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An aqueous homogenous zero-energy suspension reactor (1962)

Auteur	KEMA, J.A.H.Kersten, Cenerini,
Datum	1962
Classificatie	1.01.8.41/17 (KEMA - KSTR)
Voorkant

INTRODUCTION

This paper reports on investigations on the neutron physics of an aqueous 
homogeneous subcritical assembly at room temperature. From these data, 
information on the flow behaviour and the colloid chemical properties of the 
suspension was obtained. A detailed description of the construction and the 
instrumentation of the assembly is given by WENT et al. (1960). Some of the 
results have already been reported at the Geneva Conference of 1958 by DE JONG 
et al. (1958).
Two different types of reactor vessels were investigated. The first one was a 
cylindrical vessel with conical ends and an inlet at the bottom and an outlet at the 
top. The second one was a spherical vessel with a concentric inlet and outlet, both 
at the top. In the former vessel flow was laminar, and in the latter it was turbulent.
A suspension of UO2 particles (enriched in 235U up to 20 per cent) was used as a 
fuel. Essential parameters were the size, shape and surface condition of the 
particles. The size was fixed by an upper limit of about 15 microns in order to 
give  an efficient separation of fission products from the UO2 particles by the 
fission recoil process and also to have not too large a settling velocity.* The lower 
limit was about 3 microns in order to facilitate concentration adjustment by the use 
of hydrocyclones. The particles must be smooth and preferably spherical to reduce 
attrition and erosion during circulation. Finally, the particles were sintered at an 
elevated temperature to reduce the active surface. The methods used to fabricate 
these particles have been described by HERMANS (1958).
The colloid chemical behaviour of the suspension (which determines whether the 
particles are flocculated or not) is determined by the pH of the liquid. Further
details are given in a following paper by KALSHOVEN (1962).

* The measurements on the recoil separation efficiency by MARKESTEIN and
VAN DER PLAS (1962) have demonstrated that smaller particles, up to 5.5 “u”, 
are  desirable. However, the larger particles used here have a settling velocity 
comparable with the settling velocity of the smaller particles in water of 250°C.

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