An important research line in nuclear physics nowadays is the study of unstable nuclei.Within this, one area of interest is the study of delayed neutron emission which is of relevancefor di erent elds such as astrophysics, nuclear technology and nuclear structure. Thestudy of di erent aspects of decay of exotic nuclei, such as half lives and neutron emissionprobabilities, provide information about their structure and these measurements are sometimesthe only ones that can be performed in nuclei with very low yields.The work presented here aims at measuring the neutron activity of a 252Cf source. Thegoal is to verify the activity provided by the manufacturer and reduce its quoted uncertainty.The method used to obtain the 252Cf neutron source activity is based on the measurement ofthe gamma ray spectrum of the ssion products [1]. Once calibrated this source will be usedto calibrate a neutron detector designed at UPC that is currently being used to measure ð€€€delayed neutron emission. However that is beyond the scope of this work.The rst chapter of this document describes the theoretical concepts of ð€€€delayed neutronemission; it also presents a brief summary about the UPC neutron detector prototypethat we aim at calibrating, an overview of di erent types of neutron sources and the calibrationmethod of the detector. The second chapter refers speci cally to the characteristics of252Cf neutron source calibrated and the experimental setup. Chapters three and four detailthe procedure for the determination of the activity of the 252Cf neutron source studied passingthrough the germanium detector calibration. The last chapter presents the conclusionsof the results of this study and improvements to perform in future similar calibrations ofthis type.