kind.
Ac-225 is an alpha emitter with a half-life 9.9 days. It is unusual for an alpha emitter to be so short-lived.
Actinium-225 is obtained by bombarding radium-226 with an accelerated proton (in a cyclotron).
Radium-226 is a Naturally Occurring Radioactuve Material (NORM) - a decay product of uranium-238.
Radium-226 + proton —> Actinium-227 —> Actinium-225 + 2 neutrons [the last step has about a 9-hour decay half-life]
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(2) In recent years, especially in Canada, nuclear power plant operators have tried to improve their public relations image by promising to produce medical isotopes in large power reactor such as those at Darlington and at Bruce. This is quite unnecessary, and it is not at all common practice. But it creates a misleading impression in peoples’ minds that nuclear power is somehow essential for modern medicine, which is not at all true, and therefore "we must never get rid of nuclear power because our hospitals and doctors need the isotopes".
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(3) In effect, this is a marketing ploy based on a lie, or shall we say a half-truth. I produced a fact sheet on this subject a couple of years ago: [
http://www.ccnr.org/medical_fact_sheet_2022.pdf ].
The one-page fact sheet without the accompanying notes is hete: [
http://www.ccnr.org/med_facts_flyer.pdf ]
(The notes appended to the fact sheet go into some interesting detail.)
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(4) The general rule is this: All medical isotopes can be produced using only particle accelerators or research reactors. There is no need for large power reactors to produce medical isotopes.
There is one notable exception to this general rule, and that is the powerful gamma-emitting material, cobalt-60, originally produced in research reactors at Chalk River.
To begin with, cobalt-60 was produced for medical use to fight cancer by shrinking tumours with powerful gamma rays. The demand for this therapeutic use of cobalt-60 can be satisfied quite easily by research reactors such as those that operated at Chalk River – the NRX and NRU reactors. That’s because the demand is not great, a little cobalt-60 for cancer therapy goes a long way…. (By the way, hospitals that can afford it such as those in Winnipeg and Saskatoon have stopped using cobalt-60 therapy as there are superior therapeutic alternatives having fewer bad side-effects.)
BUT . . . there are also large “sterilization” facilities that use an enormous amount of cobalt-60 for the sole purpose of sterilizing medical equipment using massive doses of gamma radiation. This is not a direct medical use of cobalt-60, but rather an industrial use that provides a service to the medical community. (There is also a limited market for “food irradiators”using cobalt-60.)
To satisfy this industrial demand, for many years Canada has been producing very substantial amounts of cobalt-60 in the Pickering reactors near Toronto. Some of the “control rods” needed to absorb neutrons (to control the nuclear reaction) are made of non-radioactive cobalt-59. When a cobalt-59 atom absorbs a neutron it changes into a highly radioactive gamma emitter, cobalt-60. That material is then marketed and sold for use in such industrial irradiators.
There are additional non-medical industrial uses for cobalt-60. To the best of my knowledge, there is no other isotope that is produced in such large amounts, and none (except cobalt-60 for industrial use) that has been produced as a matter of course in large power reactors.
It is important to note, however, that the actual use of cobalt-60 for cancer therapy does not require such mass-production.
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(5) Not all radio-isotopes can be produced using an accelerator, but a great many of them can be, including some of the newest and most exciting ones such as actinium-225 as mentioned above.
However, those isotopes that are created in reactors do not need anything more than a few relatively small research reactors. For example, technetium-99m is by far the most widely-used medical isotope in the world, with over 25 million “doses" used every year. The 50-year old NRU research reactor at Chalk River — generating only 125 megawatts of heat, compared to over 1500 megawatts of heat for even the smallest commercial CANDU reactors at Pickering — produced between 1/3 and 1/2 of the entire world’s supply of technetium-99m until it was permanently shut down.
There were only four other reactors in the western world at that time that were also producing technetium-99m, and they were all very old research reactors much smaller than the NRU (one in Belgium, one in South Africa, and in Argentina, and I forget the other one.)
And by the way, there have been several alternative technologies capable of producing technetium-99m using accelerators, involving no nuclear reactors at all, one of them at the University of Sherbrooke here in Quebec.
Best regards,
Gordon.