The measurement of neutron diffusion parameters in heavy and light water concentrations by the pulsed neutron technique

Abstract

Neutron diffusion parameter measurements have been made at 21°C in 20, 50, and 80 percent concentrations of heavy and light water, including pure H20 and D2 0 as moderators. Pulsed neutron techniques were used with a 250-kv Cockcroft-Walton accelerator as the pulsed source. The range of bucklings used was from 0.05 cm⁻² to 0.70 cm⁻².

The values for the diffusion coefficient, Dₒ; the diffusion cooling coefficient, C; and the transport mean free path, A_tr, were determined from the expansion of the decay constant to second order using iteration procedure. The values of Dₒ, C, and A_tr are tabulated below for the various concentrations, including pure H₂O and D₂O.

<table style="width:100%"> <tr> <th>Percent D₂0</th> <th>Dₒ x 10⁻⁴ (cm²sec⁻¹)</th> <th>C x 10⁻⁵ (cm⁴sec⁻¹)</th> <th>λ_tr (cm)</th> </tr> <tr> <td>0</td> <td>3.634±0.048</td> <td>0.161±0.008</td> <td>0.443</td> </tr> <tr> <td>20</td> <td>3.779±0.017</td> <td>0.170±0.032</td> <td>0.515</td> </tr> <tr> <td>50</td> <td>6.964±0.044</td> <td>0.74±0.12</td> <td>0.915</td> </tr> <tr> <td>80</td> <td>11.75±0.68</td> <td>2.19±0.42</td> <td>1.602</td> </tr> <tr> <td>100</td> <td>19.66±1.37</td> <td>3.56±1.08</td> <td>2.670</td> </tr> </table>