Internal swelling reactions (ISR) can lead to the degradation of concrete due to expansion induced by such chemical reactions. They classically include the Delayed Ettringite Formation (DEF), the Alkali-Aggregate Reaction (AAR) and the occurrence of both simultaneously. The DEF may be developed in massive concrete structures under specific conditions, such as nuclear power plants that contain prestress reinforcement. Containment vessels are in France biaxially prestressed, which leads to concrete creep. Recent research works show the importance of the effect of prestressing on the reduction of swelling due to ISRs, or even its cancellation for certain values of prestressing. These phenomena must therefore be studied and quantified, especially if the operating life of these facilities needs to be extended. This work aims to carry out an experimental program under realistic conditions to study the coupling effect of ISR and creep. Innovative testing frames have been specifically designed for this study to induce a biaxial compressive stress state. Preliminary studies were done, and they verified the good functionality of the biaxial frames for concrete creep test. These tests allowed to assess the reliability of the optical fiber strain measurements as well as the associated data acquisition system. The experimental program has already been launched and concrete specimens were cast. The specimens were immerged in water and heated to 38°C for one month after an autogenous cure. Half of the concrete specimens were loaded biaxially, while the remaining half were left unloaded to measure their free swelling. To be representative of the history undergone at the early age of a massive structure, a temperature cycle in a climatic chamber under humid conditions is applied to concrete specimens to ensure the development of the DEF.