Having seen the devastation of atomic bombs, scientists, including
those who worked on the Manhattan project, campaigned against
further nuclear weapon development. They wanted to turn the giant
industries associated with the Manhattan project into peaceful
applications, especially as an energy supply.
Basic Reactor Elements
Basic elements of fission reactors are listed.
The diagram showing these elements is given below.
- reactor core for holding fission material or fuel
- moderator for slowing fast neutrons
- control rods holding neutron absorbers to control rate of fission
- monitoring system containing devices and indicators of operation
- energy transfer system to take the heat away
How does that Nuclear Reactor work?
The propulsion plant of a nuclear-powered submarine uses a nuclear reactor
to generate heat. The heat comes from the fissioning of nuclear fuel
contained within the reactor. Since the fissioning process also produces
radiation, shields are placed around the reactor so that the crew is
The nuclear propulsion plant in this ship uses a pressurized water reactor
design which has two basic systems - a primary system and a secondary system.
The primary system circulates ordinary water and consists of the reactor,
piping loops, pumps and steam generators. The heat produced in the reactor
is transferred to the water under high pressure so it does not boil.
This water is pumped through the steam generators and back into the
reactor for re-heating.
In the steam generators, the heat from the water in the primary system is
transferred to the secondary system to create steam. The secondary system
is isolated from the primary system so that the water in the two systems
does not intermix.
In the secondary system, the steam flows from the steam generators to drive
the turbine generators, which supply the ship with electricity, and to the
main propulsion turbines, which drive the propeller. After passing through
the turbines, the steam is condensed into water which is fed back to the
steam generators by the feed pumps. Thus, both the primary and secondary
systems are closed systems where water is recirculated and renewed.
Since there is no step in the generation of this power which requires the
presence of air or oxygen, this allows the ship to operate completely
independent from the earth's atmosphere for extended periods of time.
Core and fuel
- Uranium, m.p. 1403 K, phase transition, 933 K
- UO2, m.p. 3138 K (suitable), UO2 clad in Zircaloy or stainless steel.
Moderators are compounds containing light nuclides such as H, D, He, C, O, F.
Materials with low neutron-capture cross section are desirable.
The following substances are commonly used as moderators.
- H2O, D2O
- He (100 Atm and 1273 K)
- Be (high temperature liquid metal).
- Na (773 to 873 K used in breeder reactor)
- BeF2 + ZrF4 (for GCR)
Control Rod Materials
Materials with high termal-electron-capture cross section are desirable.
Usually, cadmium, boron, carbon, cobalt, silver, hafnium, and gadolinium
are common elements used in control rods.
For example, the abundance and cross section of gadolinium are listed below:
|Abundance and cross section of gadolinium isotopes
|Mass Number ||152 ||154 ||155 ||156 ||157 ||158 ||160
|Abundance % ||0.20 || 2.15 ||14.73 ||20.47 ||15.68 ||24.87 ||21.80
|125 ||90 ||61,000 ||2 ||255,000 ||2.4 ||0.7
After the war, the United States set up a Civilian Power Reactor Program
(CPRP) to coordinate the study of nuclear reactors for peaceful
application of nuclear energy. The Atomic Energy of Canada,
Limited was and still is the Canadian body for nuclear technology
After WW II, CPRP was set up to find out the most economical and safe
way to convert fission energy The first few nuclear reactors were
built to study how nuclear reactors function, and perhaps to
produce plutonium for atomic bombs. to electric energy.
The Program decided to investigate the following eight types
of power reactors:
- Fast Breeder Reactors (FBR)
- Aqueous Homogeneous Reactors (AHR)
- Heavy Water Moderated Reactors (HWR) (the CANadian Deuterium Uranium (CANDU) reactor)
- Pressurized Water Reactors (PWR)
- Boiling Water Reactors (BWR)
- Organic-Cooled Power Reactors (OCPR)
- Sodium Graphite Reactors (SGR)
- Gas-Cooled Reactors (GCR)
For fear of running out of supply in the future, scientists and engineers
tried to build fast breeder reactors (FBR) that produce more fuel than
they consume while generating power.
The 233U cycle (or thorium cycle) makes use of the reactions,
232Th (n, b) 233U.
The 239Pu cycle (or the uranium cycle) makes use of the reaction
238U + n ® 239U ( ,
2 b) 238Pu
The neutron-capture cross section is 2.7 b for 238U.
Reactor Links on the Internet
These links are available March, 2000. They, however, are subject to
changes, because they are under the control of other companies.
The 1350-megawatt Advanced Boiling Water Reactor (ABWR), developed
jointly by GE, Tokyo Electric Power Co., Hitachi, Ltd., and Toshiba Corp.,
represents more than 30 years of disciplined evolution to progressively
simpler designs. The ABWRs began operation in 1996 and 1997.
How Does a Nuclear Reactor Work? the concept of nuclear submarine.
Overview of Plant Design / Operation / Maintenance
Links to nuclear power plants of the world.
Nuclear Power Reactors in operation and under construction at the end of 1997
Westinghouse Energy Systems Whole systems of nuclear reactors designed,
built, and managed by Westinghouse.
Nuclear Links at Nuclear Engineering, the University of
California at Berkeley.
The McMaster Nuclear Reactor is a 2-MW pool-type distilled water reactor
with enriched uranium fuel, up grated to 5 MW, flux of 1e14 neutrons
cm2. Information is limited.
The Integral Fast Reactor (IFR) page from the Department
of Nuclear Engineering, University of California at Berkeley for
informational purposes. The following diagram shows the concept of IFR
on the site.