nuclear power-light water reactors

Nuclear power - light water reactors

Nuclear power has reliability and economically contributed almost 3 per cent India and almost 20 per cent electricity generation in U.S. over past 2 decades. It remain the single largest contributor (more than 70 percent of  non-green house emitting electrical power generation in U.S.) .

If current operating nuclear power plants don’t  operate beyond 60 years the total fraction generated energy from nuclear power will begin to decline-even with the expected addition of new nuclear generating capacity.

Continued safe and economical operation of current reactors for an even longer period of commercial operation, beyond current license renewal life time 10 years is low risk option to fill up the gap and add new power generation at a fractional if the cost of building new plants.

To provide technical basis for this life extension the following five  R& D  pathways have been identified .

The nuclear materials aging and degradation pathway will conduct research  to develop the scientific basis for understanding and predicting long term environmental degradation behavior of materials in nuclear power plants. Data  methods to assess performance systems, structural’s, and components essential  to safe and sustained nuclear power plant  operation will be developed.

The advanced LWR ( light water reactor ) nuclear fuel development pathway will improve the scientific knowledge basis for understanding and predicting fundamental nuclear fuel and cladding performance in nuclear power plants. This information will be applied to the development of high performance, high burn up fuels with improved safety cladding integrity and improved nuclear fuel economic.

Light water reactors

The nuclear fission reactors used in U. S. for electric power generation are classified as light water reactors in constraint to heavy water reactor in caved light water (ordinary water) is used as the moderator in U.S. reactors as well as the cooling agent  and then means by which heat is removed to produce steam for turning turbines of electricity generators. The use of ordinary water makes it necessary to do certain amount of enrichment of uranium fuel before the necessary criticality  of reactor can be maintained.

The two verities of light water reactors are pressurized water reactor (PWR) boiling water reactor (BWR)

Uranium enrichment

Natural uranium only 0.7  per cent U-235, the fissionable isotope. The other 99.3 per cent of U- 238 which not fissionable. The uranium is usually enriched to 2.5 per cent to 3.5 per cent U-235 for use U.S. light water reactors. While the heavy water Canadian reactors typically use natural uranium . Even with the necessity  of enrichment, it is still takes only about 3 kg of natural uranium to supply needs of American for a year.

Uranium enrichment has historically has been accomplished by making the compound uranium hexafluoride and diffusing it through a long pathway of porous material (like kilometers) and making use of slightly higher diffusion  rate of light U-235 compound. There have been tests of centrifugal separators, but modern efforts are directed towards laser enrichment procedures.

The uranium fuel is fission reactors will not bomb, it takes enrichment to over 90 per cent to obtain the fast chain radiation necessary  for weapons application. Enrichment  to 15 per cent to 30 per cent is typical for breeder reactors.




Heavy water reactors

Nuclear fission reactors used  in Canada use heavy water as a moderator in their reactors. Since deuterium in heavy water is slightly more effective in slowing down the neutrons from the fission reactions and uranium fuel need no enrichment and can be used as mined. The Canadian  sleigh reactors are commonly called Candu  reactors.

The family of nuclear reactors known as light water reactors (LWR) cooled and moderated using ordinary water, tend to be simpler and cheaper to build than other types of nuclear reactors, and are well known to process excellent safety and stability characteristics, due to these factors, they make up the vast majority of civil nuclear reactors and naval propulsion  reactors in service thought world of 2009. LWR can be sub divided into three categories -pressurized water reactor (PWRs) , boiling water reactors (BWR) and super critical water reactors ( SWRs). Various agencies of U.S. federal governments were responsible for initial
Development  of PWRs and BWR s .

The leaders of national experience with PWRs  offering rectors for export are United States ( which offers the passivity -safe AP 1000 a Westing  House  design as well as several smaller, modular passivity safe  PWRs such as the Babcock and Wilcox M Power and the Nu scale MASWER )  and Russian  Federation offering both WER -1000 and WER- 1200 for export, the Republic of France offering Areva EPR  for export and  Japan ( offering Mitsubishi advanced pressurized water reactor for export , in addition both people Republic of China  and Korea are both  noted to be rapidly ascending into front rank of PWR constructing nations as well , with Chinese being engaged in a massive program of nuclear energy expansion and Koreans are both noted to be rapidly designing and constructing their  second generation of indigenous designs.

The leaders in national experience with BWRs offering reactors for export are U.S. and Japan with alliance of General Electric (of  U.S. ) and Hitachi (of Japan ) offering advanced boiling water reactor (ABWR) and economic simplified  water reactors ( ESBWR )  for construction and export . In addition Toshiba also offers ABWR variant  for construction  in Japan as well.

The other types of  nuclear reactor in use for power generation are heavy water moderated  reactors built by Canada ( Candu ) and the Republic of India (AHWR) an advanced gas cooled reactor (AGCR) built by U.K., the liquid metal cooled reactor ( LMFBR) built by Russian federation ,the Republic of France  and Japan and graphite moderated water cooled reactor (RBMK) found exclusively with Russian federation and former soviet states.

Though electricity generation capabilities are comparable all these types of reactors due to the aforementioned features and extensive experience with operation of LWR it is favored  in the vast majority of nuclear power plants. Though CANDU / AHWR has comparatively small (but quiet dedicated ) following in addition light water reactor make up the vast majority reactors that power naval nuclear powered vessels.

The reason for near exclusive LWR  are abroad nuclear naval vessels is the level of the inherent safety built it to these types of reactors. Since light water reactor is used as both coolant neutron moderated in these reactors. If one reactor fails or suffers damage due to military action, leading to a compromise of reactor core integrity, the resulting  release of light water moderator will act to stop the  nuclear reaction and shut reactor down. The capability is known as negative void coefficient of reactors.  Currently  offered LWR include the following .

.. ABWR
- AP 1000
- ESBWR
-- European pressurized reactor
- WER
India because enriched uranium shortage India planned and constructed and depend on heavy water reactors. Ho-mi  Bhabha father nuclear energy in India would created a breeder reactor economy on easy steps.
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1. Construct natural uranium fuelled, heavy water reactors which would produce a electrical power and used  as a by product of Plutonium.

2. Construct plutonium fast breeder reactor for power and more Plutonium as well as U-233 Thorium.

3. Later build u-233 thorium breeder reactor.

India could avoid the costly the costly complicated enrichment process needed for light water reactor and could use its own supplies of natural uranium which to carry out program. By that time  the breeder reactor would be operational zed  and India could use its vast volumes of thorium fuel hundred of  these breeder a capacity  which we wanted.

Because India not having enough heavy water pressurized heavy water reactor program effected considerably. In addition uranium not available in India and it has to depend on foreign countries for fuel. India now going ahead  building light water reactors with  latest international technology and with supply of enriched uranium from supplier.

Now nuclear power corporation of India planning to   build nuclear light water reactors with international technology from France , U.S. and Japan. NPCIL (Nuclear power corporation of India  ) planning to increase nuclear energy capacity to 63,000 M.W. by 2032.

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