Fuel rod errors are to blame for the alarm at the Chinese nuclear power plant. • The Register

You may have seen panic on the news about a Chinese nuclear reactor going wrong and a warning of an “imminent radiological threat”. Don’t worry: it’s a routine fuel rod problem.

CNN made exclusive claims Monday after seeing a June 8 memo indicating that “noble gases in the primary circuit” of the coolant system at the Taishan-1 Nuclear Power Plant have accumulated.

The letter was written by the nuclear technology company Framatome, which is largely owned by the French energy giant EDF, and which was entrusted with the planning and operation of the Franco-Chinese power plant. The plant in Guangdong Province went online in December 2018 and serves the production centers in Guangzhou and Shenzhen. Framatome wrote to the U.S. Department of Energy to request permission to access American technical data and resources to help address the issue. The biz went on to claim that Chinese regulators are increasing the limit on the amount of gas that can be released from the coolant circuit, exceeding French safety standards in order to avoid plant shutdown.

This memo raised fears that Beijing might be covering up a nuclear disaster. However, the truth is less terrifying.

EDF said the build-up of inert gases – understood as xenon and krypton – was due to a failure in one or more of the fuel rods and their seals. These gases were collected, treated and released “according to regulations,” added the electricity giant.

When the uranium in the reactor’s fuel rods is hit by neutrons and split, it splits into smaller elements, including the radioactive isotopes iodine, krypton and xenon. It is expected that small amounts of these fission fragments will leak out. However, if the fuel tanks are pierced, broken or otherwise defective, more material is released into the coolant circuit. This is where the above-mentioned gas accumulation comes from, it is said: radioactive fission by-products that escape from the fuel into the primary coolant circuit. This gas had to be removed from the coolant, and the fuel responsible for the leaks must eventually be repaired.

Damage to fuel rods is not uncommon. A report from the US government [PDF] from last year stated that in pressurized water reactors between 1994 and 2004 an average of 1.6 fuel rods leaked per failed fuel element worldwide. We find that each assembly typically contains between 170 and 230 fuel rods and up to 65 percent of the fuel assemblies. Fuel failures in the US were caused by grid-to-rod rubbing.

“For pressurized water reactors (PWRs), which is the most common type of reactor in the US, as well as the type of reactor at the Taishan Nuclear Power Plant, the main sources of fuel leakage are debris and the lattice-to-rod friction that occurs when a nuclear fuel rod hits the spacer grids of metal that hold the rods in place, “Katie Mummah, a PhD student in nuclear engineering at the University of Wisconsin-Madison, told The Register.

“Less common, but still the occasional failure, is corrosion, manufacturing defects, and fuel handling errors. Most of the failures are also quite small, small holes or hairline cracks. Larger failures that lead to the washing out of fuel pellets are rarer, when a fuel pellet or a partial pellet can fall out of the fuel element. “

Fuel failures … are undesirable as leaking or damaged fuel assemblies require additional inspection and handling. However, they are not considered a major safety concern

She added that a fuel rod problem does not usually result in a reactor being shut down. The containers are usually left in place until the reactor is refueled and then fixed in place.

“Fuel failures are generally not considered events that require press releases,” she said. “They often do not change the reactor output and generally do not switch off the reactor.

“They are undesirable because leaky or damaged fuel assemblies require additional inspection and handling and ultimately require different storage and transport containers after unloading from a spent fuel pool. However, they are not considered a major safety concern.”

But what about the detection of admittedly radioactive krypton and xenon? Well, as noble gases, they are chemically inert, so any damage to the actual system should be minimal or nonexistent.

Xenon-133 is one of the possible fission fragments. It has a habit of sliding through pipes and walls, it has a half-life of just over five days, and it has been FDA approved for mapping lung function and blood flow. The gas breaks down through beta radiation and also emits a small amount of gamma rays. Xenon-137, on the other hand, has a half-life of about four minutes and Krypton-90 has a half-life of 32 seconds, although other fission fragments can have half-lives that are much longer.

A slight increase in gamma radiation was observed around the facility, confirming that a certain amount of radioactive material was escaped or discharged.

According to CNN, US officials did not believe this episode was a crisis but said it should be monitored. The Chinese authorities also said the whole matter was not an issue and everyone should just calm down. Of course they would say so, but in this case they seem right.

“Since the commercial start-up, the Taishan Nuclear Power Plant has strictly controlled the operation of the units in accordance with operating license documents and technical procedures,” the Chinese government told CNN. “All operational indicators of the two units have met the requirements of the nuclear safety regulations and the technical specifications of the power plant.”

Meanwhile, Framatome stated in a public statement that “according to the data available, the system is operating within the safety parameters”. The United Nations International Atomic Energy Agency added: “At this point the agency has no evidence of a radiological incident.”

So there it is, a new reactor dealing with some early fuel rod wobble. Far be it from us to accept the word of the energy companies, but if we panic about a disaster it should be a real disaster, and not a slip that nuclear engineers can more than handle. You can now get out of your bunker. ®

Comments are closed.