R. Benzing et al., Apparent neutron emissions from polyethylene capsules during neutron activation and delayed neutron counting, J RAD NUCL, 244(2), 2000, pp. 447-451
At Imperial College uranium is determined at very low levels in environment
al samples by delayed neutron counting. High density polyethylene capsules
are used for transporting the samples in a pneumatic transfer system, from
the reactor, to the neutron detection rig. The detector has a background of
3.6 counts per minute, however the empty transport capsules produce 11.0 c
ounts above the background. We have determined that neither uranium in the
polyethylene or from contamination of the capsule nor N-17 from the O-17(n,
p)N-17 and O-18(n,d)N-17 reactions are the cause. Th is paper reports the r
esults of the investigation into the source of the extra counts.