The medical isotopes we use today are made using nuclear fuels that could also be used to create nuclear weapons. What's more: it’s not even necessary. So why use them? That's the gist of the argument that Robert Gould and Victor Sidel make in their recent policy statement proposal.
As a new Peace Caucus member, I was pretty ignorant about all this nuclear medicine vocabulary, so I thought I’d do a little research to help myself understand. I hope you find this helpful too.
The most common medical isotope used in hospitals is called technetium-99m. It emits gamma rays and has a half-life of 6hrs, meaning that it is radioactive just for a short period of time. It is put into solution and injected into the blood stream of patients. Scanners then detect the gamma rays that escape, and create an image based on what they record. After about 24 hrs just a small fraction of the radioactive isotope remains, the majority of the technetium-99m having converted to technetium-99, a relatively inert material.
So let's go another step back to better understand how this radioactive isotope gets to the hospitals. Where does technetium -99m come from? Well, actually it is comes another radioactive material, molybdenum-99. Molybdenum-99 radioactively decays into technetium-99m. That's why, it's sometimes called a technetium “cow”. Nuclear medicine units at hospitals "milk" the technetium “cow” to extract technetium-99m. This is a simple chemical extraction process. After about one week, the technetium cow stops emitting technetium-99m in significant amounts and a new shipment must be ordered.
1. See this list of major uranium mining operations
2. NRU supplies molybdenum-99 to MDS Nordion, who then further refine it and send it to hospitals worldwide.
But how is molybdenum-99 made? Well, this is the problem. For the time being, there are just four major worldwide molybdenum-99 suppliers. One supplier, the NRU reactor in Chalk River, Ontario, supplies 40% of the world’s molybdenum-99. At NRU and most other reactors, molybdenum-99 is produced by a nuclear fission reaction that starts with Highly Enriched Uranium (HEU). HEU is the same material that was used to make the first fission bombs, like the bomb dropped on Hiroshima. So HEU is a very dangerous material. Many organizations consider that obtaining or creating HEU may be the most difficult part of making a nuclear weapon.
What is HEU, exactly? HEU is a form of uranium that has a large amount of the isotope 235-U. 235-U is the most abundant naturally occurring fissile material. Fissile just designates a material that can sustain a nuclear chain reaction if it is in a large enough quantity (critical mass) and if packed densely enough. But, over 99% of natural uranium occurs in the 238-U isotope, which is non-fissile. So uranium is extracted and sent to enrichment facilities. Low-Enriched Uranium (LEU) contains 20% 235-U, whereast HEU contains >85% 235-U. Generally speaking, HEU can be used to make a nuclear weapon whereas it would be extremely difficult to make a nuclear weapon using LEU. Enriching uranium is considered one of the most difficult steps in creating a nuclear weapon.
So, you'd think it would be in the interest of society to limit the production and access to HEU, right? That’s just what this APHA policy statement is trying to encourage. The technology to create molybdenum-99 from LEU is currently available; it’s just that government and industry are having difficulty making it happen (Atomic Energy of Canada Ltd, a crown corp. recently gave up on the development of a HEU-using medical isotope reactor called MAPLE - a particularly scathing account of the difficulties faced in it's development)
For more information:
• National Academies report on Medical Isotope Production Without Highly Enriched Uranium [a good reference that seems in line with the aims of the proposed APHA resolution]
What can you do?
• If you have shares in MDS Nordion, the major molybdenum supplier in North America, why not write to the president to ask him what he's doing to convert to LEU sources
• If you live in Canada, Netherlands, France or Belgium, write to your local representatives in order to express your concern with the use of HEU in the production of medical isotopes
