GB1150387A - Nuclear Reactors - Google Patents

Abstract

1,150,387. Reactors. ENGLISH ELECTRIC CO. Ltd. 8 Sept., 1967 [9 Sept., 1966], No. 40493/66. Heading G6C. A reactor core 16, together with its associated coolant circuit 17 to 22, is housed within a concrete containment structure 10 in a primary vault 11 which is in communication with a secondary (or suppression) vault 12 situated below it, through a number of tubes 13 which extend below the surface 14 of a mass of water constituting a suppression pond 15 in the vault 12. The reactor is steam-generating and the coolant circuit contains a substantial quantity of heated water and steam, the release of which into the primary vault 11 under accident conditions would cause the pressure in the latter to rise sharply. In addition, the loss of coolant would cause a substantial rise in the temperature of the fuel and consequently also of the atmosphere in the primary vault, also producing an increase in pressure. This second pressure increase may occur as long as ten minutes after the accident, and the existence of relatively high pressures in the vaults for such a comparatively long time introduces a serious danger of volatile radio-active materials escaping through the concrete containment structure 10. In one method for relieving the pressure in vault 11 after an accident, the space within vault 12 above the pond surface 14 contains nitric oxide which combines with oxygen in the air from vault 11 which passes through the tubes 13 and then bubbles through the pond 15, forming nitrogen dioxide which is hydrolysed by the water in the pond to give a solution of nitrous and nitric acids. In a second method, the pond 15 comprises a weak solution of a hydroxide, preferably one (e.g. NaOH or KOH) capable of reacting with CO 2 to give a water-soluble carbonate. The primary vault 11 or the space within vault 12, or both, contain CO 2 gas which is kept out of contact with the pond 15 by floating a film of oil on the surface 14 of the pond. If the vault 11 contains CO 2 , when an accident occurs this will bubble into the pond 15 and react with the hydroxide, whereas if the vault 12 contains CO 2 , the disturbance caused by the bubbling of CO 2 or air from the vault 11 will disrupt the oil film so bringing the CO 2 above the surface 14 into contact with the water of the pond. In a third method, either the primary vault 11 or the space within vault 12, or both, are filled with a gas (e.g. NH 3 ) soluble in water. Again a suitable oil film is used on the pond surface 14, the pond 15 comprising water only. In all three methods, the pond 15 serves to condense the steam escaping from the coolant circuit.