Data Assimilation Using Subcritical Measurement of Prompt Neutron Decay Constant
Nuclear Science and Engineering / Volume 194 / Number 11 / November 2020 / Pages 1089-1104
Technical Paper / dx.doi.org/10.1080/00295639.2020.1720499
Articles are hosted by Taylor and Francis Online.
The prompt neutron decay constant 
in a steady-state subcritical system can be directly measured using a reactor noise analysis method such as the Feynman-
method. To reduce the nuclear data–induced uncertainty of 
for a target system, this study investigates the applicability of data assimilation techniques, i.e., the bias factor method and the cross-section adjustment method, based on a subcritical measurement of 
conducted at Kyoto University Critical Assembly (KUCA). The sensitivity coefficients of 
and 
with respect to the nuclear data were efficiently estimated using a deterministic SN transport code with first-order perturbation theory. As a result, the a priori relative uncertainty of 
due to the 56-group SCALE covariance data can be reduced if there is strong correlation between the measured 
and the target 
. The experimental value of 
contributes to improving the nuclear data of total fission spectrum 
and total fission neutron number 
via strong correlations between 
and prompt 
and between 
and prompt 
, by utilizing the sensitivity coefficients of 
with respect to prompt 
and 
.
