|dc.description.abstract||The Department of Energy and the Idaho National Laboratory are developing a
Next Generation Nuclear Plant (NGNP) to serve as a demonstration of state-of-the-art
nuclear technology. The purpose of the demonstration is two fold: 1) efficient low cost
energy generation and 2) hydrogen production. Although a next generation plant could
be developed as a single-purpose facility, early designs are expected to be dual-purpose.
While hydrogen production and advanced energy cycles are still in their early stages of
development, research towards coupling a high temperature reactor, electrical generation
and hydrogen production is under way. Many aspects of the NGNP must be researched
and developed to make recommendations on the final design of the plant. Parameters
such as working conditions, cycle components, working fluids, and power conversion
unit configurations must be understood.
Three configurations of the power conversion unit were modeled using the
process code HYSYS; a three-shaft design with 3 turbines and 4 compressors, a
combined cycle with a Brayton top cycle and a Rankine bottoming cycle, and a reheated
cycle with 3 stages of reheat were investigated. A high temperature steam electrolysis
hydrogen production plant was coupled to the reactor and power conversion unit by
means of an intermediate heat transport loop. Helium, CO2, and an 80% nitrogen, 20%
helium mixture (by weight) were studied to determine the best working fluid in terms
cycle efficiency and development cost. In each of these configurations the relative heat
exchanger size and turbomachinery work were estimated for the different working fluids. Parametric studies away from the baseline values of the three-shaft and combined cycles
were performed to determine the effect of varying conditions in the cycle.
Recommendations on the optimal working fluid for each configuration were made.
The helium working fluid produced the highest overall plant efficiency for the
three-shaft and reheat cycle; however, the nitrogen-helium mixture produced similar
efficiency with smaller component sizes. The CO2 working fluid is recommend in the
combined cycle configuration.||en