Don’t count on MAPLE to deliver medical isotopes

- I am a nuclear physicist and the manager of reactor physics and systems behaviour, office of the chief engineer, Atomic Energy of Canada Limited (AECL). From 1994 to 2004, I was AECL's general manager, isotope business, responsible for reactor isotope supply at the Chalk River, Ont., nuclear reactor. In 1996, I assumed the additional role of project director, leading the development, design, engineering, licensing, construction and commissioning of two Multipurpose Applied Physics Lattice Experimental (MAPLE) reactors and an associated processing facility.

Contrary to reports that the MAPLE reactors are the short-term answer to today's global medical isotope shortage, I can confirm there are significant technical and regulatory hurdles that require, in the best-case scenario, at least five to six years of intensive research and analysis before we can even consider bringing the MAPLE reactors on-line.

In May 2008, AECL announced the discontinued development of the MAPLE reactors. The main hurdle to completing the reactors was, and remains, resolving a power coefficient of reactivity (PCR) issue.

The MAPLEs were first-of-a-kind experimental reactors with technical risks known at the onset. The reactors were licensed by the Canadian Nuclear Safety Commission (CNSC) to operate with a small negative PCR. That means the core reactivity was to decrease as power increased. In June 2003, commissioning was put on hold when test data analysis indicated the reactor had a small positive PCR. Extensive scientific analysis, consultations with the Korea Atomic Energy Research Institute and tests conducted between June 2003 and May 2008 could not resolve the PCR issue.

In addition, neither AECL nor its retained experts, including Brookhaven National Laboratory, Idaho National Laboratory and Argentine company INVAP, which recently completed Australia's Open Pool Australian Lightwater (OPAL) research reactor, were able to determine the cause of the positive PCR.

The resolution of this issue was, and is, a potentially insurmountable hurdle to safely commissioning the MAPLE reactors as currently designed. AECL will never operate an unsafe reactor.

The last test conducted by AECL, in April 2008, showed no reduction in positive PCR value. Following this ultimate result, the decision was taken not to pursue further testing.

There was another test planned later in 2008. Even if it had been conducted, however, and even if we had continued down the expensive path of development, further testing would still have been required, and the MAPLEs would still be years away from being licensed for isotope production.

While the PCR issue is the most definitive reason for discontinuing the MAPLEs project, it was clear that we faced serious additional project risks due to the use of highly enriched uranium (HEU) in the production process. Post 9/11-heightened awareness of nuclear non-proliferation changed the risk equation markedly toward the possibility that an HEU-based facility would prematurely become obsolete.

The MAPLE reactors are currently in an extended shutdown state, not in "hot standby mode," as per some media reports. Before the MAPLEs could be brought into service, AECL would need to:

• Take the MAPLE reactors out of their extended shutdown state;

• Certify MAPLE operating staff;

• Obtain CNSC approval to run further tests to address the PCR issue;

• Successfully determine the causes of the PCR issue;

• Make safety cases for completing reactor commissioning and irradiating HEU targets for isotope production, on an ongoing basis;

• Obtain CNSC approval to commission the isotope processing facility and commission it with irradiated targets;

• Demonstrate the quality and quantity of the isotopes produced; and

• Obtain CNSC approval to place the MAPLEs and processing facility into service.

Beyond this, there are requirements for isotope distributors to get approvals of MAPLE-produced isotopes by regulatory bodies such as Health Canada and the U. S. Food and Drug Administration. These hurdles, in a best-case scenario in which the PCR issue is resolved, would take at least five to six years to overcome before the MAPLE reactor and the processing facility could be brought online to produce medical isotopes.

Likewise, if we were to redesign the reactor core, as some recommend, AECL estimates that it would take seven to 10 years to do so, with no guarantee that the PCR issue wouldn't reoccur or that other first-of-a-kind technical risks would not materialize.

Resurrecting the MAPLE project is not a quick fix to today's global isotope issue. In fact, based on my knowledge of the project, I hesitate to say it is a medium-or even long-term fix to the problem.


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