Development of an experimental equipment to nondestructively measure the rod power distribution and analysis with a new fuel assembly

To exactly measure the rod power distribution without disassembling is developed a gamma scanner with a wide slit enough to fully cover HANARO fuel assembly horizontally. The distribution is numerically reconstructed from the gamma-scanning result of 36-rod fuel assembly in fresh clean state using new gamma scanner. From the distribution determined from the gamma-scanning result, it is confirmed that this assembly consists of standard fuel rods and reduced fuel rods. When the gamma scanner with a narrow slit is used, the measured result and the result simulated by MCNP do not agree well. But the results with a wide slit agree well. Accuracy of the distribution is not improved. The errors are caused by the fact that the gamma energy is too low. There would be no problem as the gamma energy from the irradiated assembly is high. Therefore, we are looking forward to exactly measuring the distribution using new gamma scanner and the irradiated assembly