This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: 3- Heavy water reactors:-Heavy water reactors use heavy water as a neutron moderator. Heavy water is deuterium oxide, D2O. Deuterium is an isotope of hydrogen. Most hydrogen atoms have a nucleus that consists of only a single proton, but deuterium has a proton and a neutron, which makes it approximately twice as heavy as a regular hydrogen atom. Heavy water has two atoms of deuterium bonded to an oxygen atom. Neutrons in a nuclear reactor that uses uranium must be slowed down so that they are more likely to split other atoms and get more neutrons released to split other atoms. Light water can be used, as in a light water reactor, but since it absorbs neutrons the uranium must be enriched for criticality to be possible. The most common pressurised heavy water reactor is the CANDU reactor.Proponents of heavy water reactors suggest that because such reactors can be fueled with unenriched uranium there is less risk of nuclear proliferation; an ideal product to be marketed to nations that have no legitimate use for uranium enrichment facilities. While there is no need for fuel enrichment, heavy water reactors produce more plutonium as a by-product of normal use, which can be used in nuclear weaponry. India produced its plutonium for Operation Smiling Buddha, its first nuclear weapon test from plutonium extracted from a CIRUS reactor. Heavy water reactors require a set of safeguards to prevent their exploitation in such a fashion.4-. Gas Cooled Reactor (GCR) and Advanced Gas Cooled Reactor(AGCR) :-These are generally graphite moderated and CO2cooled. They can have a high thermal efficiency compared with PWRs due to higher operating temperatures. There are a number of operating reactors of this design, mostly in the United Kingdom, where the concept was developed. Older designs (i.e. Magnoxstations) are either shut down or will be in the near future. However, the AGCRs have an anticipated life of a further 10 to 20 years. This is a thermal neutron reactor design. Decommissioning costs can be high due to large volume of reactor core....
View Full Document
- Spring '09
- Nuclear power reactor types, Neutron moderator, Autonomous Reactor