SHIELDING OF PIPES IN THE HFIR PRIMARY COOLANT SYSTEM

The thicknesses of ordinary concrete required to shield pipes in the ORNL High Flux Isotope Reactor primary water system were computed for normal operating conditions and for abnormal conditions such as a defective fuel plate or a meltdown of the fuel within the reactor. About 6 ft of concrete is required for the pipes at the outlet of the reactor, and 2 ft of concrete is required for the pipes located about 1 1/2 min downstream from the reactor vessel-. These thicknesses of concrete reduce the radiation levels to below the specified tolerances of: (a) 0.75 mr/hr during normal operation or operation with one defective fuel plate; (b) 1 r/hr immediately after the meltdown of 1% of the fuel; and (c) 1 r/hr 24 hr after a total fuel melidown. Shielding thicknesses required for other tolerances may be estimated from graphs and tables which are presented. (auth