NC State's PULSTAR Reactor is a 1 MW pool-type
with 4% enriched, pin-type fuel consisting of UO2 pellets in zircaloy">research reactor with 4% enriched, pin-type fuel consisting of UO
2 pellets in zircaloy cladding.image:Pulstar1.jpg, The control room of North Carolina State University, NC State's Pulstar Nuclear Reactor.
A swimming pool reactor, also called an open pool reactor, is a type of
nuclear reactor
A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat fr ...
that has a
core (consisting of the fuel elements and the
control rods) immersed in an open pool of usually water.
The water acts as
neutron moderator, cooling agent and radiation shield. The layer of water directly above the reactor core shields the radiation so completely that operators may work above the reactor safely. This design has two major advantages: the reactor is easily accessible and the whole primary cooling system, ''i.e.'' the pool water, is under normal pressure. This avoids the high temperatures and great pressures of
nuclear power plant
A nuclear power plant (NPP) is a thermal power station in which the heat source is a nuclear reactor. As is typical of thermal power stations, heat is used to generate steam that drives a steam turbine connected to a generator that produces ...
s. Pool reactors are used as a source of
neutron
The neutron is a subatomic particle, symbol or , which has a neutral (not positive or negative) charge, and a mass slightly greater than that of a proton. Protons and neutrons constitute the atomic nucleus, nuclei of atoms. Since protons and ...
s and for training, and in rare instances for processing heat but not for electrical generation.
Description
Open pools range in height from 6m to 9m (20' to 30') and diameter from 1.8m to 3.6m (6' to 12'). Some pools, like the one at the Canadian
MAPLE
''Acer'' () is a genus of trees and shrubs commonly known as maples. The genus is placed in the family Sapindaceae.Stevens, P. F. (2001 onwards). Angiosperm Phylogeny Website. Version 9, June 2008 nd more or less continuously updated since h ...
reactor, are rectangular instead of cylindrical and often contain as much as 416,000 litres (110,000 gallons) of water. Most pools are built above floor level but some are completely or partially below ground. Ordinary (light)
water
Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as ...
- and
heavy water-only types exist as well as so-called "tank in pool" designs that use heavy water moderation in a small tank situated in a larger light water pool for cooling.
Life preservers are sometimes located around the facility to rescue personnel that may fall into the pool, further adding to the appearance of a swimming pool-like environment.
Normally the reactor is charged with low
enriched uranium (LEU) fuel consisting of less than 20%
U-235 alloyed with a matrix such as
aluminium
Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
or
zirconium. Highly enriched uranium (HEU) was the fuel of choice since it had a longer lifetime, but these have been largely phased out of non-military reactors to avoid
proliferation issues. However most often 19.75% enrichment is used, falling just under the 20% level that would make it highly enriched. Fuel elements may be plates or rods with 8.5% to 45%
uranium
Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
.
Beryllium
Beryllium is a chemical element with the symbol Be and atomic number 4. It is a steel-gray, strong, lightweight and brittle alkaline earth metal. It is a divalent element that occurs naturally only in combination with other elements to for ...
and
graphite
Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...
blocks or plates may be added to the core as neutron reflectors and neutron absorbing rods pierce the core for control.
General Atomics of
La Jolla, CA manufactures
TRIGA reactor fuel elements in
France
France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
for the majority of these types of reactors around the world. Core cooling is accomplished either by
convection
Convection is single or multiphase fluid flow that occurs spontaneously due to the combined effects of material property heterogeneity and body forces on a fluid, most commonly density and gravity (see buoyancy). When the cause of the c ...
induced by the hot core or in larger reactors by forced coolant flow and
heat exchangers.
Various stations for holding items to be irradiated are located inside the core or directly adjacent to the core. Samples may be lowered into the core from above or delivered pneumatically via horizontal tubes from outside the tank at core level. Evacuated, or
helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic ta ...
filled horizontal tubes may also be installed to direct a beam of neutrons to targets situated at a distance from the reactor hall.
Applications
Most
research reactors are of the pool type. These tend to be low power, low maintenance designs. For example
AECL's
SLOWPOKE is licensed to run unattended for up to 18 hours.
Boron neutron capture therapy
Neutron capture therapy (NCT) is a type of radiotherapy for treating locally invasive malignant tumors such as primary brain tumors, recurrent cancers of the head and neck region, and cutaneous and extracutaneous melanomas. It is a two-step pro ...
is another, medical use.
See also
*
Pressurized water reactor
A pressurized water reactor (PWR) is a type of light-water nuclear reactor. PWRs constitute the large majority of the world's nuclear power plants (with notable exceptions being the UK, Japan and Canada). In a PWR, the primary coolant (water) i ...
*
CANDU reactor
*
NRX
*
TRIGA
References
{{DEFAULTSORT:Pool-Type Reactor
Nuclear reactors