Physics Update: A new compact detector may
help international inspectors peer inside a working nuclear
reactor in a non-intrusive way by directly measuring the flux
of anti-neutrinos coming out. Since their first use, nuclear
reactors have, at least in principle, been closely related with
nuclear weapons. For example, reactors produce plutonium which
can later be fashioned into bomb material. The question of how
to monitor the actual operation of a particular reactor and
compare the changing plutonium inventory to what is expected
from normal operations (producing electric power, say) is a
large component of nuclear non-proliferation efforts.The
cubic-meter-scale detector, proposed by Adam Bernstein, leader
of the Advanced Detectors Group at Lawrence Livermore National
Laboratory (925-422-5918,
[email protected])
and built by a team from Livermore and Sandia National
Laboratories California branch, would not attempt to monitor
the reactor's performance on a moment by moment basis. Instead
its sensitivity is more attuned to the number of antineutrinos
produced over hourly, daily and weeklong intervals. These time
scales, Bernstein says, are well suited to the kind of
monitoring performed by the International Atomic Energy Agency
(IAEA). The detector built by the LLNL/SNL collaboration
operates unattended for long periods without significant
maintenance, is self-calibrating, and does not affect plant
operations in any way (see illustration of a detector at work,
http://www.aip.org/png/2008/295.htm
). Data from the detector is acquired remotely in real time.
The detector module can be made tamper-proof using standard
techniques, and the anti-neutrino signature seen by the
detector (the arrival of a positron followed 30 microseconds
later by a neutron) is hard to mimic with surrogate neutron or
gamma sources. In conjunction with knowledge of the input fuel
load and core design, the observed anti-neutrino flux provides
a direct measure of the reactor's power and isotopic
content.
