What we know today has further refined what the problem is, but there are still many questions about what exactly has gone wrong at Taishan unit 1.
5 individual fuel rods among the 241 fuel assemblies in the reactor core have damage. Each assembly houses multiple individual rods that contain nuclear fuel pellets. There are a total of 60,000 fuel rods contained in the 241 assemblies in the reactor core. This estimate is provided by the Chinese government’s nuclear ministry. They did not describe how this estimate was produced.
The government claimed there have been no leaks to the environment. They failed to mention the release of xenon and krypton radioactive noble gases on April 8th. This was a purposeful venting of gases, so they appear to be playing semantics. Leaks are uncontrolled. Venting is controlled, so they don’t call it a “leak”. Environmental radiation levels are difficult to independently confirm.
The April leak was detected in Hong Kong by their radiation sensor network. Hong Kong’s government has been under immense pressure to go along with the wishes of the Chinese government in recent years. How impartial Hong Kong is able to be right now is in question. Sensors for other independent parties are at a far distance. Taiwan is too far to realistically catch releases from this plant. There is a CTBTO station in the area near Taishan, that information is not regularly made public.
If Taishan will need to vent radioactive gas from the reactor system again is not currently known. Authorities have not talked about that potential issue. Some news reporting this week incorrectly described the xenon and krypton gases as being inert gases purposely used to manage reactor systems. This is incorrect. While xenon and krypton are inert noble gases, they are not created and used to manage reactor systems and the ones leaking from the fuel are radioactive gases with a public health risk. Xenon poses a particular risk to operating nuclear reactors through xenon poisoning.
The Chinese ministry described the problem with the fuel as being related to the production, transport, or loading of the fuel. This indicates the problem may have been damage to the assemblies before the reactor began this round of operation. The question now is how extensive is the damage to these fuel rods? Severe damage can prevent control rods from properly inserting, causing problems with controlling the power and nuclear reaction in the core. This level of damage could also make removal of the damaged assemblies problematic. If fuel pellets have fallen out of the damaged fuel rods, this can cause a number of problems with reactivity of the fuel core or damage to reactor systems that would be expensive and time consuming to repair.
Chinese authorities have tried to describe this as a trivial problem. China has an extensive nuclear power fleet. France has a large decades old fleet of pressurized water reactors. France would have their own capability and experience dealing with leaking fuel rods in similar reactor designs. Framatome’s need to share some exclusive US experience or technology with their Chinese counterpart indicates this is more problematic than a few fuel rods merely leaking excess radioactive gases into the coolant water.
The reported increase in allowable levels of radiation by Chinese authorities has been clarified to be permissible levels of radiation within the reactor systems and coolant. That level was raised to allow the reactor to continue to operate. This is not a direct risk to the public. It is an increased radiation exposure to the workers at the plant that have to enter the controlled areas of the reactor building. If more gas ventings are required, this will create a risk to the public.
The extent of the fuel damage is the big question. The activity around the problem at the plant shows that this is more than routine leaking fuel assemblies. More significant damage can cause larger problems with operating the reactor safely and could cause long term damage that is expensive to repair. If there is a manufacturing problem involved, this brings all of the fuel in both reactor units into question. If more fuel assemblies begin to fail either through cracks or with catastrophic failures, this could take the problem into more dangerous territory. It is not currently known what they suspect has caused this damage of the three potential causes cited.
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