The IEA-R1, swimming pool research reactor, from the Institute of Energy and Nuclear Research (IPEN), among other uses, the instrumental neutron activation analysis technique is widely used, and successfully, by the Neutron Activation Laboratory (LAN), using the comparative method. In this method a sample is irradiated simultaneously with a standard. In order to overcome the difficulty of a multi-elementary analysis, because it was necessary to prepare several standards, the k0 method of neutron activation was developed. In method k, the concentration of sample elements is calculated in relation to a comparator element, generally gold. However, for the use of the k0 method, it is necessary to accurately determine the detection efficiency in the energy range of interest and the geometry of the experimental arrangement. In order to circumvent the manual processing of the data in spreadsheets, which could be affected by errors, a free code web software was developed for calibration in absolute efficiency of an HPGe type detector for neutron activation analysis based on the k0. We used the free, low learning curve standardized Python programming language in the eScience project, which is part of the software, and the Django web framework with a simple and intuitive interface. In the system it is possible to register the detectors, radioactive sources and their manufacturers, projects and spectra, attributes necessary to calculate the absolute efficiency of an HPGe type detector. In addition to calculating efficiency, the system plots the graph with the efficiency points, trend curve, with possibility of adjustments, and error bar representing the uncertainties. The system issues reports on spectra and efficiency data for each project. The reports make it possible to check the data as well as its use in other applications. Because it is a web software, its access is allowed from any device with an internet connection. Another result obtained with the system is the reduction of the possibility of errors with the manual treatment of the data in spreadsheets.