Atomic Energy of Canada Ltd (AECL) announced that it had decided to immediately discontinue development work of the two MAPLE research reactors at its Chalk River Laboratories in Ontario.
|AECL's Dedicated Isotope Facilities, consisting of MAPLE 1 and MAPLE 2 and the New Processing Facility (Image: AECL)
The MAPLE (Multipurpose Applied Physics Lattice Experiment) is a pool-type reactor with a compact core of low-enriched uranium fuel surrounded by a vessel of heavy water. The two MAPLE units were to be the world's first reactors dedicated exclusively to medical isotope production. Once completed, the reactors could have supplied the entire global demand for molybdenum-99, iodine-131, iodine-125 and xenon-133. At any one time, one MAPLE reactor was to be the primary isotope producer while the other reactor would be available for full back-up.
The first two 10 MW MAPLE units were undergoing commissioning at Chalk River. The reactors were originally scheduled to start up in 2000. One unit went critical in 2000, the second in 2003, but commissioning encountered major technical problems.
AECL said that it has now decided to end development of the reactors after a series of reviews which considered, among other things, the costs of further development, as well as the time frame and risks involved with continuing the project.
Hugh MacDiarmid, AECL's president and CEO, said, "We are making the right business decision given the circumstances." He added, "This was a difficult choice given the tremendous efforts expended by our people on development of the MAPLE reactors. Nevertheless, our board of directors and senior management have concluded that it is no longer feasible to complete the commissioning and start-up of the reactors."
NRU to meet isotope demand
AECL said that its decision to discontinue development of the MAPLE reactors will not impact the current supply of medical isotopes as commercial agreements between MDS Nordion and AECL provide for isotope production to continue through AECL's 135 MW National Research Universal (NRU) reactor and associated facilities in Chalk River. The NRU, which first entered service in 1957, currently has an operating site licence from the Canadian Nuclear Safety Commission (CNSC) that is valid until October 2011. AECL said that it will work closely with the CNSC and MDS Nordion on the requirements for continued production beyond that date.
MacDiarmid added, "We recognize the important role that NRU plays in the supply and delivery of medical isotopes to patients in North America and around the world. AECL is committed to supplying medical isotopes from NRU in a safe and reliable manner."
MAPLE reactors can have a thermal power of 5 to 40 MW. The Korea Atomic Energy Research Institute (KAERI) has built a 30 MW version of it, known as Hanaro, which started up in 1995 and is operating successfully. MAPLE had also been short-listed for Australia's 20 MW replacement research reactor in 1999.
MDS Nordion, a leading provider of medical isotopes and radiopharmaceuticals, originally ordered the two Chalk River MAPLE reactors. However, it later opted out of the contract due to excessive delays in the units' commissioning. In a statement, MDS said that it was "disappointed that AECL has stated it will not complete the MAPLE project despite significant investment and effort over the past 12 years."
Stephen DeFalco, president and CEO of MDS, commented: "The most important issue has always been the continuity of medical isotope supply for patients worldwide." He added, "We are pleased that the government has asked AECL to pursue the extension of the NRU operation beyond its current licence and to ensure the ongoing supply of these critical medical isotopes."
The NRU, which supplies about one-third of the world's radiotherapy isotopes, was forced to stay shut down after CNSC staff objected to the slow pace of AECL's work to upgrade certain safety systems in November 2007. CNSC said AECL had been in violation of its licence to operate the reactor.
On 12 December 2007 a bill was passed by parliament to stay CNSC's authority on certain specific parts of NRU's coolant system for 120 days in order to allow AECL to restart the unit sooner. This was necessary, the government had argued, to safely bring NRU back into operation as soon as possible in order to end the shortage of medical isotopes that was beginning to threaten Canadians' health treatment.