Gas Cooled Reactor Systems

It Is recommended that further work be done by reactor engineers to determine whether such a shield Is feasible and to assess its effect on vessel size, radioactive inventory, permissible man access times following removal of the vessel Internals, and reactor operational characteristics. 

This feature Is discussed In Section 7 of the report and It Is recommended that further work should be done to confirm more positively the feasibility of the concept. This should include analyses of a PCRV with planes of weakness for the range of load combinations applicable during construction, commissioning and operation, and a more detailed assessment of how best to form the planes and of the materials to use. If this work confirmed present conclusions, consideration should then be given to supporting the analytical work by model testing. 

Several possible methods of forcefully breaking up the activated region of the PCRV have been considered and some of these appear feasible. See Section 6.4 of the report. 

Traditional explosive techniques appear to be a very effective way of breaking up homogenous concrete and a considerable amount of work has been done by TWC under Project 3 of the CEC programme on decommissioning This technique does, of course, have the 

High temperatures, up to 900°C, can be used to degrade concrete. Whilst such a technique would be Impractical on a large scale. It could be very useful for tackling localised problems. 

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W. D. Fowler, C. L. Rickard, and H. B. Stewart, Progress and economics in High Temperature Gas-Cooled Reactor systems. General Atomic Rept. GA-7407, September 1, 1966. 

The Initial brief for the study was that It should consider only civil engineering aspects of nuclear power plants based on gas cooled reactor systems. The brief, however, was extended to Include an assessment of the civil engineering aspects of decommissioning light water cooled reactor systems, particularly the pressurised water reactor. 

In so far as gas cooled reactor systems are concerned, detailed recommendations in respect of further work are as follows ... 

Gas cooled nuclear generating plants In commercial operation In the U.K. at the present time are based either on the magnox reactor system or the advanced gas cooled reactor system. The magnox reactor systems utilise single cavity pressure vessels, the earlier ones being of steel construction, the later ones of prestressed concrete. The advanced gas cooled reactor systems utilise either single cavity or multicavity pressure vessels of prestressed concrete construction. 

POSSIBLE FEATURES TO AID DECOMMISSIONING OF GAS COOLED REACTOR SYSTEMS... 

The advanced gas-cooled reactor systems are given in Table 1.4. The reactor pressure vessels are made either in prestressed concrete pressure vessels or in double PCCV. 

XV-8] Generation IV road map - R D scope report for gas cooled reactor systems. Nuclear Energy Research Advisory Committee and the Generation IV International Forum, GIF-004-00 (December 2002). 

The AHTR is a liquid cooled, high-temperature reactor, a fact that significantly increases the electrical efficiency (4 to 8%) relative to that of gas cooled reactors with the same exit coolant temperatures. Gas cooled reactor systems have high pumping costs relative to those of liquid cooled systems. Because gas cooling has high pressure losses, practical designs of gas cooled... 

The metal is a source of nuclear power. There is probably more energy available for use from thorium in the minerals of the earth s crust than from both uranium and fossil fuels. Any sizable demand from thorium as a nuclear fuel is still several years in the future. Work has been done in developing thorium cycle converter-reactor systems. Several prototypes, including the HTGR (high-temperature gas-cooled reactor) and MSRE (molten salt converter reactor experiment), have operated. While the HTGR reactors are efficient, they are not expected to become important commercially for many years because of certain operating difficulties. 

As previously stated, uranium carbides are used as nuclear fuel (145). Two of the typical reactors fueled by uranium and mixed metal carbides are thermionic, which are continually being developed for space power and propulsion systems, and high temperature gas-cooled reactors (83,146,147). In order to be used as nuclear fuel, carbide microspheres are required. These microspheres have been fabricated by a carbothermic reduction of UO and elemental carbon to form UC (148,149). In addition to these uses, the carbides are also precursors for uranium nitride based fuels. 

Malinauskus, A.P., de Nordwall, H.J., Dyer, F.F., Wichner, R.P., Martin, W.J. and Kolb, J.O., Fission product behavior during operation of the second Peach Bottom core. In Proceeding of the Symposium on Gas-Cooled Reactors with Emphasis on Advanced Systems, Vol. 1, IAEA-SM-200/50, IAEA, Vienna, 1976, pp. 237 249. 

An important parameter in the evaluation of the safety of a reactor system is the release of fission products from the fuel. The fuel in the high-temperature gas-cooled reactor (HTGR) consists of spherical particles (U, ThC2) that are coated with a material presenting a diffusion... 

Sakaba, N., et al. (2007), Conceptual Design of Hydrogen Production System with Thermochemical Water-splitting Iodine-Sulphur Process Utilizing Heat from the High-temperature Gas-cooled Reactor HTTR , International Journal of Hydrogen Energy, 32 (17), pp. 4160-4169. 

Fukada, S., Y. Edao, M. Terashita (2009), Chemical Heat Pump System Working at Exhaust Temperature of High-temperature Gas-cooled Reactor , International Journal of Hydrogen Energy, 34, 540-546. 

Gas cooled reactors use carbon dioxide under pressure as a recirculating heat transfer medium (coolant) between the hot nuclear reactor core and water in a secondary circuit in order to raise steam and electrical power in an otherwise conventional high pressure steam generator/turbine/condenser loop. The role played by ion exchange is denoted by systems A-D in Figure 8.22. 

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