AN INTEGRAL REACTOR PHYSICS EXPERIMENT TO INFER ACTINIDE CAPTURE CROSS-SECTIONS FROM THORIUM TO CALIFORNIUM WITH ACCELERATOR MASS SPECTROMETRY Page: 5 of 5
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G. YOUINOU et al., ND2010 Proceedings
Furthermore, there is some operational evidence that cross talk
among samples is reduced. This effect has been observed with
other AMS projects at ATLAS. A negative to using a quartz
liner is that source performance as measured by charge-state
distribution and maximum beam intensity is somewhat reduced.
But the beam energy is limited by the bending power of the
FMA system and use of high charge state ions is not required. A
mass-to-charge ratio of ~8-9 should be quite adequate for these
measurements.
Ion identification and counting. One of the major
challenges of AMS of heavy nuclides at ATLAS is the need for
separation or discrimination of a desired species from
backgrounds of ions having similar mass-to-charge ratios
present as chemical impurities or interference of ion-source
materials. This separation or discrimination is best achieved at
ATLAS by using the FMA which has a very large dispersive
power and can analyze very heavy ions (in its acceptance region
of electrostatic and magnetic rigidities). A proof of concept and
first measurements of rare species in the actinide region were
successfully performed [5] (since this experiment considerable
improvement has been made in the focal-plane detector of the
FMA). The typical setup consists in accelerating and
decelerating a desired ion so that its energy matches the
electric-rigidity acceptance of the FMA. A stripping process
(typically the only one along the machine, improving thus
efficiency) allows the heavy ions to reach the high charge state
needed for magnetic-rigidity acceptance of the FMA.
In the case of actinide nuclei, Z identification at the energies
compatible with the FMA acceptance is likely to be impossible.
However, the high redundancy of energy, energy-loss and
time-of-flight signals available from that detector is expected to
contribute to the mass-to-charge determination and to a high
level of background discrimination.
4.2 Methods available at INL
The materials to be irradiated in ATR will be prepared,
characterized, and encapsulated at the Materials and Fuels
Complex at Idaho National Laboratory. Pre-irradiation samples
will be archived for concurrent post-irradiation analysis by AMS
at ATLAS. The heaviest isotope of each mass chain will also be
analyzed pre-irradiation by AMS at ATLAS.
Once purified, the materials would be precipitated in a form
suitable for irradiation in the reactor and for measurement by
AMS. As halides present a problem for the ECR source, the
likely final form will be an oxide. To facilitate handling of these
mg quantities, innocuous filler such as aluminium may be used.
Once a solid form has been achieved, the material would be
individually loaded and welded into a small stainless steel
canister.
Pre-irradiation analysis of the materials at INL will be done
using conventional analytical and radiochemical techniques.
Isotopic ratios will be measured using both Inductively-Coupled
Plasma Quadrupole Mass Spectrometry (ICP-QMS) and
Thermal Ionization Mass Spectrometry (TIMS). Elementalcontaminations will be measured using an automated
gas-pressurized extraction chromatography (GPEC) system.
This system has previously been used for measuring uranium
and plutonium contamination in americium from dismantled
AmBe sources [6].
5. CONCLUSION
The principle of the proposed experiment is to irradiate
very pure actinide samples in the Advanced Test Reactor (ATR)
at INL and, after a given time, determine the amount of the
different transmutation products. The determination of the
nuclide densities before and after neutron irradiation will allow
inference of effective neutron capture cross-sections.
This approach has been used in the past and the novelty of
this experiment is that the atom densities of the different
transmutation products will be determined using the Accelerator
Mass Spectrometry (AMS) technique at the ATLAS facility
located at ANL. The detection limit of AMS is orders of
magnitude lower than that of standard mass spectrometry
techniques (abundances as low as 10-2 can be detected), thus
allowing more transmutation products to be measured and
consequently more neutron cross-sections to be inferred from a
single sample.
It is currently planned to irradiate the following isotopes:
232Th, 235U 2l36U, 238U 237Np 238 239x_ 240 241 242
241Am 243m and 248Cm.
6. ACKNOWLEDGMENTS
This work is supported by the U.S. Department of Energy, Office
of Science, Office of Nuclear Physics, under DOE Idaho
Operations Office Contract DE-AC07-05ID 14517 as well as by the
ANL Contract DE-AC02-06CH11357 and by the ATR National
Scientific User Facility. The help provided by Antoine Petiot,
summer intern from the Ecole des Mines de Paris supervised by
Joseph Nielsen from the Irradiation Testing Department at INL, in
running the MCNP calculations is gratefully acknowledged. The
involvement of Mitchell Meyer, scientific program manager at
ATR-NSUF is also gratefully acknowledged.
7. REFERENCES
[1] M.Salvatores, "Nuclear Data for Advanced Fuel Cycles",
Proc. Int. Conf. IEMPT-10, Mito, Japan, 6-10 October 2008
[2] L.M. Bollinger et al, Nucl. Instr. and Meth. B 79 (1993), 753
[3] G. Youinou et al., INL/EXT-10-17622 (2010) available at
www.inl.gov/technicalpublications/Documents/4460753.pdf
[4] N. Kinoshita et al, "Ultra-Sensitive Detection of p-Process
Nuclide Sm146" J. Phys. G: Nucl. Part. Phys. 35, 014033 (2008)
[5] M. Paul et al, "AMS of heavy elements with an ECR ion
source and the ATLAS linear accelerator", Nucl. Instr. and
Meth B 172, (2000), 688.
[6] James Sommers et al, "Characterization of a sealed
Americium-Beryllium (AmBe) source by inductively
coupled plasma mass spectrometry", J. Radioanal. Nucl.
Chem., 282, (2009), 929.
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Youinou, G.; Salvatores, M.; Paul, M.; Pardo, R.; Palmiotti, G.; Kondev, F. et al. AN INTEGRAL REACTOR PHYSICS EXPERIMENT TO INFER ACTINIDE CAPTURE CROSS-SECTIONS FROM THORIUM TO CALIFORNIUM WITH ACCELERATOR MASS SPECTROMETRY, article, April 1, 2010; Idaho. (https://digital.library.unt.edu/ark:/67531/metadc1012807/m1/5/: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.