American Nuclear Society

Home / Publications / Journals / Nuclear Science and Engineering / Volume 152 / Number 2

Experimental Determination of the Decay Constants and Abundances of Delayed Neutrons by Means of Reactor Noise Analysis

Ricardo Diniz, Adimir dos Santos

Nuclear Science and Engineering / Volume 152 / Number 2 / February 2006 / Pages 125-141

Technical Paper /

A reactor noise approach has been successfully performed at the IPEN/MB-01 research reactor facility to determine experimentally the effective delayed neutron parameters i and i in a six-group model. The method can be considered a novel one because it exploits the very low-frequency domain of the spectral densities. The proposed method has some advantages to other in-pile methods since it does not perturb the reactor system and consequently does not "excite" any sort of harmonic modes. As a by-product and a consistency check, the eff parameter was obtained without the need of the Diven factor and power normalization, and it is in excellent agreement with independent measurements. The theory/experiment comparison shows that for the abundances the JENDL3.3 presents the best performance, while for the decay constants the revised version of ENDF/B-VI.8 shows the best agreement. The best performance for the eff determination is obtained with JENDL3.3. In contrast, ENDF/B-VI.8 and its revised version performed at Los Alamos National Laboratory overestimate eff by as much as 4%. The eff results of this work totally support the proposal by Sakurai and Okajima to reduce the thermal delayed neutron yield of 235U.

Questions or comments about the site? Contact the ANS Webmaster.