Light water-cooled graphite-moderated reactors

Many see the commercial nuclear power station as a hazard to human life and the environment. Part of this is related to the atomic-weapon heritage of the nuclear reactor, and part is related to the reactor accidents that occurred at the Three Mile Island nuclear power station near Harrisburg, Pennsylvania, in 1979, and Chernobyl nuclear power station near Kiev in the Ukraine in 1986. The accident at Chernobyl involved Unit-4, a reactor that was a light water cooled, graphite moderated reactor built without a containment vessel. The accident resulted in 56 deaths that have been directly attributed to it, and the potential for increased cancer deaths from those exposed to the radioactive plume that emanated from the reactor site at the time of the accident. Since the accident, the remaining three reactors at the station have been shut down, the last one in 2000. The accident at Three Mile Island... 

A 1.2.5 Light water-cooled graphite-moderated reactors RBMKandEGP... 

RBMK light water cooled, graphite moderated, channel type reactor (Soviet design)... 

In 1986, an accident occurred at the Chernobyl Unit 4 reactor near Kiev in Ukraine. The Chernobyl reactor was a light water-cooled graphite-moderated (LWG) reactor. This accident led to the release of a large amoimt of airborne radioactivity and the death of many of the responders. As a result of this accident, several countries with smaller nuclear power programs ceased the pursuit of nuclear power electricity generation. 

Uranium enrichment and fuel fabrication For light-water-moderated and light-water-cooled reactors (LWRs) and for advanced gas-cooled graphite moderated reactors (AGRs), the uranium processed at the mills needs to be enriched in the hssile isotope Enrichments of 2-5% are required. Before the enrichment, the uranium oxide (UsOg) must be converted to uranium tetra-fluoride (UF4) and then to uranium hexa-fluoride (UFg). 

Kotthoff, K. Graphite-moderated, light-water-cooled, pressure-tube reactors, in Ullmann s Encyclopedia of Industrial Chemistry, Volume A17 Nuclear Technology, p. 682-694 (1991)... 

Following a general survey of the basic types of nuclear power reactor, separate chapters are devoted to each of the principal designs—the gas-cooled graphite-moderated reactor, the light-water-moderated reactor, the heavy-water-moderated reactor, and the fast reactor. Each chapter includes a discussion of the evolution of the design and a detailed description of one or more typical power plants. 

FIG. 20.2. Russian graphite-moderated boiling light water cooled power reactor, RBMK. 

SCOTT-R, Once-Through, Graphite Moderated, Light Water Cooled Tube Reactor (WH, 1962)... 

The Hanford N Reactor. The Hanford N reactor was built in 1964 for purposes of plutonium production during the Cold War. It used graphite as moderator, pierced by over 1000 Zircaloy 2 tubes. These pressure tubes contained slightly enriched uranium fuel cooled by high temperature light water. The reactor also provided 800 MWe to the Washington PubHc Power Supply System. This reactor was shut down in 1992 because of age and concern for safety. The similarity to the Chemobyl-type reactors played a role in the decision. 

It is a boiling water pressure tube (channel) reactor, cooled by light water and moderated by graphite. (In pressure tube (channel) reactors the nuclear fuel, made from low enriched uranium oxide, is contained in a set of parallel and closely spaced tubes or channels.) On passing, it has to be said that water reactors are numerous in the world, although the majority of these reactors are of the pressure vessel type, where all the nuclear fuel is contained in a strong vessel and not in a set of parallel pressure channels. 

Several candidate materials are available for possible use as a moderator in the gas-cooled reactor. These materials include light water, heavy water, metallic hydrides (e.g., zirconium hydride), beryllium metal, beryllium oxide, and graphite. Of these, the most commonly proposed moderator materials are graphite, heavy water, and beryllium oxide. 

Includes gas-cooled, heavy water, graphite-moderated light water, and liquid metal-cooled fast-breeder reactors. Includes reactors of all types planned or under construction. 

A thermal heterogeneous reactor, fuelled with highly enriched uranium, light water moderated and cooled, graphite reflected. 

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