By Dale Bailey
Professor Medical Imaging Science
Royal North Shore Hospital and University of Sydney.
Interest in things radioactive peaked a few weeks’ ago when a small pellet containing a moderate amount of the radioisotope Caesium-137 (137Cs) was lost from a truck in Western Australia. The radioactive source contained about 20 Gigbecquerels (20 GBq) of 137Cs, roughly equivalent to twice the amount of similar radioactive materials that are given to tens of patients weekly in Australia for their cancer treatment.
The difference, though, is that the cancer treatment radiation only has a physical half-life for radioactive decay of a few days whereas the lost source has a 30 year half-life. In general, when dealing with radioactive decay we use the rule of thumb that the radiation is all but undetectable after about 10 half-lives have elapsed – in the case of 137Cs that would be 300 years.
The media interest that was generated by this loss, and its subsequent amazing recovery, asked many questions including how could such a source be lost “off the back of a truck”, what was it used for, what is the likelihood that it will be found, and why and where is radiation used in our society.
Radioactive devices are everywhere in health
Speaking from my position as a physicist working in a hospital, I often comment that the hospitals would just about grind to a halt if we did not have access to radioactive devices and sources. Not just for medical imaging (X-rays, CT scans, PET scans) but for a wide range of other tasks such as sterilising blood prior to transfusion, accurate positioning of hip and knee replacements in theatre, monitoring bone strength in osteoporosis and other conditions of accelerated bone loss, guiding surgeons to lymph nodes that drain the lymphatic fluid from certain tumours, pain relief from targeted radiation therapy, guiding cardiologists performing life-saving heart procedures, and so on.
The formal investigation into the loss of the 137Cs in WA will no doubt uncover what procedures were not followed for this event to have occurred as there are literally hundreds of movements of radioactive materials by road, rail and air around metropolitan, regional and rural Australia every day generally without incident.
One bright point to this story was the use of a new, Australian-designed radiation monitor that was able to detect the radiation being emitted by the source in a vehicle travelling at 70 km/h along the highway. We use conventional hand-held radiation detectors on a daily basis in the hospital to monitor patients treated with radiation to allow them to leave the hospital after achieving a suitably low level of emitted radiation, and I know to find the lost source with such a device would have been a painstaking task with an anticipated low level of success, akin to finding a needle in a haystack, however the haystack in this case could have been anywhere along a 1400 km stretch of mostly uninhabited desert highway.
However, the new detector developed by our national nuclear science agency, ANSTO, was able to locate this lost source quite quickly. This was a stunning outcome. For an agency that is largely unknown to most Australians this was a welcome brief moment in the sun for them to celebrate the success of one of their innovations and showcase Australia’s commendable track record of developments in nuclear science and technology.
Australian nuclear science and technology plays a significant role in regional and international activities. The main outward-facing activity relates to production of medical radiopharmaceuticals, however, there are many other activities related to nuclear science co-operation with our neighbours.
We provide training in medical imaging and therapy as well as industrial activities and monitoring to countries such as PNG, Indonesia, Malaysia, Thailand, Vietnam and other UN member states in subcontinental and south-east Asia.
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This is all set to be elevated to a new higher level, though, with the announcement of the AUKUS trilateral agreement and that Australia will acquire nuclear-powered submarines over the next few decades. Setting aside the arguments for and against this defence capability, the step-up required to support these sophisticated boats will have enormous spin-offs in nuclear science in general. These subs are likely to be commanded by captains with a nuclear engineering qualification and health physicists will likely be permanently stationed on board.
Skills required for nuclear future?
The skills required extend beyond the traditional STEM fields to trades such as welders, boilermakers and hydraulic engineering. As Vice Admiral Jonathan Mead, chief of the AUKUS submarine taskforce, commented recently the ecosystem to support these subs will be significant. This will have many positive benefits beyond simply defence and will generally support nuclear science and technology in Australia.
For the high school students currently studying physics and maths because of their love of these subjects there will be many bright future prospects for you for a career using your brain and these most fundamental of all scientific tools.
The “nuclear” aspects of the AUKUS project do not extend to nuclear weapons and domestic nuclear energy. While the subs will be nuclear powered they will not be nuclear capable in terms of weapons. And the use of a self-contained nuclear propulsion unit in a sub, which has a working life of 30 years and does not require routine servicing, does not represent a slippery slope into the development of a domestic nuclear energy programme.
While some argue that nuclear power will be a requisite to provide baseload electricity generation capability when renewables are not operational the technology is moving so fast that we can continue to hedge our bets while decarbonising our economy.
Perhaps one day small modular (nuclear) reactors (SMRs) may have a role to play but they are not there yet. And in the meantime other non-uranium based “nuclear” reactors such as those based on thorium may become a viable option.
As someone involved in using nuclear products in the diagnosis and treatment of disease I welcome this increased interest and see that many parts of Australian society will benefit from having a larger, more highly skilled workforce able to harness the potential of nuclear science and technology for all.
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