Program - Brookhaven National Laboratory

Lead and lead-based alloys are - among others - considered as target materials for high power spallation
neutron sources, either as a part of the driver device in accelerator driven systems (ADS) or as a scientific
facility for neutron applications. At the Paul Scherrer Institute (PSI), solid lead targets have been used
very successfully already for more than 10 years in the Swiss Neutron Source SINQ on a Megawatt level.
In 2006, also at PSI, a demonstration experiment had been performed showing the qualification of the
liquid metal alloy Lead-Bismuth Eutectic (LBE) as suitable target material (MEGAwatt PIlot Experiment
to MEGAPIE). A very recently launched project at SCK-CEN Mol (Belgium), aimed to demonstrate the
feasibility of ADS on an industrial scale (MYRRHA), uses also LBE as target material. LBE is as well
foreseen as preferred target material for the development of radioactive beams at CERN-ISOLDE. Besides
the knowledge on target and structure material behavior under extreme conditions - e.g. corrosion due
to the liquid aggregate state of the metal, embrittlement, radiation damage and many others - also the
radionuclide inventory, induced during the proton irradiation by a broad variety of nuclear reactions, is
of vital importance for both a safe operation of the facility and a final or intermediate disposal of the
waste. Theoretical predictions based on several nuclear reaction models estimate the amount of produced
residues, but need benchmarks for checking the reliability. Moreover, the quality of calculations depends on
the accurateness of the nuclear data to be used in the models. Especially the knowledge on cross sections
for the production of long-lived isotopes need further improvement. We studied the proton-induced residue
nuclide production of long-lived radionuclides like 10Be, 26Al, 36Cl, 129I and others from lead and bismuth
in thin target irradiations with proton energies up to 2.6 GeV and derived the excitation functions for these
isotopes [1,2]. Such radionuclides, with half-lives between 0.3 and 15.7 million years, cannot be measured by
conventional decay counting techniques like gamma-spectroscopy, but have to be determined by accelerator
mass spectrometry (AMS) after chemical separation of the elemental fractions from the matrix elements.
Highly-sophisticated separation procedures, applied step-by-step, were developed to obtain samples suitable
for AMS. We will present in this report a summary of these cross section measurements. Investigations on
integral experiments, e.g. the determination of the radionuclide inventory both of the MEGAPIE target
and a lead target from the SINQ are currently underway.
[1] D. Schumann et.al., AIP Conference Proceedings 769, Melville, New York, 2005,p. 1517 [2] D. Schumann
et.al.,J.Phys.G: Nucl. Part. Phys. 38 (2011) 065103
DB 4 4:40 PM
Partial Cross Sections of Neutron-Induced Reactions on nat Cu at En = 6,8,10,12,14 and 16
MeV for 0νββ Background Studies
M.E Gooden, J.H. Kelley
North Carolina State University, Raleigh, NC 27695 and Triangle Universities Nuclear Laboratory,
Durham, NC 27710
B.A. Fallin, S.W. Finch, C.R. Howell, G. Rusev, A.P. Tonchev, W. Tornow
Duke University and Triangle Universities Nuclear Laboratory, Durham, NC 27710
Partial cross-section measurements of (n,xγ) reactions on nat Cu were carried out at TUNL using monoenergetic
neutrons at six energies of En = 6, 8, 10, 12, 14, 16 MeV. These studies were performed to provide
accurate cross-section data on materials abundant in experimental setups involving HPGe detectors used
to search for rare events, like the neutrino-less double-beta decay of 76 Ge. Spallation and (α,n) neutrons
are expected to cause the largest source of external background in the energy region of interest. Pulsed
neutron beams were produced via the 2 H(d,n) 3 He reaction and the deexcitation γ rays from the reaction
nat Cu(n,xγ) were detected with clover HPGe detectors. Cross-section results for the strongest transitions in
63 Cu and 65 Cu will be reported, and will be compared to model calculations and to data recently obtained
at LANL with a white neutron beam.
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