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helium test facility
The Helium Test Facility
PBMR planned to build a high temperature (>700C) high pressure (60bar) demonstration reactor at Koeberg which will make use of helium as the working gas. Many of the components and systems to be used in this reactor have never been built before. It was therefore both prudent and realistic from a safety perspective to test as many of these components, or sub-systems, as soon as possible to ensure that they will indeed work in the final reactor.
The HTF has specifically been built to test components and systems in helium at the very high temperatures and pressures that will be experienced in the Pebble Bed Modular Reactor. Although these tests are for a nuclear reactor, it is important to note that the HTF is not a nuclear test facility as it does not use any nuclear material just helium and heat from electrical heaters.
Some of the systems undergoing testing on the HTF are:
  • The Fuel Handling System (FHS): The purpose of this system is to be able to add, remove and transport graphite spheres, containing the nuclear fuel particles, to the reactor core and remove them again. The functionality of the FHS has been proved through a number successful tests; to date more than 18 000 fuel sphere passes were completed. The FHS was fitted with a reactor core unloading device (CUD) during the latter part of 2009. The CUDs function is to remove the spheres from the reactor core, measure, sort and distribute the spheres back to the reactor or to divert scrap spheres to storage. All these actions are done automatically. One can view the fuel spheres as the blood of the reactor and the FHS as the blood vessel network of the reactor.
  • The Reactivity Control System (RCS): This system is required to control the nuclear reactivity in the reactor. This is like the throttle of a motorcar which can accelerate or decelerate the vehicle. It is accomplished by raising and lowering long rods, capable of absorbing the radioactivity, into the core. When it is fully inserted in the event of a unplanned situation it must be able to shut down the reactor.
  • The Reserve Shutdown System (RSS): It is required by the National Nuclear Regulator that any nuclear reactor has to have a secondary, completely separate in-mechanism system capable of shutting down the reactor. The RSS does this by dumping small absorber spheres (SAS) into cavities in the core which results in the reactor shutting down.
These 3 systems are currently the biggest and most important units but there are some other smaller systems also being tested. The beauty of the HTF, and which makes it cost efficient in the long term, is its capacity to modify or add test systems to the existing test facilities.
This test facility naturally also needs various maintenance and support functions to keep it running. There are well equipped workshops including a machine shop, a welding area, instrumentation shop and some electrical maintenance capability.
The HTF achieved 250 000 accident-free operating hours for the period 1 April 2007 to 3 June 2009, the first PBMR operating test facility to achieve this safety milestone.
The HTF is now in a care and maintenance state.
Last Updated: 6 February 2017
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