Reactor with a fast-resonance neutron spectrum, cooled by supercritical-pressure water with a bidirectional coolant flow scheme

Abstract

A scheme for circulating coolant and cooling the core that has advantages over the designs of similar nuclear power systems is proposed for light-water reactors with supercritical coolant parameters and a fast-resonance neutron spectrum. A negative void coefficient of reactivity is obtained for the entire run of a fuel assembly without building a blanket. A more uniform distribution of the energy release over the core volume is achieved without using complicated fuel-enrichment schemes. The nonuniformity of the coolant temperature distribution at the core exit is decreased. The fuel assemblies operate with a much lower temperature drop over the core height. The core has a small reactivity excess on burnup and a BR of about 1, for which the most difficult operating regimes (flooding with cold water) can be handled with standard means (placement of absorbing organs of the safety and control system in ~2/3 of the fuel assemblies).The cost of the equipment of the steam-generating facility comprises 70% of the capital costs of constructing the power-generating units of a nuclear power plant. If the thermal scheme is complicated and the coolant parameters are low, the efficiency of nuclear power plants with VVÉR and RBMK reactors is 33-35% as compared with 50% for thermoelectric power plants. The main problems of new designs are to decrease the specific capital investments in a facility, use simplified schemes and processes, and decrease the construction time while ensuring a high level of safety. Reactors with light-water coolant at supercritical pressure permit solving these problems most completely. A simple thermal scheme (steam from the reactor flows directly onto the turbine) and the elimination of a large amount of expensive equipment (steam generators, pumps, pipelines, second-loop fixtures) decrease the metal content by 60%. High steam parameters (pressure ~25 MPa, temperature 535-545°C) and a single-loop scheme will make it possible to obtain a facility efficiency of 44%. Reducing the required amount of coolant in the core will make it possible to arrange the fuel elements in closely-spaced lattices, and the reactor will have a fast neutron spectrum with a breeding ratio of about 1.The GIF international program for developing generation-IV reactors has been ongoing since 2000. In this program, water-cooled reactors with supercritical-pressure coolant will also be among the advanced future reactors.Japanese scientists are working most intensively in this field. They have proposed reactor designs with a thermal neutron spectrum SCPR [1, 2] and a fast neutron spectrum SCFR [3]. The latter reactor will use a mixed fuel based on depleted uranium oxide and uranium oxide enriched with weapons plutonium. The core consists of 270 fuel assemblies with uranium and plutonium dioxide fuel and 163 fuel assemblies with fuel consisting of depleted uranium (blanket). The reactor vessel and blanket are cooled with 280°C and 25 MPa water moving from top to bottom. At the bottom, the flows are mixed and cool the core in the up c...

Investigation of Stress Corrosion Cracking Resistance of Irradiated 12Cr Ferritic-Martensitic Stainless Steel in Supercritical Water Environment

“…Increasing the coolant pressure to 25 MPa and the reactor outlet coolant temperature to 550 °C increases the thermal efficiency of the units (up to 45%) and reduces the environmental impact by reducing heat losses in the thermodynamic cycle from 67% (WWER-1000) to 55% (WWER SWC) [ 1 , 2 , 3 , 4 , 5 ]. Another advantage of SWCR is the possibility of different active core designs: with a thermal neutron spectrum for operation in an open fuel cycle with UO 2 fuel and with a fast neutron spectrum for operation in a closed fuel cycle with MOX fuel [ 6 ]. So, it is important to identify candidate materials for the SWCR and validate the safety and effectiveness of their use.…”

Determination of the region of vibroacoustic resonances of coolant and fuel assemblies in advanced enhanced-power reactors

“…The computational methods and algorithms which have been developed can be used to make a quantitative evaluation of the range of variation of the natural frequency of the coolant pressure oscillations for VVER-1700 (reactor with a fastresonance neutron spectrum) and VVER-1200 (reactor with a thermal neutron spectrum). The data of [8,9] are used to determine the particulars of the appearance of resonance between the acoustic oscillations of the coolant and the vibrations of the in-vessel apparatus, fuel assemblies, and fuel elements in these reactors as compared with VVER-1000. Diagram showing the cooling of a reactor with a fast-resonance neutron spectrum VVER-1700: 1) safety and control rods; 2) cover; 3) inner cover; 4) vessel; 5) thermal insulation; 6, 7) in and out pipe connections, respectively; 8) core; 9) shaft; 10, 11) descending and ascending sections, respectively; 12) separation shell.…”

“…The thermohydraulic parameters in the fuel assembly model over the height of the core are taken from the data of [9]; the construction and dimensions of the reactor vessel and in-vessel elements, cartogram of the core, and dimensions of the fuel assemblies and fuel elements are taken to be as close as possible to the VVER-1000 characteristics.…”

Supercritical-pressure water cooled thermal reactor with uranium–plutonium–thorium fuel cycle and bidirectional coolant flow articles

“…In a reactor with a thermal neutron spectrum, the cold moderator is confined inside tubes -"water elements" between which the fuel elements, cooled by the ascending coolant, are arranged in a closely spaced lattice. A difficulty is smoothing the energy-release field, since the moderator is substantially heated and its density varies along the height of the core.For reactors with a fast neutron spectrum, it is suggested that a bidirectional cooling scheme be used to smooth the energy release over the core height [3,4].In the present article, we present the results of a physical calculation, performed using different program systems, and a comparative analysis of a reactor with a thermal neutron spectrum with uni-and bidirectional cooling schemes. Uranium-plutonium-thorium fuel loads are considered.…”

“…For reactors with a fast neutron spectrum, it is suggested that a bidirectional cooling scheme be used to smooth the energy release over the core height [3,4].…”