Kajian Performa Passive Residual Heat Removal System (PRHRS) pada System-Integrated Advanced Modular Reactor (SMART)

SMART (System-Integrated Advanced Modular Reactor) merupakan desain reaktor multifungsi Generasi III+ tipe SMR (Small Modular Reactor) yang dikembangkan oleh KAERI (Korean Atomic Energy Research Institute) dengan kapabilitas produksi listrik 107 MWe dan energi termal 365 MWt. Sistem SMART meliputi berbagai fitur keselamatan untuk mengatasi LOCA (Loss of Coolant Accident) dan skenario kecelakaan lainnya. Salah satu dari fitur tersebut adalah Passive Residual Heat Removal System (PRHRS) atau sistem pembuang sisa panas pasif yang bekerja tanpa membutuhkan sumber daya elektrik. Sistem ini bekerja sesuai dengan prinsip sirkulasi alam sehingga bergantung pada aspek termal, tekanan, dan pengaruhnya terhadap aliran massa. Ketiga aspek tersebut dapat mempengaruhi kapabilitas pembuangan panas pada sistem. Data performa PRHRS reaktor SMART pada beberapa kondisi kecelakaan yang diperoleh melalui studi eksperimental maupun simulasi termohidrolika dianalisis pada kajian ini. Hasil analisis menunjukkan unjuk kerja pembuangan sisa panas yang baik oleh PRHRS SMART dengan waktu aktuasi yang tepat dan pendinginan yang stabil. Dengan kapabilitas multifungsi dan kemampuan pendinginan yang baik pada berbagai skenario kecelakaan, SMART memiliki potensi tinggi untuk kelak diterapkan di Indonesia.

Design of thermoelectric devices for extracting foreign objects from the human body by freezing

Objectives.The purpose of the article is to consider the designs of thermoelectric devices (TEC) for extracting foreign objects (IO) from the human body by freezing with various options for removing heat from the hot junctions of the thermoelectric module (TEM).Method. Modifications of thermoelectric devices are described for extracting the IO from the human body by freezing it to a special probe. Their technical design differs in the way of heat removal from the TEM hot junctions, for which air heat removal, melting working substances and preliminary cooling of the radiator are used. The basic relationships for calculating the technical means intended for the removal of heat from the hot junctions of the TEM are presented.Result. The graphs of the dependence of the temperature change of the TEM hot junctions in time are obtained for different values of its heat output when using an air heat removal system and the time of complete penetration of various working substances used in the device.Conclusion. The data obtained show that for the operating conditions of the TEC, the temperature of the hot junctions of the TEM with an air heat sink does not go beyond the permissible limits. With a module power of 8 W, 12 W and 16 W, the temperature of the hot junctions of thermoelements stabilizes rather quickly and takes the value of 308 K, 313 K and 318 K. maintaining their stable temperature is most preferred is nickel nitrate, less - elaidic acid and paraffin. Calculations of the design of a device with a pre-cooled radiator system also show the efficiency of heat removal from the hot junctions of the TEM for the duration of the entire procedure for removing the IO from the human body.

Gallium nitride heterostructure field-effect transistor with a heat-removal system based on a trench in the passivation layer filled by a high thermal conductivity material

The self-heating effect poses a main problem for high-power electronic and optoelectronic devices based on gallium nitride. A non-uniform distribution of the dissipated power and a rise of the average temperature inside the gallium nitride heterostructure field-effect transistor lead to the formation of a hot spot near the conducting channel and result in the degradation of the drain current, output power and device reliability. The purpose of this work is to develop the design of a gallium nitride heterostructure field-effect transistor with an effective heat-removal system and to study using numerical simulation the thermal phenomena specific to this device. The objects of the research are the device structures formed on sapphire, each of whom features both a graphene heat-eliminating element on its top surface and a trench in the passivation layer filled by a high thermal conductivity material. The subject of the research is the electrical and thermal characteristics of these device structures. The simulation results verify the effectiveness of the integration of the heat-removal system into the gallium nitride heterostructure field-effect transistor that can mitigate the self-heating effect and improve the device performance. The advantage of our concept is that the graphene heat-eliminating element is structurally connected with a heat sink and is designed for removing the heat immediately from the maximum temperature area through the trench in which a high thermal conductivity material is deposited. The results can be used by the electronics industry of the Republic of Belarus for developing the hardware components of gallium nitride power electronics.

Experimental Study on the Residual Heat Removal System in HTR-10

The 10MW high temperature gas-cooled reactor (HTR-10) is a modular pebble-bed type reactor, of which the inlet and outlet helium temperature are 250 and 700 °C, respectively. It reached to its first criticality in December, 2000, and operated for nearly twenty years successfully. Currently, HTR-10 is the only pebble-bed type high temperature gas-cooled reactor that can operate in the world. To verify the natural circulation operating characteristics and safety features of the passive residual heat removal system, a series of experimental studies have been performed under different operation conditions of HTR-10, which include the performance tests of the passive residual heat removal system under various reactor operating power, different ambient temperature and single loop run mode. According to the data collation and result analysis, it shows that the performance of the residual heat removal system in HTR-10 meets the design and safety requirements.