[en] Compared to the standard Cu(In,Ga)Se${}_2$ (CIGSe) solar cells with a 2-3 μm thick absorber, ultrathin CIGSe SCs with less than 500 nm absorber thickness have the advantages of high-volume efficiency and less raw materials consumption. However, the reduced thickness of CIGSe causes insufficient light absorption and hinders the achievement of high efficiency for the ultrathin solar cells. Light trapping nanoparticles (NPs) can increase light absorption in solar cells. In addition, if the opaque Mo back contact was replaced with a transparent conductive material, the NPs can trap the light incident from the front and rear side simultaneously, which results in a bifacial semi-transparent ultrathin (BSTUT) CIGSe solar cell. In${}_2$O${}_3$: Sn (ITO) has good conductivity and relative high transparency, which fits the requirements of the back contact for BSTUT CIGSe solar cells. This thesis optimizes the front and rear photovoltaic (PV) performance of the ITO-based BSTUT CIGSe solar cells under three aspects, namely Na doping, back contact interface modification and light management. Firstly, four different Na doping methods are compared to decide about the optimal strategy for ultrathin CIGSe on ITO substrates. The four methods are Na diffusion from soda-lime glass (SLG), a NaF precursor, NaF post-deposition treatment (PDT), and a NaF precursor combined with PDT. When comparing the PV performance of the samples with different Na incorporation methods, the solar cells with NaF PDT doping exhibit the maximum enhancement compared to the reference (Na-free solar cell). In addition, the NaF PDT dose is optimized in detail and the resulting samples are characterized with multiple methods to explore the working mechanism of NaF PDT and the potential efficiency of BSTUT CIGSe solar cells. The NaF PDT mainly increases the doping density N${}_A$ in the CIGSe absorber and enlarges the contact potential difference V${}_D$ at the CIGSe/CdS interface. The NaF PDT can also increase the recombination velocity S${}_b$ and reduce the effective back barrier E${}_{CIGSe/ITO}$ at the CIGSe/ITO interface. Combining those two effects, the NaF PDT levels up the open circuit voltage V${}_{oc}$ of the solar cells, even though the short circuit current density j${}_{sc}$ is slightly decreased. We also verify this working mechanism of NaF PDT via SCAPS simulation. The average optimal efficiency Eff of the solar cells is 12.1% with 622 mV V${}_{oc}$, 29.6 mA/cm${}^2$ j${}_{sc}$, and 65.6% fill factor FF. Secondly, SiO${}_2$ point contacts are integrated at the CIGSe/ITO interface to modify the S${}_b$ at the back interface. For comparison, we use Mo back contacts as references for the SiO${}_2$ passivation effects. Consistent with our previous work, the point contacts increase the PV performance of the Mo-based solar cells. However, SiO${}_2$ passivation deteriorates the V${}_{oc}$ of our ITO-based ultrathin CIGSe solar cells. SCAPS simulations suggest that the barrier height E${}_h$ at the CIGSe/ITO interface decides about the effect of passivation (decreasing S${}_b$) of SiO${}_2$ for the ultrathin CIGSe SCs. According to the simulations, a decreasing S${}_b$ increases the effective barrier height E${}_{h,e}$ when E${}_h$ > 0.17 eV (Schottky-like contact), which means passivation is detrimental for the V${}_{oc}$ of the ultrathin CIGSe solar cells. The CIGSe/ITO interface is a Schottky-like contact, so the SiO${}_2$ point contacts decrease the performance of the ITO-based BSTUT CIGSe solar cells. On the contrary, a decreasing S${}_b$ increases the collection efficiency of photogenerated carriers when E${}_h$< 0.17 eV (quasi-Ohmic contact), so passivation benefits the solar cells. The decreased S${}_b$ increases the E${}_{h,e}$ slightly, but the overall E${}_h$ is small for the solar cells with a quasi-Ohmic contact. The improved collection efficiency of the photogenerated carriers dominates the passivation effects and benefits the Eff of the solar cells. The CIGSe/Mo interface reveals a quasi-Ohmic back contact, so the passivation increases the Eff of Mo-based ultrathin CIGSe SCs. Thirdly, the front and rear efficiency of BSTUT CIGSe solar cells are optimized using different substrates (SLG and alkali-free pgo glass), ITO thicknesses (100-400 nm) and various NaF PDT doses (0-8 mg). SLG-based solar cells show better front PV performance due to the extra incorporation of Na in the CIGSe co-evaporation process. However, solar cells on pgo glass show higher efficiency under rear illumination because alkali-free glass has a higher transparency than SLG, especially in the long wavelength range. The thicker ITO increases both the front and rear V${}_{oc}$ of the solar cells due to the Burstein-Moss shift in the ITO layer, which decreases the valence band offset ΔE${}_v$ at the CIGSe/ITO interface. However, the rear Eff is evened for solar cells on different thicknesses of ITO because thicker ITO also induces more sever parasitic absorption and leads to a lower rear j${}_{sc}$. For BSTUT CIGSe solar cells with different NaF PDT doses, the rear PV performance trend is similar to the one under front illumination. The solar cell with the optimal conditions (300 nm ITO, 4 mg NaF PDT) achieves 11.8% front Eff and 6.4% rear Eff. Fourthly, SiO${}_2$ nanoparticles (NPs) are inserted at the CIGSe/ITO interface to enhance the overall light absorption of BSTUT CIGSe solar cells. The NPs induce waveguide modes and enhance front and rear absorption in the ultrathin CIGSe layer. The NPs also induce jet-like forward scattering, which further increases the collection efficiency of photogenerated carriers under the rear illumination. Compared to the references, the front j${}_{sc}$ increases by 4.1-4.4 mA/cm${}^2$ and the rear j${}_{sc}$ by 6.4-7.4 mA/cm${}^2$ for the BSTUT CIGSe solar cells with SiO${}_2$ NPs. The front and rear V${}_{oc}$ gain of the solar cells with NPs can be quantitatively estimated by the relation between j${}_{sc}$ and V${}_{oc}$, which means the passivation effects of the SiO${}_2$ NPs are trivial compared to the dominating light trapping effects. Compared to state-of-the-art Mo-based ultrathin CIGSe solar cells (15%), our BSTUT CIGSe solar cells still have room for performance improvement, especially in V${}_{oc}$. The record V${}_{oc}$ is 733 mV for Mo-based and 635 mV for our ITO-based ultrathin CIGSe SCs. For the j${}_{sc}$, however, the record-high j${}_{sc}$ is 26.4 mA/cm${}^2$ for Mo-based and 31.1 mA/cm${}^2$ (front illumination) for our ITO-based SCs with light trapping SiO${}_2$ NPs, which shows an advantage of the BSTUT CIGSe solar cells. The bifacial Eff is 15.0% from summing up 100% front and 30% rear Eff of our best solar cell, which is close to the 15.2% record of the Mo-based ultrathin CIGSe solar cells. The findings in this thesis can help exploit solar energy with higher efficiency and lower fabrication cost. A summary and outlook will be presented at the end about how the efficiency of BSTUT CIGSe SCs could be further optimized.

[en] The dynamical model of full-range feedback has been proposed and the method to determine the dynamical parameters of slow components in power feedback for individual operation cycles of the IBR-2 pulsed reactor has been studied. Using the quasistationary equation of reactivity balance, the total effect of power feedback which is the sum of fast and slow components of reactivity change has been calculated. The shape of curves of this effect shows that the dynamical model of power feedback in the IBR-2 pulsed reactor consists of three components: a proportional block and two inertial blocks of slow action (a faster block with a positive transfer coefficient and a time constant of several tens of hours). The parameters of slow dynamical process have also been determined. Curves of reactivity change obtained from the model are in good agreement with the ones from the experiment

[en] The investigation of the dependence of main fast reactivity effects of the IBR-2 pulsed reactor, i.e. isothermal effect, flow effect and effect of fast power feedback, on the energy production has been carried out. It has been shown that the main fluctuations of reactivity are correlated with the random change of the temperature of sodium. The absolute isothermal coefficient of reactivity weakly increases with the power production (by 20% during the whole operation time of the reactor). The fast power reactivity coefficient has decreased practically by a factor of 6 from -12β_p/MW (in 1982, the start-up of the reactor) to -2 β_p/MW (in 2006, the stop of operation) and has a complicated dependence on the energy production. It has been shown that the flow fluctuation of coolant sodium through the core is small and influences weakly the random change of reactivity. The total sodium flow effect does not practically change with the power production

[en] The influence of shut-down during the operation on the power feedback reactivity change with the dynamics of the IBR-2 fast pulsed reactor has been considered. The investigation result has shown that shapes of reactivity curves are related to the time from the beginning of the reactor cycle, to the duration after the shut-down, and to the number of shut-down events during the cycle of the reactor. It has been shown that the reactivity effects due to the shut-down appeared during 2 days after the shut-down and after then disappeared. Total reactivities after the shut-down events vary between +0.12 and -0.05 % Δk/k. In many practical cases, the negative range on reactivity curves ('pit') after the shut-down events is formed and its duration and depth are related to the operation time after the shut-down and to the moment of the shut-down from the beginning of the reactor cycle. The depth of 'pit' may reach 0.05% Δk/k and its duration varies between a few hours and several tens of hours. The knowledge of the reactivity change after the shut-down allows the consequence of various accidental situations to be explained and the operator to foresightly predict the reactor state during the following power operation

[en] From the analysis of operation data of the IBR-2 pulsed reactor in the period 1982-2006 the dependence of extra reactivity as a function of energy production of the reactor has been obtained. It shows that at the beginning of the reactor operation in addition to the pure burn-up effect, there is also a positive effect probably related to the densification of fuel and structural changes of materials in the core. The effect decreases with time and tends to zero. Only the effect of pure burn-up remains after the 40000 MW·h burn-up, and from this point the extra reactivity is linearly decreased with the coefficient k_B=-4.2975·10^-5%/MW·h. The formula to calculate the energy production coefficient of reactivity at any time of the reactor operation has also been obtained. The energy production coefficient of reactivity consists of two components: the coefficient of pure burn-up and additional positive coefficient of reactivity

[en] The program at the Shanghai Institute of Nuclear Research has been put in practice since the middle of 1960s for the development of cyclotron-produced radiopharmaceuticals and tritium compounds to meet the needs of modern biomedical practice. The method of production, the quality control and fundamental pharmacology have been studied, and radionuclides and labelled compounds have been provided for users primarily for investigation. The domestically made 1.2m cyclotron in the SINR is capable to produce the extracted beams of 16 MeV deuteron, 32 MeV alpha and 8 MeV proton particles at 20-50 μA. For the production of radionuclides, (d,p), (d,n), (d,2n), (d,α), (α,2n) and (p,n) reactions are used, but alpha and deuteron are predominant. More than 20 radionuclides have been made. They are Na-24, K-42, As-74, Hg-197m, Sr-85, Rb-86, Cu-64, Zn-65, Ga-67, In-111, Tl-200, Tl-201, Tl-202, Co-56, Co-57, Ge-68, Mn-54, Na-22, Be-7, Ga-66, Ga-68, C-11, Cu-61 and I-123. The establishment of the special irradiation facility, target system, rapid radiochemistry as well as quality control has been achieved. The production of injectable solution, tritium-labelled compounds and others is reported. (Kako, I.)

[en] A simple lumped parameter model is established to investigate the performance of a solar powered adsorption air conditioning system driven by flat-type solar collectors with three different configurations of glazes: (i) single glazed cover; (ii) double glazed cover and (iii) transparent insulation material (TIM) cover. The dynamic performance of a continuous adsorption cycle using a double adsorber along with heat recovery is measured in terms of the temperature histories, gross solar coefficient of performance and specific cooling power. Also, the influences of some important design and operational parameters on the performance of the system are studied. It is found that the chosen three types of collector configurations make no big difference on the performance, but the adsorbent mass and lumped capacitance have significant effects on the system performance as well as on the system size. Simulation results indicate that the effect of overall heat transfer coefficient is not predominant if the cycle duration is longer. Also, there exists an optimum time to initiate the heating of the adsorbent bed in a day's operation

[en] Analysis of the relationship between the parameters of slow power feedback and power production in the pulsed fast reactor IBR-2 has been accomplished. The investigation result has shown that unlike the parameters of fast power feedback, the parameters of slow dynamics are not related to energy production and have considerable noise components. This is caused by the fact that the slow dynamics of the reactor is generated by the processes in the structural components around the reactor vessel, in which relatively mild radiation, thermal and mechanical conditions are observed. The most possible causes of the random change in the parameters of slow dynamics from one reactor cycle to another are the irreversibility of displacement of the stationary reflectors, change in the parameters of the cooling systems of the stationary reflectors. This randomness in the dynamics of the reactor does not influence the reliability and safety of the reactor

[en] For the nuclear power industry, due to characteristics of its own, its economy is quite different from that of the traditional fossil-fuel power. This paper studied the basic characteristics of the nuclear power economy and the status of economy of domestic nuclear power, and analyzed the main ways to improve the nuclear power economy. (authors)

[en] Ionic solids MgO, CaO, and Fe₂O₃ exchange surface and lattice oxide anions with H₂¹⁸O as monitored by pulsed reactor-GC-MS studies. Depending on the temperature, the process can be controlled to exchange only OH, or additional surface lattice O^2-, or additionally, interior lattice O^2- (up to 16 layers deep). Exchange of surface oxide has an activation energy 5 times lower than exchange of bulk-lattice oxide, and the latter is probably controlled by E_a(diffusion). High surface area, small particles size MgO samples exchange most readily. Exchange studies with D₂O have shown that surface OH can be quantitated by the same pulsed reaction-GC-MS technique. These experiments have allowed the synthesis of isotopically labeled Mg¹⁸O, which has proven useful for clarifying surface adsorption/decomposition chemistry. An example is given where the Mg¹⁸O yielded labeled formic acid in the surface decomposition of an organophosphorus compound, proving that surface and lattice oxide can take part in such adsorption/decomposition processes. 34 refs,. 5 figs., 3 tabs