Hair-size leak in nuclear reactor

(AAP) Scientists are yet to find a guaranteed solution for an ongoing problem with Australia's only nuclear reactor, but will shut it down again later this month to attempt further repairs.

The $430 million Open Pool Australian Lightwater (OPAL) reactor, at Lucas Heights in
Sydney's south, is designed in part to produce nuclear medicines and imagery
services used in the treatment and diagnosis of human diseases including cancer.
However, since its installation in 2006 the reactor has operated for only a short
period because of teething problems in the lead-up to its anticipated full
commissioning by the end of this year.
"The issues are more in the category of being frustrating than being substantial,"
Australian Nuclear Science and Technology Organisation (ANSTO) chairman Ziggy
Switkowski said.
Shutdowns of the reactor, operated by ANSTO, have been caused by the displacement of
fuel plates in the reactor core - an issue rectified by redesigned componentry
approved by independent regulator, the Australian Radiation Protection and Nuclear
Safety Agency (ARPANSA).
However, leaks that allow ordinary water to dilute molecularly altered heavy water
around the reactor have not yet been fixed, despite being identified in 2006.
"This is not a safety issue, it's an issue, however, that affects the efficiency of
the reactor," Dr Switkowski said.
There were believed to be seven or eight leaks, the largest measuring 10 micrometres
- "about the width of a human hair", Dr Switkowski said.
The position of the leaks had made their repair difficult, and one attempt already
had proved unsuccessful, he said.
Later this month, reactor operations will cease while the heavy water is drained and
replaced.
During the shutdown attempts will be made to clamp the gaps.
Future shutdowns could be avoided with plans to purify heavy water by pumping it
through an enrichment plant, to be developed nearby.
However, Dr Switkowski said he was confident the underlying problem could be solved.
"It's so frustrating to be able to see where the problem is but not just be able to
go down there and fix it ... and it's all just caused by a leak the size of a hair."
All remediation work is being carried out under warranty by the reactor's
Argentinian manufacturer.
When the reactor is closed, ANSTO must import all nuclear medicines at a cost of
about $100,000 per week.
Any modification to the reactor must be approved by ARPANSA.
Dr Switkowski shot down calls from the Australian Greens for the reactor to be
permanently shut down because of the leaks.
"The notion that confronted with some engineering challenges for a new reactor we
would give up and walk away is unacceptable to us and I think is a ridiculous
suggestion," he said.