WETFUEL: Water Extraction Tests on nuclear FUEL

Scope

Following discharge from the reactor core, spent fuel assemblies of Light Water Reactors are stored in pools linked to the reactor via a transfer tunnel. Reactor spent fuel pools are never used up to their design capacity because of the need for operational buffer capacity during core reloads. In addition to the reactor pools, utilities have therefore often additional storage, which can be a spent fuel pool in a different building (wet storage) or a building that hosts casks in which fuel elements are stored under inert gas (dry storage).

Belgium and Germany have experience already since many years with dry storage facilities based on casks for storage and transport.[1] Until recently, only intact fuel rods were stored under dry conditions although there were no scientific reasons for rejecting dry storage for non-intact fuel rods, especially not if they are dried and stored under inert gas in a sealed capsule. Technological solutions for the safe and reliable encapsulation of damaged fuel rods exist already for a long time (hot-cell technology), but the issue of drying a defective fuel rod that had been stored for an extended period of time under water, was largely unknown at the time this project was launched.


[1] Survey of Wet and Dry spent fuel storage, IAEA-TECDOC-1100 (IAEA, Vienna, 1999) ISSN-1011-4289

The project WETFUEL (Water Extraction Tests on nuclear FUEL) was initiated in 2012 to fill this knowledge gap and provide scientific and technological data on the removal of water from damaged spent nuclear fuel.

Objectives

The wetting and drying tests were performed in the hot laboratories of SCK CEN

  • A device was developed to insert water in a true spent fuel column and subsequently different drying techniques were applied: direct vacuum drying, heat or gas assisteddrying etc.
  • Segments were taken from defective and intact fuel rods, irradiated in Tihange I.
  • Quantitative information on the drying process of a real spent fuel segment were derived.

Results

The results of the project contributed to the industrial implementation, which is today implemented in Germany and Belgium. Several open literature publications were issued:

 SCK CEN contact: Marc Verwerft