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The challenge of long-lived alpha emitters in the Chalk River legacy wastes

Concerned Citizens of Renfrew County and Area, January 22, 2024 (revised September 17, 2024)

Why is so little Chalk River waste suitable for near surface disposal? 

Extensive research work at the Chalk River Laboratories on nuclear reactor fuels, and in the early days, on materials for nuclear weapons, produced waste with large quantities of long-lived alpha emitters.  This waste is difficult to manage and can even become increasingly radioactive over time.  

According to the International Atomic Energy Agency, because of the presence of long-lived alpha emitters, waste from nuclear research facilities is generally classified as intermediate level, and even in some cases, as high level. This waste cannot be put in a near surface disposal facility because its radioactivity will not decay to harmless levels during the period that the facility remains under institutional control.   

Alpha emitters decay by throwing off an alpha particle, the equivalent of a helium nucleus, with two protons and two neutrons.  The external penetrating power of an alpha particle is low, but alpha emitters have extremely serious health effects if ingested or inhaled. They can lodge in your lungs and cause cancer.

Research at Chalk River and all other nuclear laboratories is ultimately based on three long-lived alpha emitters — thorium-232, uranium-235, and uranium-238. These are the “naturally occurring” or “primordial” radionuclides.  They were created by large stars and then incorporated into the Earth and the solar system when they formed some 4.5 billion years ago.  The waste inventory proposed by Canadian Nuclear Laboratories for the Near Surface Disposal Facility (NSDF) includes over six tons each of thorium-232 and uranium-238……………………………………………………..

Hazards increase when uranium and thorium are mined and concentrated from ores and used in their pure form.  Marie Curie, who spent much of her career isolating radium and polonium from uranium, died of radiation-induced leukemia at age 66. She was buried in a lead-lined tomb because her corpse emitted so much radiation.

When thorium-232, uranium-235, and uranium-238 are irradiated in a reactor, as at Chalk River, they absorb neutrons and produce significant quantities of new, man-made, long-lived alpha-emitters.  Irradiated uranium-238 absorbs a neutron and temporarily forms uranium-239.  Uranium-239 transmutes to neptunium-239, which quickly transmutes to long-lived plutonium-239, with a half-life of 24,000 years. 

Plutonium-239 is “fissile” – it can readily support a chain reaction.  It is what the early Chalk River researchers produced for the manufacture of U.S. nuclear weapons, by separating the plutonium from irradiated reactor fuel.  They also used the separated plutonium to make “mixed oxide” (MOX) reactor fuel, mixing it with fresh uranium………………………………………….

Detecting alpha emitters in mixed waste is expensive and challenging. Putting inadequately characterized waste in the NSDF would invalidate its safety case.

Unfortunately, the NSDF Project lacks adequate waste characterization procedures.  If the project is allowed to proceed, workers and future Ottawa valley residents could be exposed to unknown quantities of long-lived alpha emitters and suffer the serious health effects associated with them. https://concernedcitizens.net/2024/09/17/the-challenge-of-long-lived-alpha-emitters-in-the-chalk-river-legacy-wastes/

September 19, 2024 - Posted by Christina Macpherson | Canada, radiation