Repairs progress at isotope reactors

Thursday, 20 May 2010

Major repairs to the National Research Universal (NRU) reactor at Chalk River in Canada and the High Flux Reactor (HFR) in the Netherlands are progressing well, according to the latest updates from Atomic Energy of Canada Ltd (AECL) and NRG. 
 

External cleaning of the reducer walls at HFR (Image: NRG)

NRG's HFR was taken offline in February to address problems with corrosion in concrete-encased aluminium pipes carrying cooling water, leading to tiny bubbles of gas in the primary cooling system. The work so far has involved stripping off the concrete from the pipes, known as reducers, followed by detailed inspections which have identified four locations where the pipes have been affected by galvanic corrosion.

Based on the results of the inspection work and measurements it has taken, NRG has decided to carry out local repairs to the pipes rather than replacing the reducers completely. NRG has now received the go-ahead from the relevant authorities to begin the repairs to the corroded pipes, which will entail removing the corroded parts and welding in new aluminium piping.

The entire repair project is currently predicted to take 25 weeks to complete, which would in theory see the reactor fit to return to service in mid-August.

End in site at Chalk River?

It has now been over a year since the discovery of a heavy water leak on 15 May 2009 forced AECL to shut the NRU and carry out extensive repairs. However, the company's latest bulletin on the project reports that 71% of the necessary weld repairs and associated non-destructive examinations have now been completed, and nine of the ten identified sites have now been repaired.

The unit is still expected to return to service by the end of July, AECL says.

NRU and HFR are the two main producers of the world's supply of molybdenum-99, which decays into technetium-99 en route to thousands of hospitals for use in imaging procedures. In the two reactors' absence, reliable but reduced supplies of the isotope have been maintained through close coordination between the other reactors capable of supplying it, namely Belgium's BR-2, the Safari reactor in South Africa and the Osiris and Orphee reactors at Saclay in France.

 

Researched and written

by World Nuclear News