ANS is committed to advancing, fostering, and promoting the development and application of nuclear sciences and technologies to benefit society.
Explore the many uses for nuclear science and its impact on energy, the environment, healthcare, food, and more.
Division Spotlight
Fuel Cycle & Waste Management
Devoted to all aspects of the nuclear fuel cycle including waste management, worldwide. Division specific areas of interest and involvement include uranium conversion and enrichment; fuel fabrication, management (in-core and ex-core) and recycle; transportation; safeguards; high-level, low-level and mixed waste management and disposal; public policy and program management; decontamination and decommissioning environmental restoration; and excess weapons materials disposition.
Meeting Spotlight
ANS Student Conference 2025
April 3–5, 2025
Albuquerque, NM|The University of New Mexico
Standards Program
The Standards Committee is responsible for the development and maintenance of voluntary consensus standards that address the design, analysis, and operation of components, systems, and facilities related to the application of nuclear science and technology. Find out What’s New, check out the Standards Store, or Get Involved today!
Latest Magazine Issues
Apr 2025
Jan 2025
Latest Journal Issues
Nuclear Science and Engineering
May 2025
Nuclear Technology
April 2025
Fusion Science and Technology
Latest News
Norway’s Halden reactor takes first step toward decommissioning
The government of Norway has granted the transfer of the Halden research reactor from the Institute for Energy Technology (IFE) to the state agency Norwegian Nuclear Decommissioning (NND). The 25-MWt Halden boiling water reactor operated from 1958 to 2018 and was used in the research of nuclear fuel, reactor internals, plant procedures and monitoring, and human factors.
C.-K. Chris Wang, Thomas E. Blue, Reinhard Gahbauer
Nuclear Technology | Volume 84 | Number 1 | January 1989 | Pages 93-107
Technical Paper | Radioisotopes and Isotope Separation | doi.org/10.13182/NT89-A34199
Articles are hosted by Taylor and Francis Online.
A neutronic study of an accelerator-based neutron irradiation facility (ANIF) for boron neutron capture therapy (BNCT) was performed using three-dimensional Monte Carlo transport calculations. The major components of the ANIF are a radio-frequency quad-rupole proton accelerator, a 7Li target, and a moderator assembly. Neutrons are generated by bombarding the 7Li target with 2.5-MeV protons. The neutrons emerging from the 7Li target are too energetic to be used for BNCT and must therefore be moderated. Calculations show that, among all materials for the ANIF, beryllia (BeO) and heavy water (D2O) are the best moderators. Between them, beryllia provides better neutron spectra, but D2O gives higher neutron intensities. Adding alumina (Al2O3) to D2O improves the neutron spectra, but it also increases gamma-ray contamination. The overall performance of an ANIF was evaluated for a moderator assembly composed of a 20.0-cm-high x 12.5-cm-radius beryllia cylinder reflected by 30.0 cm of alumina. Calculations show that the addition of the alumina reflector doubles the epithermal neutron intensity at the irradiation port. A 0.05 g/cm2 thick layer of 6Li was placed between the beryllia moderator and the alumina reflector to reduce the number of thermal neutrons escaping from the beryllia to the alumina, and therefore the capture gamma rays produced by aluminum in the reflector. Also, a 0.025 g/cm2 thick layer of 6Li was placed at the irradiation port of the moderator assembly to remove thermal neutrons from the field. Finally, a neutron shield of 10.0-cm-thick D2O wrapped with 6LiF was placed around the moderator assembly except at the irradiation port. The useful neutron flux (which is the flux of neutrons with energies greater than ∼1 eV) at the irradiation point, which is in front of the moderator assembly, is 4.87 x 108 n/cm2.s for a 10-mA proton beam. The corresponding total absorbed dose rates for neutron and gamma rays are 1.9 and 0.64 cGy/min, respectively. The ratio of the total neutron absorbed dose rate to the useful neutron flux is 6.5 x 10-11 cGy/n·cm-2, which is slightly higher than, but comparable to, the value of this ratio that has been estimated for moderated reactor neutron fields. The maximum usable depth (MUD) in a head phantom is calculated to be ∼7.5 cm assuming that the 10B concentration is 30 µg/g in tumor and 10 µg/g in blood, and the singlesession treatment time is 1.6 h. If the beryllia cylinder in the moderator assembly were replaced by a 15.0-cm-high x 12.5-cm-radius cylinder of heavy water, the treatment time would be reduced to 30 min, at the price of a higher entrance neutron dose to normal tissue and thus lower therapeutic gains and MUD.
