دانلود رایگان مقاله تامین انرژی پایدار با تقویت HTGR اورانیوم آب دریا

Abstract

Sustainable and safe energy supply with High Temperature Gas-cooled Reactor (HTGR) fueled by uranium from seawater have been investigated and discussed. From the view point of safety feature of self-regulation with thermal reactor of HTGR, the uranium resources should be inexhaustible. The seawater uranium is expected to be alternative resources to conventional resources because it exists so much in seawater as a solute. It is said that 4.5 billion tons of uranium is dissolved in the seawater, which corresponds to a consumption of approximately 72 thousand years. Moreover, a thousand times of the amount of 4.5 trillion tU of uranium, which corresponds to the consumption of 72 million years, also is included in the rock on the surface of the sea floor, and that is also recoverable as seawater uranium because uranium in seawater is in an equilibrium state with that. In other words, the uranium from seawater is almost inexhaustible natural resource. However, the recovery cost with current technology is still expensive compared with that of conventional uranium. Then, we assessed the effect of increase in uranium purchase cost on the entire electricity generation cost. In this study, the economy of electricity generation of cost of a commercial HTGR was evaluated with conventional uranium and seawater uranium. Compared with ordinary LWR using conventional uranium, HTGR can generate electricity cheaply because of small volume of simple direct gas turbine system compared with water and steam systems of LWR, rationalization by modularizing, and high thermal efficiency, even if fueled by seawater uranium. It is concluded that the HTGR fueled by seawater uranium with the current technology enables the energy sustainability for approximately 72 million years with superior inherent safety features and lower cost of 6.07 cents/kWh (7.28 yen/kWh) than the 7.34 cents/kWh (8.80 yen/kWh) cost of LWR using conventional uranium.

5. Conclusions

Utilization of uranium resources is investigated to achieve safe, sustainable, and economic energy supply by taking the advantage of safety feature of HTGR. To sustain nuclear energy safely with HTGR, the uranium resources should be inexhaustible and obtained surely because the thermal spectrum reactor of HTGR is not preferable to breed fissile fuel material. Moreover, the cost should be reasonable to be accepted as commercial utilization. However, the amount of conventional uranium corresponds to consumption of approximately 290 years, and it is not much enough to sustain the energy supply eternally. Moreover, conventional uranium has problems from the view point of energy security, i.e., geology and concession. On the other hand, total uranium from seawater amounted to 4.5 billion tU, which corresponds to a duration period of about 72 thousand years. Seawater uranium is dissolved in equilibrium state with approximately 4.5 trillion tU of uranium at the surface of the sea floor. This suggests that almost all of the uranium resources can be recoverable. The duration period becomes 72 million years. In other words, seawater uranium is almost inexhaustible. Moreover, seawater uranium should be recovered before exhaustion of conventional uranium from the viewpoint of energy security because the uranium mining concession, which is necessary to supply the uranium resources sustainably, is difficult to obtain to fulfill the entire requirement. The target cost of uranium from seawater is 110 $/kgU, which is lower than the current uranium price of 120 $/kgU. However, with current technology, the achievable cost is 208 $/kgU, which is not reasonable comparing with conventional uranium cost.