The objective of this report is to detail the work done during the TP IV project at EPFL. The idea is to look into the activation of concrete and metallic structures of the EPFL’s nuclear reactor: CROCUS. This study has been done by two ways: MCNP computations and TLD measurements. The results are consistent between the two methods, as both show that the concrete roof is more activated than the other part of the cavity. However, the MCNP model seems to overestimate the radioactivity of the roof when compared to the walls. Indeed, a factor four has been found between them and with the TLD’s only a factor two. Moreover, the MCNP model gives high numbers for the activity in the concrete wall. Indeed, an activity of around 3 kBq/cm3 was found for the ten first centimetres of concrete in all the walls. The mains isotopes responsible for this activity are: 60Co and 133Ba, they are both long-lived radionuclides and it would be interesting to look at they concentration with time.