Systems and methods for storing spent nuclear fuel below grade that affords adequate ventilation of the spent fuel storage cavity. Although the hardware designs have been fabricated in integrated circuit products with limited inputoutput pins, the techniques and systems enable the hardware designs within the integrated circuit products to be comprehensively analyzed, diagnosed, and debugged at the HDL level at speed. In some embodiments, the rotational frequency of the air supply fans is controlled based on a pressure differential between an inlet region and an exhaust region within the enclosed space.