Validation of the Monte Carlo model developed to assess the activity generated in control rods of a BWR

Control rods are activated by neutron reactions into the reactor. The activation is produced mainly in stainless steel and its impurities. The dose produced by this activity is not important inside the reactor, but it has to be taken into account when the rod is withdrawn from it. The neutron activation has been modeled with the MCNP5 code based on the Monte Carlo method. The number of reactions obtained with the code can be converted into activity. In this work, a detailed model of the control rod has been developed considering all its components: handle, tubes, gain, and central core. On the other hand, the rod has been divided into 5 zones in order to consider the different axial exposition to neutron flux into the reactor. Results of the Monte Carlo simulation for the neutron activation constitute a gamma source in the control rod. With this source, applying again the Monte Carlo method, doses at certain distance of the rod have been calculated. Comparison of calculated doses with experimental measurements leads to the validation of the model developed.