Low temperature vacuum evaporation process for sea water desalination using waste heat from PHWRs

摘要

Most of the nuclear reactors in India are of the PHWR type and use natural uranium oxide (UO_2) as fuel. Heavy water (D_2O) is used as the coolant and moderator. About 40 and 100 MW(th) waste heat are available in the moderator system of 220 and 500 MW(e) PHWRs, respectively. A significant part of this waste heat can be utilized for sea water desalination, producing fresh water in the coastal nuclear power stations. Coastal regions generally face water scarcity problems and normally do not have any source of good quality water. The available raw waters have a higher salt content, leading to a high production cost for makeup demineralized (DM) water. A scheme has been suggested that produces up to 1000 t/d of pure water by sea water desalination using the waste heat of the D_2O moderator in a 500 MW(e) coastal PHWR to meet the makeup DM water requirements of the power station. The low temperature vacuum evaporation (LTE) desalting system, using the waste heat of the D_2O moderator for producing low cost pure water from sea water, is discussed. The technical specifications and performance of the 30 t/d LTE desalination plant set up and operated at the Bhabha Atomic Research Centre (BARC) are presented. Also discussed si the performance of a water jet ejector for creating and maintaining the vacuum in the system and for pumping out the concentrated brine from the evaporator system. Details are given of a proposed 15 t/d LTE desalination pilot plant coupled to a nuclear research reactor (CIRUS) at BARC, utilizing part of the waste heat of the reactor coolant for conducting an immediate practical demonstration.