A water leak in the high flux reactor (HFR) at Petten in the Netherlands has led to an “unplanned” outage that is expected to impact the near-term supply of isotopes used in several medical imaging exams worldwide.

The leak was found this week in the reactor beam tube cooling system. The cause of the leak is unknown, but the reactor will remain in standby status until a full investigation into the leak is carried out. The Nuclear Medicine Europe Emergency Response Team is planning additional inspections to determine how to best resume production, reported NEI Magazine.

While the leak does not pose a risk to workers or the public, it is expected to impact supply and distribution of medical isotopes. This specifically applies to molybdenum-99 (Mo-99), which is used to produce technetium-99m, a widely-used radioisotope in nuclear cardiology; and lutetium-177 (Lu-177), which is often used for therapeutic applications, according to Nuclear Medicine Europe.

“Targets were scheduled to be irradiated in the HFR reactor for both Mo-99 and Lu-177 production and the delayed restart will impact the supply of these radioisotopes in the coming week(s),” said the association in a statement.

One of the few reactors in the world that produces medical isotopes, healthcare providers rely on the HFR to produce raw materials that are used for 30,000 patients each day. It also is a place for research on safe and new nuclear energy.

Having been shut down for a few days for refueling, the reactor was expected to resume operations on January 20. But an inspection conducted by nuclear service provider Nuclear Research and Consultancy Group (NRG) revealed the leak and pushed back the restart date. "During the inspection, we saw that there was a leak in the ceiling of the basement. It was found to be a leak in the cooling system. We then cut off the water supply. The leak was over, but the problem was of course not solved,” said NRG spokesperson Cora Blankendaal.

HFR performed endoscopic inspections on difficult to access piping but was unable to determine the cause of the leak.

In the meantime, medical practices are encouraged to consult their radioisotope suppliers to determine the specific impact the leak will have on their orders. They should also prepare for a near-term radioisotope shortage as the length of time for repairs is still unclear.

Nuclear Medicine Europe is expected to update practices on the situation on January 31 or earlier if information is available sooner.

The HFR reactor has been in operation since 1961 and is due to be replaced by the new PALLAS reactor in the 2020s. Construction of the PALLAS reactor is currently underway.

Regulatory review and approval following the discovery of the root cause for the leak will be required before the reactor can resume service, according to SNMMI.

A hydrogen leak in 2017 led to the shutdown of South Africa’s Pelindaba facility, operated by NTP Radioisotopes, for three months. The facility resumed operations in late February 2018. The shutdown cost it 3.5 million rand ($300,885) daily and led to a suspension in both domestic and international orders. This forced providers to temporarily turn to other nuclear sources for support.

The reactor closed again shortly after this in May due to safety issues and did not reopen until November to help with a shortage caused by an 11-day closure of the Open Pool Australian Lightwater (OPAL) reactor in Australia for maintenance.

In 2019, Australia once again shut down its OPAL reactor due to a valve issue. Nuclear medicine experts estimated that the shutdown was expected to impact up to 15,000 patients a week, with doses going only to the most urgent cases. The South African reactor was also down at the same time for maintenance.