Transuranic waste detection by photon interrogation and on-line delayed neutron counting A. Lyoussi a, * , J. Romeyer-Dherbey a , F. Jallu a , E. Payan a , A. Buisson b , G. Nurdin b , J. Allano b a CEA-DRN-DER-SSAE, 13108 Saint Paul lez Durance cedex, France b DGA-DRET-ETCA-DPN, 92114 Arcueil, France Received 26 October 1998; received in revised form 4 June 1999 Abstract A comprehensive program is currently in progress at several laboratories for the development of sensitive, practical, non-destructive assay techniques for the quanti®cation of low-level transuranics (TRUs) in bulk solid wastes. This paper describes the method being developed to assay high density TRU waste packages using photon inter- rogation. The system uses a pulsed electron beam from an electron linear accelerator to produce high-energy photon bursts from a metallic converter. The photons induce ®ssions in a TRU waste package which is inside an original neutron separating and counting cavity (NS2C). When ®ssion is induced in trace amounts of TRU contaminants in waste material, it provides ``signatures'' from ®ssion products that can be used to assay the material before disposal. We give here the results from counting photo®ssion-induced delayed neutrons from 239 Pu, 235 U and 238 U in sample matrices. We counted delayed neutrons emitted after each pulse of the LINAC by using the sequential photon interrogation and neutron counting signatures (SPHINCS) technique which had been developed in the present framework. The SPHINCS method enhances the available counts by a factor of about 20 compared with the counting of delayed neutrons only, after the irradiation period. Furthermore, the use of SPHINCS measurement technique coupled with the NS2C facility improves the signal-to-noise ratio by a factor of about 30. This decreases the detection limit. The electron linear ac- celerator operates at 15 MeV, 140 mA, and 2.5 ls wide pulse at a 50 and 6.25 Hz rate. The dynamics of photo®ssion and delayed neutron production, NS2C advantages and performances, use of an electron linear accelerator as a particle source, experimental and electronics details, and future experimental works are discussed. Ó 2000 Elsevier Science B.V. All rights reserved. PACS: 41.50.+h Keywords: Photo®ssion; Transuranians; LINAC; Bremsstrahlung Nuclear Instruments and Methods in Physics Research B 160 (2000) 280±289 www.elsevier.nl/locate/nimb * Corresponding author. Tel.: +04-42-25-75-88; fax: +04-42-25-23-67. E-mail address: lyoussi@cea.fr (A. Lyoussi). 0168-583X/00/$ - see front matter Ó 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 5 8 3 X ( 9 9 ) 0 0 5 8 6 - 8