CROCUS
Encyclopedia
Research reactor
Research reactors are nuclear reactors that serve primarily as a neutron source. They are also called non-power reactors, in contrast to power reactors that are used for electricity production, heat generation, or maritime propulsion.-Purpose:...
at École Polytechnique Fédérale de Lausanne
École polytechnique fédérale de Lausanne
The École polytechnique fédérale de Lausanne is one of the two Swiss Federal Institutes of Technology and is located in Lausanne, Switzerland.The school was founded by the Swiss Federal Government with the stated mission to:...
in Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
, sometimes described as zero power but in fact limited to 100 W
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
.
This low power means that within a few hours of shutdown, it is safe for personnel to enter the biological shield, as the residual radioactivity of the core
Nuclear reactor core
A nuclear reactor core is the portion of a nuclear reactor containing the nuclear fuel components where the nuclear reactions take place.- Description :...
has decayed
Radioactive decay
Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...
to safe levels. The biological shield consists of a concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
wall, with a 14-ton door for personnel access. There is also a removable 50-ton concrete trapdoor in the top of the shield, to allow for fuel and equipment changes.
CROCUS uses low-enriched uranium
Enriched uranium
Enriched uranium is a kind of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Natural uranium is 99.284% 238U isotope, with 235U only constituting about 0.711% of its weight...
(LEU) metal fuel, immersed in a tank of demineralised light water which acts as moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....
and reflector. There is no special provision for cooling required.
CROCUS is controlled by two control rods and by adjusting the water level in the moderator tank. A neutron source is placed under the core to aid startup. In addition, there are two safety control rods and four surge tanks, making six independent safety systems. Any one of these six is capable of producing a complete emergency shutdown (scram
Scram
A scram or SCRAM is an emergency shutdown of a nuclear reactor – though the term has been extended to cover shutdowns of other complex operations, such as server farms and even large model railroads...
) in less than one second, and is triggered automatically should power exceed the authorised level.
CROCUS is used for teaching reactor physics.
External links
CROCUS page at the École Polytechnique Fédérale de LausanneÉcole polytechnique fédérale de Lausanne
The École polytechnique fédérale de Lausanne is one of the two Swiss Federal Institutes of Technology and is located in Lausanne, Switzerland.The school was founded by the Swiss Federal Government with the stated mission to:...
website.