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01 POWER ISLAND / Overview of Light Water.docx
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The pattern of sea water flow should be carefully considered.

  1. Switchyard

The switchyard should be arranged close to the main transformer which is located near the turbine building, and also in a place convenient to connect it with the transmission line. In deciding the switchyard arrangement, future extension plans of the plant should also be taken into consideration.

Conventional switchgear is located inside buildings in order to protect them

against briny air damage, however, gas-insulated switchgear (GIS) not requiring any protection building is being used in recent plant designs.

  1. Reactor building and reactor auxiliary building

The reactor building and the reactor auxiliary building of a PWR plant are important for the reactor safety. The foundations of these structures must be directly supported by hard bedrock. Geological surveys are carried out using techniques such as boring and test pits. Locations of and excavation levels for these buildings are determined, based on the test results obtained, so as not to interfere with any fracture zones or other weak points found in the ground. Furthermore, the locations of the buildings are evaluated as to their appropriateness for minimizing radiation exposure at the site boundary under the normal plant operation and hypothetical accident conditions, based on meteorological observations and wind tunnel test results.

  1. Turbine building

The turbine building should be located as close as possible to the reactor building so as to minimize the pressure loss in the line from the steam generators to the high pressure turbine. Hie turbine building of a PWR power plant does not contain any radiation controlled area, its structure is steel framed without any shielding concrete, similar to that of a fossil-fueled plant, and various design options of the building layout are feasible in relation to the reactor building.

  1. Water supply and treatment system

A NPP needs large amount of make-up water. Therefore, a water supply and treatment system composed of large tanks, pumps and a desalination unit is set up outside buildings.

  1. Radioactive waste storage building

Low level radioactive waste drums are stored in a reinforced concrete building with wall thicknesses sufficient for radiation shielding. The radioactive waste storage building should be arranged so that the transportation of

waste drums has minimum effects on the radiation exposure at the site boundary and the waste drums are managed in a centralized manner.

  1. Cask storage building

The cask storage building is a building to temporarily store spent fuel casks before shipment of the spent fuel to a reprocessing plant. In some recent plants, spent fuel casks are temporarily stored in areas prepared inside the reactor buildings. The total cask storage capacity of the building(s) depends on the number of spent fuel assemblies to be shipped out of the plant each time, as well as on carrier ship capacity.

  1. Harbor facilities

In order to bring in heavy components to the site during the plant construction period and to carry out spent fuel casks after the start of the plant operation, it is recommended to provide a harbor facility suitable for 3,000 ton class carrier ships. In that case, water depth of more than 10 m is required.

  1. Access control system

An access control facility should be provided for the purpose to assure that the function of plant safety systems required to safely shut down the reactor will not be lost due to illegal personnel entrances. Access control areas should be established, and any illegal access or entry to the areas should be monitored and controlled by providing warning systems and other necessary measures. In addition, access of any personnel to radiation control areas containing radioactive equipment or material should be controlled as a part of the access control system.

NSRA, Japan

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