Many countries plan to store their spent nuclear fuels (SNFs) in geological repositories. Before permanent storage, it is essential to have systematic measurements using non-destructive techniques in order to assess safety, operational and safeguard parameters. One important safety criterion relates to the decay heat of the SNF. Calorimetric measurements, which directly measure the decay heat, cannot be envisioned for every SNFs due to time constraints. Therefore, decay heat must be experimentally determined using other measurement techniques such as gamma and neutron measurements. This work presents results on the prediction of decay heat using an HPGe detector and the DDSI instrument. This work aims at investigating the performance of a combination for decay heat prediction of such instruments by studying two high-performance systems. In this work, an HPGe detector is used for gamma measurements, and the prototype Differential Die-away Self-Interrogation (DDSI) instrument is used for neutron measurements. Previous works have predicted the decay heat using experimental results of either the HPGe device or the DDSI device. However, combining information from both devices increases the prediction capability as both devices look at different SNF properties.