Design, Construction, and Modeling of a²⁵²Cf Neutron Irradiator

Abstract

Neutron production methods are an integral part of research and analysis for an array of applications. This paper examines methods of neutron production, and the advantages of constructing a radioisotopic neutron irradiator assembly using252Cf. Characteristic neutron behavior and cost-benefit comparative analysis between alternative modes of neutron production are also examined. The irradiator is described from initial conception to the finished design. MCNP modeling shows a total neutron flux of 3 × 105 n/(cm2·s) in the irradiation chamber for a 25 μg source. Measurements of the gamma-ray and neutron dose rates near the external surface of the irradiator assembly are 120 μGy/h and 30 μSv/h, respectively, during irradiation. At completion of the project, total material, and labor costs remained below $50,000.

Response to “Comment on ‘Solid-State Neutron Detection Based on Methylammonium Lead Bromide Perovskite Single-Crystals’”

“…Several papers report this well-known behavior. For example, Anderson et al plotted the neutron spectrum for a moderated and unmoderated 252 Cf source in Figure 9 in their paper . As the energy of the neutrons interacting with 10 B decreases, the alpha creation intensity increases.…”

“…(a) 10 B neutron capture probability at various neutron energies. , (b) Calculated neutron fluence spectrum for moderated 252 Cf . Reprinted from ref . Available under a CC BY 4.0 license.…”

“…Figure a here shows the cross-section versus energy for neutrons in 10 B and Figure b shows the calculated neutron fluence spectra from a moderated 252 Cf source. ,, Figure b is a simulation from Anderson et al of the neutron fluence from a moderated 252 Cf source. This spectrum is later used below to calculate what percentage of detected neutrons captured by the 10 B layer are thermal, epithermal, and fast neutrons.…”

Comment on “Solid-State Neutron Detection Based on Methylammonium Lead Bromide Perovskite Single Crystals”

“…It is considered as an epithermal–fast neutron emitter with the most probable neutron energy in the range of 1–5 MeV, whereas thermal neutrons have a kinetic energy around 2.5 × 10 –8 MeV, i.e., 8 orders of magnitude lower. Moreover, several studies , have shown that even with the use of moderators, the neutron spectrum of 252 Cf can have a significant epithermal and fast flux component, as demonstrated by three D 2 O moderated spectra on Figure b. Thus, using only moderation is not sufficient to estimate the thermal neutron detection efficiency.…”

Sensitivity Analysis of an Advanced Transmission Measurement Method for Thermal Neutrons Absorbers Detection in Irradiated Beryllium

“…The9 Be is most frequently used because of its relatively high neutron yield due to its low neutron binding energy (≈1.67MeV). Other target materials such as 10 B,19 F 13 C or7 Li are also used[13]. The most common alpha emitters are 241 Am, 238 Pu and 239 Pu b.…”