Uranium & Fuel
A Russian company has developed and manufactured a remotely operated welding system that will be used in Russia for the production of mixed uranium- plutonium oxide (MOX) fuel assemblies for nuclear power reactors.
Moscow-based civil engineering company Nikimt-Atomstroy said the system is used to feed and fix distance-wire onto the fuel rods. The wire ensures space between the rods in the fuel assembly – space which is needed to prevent the fuel rods touching and producing excess heat which could lead to damage.
The system includes control equipment which synchronises more than 200 sensors and pneumatic cylinders. Each welding unit is equipped with two colour cameras, which allow the operator to control the wire feeding and welding process.
Russian state nuclear corporation Rosatom said the development of MOX fuel and MOX fuel assembly manufacturing in Russia will help satisfy industry demand and reduce the volume of nuclear waste. The development of the remote system could help Russia become a serious competitor in MOX fuel production and the possible commercial operation of reactors that use MOX fuel.
About 40 reactors in Europe – in Belgium, Switzerland, Germany, the Netherlands and France – are licensed to use MOX fuel, and more than 30 are doing so. In Japan about 10 reactors are licensed to use it and several have done so.
In Russia, there are no commercial reactors using MOX fuel but the BN-800 Beloyarsk-4 fast neutron reactor, where fuel loading was completed in July 2014 and commercial operation is due within months, will use MOX fuel.
A commercial MOX fuel fabrication facility was established at Zheleznogorsk in2014. The facility, which is where the new system will be used, is operated by the Mining & Chemical Combine GKhK. The facility was built as part of Russia’s so-called ‘Breakthrough’ project, which aims to develop fast reactors with a closed fuel cycle whose MOX fuel will be reprocessed and recycled.
The facility produced its first 10 kilogrammes of MOX fuel pellets in September 2014. They are expected to be used at Beloyarsk-4.
Remote distance-wire welding is one of the key issues when manufacturing MOX fuel rods, which are filled with fuel containing plutonium and other transuranics. Remote handling is needed because of the strong, penetrating ionising radiation these isotopes emit. In particular, plutonium-241, which has a half-life of 14 years, decays to americium-241, a strong gamma emitter posing a potential health hazard.
This problem does not exist with nuclear fuel containing only uranium pellets, which do not emit such radiation.