A freeze/thaw containment system is provided, having a protecting body and a flexible pouch protected by two plates of the protecting body. The two plates are attached together at a peripheral margin and form a rectangular protecting body. The peripheral margin is mounted in supporting parts of a stationary frame and sliding positioning members are secured to the peripheral margin, so that the peripheral margin is guided and allowed to be displaced inwardly during filling of the pouch, while the protecting body extends generally planar to sandwich and constrain the pouch in empty state of the pouch. This way of holding and retaining the protecting body allows for progressive conformational change of the protecting body due to the change in volume of the pouch when filled with a biopharmaceutical product, while facilitating reverse displacement of the peripheral margin during draining operations.