Conceptual Design for a 50 MW ( t ) Metallic Intermediate Heat Exchanger for the Next Generation Nuclear Plant

This UCB report summarizes preliminary design analysis for the 50 MW(t) intermediate heat exchanger (IHX) for the demonstration of hydrogen production with the Next Generation Nuclear Plant (NGNP). Sulfur-iodine (SI) hydrogen production efficiency is maximized when sulfuric acid decomposition is performed at a low pressure (~1 MPa) compared to the NGNP primary coolant pressure (~7 MPa). For a metallic IHX, however, operation with a large pressure differential may cause unacceptable creep. This report investigates creep-resistant metallic IHX designs using molten salt (MS) as an intermediate fluid, to determine the maximum operating temperature at which creep can be maintained at an acceptable level. Preliminary results indicate that a metallic He-toMS IHX may be able to operate with a peak helium inlet temperature between 850 and 900°C, while accommodating a ~ 6 MPa pressure differential with acceptable creep. By selecting a metallic IHX design that permits hydrogen production at the optimal SI process pressure, a subsequent upgrade to high-temperature (1000°C) operation using a ceramic IHX then becomes possible.