25 Jun (NucNet): A full-scale in-situ system test for spent nuclear fuel disposal is expected to begin this week at Posiva’s planned final deep geologic disposal facility at Olkiluoto, Finland.
Posiva’s owner Teollisuuden Voima Oyj (TVO) said the test will be the first of its kind and means that Posiva is making progress towards the operational test phase of its final disposal system and technology.
According to TVO, the test will last for several years. It aims to prove that the prototype processes for geological storage at Posiva’s repository are “all working concepts”. The test has been in preparation since December 2017, TVO said.
The processes include placing fuel assemblies packed in copper-steel canisters inside holes drilled in the bedrock tunnels. This is followed by backfilling the tunnels with bentonite clay and sealing them with a cast plug.
Two test canisters will be equipped with thermal resistors simulating the residual temperature of spent nuclear fuel, TVO said.
A TVO official said the temperature and pressure in the canisters, test holes and the surrounding bedrock, and the behaviour of the backfill of the tunnels, will be monitored by some 500 sensors over several years.
In December 2016, Posiva was given regulatory approval to begin construction of a deep geologic repository at Olkiluoto on the country’s southwest coast – the first final repository to enter the construction phase.
TVO said the cost of building an encapsulation plant onsite and the excavation and equipment of two final disposal tunnels is estimated at about €500m.
“So far about €1bn has been used in examining the site for final disposal and in equipment development,” Posiva's president Janne Mokka was quoted as saying.
