Continuous Neutron Source Needed

An article in the September 2002 issue of Physics Today (page 27) reports a "shortage of neutron sources available to US scientists." As many physicists and others are aware, more than three years ago, the US Department of Energy abruptly decided to permanently shut down the High Flux Beam Reactor at Brookhaven National Laboratory.

The Physics Today article reports that the shutdown decision was due to groundwater tritium from the spent fuel storage pool. Actually, the Secretary of Energy saw no public health or environmental concerns for the future operation of the reactor; he based his decision on the abundance of neutrons in the US and on economics. The US Nuclear Regulatory Commission independently determined that the tritium plume in the groundwater did not pose a health risk to any member of the public.

Now the reactor is gone, other facilities are aging, and planned new ones will meet only part of the projected demand for neutrons. Therefore, it is time to start thinking about a new continuous neutron source. Several years ago, the Advanced Neutron Source project was canceled because of cost and proliferation concerns. Since then, new information has been developed on the performance of low-enriched uranium fuels, and the nuclear industry has become extremely aware of cost in the design of future, safer reactors. A preliminary analysis of a heavy-water-cooled, particle-bed reactor fueled with low-enriched uranium indicates that a thermal flux of 10¹⁶ neutrons/(cm² · s) is achievable. It is important for researchers to have a new world-class continuous source, at an acceptable and convenient site, to complement the forthcoming accelerator-based pulsed source.