A Method of Testing Fissile Rods for Surface Contamination

摘要

1,190,986. Fuel elements. REACTOR CENTRUM NEDERLAND. 26 July, 1967 [16 Sept., 1966], No. 34420/67. Heading G6C. [Also in Divisions G1 and H1] Fissile rods are tested for surface contamination by -particle emitters by using a rod 1 as an electrode in an ionization chamber 22 and applying a low voltage (50-200 v.) to measure the primary ionization current caused by the -particles. The rod 1 may be of UO 2 with a covering of Zr alloy. Compressed argon passes from a cylinder 11 through a reduction valve 10 to an inlet 7 of a stainless steel tube 6 forming an outer electrode and envelope of the chamber 22 and passes to an outlet 8 and valve 21 which is adjusted to maintain an overpressure of 0À1 to 1 atmosphere in the chamber. The rod 1 is slid together with supporting caps 4 and 5 of insulating material into the tube 6 and secured by a bayonet joint between the tube 6 and a metal hood 34 fixed to cap 4. A wire embedded in cap 4 is connected to a clamping spring (36) (Fig. 2, not shown) in the socket engaged by the end 2 of rod 1. The chamber 22 is connected through a loadsensitive preamplifier 16 and a main amplifier 17 to an analyzer 18 which may be multi-channel or single channel with a threshold discriminator to eliminate background radiation. Measurements are made with uncontaminated rods and subtracted from the measurements with contaminated rods to determine the contamination. A device (Fig. 3, not shown) for the successive testing of large numbers of rods includes a mechanical conveyer (23) for passing rods into and out of the chamber 22 and connected to the analyzer 18 by an electro-mechanical coupling enabling badly contaminated rods to be rejected.