Monday, 4 March 2013

Isotopes in high demand for medical research

Good read: Isotopes in high demand for medical research: ..."So the question is, how to get the molybdenum-99 in the first place? Well, one way is to use the fact that it is a fission product of uranium-235. That means that inside every uranium-fuelled nuclear reactor, Mo-99 is being produced all the time – but it is mixed in with dozens of other fiercely radioactive fission products (such as cesium-137, iodine-131, strontium-90), activation products (such as cobalt-60, iron-55, niobium-93m) and transuranic actinides (such as plutonium,
americium and curium). To get the Mo-99 you would have to dissolve the fiercely radioactive irradiated fuel in boiling nitric acid and separate out the tiny amount of Mo-99 by chemical means, leaving a huge volume of highly radioactive liquid waste.
So to make the job easier, research reactors are used – no electricity production – and instead of “reprocessing” the irradiated fuel, special “targets” are introduced into the core of the reactor made of highly-enriched uranium (93.3 percent Uranium-235) and withdrawn at a predetermined
time so that the “target” can be dissolved in nitric acid etc. This has several advantages: (1) you can limit the time the target is in the reactor, cutting down on the superfluous inventory of other fission products etc; (2) you can vastly reduce the mass of material that needs to be dissolved
because the U-235 is so concentrated; (3) you can control the schedule more easily and achieve a kind of “assembly-line” procedure without shutting the reactor down.
Even if you use this nasty method for producing Mo-99 inside a nuclear reactor, and then reprocessing, you can use LEU (Low Enriched Uranium) instead of High Enriched Uranium (HEU) – it just means it takes longer and is more expensive mainly because there is a much larger mass of material to “reprocess” in order to get out the Mo-99. Argentina has been doing it this
way for quite some time.
The alternative to using a nuclear reactor is to use a “particle accelerator” to produce Mo-99. There are various ways to do this, using a cyclotron (a circular accelerator) or a linear accelerator (arranged in a straight line). In an accelerator, isotopes of various kinds can be produced by bombarding a “target” of some kind with a “beam” of very energetic (high-speed) charged particles. This is how a university or hospital can produce most if not all of the isotopes it needs
without the need for a nuclear reactor. For many years, starting in 1949, McGill University got all of its isotopes this way,"
Also good read: a bit of history on the conservative government of Brian Mulroney and the privatization of the medical isotopes produced at NRU, a bad deal that even hunts today! "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."

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