Genshiro

摘要

A radiation shield (10) is comprised of three, equiangularly extending, arcuate sections (14) which are secured to the nuclear reactor pressure vessel closure head (12) so as to annularly surround the nuclear reactor control rod drive mechanisms (26) and thereby prevent radiation emanating from the mechanisms (26) from reaching maintenance personnel who may be operatively working within the peripheral section (20) of the closure head. The shield sections (14) are bolted together by fasterners (18) and are secured to closure head lift lugs (30) by means of mounting brackets (38) and transversely extending pins (36). Clevis assemblies (34) are also pinned to the mounting brackets (38) and lift lugs (30), and lift rods (32) are threadedly engaged with the clevis assemblies (34). In this manner, when the closure head (12) is lifted from its associated pressure vessel, the radiation shield (10) remains with the closure head (12). Thermocouple electrical connector and control rod drive mechanism coolant air exhaust port access panels (68) (74) are respectively provided within the radiation shield (10), and an emergency water-gas vent line (76) is likewise accommodated by an access panel (78) also defined within the radiation shield (10). The shield (10) is vertically spaced above the closure head (12) so as to define a gap (82) therebetween, and auxiliary hinged shield panels (192) may be secured along the bottom of the shield (110) to close the gap (182).