Fuel qualification for China's HTR-PM
30 October 2013Fuel qualification is being carried out by NRG in the High Flux Reactor at Petten.
The HTR-PM project in China will adopt pebble HTR fuel, 6 cm diameter spheres, in which on the order of 10,000 TRISO coated UO2 particles are embedded in a graphite matrix. China has taken over the German technology for fuel fabrication, and has built its own HTR pebble fuel manufacturing lines.
However, for the reactor to receive an operating licence the fuel needs to be qualified. Qualification is currently underway at NRG. It consists of two phases.
First is an irradiation phase where the fuel is irradiated under controlled conditions in terms of flux and temperature until a target fuel burn-up. During irradiation, fuel integrity and performance is monitored by flux and temperature measurement, and by continuously sweeping the irradiation facility with inert gas, and measuring the fission product content in the outgoing gas stream. As long as the fission product content is below a pre-set limit, the fuel is performing well and fuel integrity is confirmed.
The second phase is to subject the irradiated fuel to a heating test, in which the coated particles should demonstrate the ability to remain intact at temperatures of 1600°C - the maximum temperature in a design-basis loss of coolant accident in an HTR. The fuel is placed in an oven, placed in shielded hot cell, and heated, while a gas stream flowing along the pebble takes fission products from the fuel to an analysing station. Particle failures will be detected. Should this second phase be successful, the fuel can be considered qualified. This procedure follows those defined in the early German HTR programmes.
The irradiation is currently being performed by NRG in the High Flux Reactor at Petten and is expected to continue until at least mid-2014. After cool-down, dismantling and non-destructive examination will be carried out in the NRG Hot Cell Laboratories in Petten. After that, pebbles will be transported to JRC-ITU, Karlsruhe for the heating test, expected in 2015.
As previous tests have shown, Chinese fuel is of good quality and a successful qualification is expected.
Computer generated bird's-eye-view of the HTR-PM plant (Source: INET)
