On the use of ?/n correlations in multiplicity counting in small samples

• The use of liquid scintillation detectors provides the possibility to acquire information about both gamma-rays and neutrons. The capability of plutonium detection via gamma/n coincidences in liquid scintillation detectors is well demonstrated in the literature, and it is also acknowledged that correlated gamma/n detection can offer better sensitivity and signal to noise ratio compared to neutron-neutron for some applications. In this paper we perform an assessment of the use of gamma/n coincidence counting in small samples, what may have use in the context of nuclear safeguards. We formulate the expected number of gamma/n coincidences and calculate the average and covariance of gamma-ray and neutron multiplicities for Pu-238, Pu-240, Pu-242 and Cf-252. The multiplicative coefficients for the Pu-240 effective mass equation was then calculated using gamma/n coincidences, and Monte Carlo simulations performed in order to model the detection of neutrons and gamma-rays inside liquid scintillation detectors. We conclude that gamma/n coincidence counting still has potential capabilities when the objective is the detection of plutonium, but its use for plutonium effective mass quantification is limited compared to n/n coincidence counting. Nevertheless, the method could still be applicable for the purpose of plutonium mass quantification by using a calibration curve that is specific to a sample's mass and size.

Ämnesord

NATURVETENSKAP  -- Fysik -- Subatomär fysik (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Subatomic Physics (hsv//eng)

NATURVETENSKAP  -- Fysik -- Acceleratorfysik och instrumentering (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Accelerator Physics and Instrumentation (hsv//eng)

NATURVETENSKAP  -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)

Nyckelord

Gamma and neutron multiplicities

Nuclear safeguards

Nuclear material accountability and control

Plutonium effective mass

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