Australia’s new nuclear reactor, OPAL, is to shut down for approximately eight weeks to address recent issues identified during its initial operation phase over the past eleven months. There are currently no safety or radiation exposure issues, and the independent regulator ARPANSA has been advised.
ANSTO’s Chief Executive, Dr Ian Smith said the shutdown will affect silicon customers as well as cause delays in neutron beam research. Radiopharmaceutical customers will not be affected, as arrangements are in place for the import of these products.
“During the shutdown equipment which has identified faults will be thoroughly investigated and where possible repaired,” he said. “This includes the heavy water dilution issue reported earlier this year, where a small amount of light water from the reactor pool was seeping into the heavy water contained in the reflector vessel surrounding the core.
“To solve the dilution problem, further pressure testing is required followed by approval of the INVAP-recommended remedy by ANSTO, and if necessary by ARPANSA. Whilst the dilution issue does not affect safety or operation, if left un-repaired it would ultimately affect the performance of the reactor,” he said.
In addition, this week, the three fuel assemblies inserted into OPAL’s core in the last monthly fuel change were each found to have one of 21 fuel plates partially dislodged. ANSTO will be undertaking a series of tests to fully determine the cause of that event.
The 16-fuel assembly core has had a smooth operational history with 39 assemblies having been successfully tested and used since operation commenced almost a year ago.
“Given that this problem has only affected those elements which had been in the reactor for the shortest period of time, it is expected that, subject to safety assessments and regulatory approvals, new fuel elements can be utilised to enable operation to recommence,” said Dr Smith.
“If the integrity of other fuel elements is not satisfactory, or regulatory approval is denied, then a ‘starting array’ of fuel would need to be manufactured with a longer shutdown eventuating. We are hopeful this will not be the case.”
ANSTO customers will be advised and kept informed as assessments continue. Supplies of reactor-produced nuclear medicines will in the meantime be imported and distributed by ANSTO.