In the wake of the furore over inaccurately reported “leaks” at China’s Taishan NPP, the International Atomic Energy Agency (IAEA Department of Nuclear Safety and Security on 17 June explained the significance of fuel cladding failures.
The China Atomic Energy Authority (CAEA) informed the IAEA on 16 June that a minor fuel cladding failure had occurred at the Taishan Nuclear Power Plant. IAEA explained that NPPs “are designed with multiple back-up and diverse safety systems as part of an approach to safety, called ‘defence-in-depth’. This means there are multiple, redundant safety systems designed to prevent any accidental radioactive release. In addition, there are multiple barriers, including the primary reactor coolant system or primary circuit and a single or double containment building, which are designed to prevent any radioactive release to the environment.”
IAEA noted that “an increase in the level of radioactivity in a primary reactor coolant is different from a radioactive leak”. The primary circuit is inside the containment and there are several further barriers to prevent releases of radioactivity to the environment. The number of fuel rods in a reactor varies depending on the reactor’s design. Some reactors could contain up to 60,000 fuel rods.
“Upon failure of a fuel cladding at a nuclear power plant, the radioactivity of the primary reactor coolant increases, but as long as it remains within the normal range of operation, as stipulated in the technical specifications, the reactor can continue to operate safely,” IAEA said.
Fuel cladding failures are a known and not uncommon occurrence within the operation of NPPs. Nuclear plants have operating procedures “which allow the ongoing monitoring of the damaged fuel elements, and operations can continue within the pre-defined safe operating parameters”.
There are operating strategies available to minimise the impact of a fuel failure and ultimately, if necessary, the reactor could be safely shutdown before the technical specification limits were to be reached. The damaged fuel elements would then be inspected and replaced, and the reactor returned to operations.