NRX was a heavy water moderated, light water cooled, nuclear research reactor at the Canadian Chalk River Laboratories, which experienced one of the world's first major reactor accidents 12 December 1952. The reactor began operation on 22 July 1947 under the National Research Council of Canada, and was taken over by Atomic Energy of Canada Limited (AECL) shortly before the 1952 accident. Heavy water is dideuterium oxide, or D2O or 2H2O. It is chemically the same as normal water, H2O, but the hydrogen atoms are of the heavy isotope deuterium, in which the nucleus contains a neutron in addition to the proton found in the nucleus of any hydrogen atom. ... In nuclear engineering, a neutron moderator is a medium which reduces the velocity of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a chain reaction. ... Nuclear power station at Leibstadt, Switzerland. ... The Chalk River Laboratories also Chalk River Labs and formerly the Chalk River Nuclear Laboratories is a Canadian nuclear research facility located in Deep River, Ontario. ... 1952 - Wikipedia /**/ @import /skins/monobook/IE50Fixes. ... 1947 was a common year starting on Wednesday (link will take you to calendar). ... Plaque on the main NRC building in Ottawa. ... Atomic Energy of Canada Limited or AECL is a Canadian federal Crown corporation with the responsibility to manage Canadian nuclear policy, promote nuclear energy and research, and to oversee nuclear waste developed by Canadian nuclear reactors as well as manage the decommissioning of older reactors. ...

NRX was for a time the world's most powerful research reactor, vaulting Canada into the forefront of physics research. Emerging from a World War II cooperative effort between the Britain, the United States, and Canada, NRX was a multipurpose research reactor used to develop new isotopes, test materials and fuels, and produce the beams of neutral particles, called neutrons, that became an indispensible tool in the blossoming field of condensed matter physics. In 1994 Dr. Bertram Brockhouse shared the Nobel Prize in Physics for his work in the 1950s at NRX, which advanced the detection and analysis techniques used in the field of neutron scattering for condensed matter research. NRX operated for 45 years, being shut down permanently in 1992. It is currently undergoing decommissioning at the Chalk River Laboratories site. Mushroom cloud from the nuclear explosion over Nagasaki rising 18 km into the air. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 940 MeV/c² (1. ... 1994 was a common year starting on Saturday of the Gregorian calendar, and was designated the International year of the Family. ... Bertram Neville Brockhouse (July 15, 1918 – October 13, 2003) was a Nobel prize-winning Canadian physicist. ... List of Nobel Prize laureates in Physics from 1901 to the present day. ...

A heavy water moderated reactor is governed by two main processes. First, the water slows down (moderates) the neutrons which are produced by nuclear fission, increasing the chances of the high energy neutrons causing further fission reactions. Second, control rods absorb neutrons and adjust the power level or shut down the reactor in the course of normal operation. Either inserting the control rods or removing the heavy water moderator can stop the reaction. In nuclear engineering, a neutron moderator is a medium which reduces the velocity of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a chain reaction. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ... A control rod is a rod made of a chemical element capable of absorbing many neutrons without decaying themselves. ... Properties In physics, the neutron is a subatomic particle with no net electric charge and a mass of 939. ...

The NRX reactor incorporated a sealed vertical aluminium cylindrical vessel with a diameter of 8m and height of 3m. The core vessel held about 175 6cm-diameter vertical tubes in a hexagonal lattice, 14,000 litres of heavy water and helium gas. The level of water in the reactor could be adjusted to help set the power level. Sitting in the vertical tubes and surrounded by air were fuel elements or experimental items. General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13 (IIIA), 3, p Density, Hardness 2700 kg/m3, 2. ... General Name, Symbol, Number Helium, He, 2 Atomic mass 4. ...

The fuel elements contained fuel rods 3.1m long, 3.1cm in diameter and weighing 55kg, containing uranium fuel and sheathed in aluminium. Surrounding the fuel element was an aluminium coolant tube with up to 250 litres per second of cooling water from the Ottawa River flowing through it. General Name, Symbol, Number Uranium, U, 92 Chemical series Actinides Period, Block 7, f Density, Hardness 19050 kg/m3, 6 Appearance silvery-white metal Atomic properties Atomic weight 238. ... This is about the river in Canada. ...

Twelve of the vertical tubes contained control rods made of boron powder inside steel tubes. These could be raised and lowered to control the reaction, with seven inserted being enough to absorb so many neutrons that no chain reaction could happen. The rods were held up by electromagnets, so that a power failure would cause them to fall into the tubes and terminate the reaction. An pneumatic system could use air pressure from above to quickly force them into the reactor core or from below to slowly raise them from it. Four of these were called the safeguard bank while the other eight were controlled in an automatic sequence. Two pushbuttons on the main panel in the control room activated magnets to seal the rods to the pneumatic system, and the pushbutton to cause the pneumatic blowdown of the rods into the core was located a few feet away. General Name, Symbol, Number Boron, B, 5 Series Metalloids Group, Period, Block 13 (IIIA), 2, p Density, Hardness 2460 kg/m3, 9. ... Pneumatics, from the Greek πνευματικός (pneumatikos, coming from the wind) is the use of pressurized air in science and technology. ...

It is claimed that the term "crud" originally stood for "Chalk River Unidentified Deposit", used to describe the radioactive scaling that builds up on internal reactor components, first observed in the NRX facility [1] (http://www.nrc.gov/reading-rm/basic-ref/glossary/crud.html). However, the word most likely entered our language in the 14th century, so this is a tall tale.

The CIRUS reactor, based on this design, was built in India. It was ultimately used to produce plutonium for India's Operation Smiling Buddha nuclear test. General Name, Symbol, Number Plutonium, Pu, 94 Chemical series Actinides Period, Block 7, f Density, Hardness 19816 kg/m3, no data Appearance silvery white metal Atomic properties Atomic weight 244. ... The so-called Smiling Buddha was the first test fission explosion by India on May 18, 1974. ... A nuclear test explosion is an experiment involving the detonation of a nuclear weapon. ...

External links

• The NRX incident, by Peter Jedicke (http://infotech.fanshawec.on.ca/faculty/jedicke/personal/nrx.htm)
• Nuclear Accidents (Georgia State University) (http://hyperphysics.phy-astr.gsu.edu/hbase/nucene/nucacc.html)
• "The Canadian Nuclear FAQ" (http://www.nuclearfaq.ca) by Dr. Jeremy Whitlock