After a serious leakage accident at the Kakrapar atomic power station in Gujarat on March 11, environmental activist group Greenpeace India has called for an immediate independent investigation of all aging pressurised heavy water reactors (PWHR) in the country. The demand comes as the nuclear regulatory authorities have failed to identify the leak even 72 hours after the accident.

“The Kakrapar accident was likely caused by degrading components and we’re concerned similar aging effects could cause accidents at other aging heavy water reactors. We need independent expert investigation into the Kakrapar accident and the immediate inspection of all other aging heavy water reactors,” Hozefa Merchant, a Greenpeace campaigner, was quoted as saying in a press release. 

On March 11 – the fifth anniversary of the Fukushima disaster – a major leak from the reactor’s cooling system was detected and an emergency was declared at Unit 1 of the Kakrapar atomic power station. Although the reactor was shut down, the Atomic Energy Regulatory Board (AERB) has stated that the leak is significant enough to be considered a level 1 accident on the International Nuclear Event Scale (INES). 

The Kakrapar unit 1, a PHWR based on CANDU (CANada Deuterium Uranium) design, is over 20 years old. There are seven more reactors in India of the same design that are over 20 years old. Any mishap in these reactors could endanger the lives of over 4 million people living around a 30 km-radius around these eight reactors.

The risk of accidents increases with age in CANDU reactors, with the inevitable degradation of hundreds of pipes that hold the fuel and transport heavy water. Due to increasing accident risks, CANDU reactors typically need to be shut down and “completely retubed” after about 25 years of operation in order to continue operating safely.

In a statement on the Kakrapar accident released on March 14, the AERB said that only the reactor’s “pressure tubes”, which hold the fuel bundles, were replaced in 2011, but that it is unclear whether all safety-sensitive aging components were replaced. “Neither Kakrapar’s operator, nor the regulator, has disclosed exactly what components or tubing failed and caused the leak. This is why an investigation into the causes of the Kakrapar accident and the condition of India’s other aging reactors is urgently needed,” Merchant said.

“The emergency at Kakrapar reminds us that all of India’s heavy water reactors are aging and more prone to accidents. The impacts of aging are not entirely well understood, so it is vital to adopt a precautionary approach to protect public safety,” added Shawn-Patrick Stensil, a Greenpeace Canada campaigner with expert understanding of the Canadian CANDU reactor design. “All of the heavy water reactors over 20 years of age should be immediately inspected so we can ensure what happened at Kakrapar doesn’t happen at another station. All inspection results should be made public and subject to independent review,” he added.

Eight of the current 18 PHWRs in India are of the CANDU design, and are over the age of 20 years. The four of the oldest reactors are located in Rawatbhata in Rajasthan and Chennai in Tamil Nadu. The total population from these eight sites that live within the 30 km radius is over 4.16 million people. The population within the 30 km radius around Kakrapar is close to a million people.