At the risk of a complicated offering, four options have been presented for the sake of covering the range that extends from a lower priced option (1A) to a high performance option (2B). Option 2B is unqualifiedly recommended for providing the most complete Producer data and the fastest and most accurate response. These density and level data can be fully utilized when computerized control and the faster (future hydraulic) rabble arm action are introduced, which will greatly facilitate achieving the desired modes of Producer operation for long range studies of both the production and the off-gas treatment processes. Option 2B is rated as the most reliable on the grounds that the largest number of crystals and photomultiplier tubes are used: similar units have been basically operational for about seven years at MERC. The ionization chambers, having intrinsically infinite lifetime, have not been used at MERC. However, these are also expected to have a high overall reliability. They are utilized in Options 1B and 2B. Not only their lifetime, but their capability of operating with a lower gamma ray total field strength and with a lower change in field strength (as is required on the coal chutes and ash hoppers) make them far superior for operation as level gauges over a seven year service period. They are also much faster than GM tubes, which will reduce the probability that the level gauges (with ion chambers) will limit the control capabilities of the Producer.