Losing its glow: High-energy beta particles from spent nuclear fuel immersed in water gives rise to Cerenkov radiation. This blue glow is created by the charged particles passing through a transparent, non-conducting liquid faster than the speed of light.

Credit: ANSTO

Related articles

• Australia's OPAL reactor recovers from failure
• Going deep into fission
• Uranium enrichment: how to make an atomic bomb
• Green nuclear power coming to Norway
• Danger passes for Sweden's nuclear reactors

SYDNEY: Australia's OPAL nuclear reactor is facing new criticism that a fault allowing water to seep into the reactor vessel renders it unsafe. The problem follows a fuel issue that already forced the new reactor to close down for ten months.

The Australian Associated Press last week quoted Scott Ludlam, an Australian Greens senator and spokesperson on nuclear issues, as saying that the reactor was unsafe and should never have been built.

ANSTO (the Australian Nuclear Science and Technology Organisation) admits that "two to three cups" of ordinary water are seeping through microscopic cracks into heavy water surrounding the reactor's core. However, they say this presents no safety issue.

Known fault

This heavy water (which contains a high ratio of the heavy isotope of hydrogen, deuterium) is found in a 'reflector vessel' where neutrons released from the nuclear reaction are slowed down to sustain the nuclear reaction and provide neutrons for research. The water is leaking into the vessel from the surrounding pool that cools the reactor core and shields workers against radiation.

The OPAL reactor, based at ANSTO headquarters in Lucas Heights, south of Sydney, creates radioisotopes for nuclear medicine and neutrons for research and irradiation of materials. While the issue hasn't affected operations, it has diluted the heavy water and rendered it less effective.

The fault has been known to ANSTO since 2006 and repairs were attempted during the shutdown period (from July 2007 to May 2008), by injecting microscopic particles of alumina into the affected area, but this was only partially successful. The reactor was previously shutdown due to a fault with uranium fuel plates in its core (see, Australia's OPAL reactor recovers from failure, Cosmos Online).

ANSTO said that it is planning to replace the heavy water in about one month and is working closely with INVAP, the Argentinean firm that designed OPAL, on long-term solutions; such as a heavy water treatment plant, which would require a further shutdown of the reactor. Despite the problem, the organisation said that the reactor poses no safety risk. This has been confirmed by Australia's nuclear safety regulatory body, ARPANSA (Australian Radiation Protection and Nuclear Safety Agency).

"One drama after another"

Though the water leak is internal, there is "clearly a problem with this reactor… [it] hasn't been doing what it is designed to do," said Ludlam, who added that this was not a direct reflection on ANSTO. "It's just that this thing has not been operational for 11 out of 14 months and they've had one drama after another," he told Cosmos Online.

Andrew Humpherson, general manager of government and public affairs at ANSTO said that having commissioning issues was not unexpected and the problems OPAL has faced are relatively "low-level and manageable". He was, however, unable to provide a cost estimate or timescale for repairs, and said the responsibility would lie with INVAP.

Humperson noted that if OPAL was a non-radioactive, industrial plant the fuel issue would have been fixed within days. "[But] because it's the nuclear industry, standards are extremely high. There's a lot of time involved in resolving what are mechanically simple problems," he said.