The document provides an overview of various types of nuclear reactors, including Boiling Water Reactors (BWR), Pressurized Water Reactors (PWR), Pressurized Heavy Water Reactors (PHWR), Gas Cooled Reactors (GCR), Advanced Gas Cooled Reactors (AGR), and Light Water Cooled Graphite Moderated Reactors (LGR). Each type is described with its operational principles, advantages, disadvantages, and specific characteristics, highlighting differences in efficiency, power generation, and safety aspects. The overall emphasis is on their use for generating electrical power and variations in design and functionality.

1. Types of Nuclear Reactors

2. Introduction
Nuclear Reactor:
A nuclear reactor is a device to initiate, and control, a sustained nuclear chain
reaction.
The most common use of nuclear reactor is for the generation of electrical
power also termed as nuclear power.

3. Types of Nuclear Reactors
1. BWR-Boiling Water Reactor
2. PWR-Pressurized Water Reactor
3. PHWR-Pressurised Heavy Water Reactor
4. GCR-Gas Cooled Reactor
5. AGR-Advanced Gas-Cooled Reactor
6. LGR-Light Water Cooled - Graphite Moderated Reactor

4. BWR-Boiling Water Reactor
 In the boiling water reactor (BWR), the water which passes over the reactor
core act as moderator and coolant. It is also the steam source for the turbine.
 The disadvantage of BWR is that any fuel leak might make the water
radioactive and that radioactivity would reach the turbine and the rest of the
loop.
 A typical operating pressure for BWR is about 70 atm at which the water boils at
about 285°C temperature. This operating temperature gives a efficiency of only
42% with a practical operating efficiency of around 32%, somewhat less than
the Pressurized Water Reactor(PWR).

6. PWR-Pressurized Water Reactor
 In the pressurized water reactor (PWR), the water which passes over the reactor
core act as moderator and coolant but does not flow to the turbine. It is sent in
a pressurized primary loop. The primary loop water produces steam in the
secondary loop which drives the turbine.
 The advantage PWR is that a fuel leak in the core would not pass any radioactive
contaminants to the turbine and condenser.
 Another advantage is that the PWR can operate at higher pressure and
temperature, about 160 atm and about 315°C. This provides a higher
efficiency than the boiling water reactor(BWR) , but PWR is more complicated
and more costly to construct.

8. PHWR-Pressurised Heavy Water Reactor
 Pressurized Heavy Water Reactor (PHWR) is a Canadian design which is
designed in Canada and subsequently exported to several countries (also
known as CANDU).
 PHWR are heavy water cooled and moderated Pressurized Water reactors.
Instead of using a single large pressure vessel as in a PWR, the fuel is contained
in hundreds of pressure tubes.
 These reactors are fueled with natural uranium and are thermal neutron
reactor designs. PHWRs can be refueled while at full power, which makes them
very efficient in their use of uranium.

10. GCR-Gas Cooled Reactor
Gas Cooled Reactor is also termed as Magnox reactor as the magnesium alloy
is used to encase the fuel, natural uranium metal.
These reactors are generally graphite moderated and CO2 cooled. The whole
assembly is cooled by blowing carbon dioxide gas past the fuel cans, which
are specially designed to enhance heat transfer. The hot gas then converts
water to steam in a steam generator.
They can have a high thermal efficiency compared with PWRs due to higher
operating temperatures.

12. AGR-Advanced Gas-Cooled Reactor
 To improve the cost effectiveness of the gas cooled reactor, it was necessary to
go to higher temperatures to achieve higher thermal efficiencies and higher
power densities to reduce capital costs.
 This entailed increases in cooling gas pressure and changing from Magnox to
stainless steel cladding and from uranium metal to uranium dioxide fuel. This in
turn led to the need for an increase in the proportion of U235 in the fuel.
 The resulting design is known as the AGR-Advanced Gas-Cooled Reactor

14. LGR-Light Water Cooled - Graphite
Moderated Reactor
In this type of reactor heat is removed from the fuel by pumping water
under pressure up through the channels where it is allowed to boil, steam
generated here drives electrical turbo-generators.
Many of the major components, including pumps and steam drums, are
located within a concrete shield to protect operators against the
radioactivity of the steam.
The design of this type of reactor is known as the RBMK Reactor.