Thermal design of housing tube, conductors and maximum permitted load current of sealed cable penetrations through the steel containment of Nuclear Power Plant

The calculations in previous publications [1,2,3] did not consider heat transfer along the steel housing tube and copper conductors of penetrations. The proposed calculations also take into account the fact that temperature in the clean zone (outside the containment wall) is 20 - 30 oС, while in the contaminated zone (inside the containment) it is 60 oС under nominal conditions, and can reach 90 and 150 oС under small and big leak conditions, accordingly. The sealed penetration construction is provided in Figure 1. The steel tube of the penetration (2) is fixed in the containment wall (1) by means of steel flanges (3) provided at the tube ends. Modules (6) with insulated copper conductors (5) run through the tube and the flanges. Stainless steel protection casings (4) are mounted on the flanges (3). The points where the modules pass through the flanges are fitted with tight seals. Each module of Elox sealed penetration contains from 1 to 40 insulated conductors, cross section of power and control cables varies from 0.81 to 254 mm2. Currents in durable mode are from 2.5 to 640 А. Each cable in the penetrations where КМЖ cables with magnesia insulation and copper tube sheathing are used is laid separately, with their sheathings soldered separately to the flanges.