332 POWER PLANT ENGINEERING
reactors it is to be enriched to about 3%, U^235 and for this uranium enrichment plant is needed which
requires huge investment and high operational expenditure. Heavy water reactors use heavy water as
their coolant and moderator. They have the advantage of using natural uranium as their fuel. Such
reactors have some operation problem too. Heavy water preparation plants require sufficient investment
and leakage of heavy water must be avoided as heavy water is very costly. Heavy water required in
primary circuits must be 99% pure and this requires purification plants heavy water should not absorb
moisture as by absorbing moisture it gets degraded. In order to have sufficient quantity of heavy water
required for nuclear power plants, the work is fast progressing in our country on four heavy water plant.
These plants are situated at Kotah (100 tonnes per year), Baroda (67.2 tonnes), Tuticorin (71.3 tonnes)
and Talcher (67.2 tonnes per year). These plants will give our country an installed heavy water produc-
tion capacity of about 300 tonnes per year.
10.16.1 Importance of Heavy Water
The nuclear power plants of Kota in Rajasthan, Kalpakkam in Tamil Nadu and Narora in U.P. use
heavy water as coolant and moderator. All these projects have CANDU reactors using natural uranium
as fuel and heavy water as moderator. After this enriched uranium natural water reactor at Tarapur, the
CANDU reactors are the second generation of reactors in India's nuclear power programme. The CANDU
reactor will produce plutonium which will be the core fuel for fast breeder reactor. In fact in breeder
reactor heavy water is used as moderator.
A CANDU reactor of 200 mW capacity requires about 220 tonnes of heavy water in the initial
stages and about 18 to 24 tonnes each year subsequently. Therefore, about one thousand tonnes of heavy
water will be required to start the different nuclear power stations using heavy water. The total capacity
of different heavy water plants will be about 300 tonnes per year if all the heavy water plant under
construction start production. It is expected that heavy water from domestic production will be available
from Madras and Narora atomic power plants. The management of the heavy water system is a highly
complicated affair and requires utmost caution. Heavy water is present in ordinary water in the ratio 1 :
- One of the methods of obtaining heavy water is electrolysis of ordinary water.
ADVANTAGES OF NUCLEAR POWER PLANT
The various advantages of a nuclear power plant are as follows:- Space requirement of a nuclear power plant is less as compared to other conventional power
plants are of equal size. - A nuclear power plant consumes very small quantity of fuel. Thus fuel transportation cost is
less and large fuel storage facilities are not needed Further the nuclear power plants will
conserve the fossil fuels (coal, oil, gas etc.) for other energy need. - There is increased reliability of operation.
- Nuclear power plants are not effected by adverse weather conditions.
- Nuclear power plants are well suited to meet large power demands. They give better perform-
ance at higher load factors (80 to 90%). - Materials expenditure on metal structures, piping, storage mechanisms are much lower for a
nuclear power plant than a coal burning power plant.
For example for a 100 mW nuclear power plant the weight of machines and mechanisms,
weight of metal structures, weight of pipes and fittings and weight of masonry and bricking
up required are nearly 700 tonnes, 900 tonnes, 200 tonnes and 500 tonnes respectively whereas