Scope:

A total of 56 facilities/areas have been identified on the Pelindaba site that need to be decommissioned at some stage in order to minimize the state’s liabilities with regard to potential safety hazards that they constitute to personnel, the public and the environment. The majority of these formed part of the former AEC’s nuclear fuel activities and these have all been shut down permanently.

Decommissioning work is ongoing and is funded by government through annual budget appropriations as well as special allocations from the Department of Minerals and Energy.

Approach to decommissioning:

Decommissioning activities are classified as phase 1, 2 and 3 decommissioning.

Decommissioning work to date:

The following facilities have been partially/fully decommissioned at Pelindaba:

This plant was housed on the following six levels in Area 14 (a 260 in by 70 in building):

This area originally housed 168 instrumentation marshalling panels to serve the control systems of the 56 enrichment stages on the main process floor, as well as the electrical back up systems for instrumentation (batteries and chargers).

The control corridor is 250 m long and 15 m wide and contained a control panel for each of the 56 modules. The whole process was controlled from a central control room, using a process computer, which was situated in an adjacent area.

This was an intermediate level in the main process hall, which housed -63 Profan compressors (used for product pressure control); - 56 in-line filters (each I m x I m); - 600 mm and 300 mm diameter header pipes with a total length of 5 630 m (the 600 mm pipes contained partitions to accommodate 5 separate gas streams);- specially designed 300 and 600 mm four-way valves to enable the independent switching of any of the 56 stages into, or out of the operation;

- 6 instrumentation transducer racks per stage to accommodate control instruments for the compressors and the valves; and -cold traps to remove product from a module if it had to be emptied for maintenance.

The 56 modules (enrichment stages) were installed in two parallel rows on this floor. Each module measured 12 m x 4 m diameter, and housed - 2 locally designed axial flow compressors, code-named 11 Mamba 11 and ,,Cheetah,,; - approximately 280 000 gas separating elements, mounted in 360 to 400 cassettes (each measuring 640 x 520 x 150 mm); - 20 sets of heat exchanger tubes; and -a complex arrangement of partitioned gas flow channels. The Mamba and Cheetah motors, 4 and 2,5 MW respectively, were mounted on either side of the module. Two instrumentation racks, for the compressor labyrinth seal control, were also situated next to each module.

Each module weighed approximately 130 t when fully assembled, and was moved by means of an aerocastor transport system from the process floor to the maintenance area and back. This method required smooth and perfectly level floors in the process and maintenance areas.

The cable basement housed all the electrical cables (approximately 200 km total length), and cooling water and compressor lubricating oil pipes also passed through this area. Pipe sizes were 300, 250 and 150 mm diameter and in total approximately 19 km were installed.

This area is below ground level and contained the cooling water and lubricating oil systems. There were 15 oil systems, each consisting of -I x 50 in' storage tank; - 2 x vertical multistage oil pumps; - 2 x heat exchangers; -2 x oil filters; and 2 x temperature control systems. Apart from these, there were also three oil storage tanks for new and used oil. The approximately I 000 in' oil inventory had been contaminated and its decontamination and recovery is included in the project. Primary and secondary cooling water systems were used, with the following main components in the basement:

112 x pumps, driven by 45 kW motors; and 56 x-plate heat exchangers.

View of Z-plant

Area 14 before decommissioning

Area 14 after decommissioning