Capacity limitation of nuclear units in grid based on analysis of frequency regulation

The increasing capacity of nuclear units in power grid poses threat to system stability and security. Load disturbance may cause overspeed of the units and trigger the overspeed protection controller （OPC）. Repeat- ing actions of valves have a strong impact on the security of the equipment and may result in a collapse of the power system. Based on the analysis of frequency regulation, mathematic models for nuclear units in the grid are established in this paper to simulate the dynamic process when load disturbance occurs. The critical action of the OPC is proposed as the constraint of safe operation for the units. The relationship between different styles of frequency regulation and the allowable capacity of the nuclear units in the grid is discussed. This research can help to estimate the capacity limitation of nuclear units in the grid.

Prospects of Technological Improvement of Nuclear and Environmental Safety of World Energy

Today, the most urgent problem of the existing and future nuclear power industry is to ensure the nuclear and environmental safety of the operation of nuclear power reactor units (NPPs) and nuclear power plants (NPPs). It is solved thanks to the application of deeply echeloned protection and an anti-accident complex of methods and means for effective control of the operation of active reactor zones (AZR). However, the danger of existing NPPs in the world from time to time manifests itself in the form of severe post-project accidents and catastrophes with the release into the environment of a significant amount of radioactive materials dangerous for all living things. The results of the analysis show that the unconditional fulfillment of the main requirements of nuclear environmental safety and biocompatibility is possible only in the so-called wave nuclear reactor of the G-V generation, which, unlike reactors of the previous generations III, II+ and IV, does not require supercritical loading of the core with nuclear fuel. In the active zone of this reactor, nuclear-physical processes governed by physical law are implemented, which exclude the operator’s participation in regulating the reactivity of the reactor’s active zone, which makes it the reactor with the highest level of nuclear and environmental safety today, which is based on the principles of so-called internal safety, free from the human factor. The possibility of burning nuclear fuel based on U238 and Th232 in it expands the reserves of energetic nuclear fuel almost to inexhaustibility. The technology of nuclear reactors of the G5 generation through the secondary use of spent irradiated nuclear fuel (SNF) for the production of energy and energy raw materials with simultaneous burning of it to an environmentally safe state is able to quickly reduce the available stocks and further production of dangerous SNF, guarantee the nuclear and environmental safety of NPPs with reactors G5 and to technologically make nuclear post-project accidents and disasters impossible at the level of physical law with the complete elimination of the human factor.

Localized Manufacture of Nuclear Power Equipment in China

The paper expresses the view that China's essential way out for developing nuclear power lies in localization of manu facture, based on her technical level and capability in designing and manufacturing nuclear power equipment. Moreover, the paper opines that domestically manufactured nuclear power equipment has a certain competitive potential with respect to quality and price, the crux lying in the neces sity of reforming the management system of nuclear power.

Calculations Energy of the (<i>nl</i>²) ¹<i>L^π</i>Doubly Excited States of Two-Electron Systems via the Screening Constant by Unit Nuclear Charge Formalism

In this work, the total energies of doubly excited states (ns2) 1Se, (np2) 1De, (nd2) 1Ge, (nf2) 1Ie, (ng2) 1Ke, and (nh2) 1Me of the helium isoelectronic sequence with Z ≤ 10 are calculated in the framework of the variational method of the Screening Constant by Unit Nuclear Charge (SCUNC). These calculations are performed using a new wavefunction correlated to Hylleraas-type. The possibility of using the SCUNC method in the investigation of high-lying Doubly Excited States(DES) in two-electron systems is demonstrated in the present work in the case of the (nl2) 1Lπ doubly excited states, where accurate total energies are tabulated up to n = 20. All the results obtained in this paper are in agreement with the values of the available literature and may be useful for future experimental and theoretical studies on the doubly excited (nl2) 1Lπ states of two-electron systems.

Reliability prediction and its validation for nuclear power units in service

In this paper a novel method for reliability prediction and validation of nuclear power units in service is proposed. The equivalent availability factor is used to measure the reliability, and the equivalent availability factor deducting planed outage hours from period hours and maintenance factor are used for the measurement of inherent reliability. By statistical analysis of historical reliability data, the statistical maintenance factor and the undetermined parameter in its numerical model can be determined. The numerical model based on the main- tenance factor predicts the equivalent availability factor deducting planed outage hours from period hours, and the planed outage factor can be obtained by using the planned maintenance days. Using these factors, the equivalent availability factor of nuclear power units in the following 3 years can be obtained. Besides, the equivalent availability factor can be predicted by using the historical statistics of planed outage factor and the predicted equivalent avail- ability factor deducting planed outage hours from period hours. The accuracy of the reliability prediction can be evaluated according to the comparison between the predicted and statistical equivalent availability factors. Furthermore, the reliability prediction method is validated using the nuclear power units in North American Electric Reliability Council （NERC） and China. It is found that the relative errors of the predicted equivalent availability factors for nuclear power units of NERC and China are in the range of-2.16% to 5.23% and -2.15% to 3.71%, respectively. The method proposed can effectively predict the reliability index in the following 3 years, thus providing effective reliability management and mainte- nance optimization methods for nuclear power units.

Variational Calculations of Energies of the (2<i>snl</i>) ^1,3<i>L^π</i>and (2<i>pnl</i>) ^1,3<i>L^π</i>Doubly Excited States in Two-Electron Systems Applying the Screening Constant per Unit Nuclear Charge

In this paper, resonance energies and excitation energies of doubly 2sns 1,3Se, 2snp 1,3P0, 2pnp 1,3De, 2pnd 1,3F0 and 2pnf 1,3Ge excited states of the helium isoelectronic sequence with Z ≤ 10 are calculated. Calculations are carried out in the framework of the variational procedure of the formalism of the Screening Constant per Unit Nuclear Charge (SCUNC). New correlated wave function of Hylleraas type is used. Precise resonance and excitation energies are tabulated and good agreement is obtained when a comparison is made with available literature values.

Protective Effects of Calpain Inhibition on Neurovascular Unit Injury through Downregulating Nuclear Factor-KB- related Inflammation during Traumatic Brain Injury in Mice

Background： In addition to neurons, all components of the neurovascular unit （NVU）, such as glial, endothelial, and basal membranes, are destroyed during traumatic brain injury （TBI）. Previous studies have shown that excessive stimulation ofcalpain is crucial for cerebral injury after traumatic insult. The objective of this study was to investigate whether calpain activation participated in NVU disruption and edema formation in a mouse model of controlled cortical impact （CCI）. Methods： One hundred and eight mice were divided into three groups： the sham group, the control group, and the MDL28170 group. MDL28170 （20 mg/kg）, an efficient calpain inhibitor, was administered intraperitoneally at 5 rain, 3 h, and 6 h after experimental CCI. We then measured neurobehavioral deficits, calpain activity, inflammatory mediator levels, blood-brain barrier （BBB） disruption, and NVU deficits using electron microscopy and histopathological analysis at 6 h and 24 h after CCI. Results： The MDL28170 treatment significantly reduced the extent of both cerebral contusion （MDL28170 vs. vehicle group, 16.90 ± 1.01 mm3 and 17.20±1.17 mm3 vs. 9.30 ± 1.05 mm^3 and 9.90 ± 1.17 mm3, both P 〈 0.001 ） and edema （M DL28170 vs. vehicle group, 80.76 ± 1.25% and 82.00 ± 1.84% vs. 82.55 ± 1.32% and 83.64 ± 1.25%, both P 〈 0.05）, improved neurological scores （MDL28170 vs. vehicle group, 7.50 ±0.45 and 6.33 ±0.38 vs. 12.33 ± 0.48 and 11.67±0.48, both P 〈 0.001）, and attenuated NVU damage resulting （including tight junction （TJ）, basement membrane, BBB, and neuron） from CCI at 6 h and 24 h. Moreover, MDL28170 markedly downregulated nuclear factor-κB-related inflammation （tumor necrosis factor-α [TNF-α]： MDL28170 vs. vehicle group, 1.15 ± 0.07 and 1.62± 0.08 vs. 1.59±0.10 and 2.18± 0.10, both P 〈 0.001 ： inducible nitric oxide synthase： M DL28170 vs. vehicle group, 4.51± 0.23 vs. 6.23± 0.12, P 〈 0.001 at 24 h; intracellular adhesion molecule- I ： MDL28170 vs. vehicle group, 1.45± 0.13 vs. 1.70 ± 0.12, P 〈 0.01 at 24 h） and lessened both myeloperoxidase activity （MDL28170 vs. vehicle group, 0.016± 0.001 and 0.016± 0.001 vs. 0.024± 0.001 and 0.023 ± 0.001, P 〈 0.001 and 0.01, respectively） and matrix metalloproteinase-9 （MMP-9） levels （MDL28170 vs. vehicle group, 0.87±0.13 and 1.10 ± 0.10 vs. 1.17 ± 0.13 and 1.25 ± 0.12, P 〈 0.001 and 0±05, respectively） at 6 h and 24 h after CCI. Conclusions： These findings demonstrate that MDL28170 can protect the structure of the NVU by inhibiting the inflammatory cascade, reducing the expression of MMP-9, and supporting the integrity of TJ during acute TBI.

Fruitless Nuclear Talks Both Iran and the United States choose to play hardball on the nuclear issue

The most recent negotiations on the Iranian nuclear issue ended without agreement on January 22 in Istanbul. Iran was on one side of the negotiating