The elevated radioactivity level in the primary circuit of Unit 1 is mainly related to the damage of fuel rods. Due to the influence of uncontrollable factors in the process of fuel manufacturing, transportation and loading, a small amount of fuel rod damage is unavoidable, and it is a common phenomenon in the operation of nuclear power units, the MEE said. Many nuclear power plants around the world have experienced similar cases of fuel rod failure but continued operation, data showed. There are more than 60,000 fuel rods in the reactor core of Unit 1 of the Taishan plant. It is estimated that about five fuel rods have been damaged, accounting for less than 0.01 percent of the total, which is far lower than the maximum fuel assemblies damage ratio (0.25 percent) in the design, according to the authority.