Tuesday, 30 January, 2007

by John Mulcair
St George Leader

Full commissioning of the new $380 million OPAL nuclear research reactor at Lucas heights is being delayed while investigations are being made of problems that can reduce its optimum performance.

The news comes as Federal Science Minister Julie Bishop is due this morning to permanently shut down the old HIFAR reactor which has operated at ANSTO since 1958.

The problem at the new OPAL reactor, which went to its full 20 megawatts power only on November 3, 2006, is that light or ordinary water, used for general cooling of the reactor as it operates, is leaking into a smaller tank of heavy water which holds the reactor itself.

The heavy water tank is at the bottom of a 13 metres deep cylindrical vessel filled with light water.

As well as cooling the core, the heavy water also critically controls the speed of neutrons produced by the chain reaction of uranium atoms as they are split.

An ANSTO spokesman said the reduction in water purity in the heavy water tank had declined only from 99.8% to 99.5%, but every effort was being made to have the OPAL operating at its optimum. The fix ANSTO proposes is to drain the heavy water from its containment vessel and fill it under pressure with the gas helium, producing bubbles to identify any cracking or any other weakness.

It is not known how long it may take to fix the problem but Australia’s nuclear regulator, the Australian radiation Protection and Nuclear Safety Agency wants a precisely documented approach. CEO John Loy said while the overall problem was not a safety matter, there were safety issues attached to some of the proposed approach, which could involve lowering the level of the light water, which also provides radiation protection.

"This is not an urgent, immediate issue, but it does have the potential over time to degrade the performance of the reactor", Mr Loy said.

The problem will not immediately affect production of nuclear medicines and industrial radioisotopes, as most have been produced at Lucas heights since last June from imported radioactive materials. This followed a small explosion in a shielded production area.

Whist the old reactor, HIFAR, is due to be officially closed down today it is licensed to remain operating until the end of February.

It has continued to make radioactive iodine which, because of its short half-life cannot be imported for treatment of thyroid cancer and other short half-life isotopes for medicine and industry.

The ANSTO spokesman said that it would not seek any extension of the operating licence for HIFAR, which expires in February.

An operating OPAL is crucial also to ANSTO’s $30 million investment in instruments and an international recruitment campaign to attract researchers to establish its Bragg Institute at the forefront of neutron-based research.

All instruments are scheduled to be online this year, but need neutrons from the reactor not only for research but for initial set-up and calibration.

The ANSTO spokesman said the effect on OPAL’s neutron flux was so small it would not affect the instruments' commissioning.