As shown by Figure 12 the lower 3 layers of the core are connected to the vertical restraint columns. The end result is the same - the production of heat to generate steam. Gas-sampling instrumentation and channel gas outlet thermocouples are also incorporated into the unit to provide monitoring.Insertion of the fuel assembly into the reactor core is handled by a single re-fuelling or charge machine. A French design, the UNGG reactor, was similar to the Magnox reactor. In between the fuel channels there are 81 control rods channels, each 127mm in diameter. They are particularly attractive in situations where enriched uranium is not easily available since they can be designed to maintain a sustained nuclear reaction with natural uranium. Brick shapes and loose keys are optimized for strength and keying is designed to accommodate core movement and seismic loading.Between each layer of graphite, inter-brick seals are incorporated for the purpose of maintaining the pressure differences generated across the walls of the fuel channels by the appropriate sizing of the flow control ported located in the top and bottom layers of bricks for cooling. In order to control the neutron density neutron absorbing control rods are raised and lowered within the core either by operator or automatic control according to the amount of power required. A primary lock is provided on the refueling machine grab, and a secondary lock is provided by a retractable drive mechanism built into the standpipe extension tube.Carbon dioxide is the gas used for transferring the heat produced form the reactor core to the boilers. Because they use a different fuel form and cladding, they avoid steam/zirconium cladding chemical reactions that can release explosive hydrogen gas under accident conditions in LWRs.
Also, because gas-cooled reactors are inherently large, they are suited to large-capacity.
The mean temperature of the hot coolant leaving the reactor core was designed to be 648 °C. The mean temperature of the hot coolant leaving the reactor core was designed to be 648The AGR was designed to have a high thermal efficiency (electricity generated/heat generated ratio) of about 41%, which is better than modern The pre-stressed concrete pressure vessel contains the reactor core and the boilers. * In a new reactor with new fuel a neutron source is needed to get the reaction going. Each reactor has a design thermal power output of 1,500 MWt driving a 660 MWe turbine-alternator set. These various reactor types will now be described, together with current developments and some prototype designs. The rods are in turn attached to restraint beams that form sixteen-sided polygons around the core at each inter-layer position, the beam ends being loosely connected as a secondary restraint feature. During normal operation, the fuel plug closure units seal the reactor pressure vessel boundary at each fuel standpipe. It used prismatic block, graphite fuel elements, a uranium–thorium fuel cycle, and helium coolant. General Design and Principles of the Advanced Gas-Cooled Reactor (AGR) In the event of a reactor trip, the clutch is also tripped to allow control rod insertion by gravity, which is controlled by a carbon disc brake and centrifugal mechanism. (See Magnox Power Station.) A French design, the UNGG reactor, was similar to the Magnox reactor. An advanced gas-cooled reactor (AGR) is a British design of nuclear reactor.AGRs are using graphite as the neutron moderator and carbon dioxide as coolant. This improved the thermodynamic efficiency to around 42%, compared to around 28% in a Magnox plant (and 32% in a modern PWR).A total of 14 AGR reactors were built on six sites in the UK (plus a small, prototype reactor). Evolving designs moved from steel pressure vessel reactors to pre-stressed concrete pressure vessels with the construction of the later plants at Oldbury and Wylfa, and the last three French Magnox class reactors of Chinon A3, St Laurent des Eaux and Bugey 1 also used pre-stressed concrete pressure vessels.The last of the UK Magnox reactors was completed in 1971 and in the UK was superseded by the Advanced Gas-Cooled Reactor (AGR). The various AGR stations produce outputs in the range 555 MWe to 670 MWe though some run at lower than design output due to operational restrictions. For their recovery, the beads are passed from the bottom of each channel through a vertical recovery pipe terminating with an isolating ball valve in the secondary shutdown room. The tendons are anchored in stressing galleries at the top and bottom of the vessel, which provide access to the tendons and from which insertion and stressing can take place. The existence of this type of crack does not immediately affect the safety of a reactor – however if the number of cracks exceed a threshold the reactor would be decommissioned, as the cracks cannot be repaired.In January 2015 Dungeness B was given a ten-year life extension, with an upgrade to control room computer systems and improved flood defences, taking the accounting closure date to 2028.In February 2016, EDF extended the life of four of its eight nuclear power plants in the UK. The AGR Design: 1500MWth/660MWe • The AGR was a natural evolution from the MAGNOX and is unique to the UK • The drive for greater thermal efficiency required a higher temperature reactor - With a requirement to produce steam at a pressure (165Bar) and temperature (540 Deg C) compatible with “normal” 660MWe steam turbines The beads are directed downloads into the channel from the open end of the delivery pipe until the channel is filled.
The reasons for the development of this reactor type were part political (development of a domestic technology) and part technical, in particular the increased thermodynamic efficiency associated with the much higher coolant temperatures of the AGR (exceeding 600 °C). Heat is removed from the fuel by forced circulation provided by the gas circulators operating at low speeds. There are several components common to most types of reactors:Fuel. They are arranged in a regular, square, lattice pattern with a distance of 460mm between their centers. The components of an AGR reactor core are discussed in further detail below.