Apparatus for measuring the content of fission products, a short service life in gasstroemen

摘要

851,328. Nuclear reactors. COMMISSARIAT A L'ENERGIE ATOMIQUE Dec. 1, 1958. [Dec. 4, 1957], No. 38707/58. Class 39(4). In a nuclear reactor cooling gas monitor, the short-lived fission products are detected to indicate the fracture of fuel element sheathing. The effect of the long-lived fission products is iluminated by a fuel recording circuit. The short-lived products decay first to krypton and zenon and then to rubidium and caesium ions which are collected so as to develop a signal separate from that due to the long-lived products. A signal corresponding to general level of radioactivity of the gas is first produced and then compared with a second signal corresponding to the general level plus the activity due to the short-lived products. As shown, a proportion of the coolant passes through chambers 1 and 2 where detection of the fission products is effected by scintillator 7, the output of which is applied to comparator circuit 13, 16. The long and short-lived products pass through 1 and 2 and the signal representing the general level of activity is applied simultaneously to amplifiers 13, 16 and a zero reading is recorded at 21. Next, the valves 3, 4 are closed, a voltage is applied to electrode 5 and the rubidium and caesium ions of the short period fission products resulting from decay in chamber 1 are collected at 5 and produce an additional signal which is applied only to valve 13. The resulting unbalance of 13, 16, being a measure of the short-lived products, is registered at 21.