Radiation-induced separation and accumulation of electric charge in supercapacitors

Nuclear Energy and Technology 0204-3327 Radiation-induced separation and accumulation of electric charge in supercapacitors* Vladimir A. Stepanov 0 1 Vladimir A. Chernov 2 Yury G. Parshikov 3 Viktor P. Lebedev 4 Yevgeny V. Kharanzhevsky 4 5 0 LLC ?Laboratory of materials of Obninsk Institute for Nuclear Power Engineering? , Pyatkinsky proezd12, Obninsk, Kaluga reg., 249030 Russian Federation 1 Obninsk Institute for Nuclear Power Engineering, National Research Nuclear University ?MEPhI? , 1, Studgorodok, Obninsk, Kaluga reg., 249030 Russian Federation 2 JSC ?SSC RF-IPPE? n.a. A.I. Leypunsky , Bondarenko square1, Obninsk, Kaluga region, 249033 Russian Federation 3 FGBUN Interdepartmental Center of Analytical Researches in the Field of Physics, Chemistry and Biology at the RAS Presidium , Profsoyuznaya st. 65 bld. 6, Moscow, 117997 Russian Federation 4 JSC ?ELEKOND? , Kalinin st. 3, Sarapul, Udmurt Republic, 427968 Russian Federation 5 Udmurt State University , Universitetskaya st. 1, Izhevsk, Udmurt Republic, 426034, Russian Federation In current sources with a radioactive isotope (CSRI), nuclear energy is directly converted into electricity due to the separation of electric charges during the decay of radioactive isotopes. It was previously shown that asymmetric supercapacitors can be used as CSRI prototypes if, after being exposed to pulsed reactor irradiation, the electric charge on their plates increases to several coulombs as a result of internal induced activity. In this paper, the electric charge separation and accumulation in supercapacitors were studied directly in the process of neutron irradiation. The study was focused on the electrophysical characteristics of cylindrical supercapacitors with an organic electrolyte produced by JSC ?ELEKOND?. A comparison of symmetric and asymmetric supercapacitors showed that an effective charge accumulation occurs in the asymmetric capacitors: it is independent of the neutron flux density and determined by the absorbed radiation dose. The electrical voltage between the plates of a symmetrical supercapacitor with a capacity of 100 F during irradiation up to an absorbed dose of 50 Gy reaches 1.24 mV. When asymmetric supercapacitors are irradiated with the same dose, a significant increase in the potential difference up to 1.15 V is observed during irradiation and for a long time afterwards (1.5?105 s) due to the electric charge redistribution (~ 5?10-3 C) in the electrolyte and carbon particles with the formation of a double electrical layer. The post-radiation increase in the capacity of asymmetric supercapacitors is ~ 5 mF. Supercapacitor; neutron irradiation; radiation-induced electric charge Introduction Currently, chemical (lithium) power sources are widely used for small-size equipment. However, these sources have limitations on miniaturization and a narrow range of positive and negative operating temperatures; they require periodic recharging, and their specific capacity does not exceed 1 kW/kg (Maltsev (ed.) 2005, Verner et al. 2008). The most promising sources can be current sources of a constant readiness, based on the direct conversion of nuclear power into electricity, in which the decay of radioactive isotopes leads to a radiation-induced separation of electrical charges (Anufrienko et al. 2006, 2008, Chernov et al. 2010, 2011, 2015, 2016) . The expected characteristics of a current source of this type (Chernov et al. 2015, 2016) significantly exceed those of lithium ones and are characterized by an energy reserve of more than 103 kWh/ kg, maximum power of 25 kW/kg and a minimum volume of 10?2 ? 10?3 cm3. In this case, the service life depends on the half-life of the isotope used, for example, the lifetime of promising isotopes of americium-241 is 460 years and of carbon-14 is 5700 years, respectively. The main application areas of CSRI are microsystem equipment and microelectromechanical systems, facilities in remote and hard-to-reach places operating under extreme conditions, monitoring, communication, and navigation systems. In preliminary studies (Anufrienko et al. 2006, 2008, Chernov et al. 2010, 2011, 2015) , various MDM (metal-dielectric-metal) structures were studied as converters of nuclear energy into electricity. They use the energy of fast particles due to the accumulated energy of secondary electrons emerging from the surface of MDM-structure layers. Calculated and experimental data were obtained on the specific energy, current and voltage under various radiation effects. It is shown that significant efficiency coefficients of radiation energy conversion can be obtained by nanostructuring MDM systems to achieve a larger working surface area of charge separation. Calculations based on the experimental data showed that, for CSRI at an absorbed dose rate of 1 Gy/s from the isotope decaying inside, currents up to 100 ?A arise at interphase areas of 103 ?104 m2 (Chernov et al. 2015) . Such areas are realized in supercapacitors and (...truncated)