The document presents a project report on boiling water reactors (BWRs) as part of a mechanical engineering course at Gujarat Technological University. BWRs, which use demineralized water for cooling and neutron moderation, produce steam directly to drive turbines, and involve specific control systems for power management. While BWRs offer advantages like lighter reactor vessels and higher thermal efficiency, they also have disadvantages such as radioactive steam and complex fuel management.

1. Gujarat Technological University
(Chandkheda, Ahmedabad)
Affiliated
Government Engineering College,
Bharuch
A project report on:
BOILING WATER REACTOR
Under subject of
Power Plant Engineering
B.E. Semester- VII
Branch- Mechanical
Presented by:
Sr. No. Name Enrollment No.
1 KHARVA TARUN 160140119034
2 KHER JAYDEEP 160140119035
3 LABBAI JISHAN 160140119037
4 LAD VIRAL 160140119038
5 LUHAR DHRUVESH 160140119039
6 MACHHI DHAVAL 160140119040
Guided By:-
Prof. U.V Joshi

2. Overview
A boiling water reactor (BWR) uses demineralized water as a
coolant and neutron moderator. Heat is produced by nuclear
fission in the reactor core, and this causes the cooling water to
boil, producing steam. The steam is directly used to drive
a turbine, after which it is cooled in a condenser and converted
back to liquid water. This water is then returned to the reactor
core, completing the loop.
The cooling water is maintained at about 75 atm (7.6 MPa,
1000–1100 psi) so that it boils in the core at about 285 °C
(550 °F).

3. In comparison, there is no significant boiling allowed in
a pressurized water reactor (PWR) because of the high pressure
maintained in its primary loop—approximately 158 atm (16
MPa, 2300 psi)
A type of light water nuclear reactor used for the generation
of electrical power
It is the second most common type of electricity-generating
nuclear reactor after the PWR (Pressurized Water Reactor)

4. BWR vs PWR
BWR PWR
The reactor core heats
water, which turns to steam
and then drives a steam
turbine
The reactor core heats water
(does not boil) then
exchanges heat with a lower
pressure water system which
then turns to steam to drive a
steam turbine

5. Control System
Changed by two ways
 Inserting or withdrawing control rods
 Changing the water flow through the reactor core
 Positioning control rods is the standard way of controlling
power when starting up a BWR
As control rods are withdrawn, neutron absorption decreases in
the control material and increases in the fuel, so reactor power
increases
As control rods are inserted, neutron absorption increases in the
control material and decreases in the fuel, so reactor power
decreases
Control by Flow of Water
As flow of water through the
core is increased, steam
bubbles are more quickly
removed, amount of water in
the core increases, neutron
moderation increases
As flow of water through the core
is decreased, steam voids remain
longer in the core, the amount of
liquid water in the core decreases,
neutron moderation decreases
More neutrons are slowed
down to be absorbed by the
fuel, and reactor power
increases
Fewer neutrons are slowed down
to be absorbed by the fuel, and
the power decreases

6. Steam Turbine
 Steam produced in the reactor core passes through steam
separators and dryer plates above the core, then goes
directly to the turbine
 The water contains traces of radionuclides so the turbine
must be shielded during operation and radiological
protection must be provided during maintenance
FUEL
Boiling water reactors must use enriched uranium as
their nuclear fuel, due to their use of light water. This is because
light water absorbs too many neutrons to be used with
natural uranium, so the fuel content of fissileUranium-235 must
be increased. This is done through uranium enrichment—which
increases the concentration of Uranium-235 from 0.7% to
around 4%.
The enriched uranium is packed into fuel rods, which are
assembled into a fuel bundle, as seen in Figure 3. There are
about 90-100 rods in each bundle, with up to 750 bundles in a
reactor. This corresponds to nearly 140 tonnes of uranium!

7. Advantages:
 The pressure inside the reactor vessel is less than PWR as
water is allowed to boil inside the reactor. Therefore, the
reactor vessel can be much lighter than PWR and reduces
the cost of pressure vessel considerably.
 Pressure vessel is subject to significantly less irradiation
compared to a PWR, and so does not become as brittle with
age.
 Operates at a lower nuclear fuel temperature, largely due to
heat transfer by the latent heat of vaporization, as opposed
to sensible heat in PWRs.
 ower risk (probability) of a rupture causing loss of coolant
compared to a PWR, and lower risk of core damage should
such a rupture occur. This is due to fewer pipes, fewer large
diameter pipes, fewer welds and no steam generator tubes.
 It eliminates the use of heat exchanger, pressuriser,
circulating pump and piping. Therefore, the cost is further
reduced.
 The thermal efficiency of this reactor plant (30%) is
considerably higher than PWR plant.
 The metal temperature remains low for given output
conditions.
 Can operate at lower core power density levels using
natural circulation without forced flow.

8. Disadvantages:
 The steam leaving the reactor is slightly radioactive.
Therefore, light shielding of turbine and piping is
necessary.
 Larger pressure vessel than for a PWR of similar power,
with correspondingly higher cost, in particular for older
models that still use a main steam generator and associated
piping.
 BWRs require more complex calculations for managing
consumption of nuclear fuel during operation due to "two
phase (water and steam) fluid flow" in the upper part of the
core. This also requires more instrumentation in the reactor
core.
 It cannot meet the sudden changes in load on the plant.
 The power density of this reactor is nearly 50% of PWR,
therefore, the size of the vessel will be considerably large
compared with PWR.
 It requires enriched uranium as a fuel.