As an important safety assessment tool, PSA plays a very important role in identifying the weak points in Nuclear Power Plants (NPP) design and optimizing plant design. Traditional PSA risk identification is mainly carried out from two dimensions: Core Damage Frequency (CDF) and Large Release Frequency (LRF). In the Generic Design Assessment (GDA) demonstration of UK HPR1000, As Low As Reasonably Practicable (ALARP) concept and Numerical Targets (NTs) are introduced, so the application scope of PSA is expanded. Risk contribution is identified not only from CDF and LRF dimensions, but also from on-site and off-site personnel radiation risk dimensions. Based on the expanded PSA application dimension, the safety level of nuclear power plants can be further improved. This study will give the methodology of PSA application in NTs 5∼9 evaluation, and the identified NPP weak points and related design improvement suggestions of UK HPR1000.
C 14 H 13 N 2 O 6 V, triclinic, P1 (no. 2), a =7.5823(2) Å, b =9.9523(3) Å, c =10.0978(3) Å, a =96.479(2)°, b =102.545(2)°, g =95.128(2)°, V =733.9 Å 3 , Z =2, R gt(F) =0.043, wRref(F 2 ) =0.108, T =296 K. Source of materialThe ligand 3-methoxysalicylalde-2-furoic acid hydrazone (H 2L) was prepared by condensing 3-methoxysalicylalde with 2-furoic hydrazide in ethanol. VO(acac) 2 (0.133 g, 0.5 mmol) was added to the solution of H 2L(0.130 g, 0.5 mmol) dissolved in 5mlmeth-anol and 5mlacetonitrile under continuous stirring. The reaction mixture was stirred for 48 h. The resulting brown solution was filtered off and allowed to evaporate slowly at room temperature. After 8-10days, brown plate crystals suitable for X-ray diffraction analysis were separated. DiscussionThe coordination chemistry of vanadium has received considerable attention due to their applicability in chemistry, biology and medicine. Mononuclear and binuclear vanadium complexes containing acylhydrazone ligands posses various structures and biological activity. The synthesis, characterization and biological activity of these complexes are of growing interest [1][2][3][4][5]. The title complex is amononuclear oxovanadium(V) species. In the crystal structure the hydrazone H 2 Lf unctions as tridentate ligand in the enolate form bonded to the VO 3+ core. The coordination environment of the vanadium atom approximates as quare pyramid. The basal plane is composed of the phenolate O3, the enolate O2 oxygen atom, the imine nitrogen N1 atom and the O1 oxygen atom from am ethoxide ion, with the mean devitation from the plane of 0.027 Å.The vanadyl oxygen atom O4 is in the apical position and it deviates from the basal plane by about 0.364.Å.C helation gives rise to one five-membered (V1−N1− N2−C9−O2) and one six-membered (V1−O3−C2−C1−C7−N1) rings. Both of the rings are slightly folded. The ligand system is practically planar with mean deviation from plane of 0.057 Å,and its angle with the coordination basal plane is 6.2°.The terminal oxo group shows the short bond distance (1.576 Å)being characteristic for V=O double bond [6] and in agreement with the vanadyl group in other vanadium (V) complexes [7,8]. The bond distances V1-O1 (1.808 Å), V1-O2 (1.935 Å)a nd V1-O3 (1.819 Å)are in the range reported in the literature [9]. The bond length of V1-N1 (2.106 Å)issimilar to that in other analogues. N2-C9 (1.305 Å)and C9-O2 (1.307 Å)distances confirm the enolate mode of coordination. There are no obvious hydrogen bond interaction and p-p packing effects observed.
In-vessel Melt Retention (IVR) system is a typical design feature of the the generation III nuclear power plant. In case of severe accident, enough water is injected into the reactor pit to cool the outside of the Reactor Pressure Vessel (RPV) to maintain the integrity of the reactor pressure vessel, so that the core melt is retained in RPV. The design concept of IVR is very meaningful for maintaining the integrity of RPV and reducing the risk of large radioactivity release, but on the other hand, it may also introduce the possibility of inadvertent reactor pit flooding during normal operation, which may threaten the integrity of RPV. At home and abroad, the research on IVR mainly focuses on whether its safety function can be realized, but less attention is paid to its potential negative impact. This paper takes the China generation III reactor with the IVR design feature for the study, carry out the possible inadvertent reactor pit flooding path analysis and frequency analysis. Based on the risk study, put forward the concerns to prevent inadvertent reactor pit flooding, which will provide guide for the subsequent IVR design and optimization.
UK version of the Hua-long Pressurised Reactor (UK HPR1000), designed by China General Nuclear Power Corporation (CGN), has been successfully completed the Generic Design Assessment (GDA), with the issue of a Design Acceptance Confirmation (DAC) from Office for Nuclear Regulation (ONR) and a Statement of Design Acceptability (SoDA) from the Environment Agency on 7 February 2022. In the UK GDA process, one of the main fundamental requirements is that the nuclear safety risk should be reduced to ALARP (As Low As Reasonably Practicable). During the UK HPR1000 design process, Probabilistic Safety Assessment (PSA) has been widely used as a key tool to inform the design and evaluate risk levels, and to demonstrate that the nuclear safety risk has been reduced to ALARP. The process of PSA ALARP demonstration is established in accordance with the methodology that reflects the UK context requirements and consistent with relevant good practice. The process is fully applied by using PSA to systematically review the risk insights and to support other topic areas. After the systematic review of PSA risk insights from internal events Level 1 PSA, internal fire Level 1 PSA, internal flooding Level 1 PSA, external hazards Level 1PSA, external flooding Level 1 PSA, seismic PSA, Spent fuel pool PSA and Level 2 PSA, the related conservatisms, potential design improvements have been identified and addressed. Current UK HPR1000 PSA results and risk insights show that the risk level of UK HPR1000 design is relatively low and the risk of UK HPR1000 design has been reduced to ALARP in GDA stage.
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