Program - Brookhaven National Laboratory

The 33 S(n,α) cross section is of interest in medical physics since it has been proposed as a possible/alternative
cooperating target to boron neutron capture therapy due to the remarkable feature of the 33 S(n,α) reaction
channel at epithermal neutron energies: alpha particle energy above 3 MeV in absence of gamma emission.
The scarce experimental data which are available at present show that, in principle, the lowest-lying and
strongest resonance occurs at neutron energy of 13.5 keV. Epithermal neutron beams of around 10 keV are
considered the optimal ones for neutron capture therapy. According to the available data, the resonance
peak at that energy is larger than the hydrogen elastic scattering cross section, the dominant mechanism of
epithermal neutron interactions in tissue. Nevertheless, the set of resonance parameters which determine
the 33 S(n,alpha) cross section at these energies present important discrepancies (more than a factor two)
between different measurements and they are not described by the most popular evaluated data bases
such as ENDF or JENDL. The present work aims to contribute in this aspect which is evinced by Monte
Carlo simulations that, even based on the most conservative values of the lowest resonances, have shown a
noticeable local increase of the dose at the isotope site with a neutron beam of 13.5 keV [1,2]. Preliminary
tests of the measurement of the 33 S(n,α) reaction were successfully performed at n TOF-CERN during
2011. In particular, the first low-lying resonance was measured (with low statistics) using a micromegastype
detector and with the 10 B(n,α) cross section as a standard. The results of this test will be shown.
The kerma-fluence factors corresponding to 10 B, 33 S and those of a standard four-component ICRU tissue
have been calculated for using them is Monte Carlo simulations of the dose deposited on tissue. The
comparison between different evaluated data and experimental data will be shown. Following its approval
by the ISOLDE and Neutron Time-Of-Flight (INTC) committee at CERN, the measurement of 33 S(n,α)
reaction cross section will be performed at n TOF-CERN in October-November 2012 [3]. The results of a
preliminary data analysis will be shown, too.
[1] I. Porras, Enhancement of neutron radiation dose by the addition of sulphur-33 atoms. Phys. Med.
Biol. 53 (2008) L1-L9. [2] I. Porras, Sulfur-33 nanoparticles: A Monte Carlo study of their potential as
neutron capturers for enhancing boron neutron capture therapy of cancer. Applied Radiation and Isotopes
69 2011)1838-1841. [3] J. Praena et al, Micromegas detector for 33S(n,alpha) cross section measurement
at n TOF, CERN-INTC-2012-006 / INTC-P-322 (04/01/2012).
NF 4 11:40 AM
Production of High Specific Activity 186 Re for Cancer Therapy Using nat,186 WO3 Targets in
a Proton Beam
M.E. Fassbender, B. Ballard, J.W. Engle, E.R. Birnbaum, K.D. John, J.R. Maassen, F.M. Nortier,
Chemistry Division, Los Alamos National Laboratory, Los Alamos NM 87545. J. W. Lenz, John Lenz
and Associates, East Lansing, MI 48823. C.S. Cutler, A.R. Ketring, Missouri University Research
Reactor Center, University of Missouri-Columbia, Columbia, MO 65211. S.S. Jurisson, Department of
Chemistry, University of Missouri-Columbia, Columbia, MO 65211. D.S. Wilbur, Radiochemistry
Division, University of Washington, Seattle, WA 98105.
Rhenium-186 is a β-γ emitter with a half-life of 90.64 h and a β end-point energy of 1.07 MeV. The isotope
is suitable to treat cancers with small dimensions (mm range). Moreover, its γ-emission at 137.15 keV is
in the energy range suitable for both γ-camera and SPET imaging. Current production methods rely on
the neutron capture induced reaction 185 Re(n,γ) in a reactor and are associated with low specific activities
(0.6 kCi/mmol), thereby limiting the application of the isotope to palliative treatments. Production via
charged particle irradiation of enriched 186 W results in a 186 Re product with a much higher specific activity;
allowing its use in therapeutic nuclear medicine. Initially, a test target of pressed, sintered nat WO3 (25.2
g; 2.54 mm thick) was proton irradiated at the Los Alamos Isotope Production Facility (LANL-IPF) to
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