Maintenance of special nuclear equipment fuelling machines [Paper No. VB-1]

Rajasthan Atomic Power Station (RAPS) has two fuelling machines which load new fuel in the core and discharge spent bundles of fuel to bay. Fuelling operation is described in detail. To sustain full power operation approximately one channel has to be fuelled per day which needs five hours of operation. Sixteen hours work a day is needed to cater for operation, breakdown and preventive maintenance of the present fuel handling system. Simultaneous operation and maintenance cannot be taken up, because redundancy is not built in the system. Breakdown maintenance consumes 80% of the maintenance time. Ram assembly and position monitoring ropes and/or its potentiometer are sources of frequent breakdown. From 1976 onwards preventive maintenance is being carried out on the machines. Some of the unusual problems faced were: (i) unscrewing of latch extension tube, (ii) inadvertent pushing of spent bundles, (iii) leaking pressure reducing valves, (iv) leaks from screwed fittings, and (v) heavy water spill. It is described how these problems were overcome. Problems faced in preventive maintenance programme are: (1) paucity of local skilled workers required for maintenance, (2) high field near workspot, and (3) non-availability of spare parts. Attempts to tackle these problems are described. For satisfactory maintenance, it is suggested that: (a) clean working area should be provided for maintenance work of precision items like separators, (b) special test facility be set up for individual components of subassemblies, (c) performance checks be carried out at more frequent intervals, (d) all drives from two different sources should be duplicated, (e) proper training programme for fuel handling personnel should be formulated, (f) two inspection bays with interconnection instead of only one should be provided, and (g) the complexity of fuelling machines should be reduced. (M.G.B.)