Quantum Beam Science Research

5-3High-Precision Measurement of Nuclear Materials=Proposal for the Advanced HKED System=

105104103102101100Counts (/keV)

UKα25mUKα1UKβ1UKβ3UKβ2
PuKα190UKβ4PuKβ1100
110Energy (keV)

120Fig.5-8 Schematic view of the advanced HKED system
The advanced HKED system is composed of an energy
recovery linac (ERL), a laser supercavity, and KED/XRFdetectors. Mono-energetic X-rays generated by collision ofhigh-energy electrons and laser quanta are used for irradiationof sample solutions. Transmitted and scattered X-rays aredetected by the KED and XRF detectors, respectively. The sizeof the ERL accelerator can be reduced using a 6-loop
configuration.

Fig.5-9 X-ray response spectrum
A Monte Carlo simulation code was used to investigate the X-ray
responses from a sample including U (200 g/) and Pu (2 g/).
The results for mono-energetic and bremsstrahlung incident
X-rays are shown with red and blue lines, respectively. A highpeak intensity of the Pu characteristic X-rays (PuKα1) can beobtained through efficient measurement of the PuKα1 line using
mono-energetic X-rays.

Nuclear material accountancy is an important issue fornuclear safeguards. Generally, destructive analysis with mass
spectrometry is used for density determination of nuclear
materials. However, non-destructive analysis is desired
because of simplicity and rapidity of the analysis, as well as
for the reduction of discharged nuclear wastes. Hybrid
K-edge densitometry (HKED) is a non-destructive analyticalmethod of nuclear materials dissolved in solution. This
technique can be applied for quantification of uranium (U)and plutonium (Pu) concentrations.
In the existing HKED system, bremsstrahlung X- raysfrom an X-ray tube are used as the incident photon source.
The broad energy distribution of the bremsstrahlung X-rays
produces background counts due to inelastic scattering that
affect the counting precision. However, if mono- energetic
X-rays are used, efficient KED and X-ray fluorescence(XRF) measurements are possible through reduction of thebackground counts. Thus, we have proposed an advanced
HKED system with mono-energetic X-rays. Fig.5-8 shows aschematic view of the advanced HKED system.
To evaluate the performance of the advanced HKEDsystem, X-ray responses were investigated using a Monte
Carlo simulation code. The result is shown in Fig.5-9. The
peak intensity of the Pu characteristic X-rays (PuKα1) can beenhanced using mono-energetic X-rays. Consequently, both
the ratio of the peak to the background count and ratio of thepeak to the total count are improved in comparison with thoseobtained when using bremsstrahlung X-rays. The counting
statistics in the region of the U K-absorption edge in the KED
spectra are also increased using mono-energetic X-rays.
Analysis of low concentrations of neptunium (Np) isdifficult with the existing HKED system because of the highbackground counts from the Pu characteristic X-rays.
However, with the advanced HKED system, by adjusting theenergy of the incident X-rays between the K-absorption
edges of Np and Pu, it is possible to measure the Np
characteristic X-rays without any influence from the Pu
characteristic X-rays.
The present technique is expected to facilitate the nondestructive rapid, and precise density determination ofnuclear materials in solutions at nuclear power plants andnuclear reprocessing facilities.

Reference
Shizuma, T. et al., Proposal for an Advanced Hybrid K-edge/XRF Densitometry (HKED) using a Monochromatic Photon Beam from Laser Compton
Scattering, Nuclear Instruments and Methods in Physics Research A, vol.654, issue 1, 2011, p.597-603.

68 JAEA R&D Review 2012