The effect of U3O8 powder re-sintering on the meat of dispersion fuel elements MTR fuel plate type

Abstract EN

The quality of nuclear fuel depends on the control of many parameters to satisfy the design requirements and specifications.

The fuel plate is the main component of the MTR fuel element, used in research reactors.

Controlling the fuel particle size during fuel plate manufacture is one of the important parameters affecting the quality of the produced fuel element.

Fuel particle size has a direct impact on the fuel element performance during its irradiation in the reactor.

This includes the degree of irradiation damage of the fuel element and its capacity to attenuate fission gases to avoid swelling.

Therefore, the design specifies the limitations on the particles size of the U3O8 powder.

In general, the particle size should be < 90 μm.

Up to 50% of the fuel powder can have particle size 45 μm.

The powder with particle size 45-90 μm is termed “specified powder” while that with particle size < 45 μm is termed “fine powder”.

Fuel powder used in the plate manufacture is produced through a series of steps.

However, it may happen that the fine powder produced in a batch is more than 50%.

If this takes place during the production of many batches, there may be an accumulation of fine powder which is not used in the fuel plates production, i.e., rejected powder.

The present work explores the possibility of reprocessing the fine powder through heat treatment (re- sintering).

Re-sintering was carried out at 1400oC for 12 hr.

The specified powder produced from this process was used in the manufacture of fuel plates.

The produced plates were examined using non-destructive and destructive tests.

Examinations showed that the produced plates suffer from the “dogboning” phenomenon which would lead to the rejection of these plates.

This was related to the morphology of the produced powder.

Examination showed that the shape of the powder produced after re-sintering is much distorted compared to the normally produced powder.