The Heavy Water Plant at Manuguru, Andhra Pradesh is based on the Bithermal Hydrogen Sulphide-Water (H₂S-H₂0) Exchange Process. This plant with a capacity of 185 MTY is the second plant based on this process, the earlier one being at Kota, Rajasthan for which the complete technology has been developed indigenously by BARC and HWB. The Manuguru site was chosen because of its proximity to Singareni coal fields and Godavari river which provide respectively large quantities of coal and water required by the plant. The nearest rail head Manuguru is at a distance of 10 KM from plant site. Based on the process package developed indigenously a Captive Power Plant (CPP) is also set up at Manuguru. The CPP consist of 3 pulverised coal fired boilers and 3 nos. of extraction condensing turbines each capable of supplying 30 MWe. and the required process steam at 32 and 8 kg/cm² pressure.

The main heavy water plant consists of two streams and the process employed is the combination of two processes namely isotopic exchange reaction between H₂S and H₂0 followed by vacuum distillation. As H₂S gas is very toxic, corrosive and hazardous in nature, care has been taken in the design of the plant, selection of equipment and materials adhering to stringent fabrication procedures and codes to ensure the production of heavy water in a safe manner. The exchange process operates at about 20 kg/cm² pressure and at a temperature of 30 to 130 °C. while the vacuum distillation plant works at a pressure of 100 mm Hg absolute. The isotopic exchange reaction which is the heart of the technology is carried out with the aid of specially designed efficient trays. The H₂S gas required for the process is manufactured in a separate unit at the plant premises by the chemical reaction between sodium sulphide and sulphuric acid. Very elaborate H₂S detection instrumentation is provided not only in the plant but also in the surrounding areas to meet the requirements of the off-site emergency plans.

Water from the nearby Godavari river, purified from both suspended and dissolved impurities forms the process feed and the D₂0 content is enriched from 150 ppm (0.015%) to 15% D₂0 by chemical exchange with H₂S and later vacuum distilled to produce 99.8% D₂0. The exchange unit is arranged in a 3 stage cascade with first stage handling large quantities of  process water and H₂S gas and consisting of three pairs of cold and hot towers operating at 30°C and 130°C respectively. The second and third stages each consist of one pair of cold and hot towers. The purified water enters the top of cold tower and travels down while hydrogen sulphide gas entering the bottom of the tower meets the water in counter current way on tower internals and the exchange of deuterium takes place. In cold tower, the water gets enriched with respect to deuterium while gas gets depleted in deuterium concentration. In hot tower, the reverse reaction takes place viz. the gas gets enriched while liquid gets depleted. By proper liquid and gas flow rates with gas in closed circuit in the pair of towers, a small quantity of enriched liquid can be withdrawn from the bottom of the cold tower as a net product. This will be further enriched in the similar manner in 2nd and 3rd stages.

The hot tower bottom liquid coming from the first stage is divided into two parts. One part is recycled to the top of humidification section located at the bottom of hot tower for heat recovery while the other part constitutes the waste. Before discarding the waste to the environment, it is necessary to recover the H₂S dissolved in the waste. For this purpose a waste stripper is provided to strip H₂S by direct steam stripping and the evolved gas and steam is put back to first stage hot towers. The enriched water from the 3rd stage  is stripped off its H₂S in a product stripper and fed to the distillation unit for further enrichment upto nuclear grade. The captive power plant is conventional type with coal coming to plant from Manuguru mines of Singareni Collieries by a combination belt conveyer and bi-cable aerial rope way system. The instrumentation of the CPP is quite modern with distributed microprocessor based controls and data acquisition systems. The CPP is an integrated one and has turbines with two extraction stages which provide steam for direct and indirect heating in the main Heavy water plant.