An Experimental Study of the Moderator Assembly for a Low-Energy Proton Accelerator Neutron Irradiation Facility for BNCT

  • C. K. Wang
  • T. E. Blue
  • J. W. Blue
Part of the Basic Life Sciences book series (BLSC, volume 54)


An accelerator-based neutron irradiation facility (ANIF), which has been proposed for BNCT, is based on a 2.5-MeV proton beam bombarding a thick lithium target. Neutrons which are emitted from the lithium target are too energetic for BNCT and must be moderated. A calculational study, which was done previously on the moderator assembly for an ANIF, shows that, with an optimized moderator assembly, an ANIF can produce a neutron flux which has quality and intensity sufficient for BNCT. In order to verify our previous calculational study, a lithium target and a non-optimized moderator assembly (a cylindrical tank of D2O) have been constructed and tested at the Ohio State University Van de Graaff proton accelerator.

The neutron spectrum was measured for neutrons emerging from the moderator assembly. The measured neutron spectrum agrees reasonably well with that obtained from Monte Carlo calculations, except for neutrons with energies above 100 keV. For those neutrons, the measured spectrum is lower by a factor of two than the calculated one. In addition to the neutron spectrum measurement, the boron-10 absorbed dose was measured on the axis of the neutron field in a 20 cm x 20 cm x 20 cm water phantom, and the result agrees quite well with that obtained from calculation.

This experiment confirms that the calculated optimized moderator assembly, consisting of a 22.5-cm thick, 25-cm diameter cylinder of beryllia (BeO) surrounded by a 30-cm thick jacket of alumina (Al2O3), produces an epithermal neutron flux of 3.12 x 107 n/cm2-s per mA of protons. For an accelerator delivering 30 mA of 2.5-MeV protons, the irradiation time for a single-session treatment can be as short as 50 minutes. The calculated ratio of absorbed neutron dose to fluence for the optimized moderator assembly is 4.9 x 10−11 cGy-cm2/n, which is equal to that of a 5-keV neutron beam. Our experimental measurements indicate that the ratio of absorbed neutron dose to fluence may in fact be lower (better) than calculated.


Neutron Spectrum Proportional Counter Boron Neutron Capture Therapy Moderator Assembly Pulse Height Spectrum 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    J. W. Blue, W. K. Roberts, T. E. Blue, R. A. Gahbauer, and J. S. Vincent, “A Study of Low Energy Proton Accelerators for Neutron Capture Therapy,” in Proc. Second Int. Symp. on Neutron Capture Therapy, Tokyo, 1985, H. Hatanaka, ed., Nishimura Co., Ltd., Niigata, Japan, p. 147 (1986).Google Scholar
  2. 2.
    Y. Oka, I. Yanagisawa, and S. An, “A Design Study of the Neutron Irradiation Facility for Boron Neutron Capture Therapy,” Nucl. Technol., 553: 642 (1981).Google Scholar
  3. 3.
    R. M. Brugger, T. J. Less, and G. G. Passmore, “An Intermediate-Energy Neutron Beam for NCT at MURR,” U.S. Dept. of Energy 1986 Workshop on Neutron Capture Therapy, R. G. Fairchild and V. P. Bond, eds., Brookhaven National Laboratory, BNL-51994, p. 83 (1987).Google Scholar
  4. 4.
    C. K. Wang, T. E. Blue, and R. Gahbauer, “A Neutronic Study of an Accelerator-Based Neutron Irradiation Facility for Boron Neutron Capture Therapy,” Nucl. Technol. 84: 93 (1989).Google Scholar
  5. 5.
    T. P. Wangler J. E. Stovall, T. S. Bhatia, C. K. Wang, T. E. Blue, and R. A. Gahbauer, “Conceptual Design of an RFQ Accelerator-Based Neutron Source for Boron Neutron Capture Therapy,” in Proc. 1989 IEEE Particle Accelerator Conf., Chicago, IL, Vol. I, p. 678 (1989).Google Scholar
  6. 6.
    P. W. Benjamin C. D. Kemshall, and A. Brickstock, “SPEC-4: A Neutron Spectrum Unfolding Code for a Spherical Proportional Counter Containing Hydrogen,” Radiation Shielding Information Center, Oak Ridge National Laboratory, PSR-99 (1976).Google Scholar
  7. 7.
    C. K. Wang and T. E. Blue, “A Neutron Spectrometer for Neutron Energies Between i eV and 10 keV,” Trans. Am. Nucl. Soc., 57:79 (1988). Google Scholar
  8. 8.
    M. B. Emmett, “The MORSE Monte Carlo Radiation Transport Code System,” Oak Ridge National Laboratory, ORNL-4972 (Feb. 1975).Google Scholar
  9. 9.
    R. W. Roussin, “BUGLE-80: Coupled 47-Neutron, 20-Gamma-Ray Group, P3, Cross-Section Library for LWR Shielding Calculations,” Radiation Shielding Information Center, Oak Ridge National Laboratory, DLC-75 (1980).Google Scholar
  10. 10.
    J. J. Doroshenko S. N. Kraitor, T. V. Kuznetsova, K. K. Kushnereva, and E. S. Leonov, “New Methods for Measuring Neutron Spectra with Energy from 0.4 eV to 10 MeV by Track and Activation Detectors,” Nucl. Technol., 33: 296 (1977).Google Scholar

Copyright information

© Plenum Press, New York 1990

Authors and Affiliations

  • C. K. Wang
    • 1
  • T. E. Blue
    • 1
  • J. W. Blue
    • 2
  1. 1.Ohio State UniversityColumbusUSA
  2. 2.Cleveland ClinicClevelandUSA

Personalised recommendations