The Isotope Crisis and the Chalk River Reactor

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Author and researcher Anna Tilman shares this understanding of the medical isotope crisis due to the failure of the reactor at Chalk River

Much ado is being made out about the shortage of medical isotopes as a result of the shutdown of Atomic Energy of Canada Limited (AECL)’s Chalk River’s 52-year old National Research Universal (NRU) reactor due to “leaks” of radioactive tritium-laced heavy water. This is the second shutdown in just 6 months at this facility which is on the shores of the Ottawa River about 185 kilometres from Ottawa.

At the time of the second reported leakage in May 2009, expectations were that the reactor would get back on track within a few months. It is now apparent that the reactor will not be functional for at least a year, and even so, if at all.

While there are many isotopes used in nuclear medicine, the critical isotope in question is technetium - 99m (Tc-99m), a short-lived decay product of Molybdenum-99 (Mo-99), and the current workhorse of radioisotopes in nuclear medicine used internally for imaging soft tissues. The short half-lives of these radioisotopes make timing a critical issue.  While M0-99 has a half-life of 66 hours, the half-life of Tc-99m is only 6 hours. In just 24 hours, only about 6% of the initial amount of Tc-99m remains, the rest having decayed to other elements.

More than 90% of the world’s supply of Mo-99 comes from the irradiation of uranium targets at five nuclear reactors in the world located in Canada, the Netherlands, France, Belgium and South Africa.  The uranium targets in question are weapons grade highly enriched uranium (enriched by more than 95%).

The NRU has typically accounted for at least 30-40% of the world supply of Mo-99 and is the main source of this isotope in the U.S. All of these reactors are more than 40 years old, well past their prime, and all have had periods of closure and shutdowns for repairs and maintenance. The Netherlands facility, the second largest producer, which is 47 years old, was shut down for a period in 2008 due to “leaks” in its cooling system caused by corrosion of its pipes and is currently shut down once more.

Leaders in nuclear medicine have described this situation as a catastrophe with detrimental impacts on patients. There are calls for a long-overdue solution to provide a continuous, reliable supply of supply of medical isotopes, as well as for an immediate solution to meet current demands.

Amidst all this concern from the medical profession and others, there seems to be little if any concern about these facilities themselves, which are prone to “leaks” of radioactive substances in water and air, use highly enriched uranium, and produce high-level radioactive waste. Certainly, these are serious health matters. And if these isotopes are so vital, why wasn’t more attention paid to these 40-year- plus (geriatric) reactors before they reached the point of no return?

Most of the radioisotopes in nuclear medicine are used for diagnostic purposes, not for cancer treatment. While the shortage of these isotopes is a very serious matter, it is not in itself life-threatening. There are alternative means of producing isotopes for nuclear medicine, rather than using nuclear reactors and hence uranium. For example, cyclotrons (particle accelerators) also produce such isotopes and in fact are used to produce fluorine-18, a short-lived radioactive isotope used for PET (Positron emission tomography) scans.( http://www.radiologyinfo.org/en/info.cfm?PG=pet) 

Then there is the rather murky issue of two MAPLE (Multipurpose Applied Physics Lattice Experiment) reactors designed by AECL to replace the aging NRU reactor at Chalk River. While construction was completed in 2000, they were never commissioned for use. Design flaws, budget overruns and safety concerns supposedly weighed in to AECL’S decision to cancel the program in May 2008, deeming these reactors not feasible to operate. Apparently, instead of being “self-braking” when the power of the reactor is increased, even a small increase in the power caused the MAPLE reactors to accelerate, creating the danger of a melt-down.( Comments via e-mail from Gordon Edwards)

While AECL is still essentially a crown corporation, over twenty years ago, the Government of Canada privatized AECL’s radio-isotope division, which was the only really profitable part of its operations. Shortly afterwards, it was sold to a private global radiopharmaceutical company, MDS-Nordion. However, AECL is responsible for designing, building and operating the reactors to produce the isotopes. In other words, the radioactive waste and the decommissioning of the reactors is a public responsibility, whereas the profits remain in the private hands of MDS-Nordion.( Comments via e-mail from Gordon Edwards)