Many counterfeit parts have been discovered in U.S. nuclear plants, potentially increasing the risk of a safety failure, the inspector general of the federal nuclear industry regulator said in a recent report released.

The report is a blow to a U.S nuclear industry that has shrunk in recent years due to competition from renewable power and plants that burn natural gas and lingering public concerns following high-profile mishaps including a 2011 tsunami at Japan’s Fukushima plant.

“Counterfeit parts are safety and security concerns that could have serious consequences in critical power plant equipment required to perform a safety function,” the report from the inspector general’s office of the Nuclear Regulatory Commission said.

The report said Department of Energy staff had identified more than 100 incidents involving counterfeit, fraudulent or suspect items (CFSI) in agency reactors in fiscal year 2021 alone.

Counterfeit parts found at reactors have included an emergency service water pump shaft, temperature sensors used to identify steam line breaks and breaker switches meant to prevent fires, it said. The report did not name nuclear reactors involved or the origin of the parts.

The report added that the NRC may also be underestimating the number of counterfeit parts in plants “because it does not require licensees to report CFSI except in extraordinary circumstances, such as those involving the failure of equipment that performs a significant safety function.”

The NRC said it is reviewing the report.

“While the report’s findings include the ongoing presence of CFSI at U.S. reactors, nothing in the report suggests an immediate safety concern,” said spokesperson Scott Burnell. “The NRC’s office of the Executive Director for Operations is thoroughly reviewing the report and will direct the agency’s program offices to take appropriate action.”

The Department of Energy did not immediately respond to a request for comment.

An advocacy group said the report shows the NRC needs to work harder to counter the problem.

“This troubling report shows that the NRC needs to do much more to ensure that counterfeit or fraudulent parts with potentially dangerous defects are kept out of U.S. nuclear power plants—including strengthening requirements for plant owners to report and correct such problems as soon as they are discovered,” said Edwin Lyman, director of nuclear power safety at the Union of Concerned Scientists, nonprofit group.

The administration of President Joe Biden has said it believes nuclear reactors will play an important role in decarbonizing the nation’s economy to fight climate change, because they do not emit a significant amount of greenhouse gases.

Nuclear power backers also point out that reactors do not release particulate pollution, which fossil fuel plants do, that can harm human health.

(Reporting by Timothy Gardner Editing by Alistair Bell)