Belgium's BR2 research reactor, which accounts for around a quarter of world production of medical isotope Mo-99 (Tc-99m), is due to close between March 2015 and July 2016 for modernisation work, the Belgian Nuclear Research Centre, SCK-CEN, has confirmed.

Work will include the replacement of the beryllium matrix, which is composed of 79 hexagonal channels containing the nuclear fuel elements, the control rods and various experiments and plugs, and forms the heart of the BR2 reactor. The matrix has been replaced twice in the past, first in the 1980s and most recently between 1995 and 1997.

SCK-CEN says that as the reactor is used the matrix wears out, impacting the reactor's flexibility and availability. As such, it is planning to take BR2 out of service between March 2015 and July 2016 to replace the component for a third time.

After this period, the reactor will be operational again, with an availability of more than 180 days a year instead of the current 120 days, according to SCK-CEN.

"Thanks to this extra flexibility and extra capacity, reactor BR2 will be better equipped to deal with the failure of other research reactors than was the case in the past," it said.

Recent years have seen global shortages of radioisotopes when major production reactors have been out of action, and security of supply remains a key concern. The work at BR2 also comes at a critical time, with the anticipated closure of another major Mo-99 producing reactor, Canada's NRU, in October 2016.

BR2 is a 100MWt tank-type light-water-cooled materials testing reactor. As well as its role in the production of radioisotopes, BR2 produces around 25% of all neutron doped silicon for semiconductors and contributes to safety for nuclear power plants. SCK-CEN says that further information on the modernisation plans will be release in late 2014.

Photo: Inside the BR2 reactor. (Source: SCK.CEN, used with permissiion)