Nereus overview
The history of energy conversion
Figure 1. the history of energy conversion systems. Please note the smoke emissions
The step towards nuclear power conversion is a logical one in the history of mankind. Figure 1 shows, in an artistic way, the history of the way in which the human race has produced energy. The way this energy in the different fuels was converted into useful energy can also be analysed. It is beyond discussion that the attainments related to the availability to mankind of cheap energy will never be given up. Human beings are somewhat reluctant to accept new developments, but when they have learned the advantages, they will only give it up when further improvements are available. Only in difficult times, as during a war, will achievements and goods considered as luxuries (temporarily) be set aside. As far as the subject of “energy” is concerned, the availability of cheap and reliable energy, good medical care and clean potable water within a manageable environment are the building stones of our prosperity and welfare. The human race has sometimes tried to turn back history, even at great costs, but it has always been in vain.
John F. Kennedy
Trends in the history of energy conversion
- The amount of energy per kg fuel increases
- The combustion unit decreases in size per kW
- Open combustion becomes enclosed, so less obvious to the users
- Emissions change from “deluted & dispersed” (Uncontrollable)
to “confined & controlled” (Manageable) - The medium for transportationbetween the combustion area and the conversiona area increases in purity, causing less corrosion and erosion
- The energy transport system starts as an open (dirty) cycle, but becomes a closed (clean) cycle
- The rotating energy conversion unit becomes standard
- The complexity of the installations increases
- The number of people to control and maintain decreases
- The weight and volume per produced kW decreases
- The total process efficiency increases constantly
- New systems never appeared as a result of a shortage of a type of fuel, but because better systems became available
- The end is always a very complex engine to fight off (in vain) the new system coming along.
- CONCLUSION 1: Resulting in energy production systems with lower through life costing per kW
- CONCLUSION 2: Nuclear power production is the next logical step in the ways humanity produces energy
- CONCLUSION 3: the (closed-cycle) gas turbine with an inherently safe nuclear heat source seems to be the next logical step in the history of energy production
So far all studies on gas turbines with a nuclear heat source have connected the heat source to the energy conversion unit by a closed-cycle system consisting of a helium gas turbine. A logical thought because it seems undoubtedly to lead to the highest efficiency and compactness. However helium gas turbines are not proven technology yet. It seems to become an expensive operation to design, construct and test such a machine.
On the other hand many studies and tests are going on to design different external heat sources for gas turbines. Heat sources which are able to burn, in a controllable and effective way, waste of refineries, biomass, industrial waste gases, pulverized coal, etc. So it seems logical to investigate whether uranium could be added to this list of fuels.
From the publications on the closed-cycle nuclear gas turbine (HTR-GT) one learns that the nuclear fuel is cooled by helium, pumped around by a recuperative gas turbine. However, the test reactor in Jülich worked with a two loupe system. The reactor was cooled by helium pumped around by a so-called helium ventilator. The heat was transported to a steam cycle via a steam generator and a steam turbine. So this test bed was actually a standard (Rankine) pressurized water reactor power plant, with a new nuclear heat source.
The logical next thought is why not change in the Jülich concept the Rankine-type secondary water-steam closed cycle into a Brayton-type open cycle and see how these systems compare with the Brayton-type open cycle for small (circa 20 MWth) plants. After all the advantages and disadvantages of gas turbines over steam plants (less components, easier for remote control, less or no manning, higher quality of fuel, etc.) have been discussed many times in publications and at conferences.