This paper is devoted to experiments with plutonium nitrate solution, most of which are poisoned with borated Pyrex tubes or Raschig rings. They were carried out in the testing equipment called Apparatus D in the experimental criticality facility at the “Section Expérimentale d’Etudes de Criticité”, today called “Service de Recherche en Neutronique et Criticité”, in Valduc (C.E.A. France) in 1966-1968. They were subcritical approaches extrapolated to critical, with the multiplication factor reached being very close to 1.000 (within 0.1%).
Experiments were performed in a 36-cm-diameter cylindrical tank, water reflected or not. In all, 122 experiments were conducted and are reported in the three experimental reports (References 1, 2 and 3): 68 poisoned by tubes, 7 poisoned by Raschig rings (occupying approximately 1/6.2 of the volume), and 47 not poisoned (used as basic experiments). Some were experiments rerun several times in order to observe the reproducibility.
(2)Retraité de l’IRSN