Passive Neutron Multiplicity Counting : simulations and measurements

This paper presents some comparison of numerical studies with experimental results of passive neutron multiplicity counting. The ESARDA NDA working group organised in 2004- 2005 a multiplicity benchmark, in order to compare algorithms for the analysis of neutron pulse trains from different neutron sources: AmLi, 252Cf, Pu, PuO2 and mixtures of PuO2 and AmLi samples. The development and testing of a specific tool that has been implemented by IRSN in the framework of this exercise is reported. The validation of the numerical calculation is presented using some theoretical cases coming from the ESARDA benchmark together with measurements done in the laboratory using certified samples (AmLi, 252Cf, Pu and PuO2). For these measurements, two data acquisition systems that perform multiplicity analysis have been used. One of them is based on the dating of neutron events and therefore has the capability to generate neutron pulse trains. The paper will present some first results using these electronic devices.