Small Modular Pressurized Water Reactor Research Articles

Wavy-attention network for real-time cyber-attack detection in a small modular pressurized water reactor digital control system

Global interest in advanced reactors has been reignited by recent investments in small modular reactors and micro-reactor design. The use of digital devices is essential for meeting the size and modularity requirements of small modular reactor controls. By fully digitizing the small modular reactor control systems, critical information can be obtained to optimize control, reduce costs, and extend the reactor’s lifetime. However, the potential for cyber-attacks on digital devices leaves digital control systems vulnerable. To address this risk, this study presents a novel wavy-attention network for sensor attack detection in nuclear plants. The wavy-attention network comprises stacks of batch-normalized, dilated, one-dimensional convolution neural networks, and sequential self-attention modules, superior to conventional single-layer networks on sequence classification tasks. To evaluate the proposed wavy-attention network architecture, the International Atomic Energy Agency’s Asherah Nuclear Simulator and a false data injection toolbox found in the literature, both implemented in MATLAB/SIMULINK, are utilized. This approach leverages changes in process measurements to identify and classify cyber-attacks on priority signals using the proposed wavy-attention network. Three false data injection attacks are simulated on the simulator’s pressure, temperature, and level sensors to obtain representative process measurements. The wavy-attention network is trained and validated with normal and compromised process variables obtained from the simulator. The performance of the wavy-attention network to discriminate between the reactor states using the test set shows 99% accuracy, as opposed to other baseline models such as vanilla convolution neural networks, long short-term memory networks, and bi-directional long short-term memory networks with 90%, 77%, and 91% accuracy, respectively. An ablation study is also conducted to test the contribution of each component of the proposed architecture. The theoretical framework of the proposed wavy-attention network and its implementation for nuclear reactor digital sensor attack detection are discussed in this paper.

Analysis of hydrogen control in a Small Modular Reactor during TLOFW severe accident

During the Fukushima Daiichi nuclear accident in 2011, hydrogen explosions occurred in all units from Unit 1 to Unit 3. Consequently, one of the lessons learned from the Fukushima Daiichi accident is the necessity of implementing hydrogen control and mitigation strategies for most Nuclear Power Plants (NPPs). This paper focuses on the incorporation of Passive Autocatalytic Recombiners (PARs) during the design phase of a small modular Pressurized Water Reactor (SMR-PWR) project. The numerical analyses are conducted using the MELCOR v. 2.2 code. Two scenarios are compared: the Total Loss of Feed Water (TLOFW) severe accident with and without PARs. Saphiro’s diagram is utilized to investigate whether the mixture's composition (hydrogen, air, steam) is flammable for both scenarios. It has been observed that the inclusion of PARs leads to a reduction in hydrogen risk (detonative or deflagrative) as the final hydrogen concentration values fall below the flammability limit. This study is preliminary, and further research is required.

Neutronic and Proliferation Resistance Analysis of Small Modular Pressurized Water Reactor with Various Fuel Types using SRAC 2006

One strategy for emission reduction in Indonesia is the dedieselization program, replacing diesel power plants with renewables. Pressurized Water Reactor (PWR) type Small Modular Reactor (SMR) is also a consideration. This study aims to compare fuel performance in SMRs. Four fuel types with varying fissile and fertile nuclides but equal fissile mass percentages were assessed: U235- U238, U235-Th232, U233-U238, and U233-Th232, using PIJ SRAC 2006 and JENDL 4.0. Parameters include neutron multiplication factor, conversion ratio, and isotope production. Results indicated that U233-U238 has a highest initial neutron multiplication factor, 1.55. Substituting uranium-238 with thorium-232 boosts neutron flux and conversion, reducing nuclear proliferation risk. While initial neutron multiplication may not be highest, thorium-232 can produce uranium-233 with high initial neutron multiplication factor. This research aids fuel selection for Indonesia SMR dedieselization program.

Reactivity control optimization of boron-free small modular pressurized water reactor with helical-cruciform metallic fuel

Small modular pressurized water reactors have the advantages of small size, modularity, inherent and passive safety, and flexible power generation for a wider range of users and applications. Helical-cruciform metallic fuel has the potential to be applied to small modular pressurized water reactors capable of its axial self-spacing plane, high power density, increasing heat transfer area, and extending the cycle length. A novel boron-free small modular pressurized water reactor NETH-HCF175M design using helical-cruciform metallic fuel is proposed in this paper. The reactivity of the core is completely controlled by burnable absorbers and control rods. Two different geometric structures of separate pins and integral pins are researched. Results indicate that Gd2O3 is a suitable neutron absorbing candidate, while Er shows the best reactivity control effect in the integral pin structure. The separate pin structure with Gd2O3 is selected as the burnable absorber design and the core depletion result shows that the core can achieve a cycle length of about 1360 effective full power days. Control rods are divided into 60 compensating rods and 60 shutdown rods for excess reactivity controlling and shutting the core. The genetic algorithm is applied to the optimization work of layout and concentration design for burnable absorbers and layout of compensating rods. Based on the optimized burnable absorbers and compensating rod designs, excess reactivity can be controlled and the core can achieve criticality at beginning of cycle. The core can be transitioned from hot full power to cold zero power with shutdown rods at BOC, which obtains a shutdown margin more than 3000 pcm. Finally, the physical characteristics of core are analyzed, including depletion simulation, pin power distribution, and reactivity equilibrium. This paper provides an overview and information practical for the reactivity control design of novel SMPWR with high-enrichment and geometric complex helical-cruciform metallic fuel.

Fuel lifetime extension for the KLT-40S small modular reactor by means of thorium-uranium fuel cycle

This paper demonstrates the results of the Monte Carlo simulation conducted with MCU-PTR software for a small modular pressurized water reactor KLT-40S. Four dispersed fuel compositions, (U238 + U235)O2, (U238 + Pu239)O2, (Th232 + U235)O2, and (Th232 + U233)O2, were examined for fuel lifetime and fuel burnup calculations.The transition to the (Th232 + U233)O2 fuel composition extends fuel lifetime by 50% and fuel burnup by 44% at design value of the fuel rod diameter. If the fuel rod diameter for (Th232 + U233)O2 fuel composition is increased to 7.2 mm, fuel lifetime is extended by 105%, and fuel burnup is extended by 38% compared to the design values.

Parametric Study of Thorium Fuel Utilization on Small Modular Pressurized Water Reactors (PWR)

Small Modular Pressurized Water Reactor (PWR) can be used to overcome the problem of electricity shortages in remote areas with fewer populations. These reactors usually use uranium-based fuel. Currently, the use of thorium-based fuels for this type of reactor has received constant attention, leading to several investigations of fuel performance. This study aims to determine the performance of thorium-based fuel in the PWR core at a power level of 300 MWt. The analysis was carried out by varying the percentage of U-233 as fissile material in Thorium (Th-233U)O2 fuel by 3%-8% and Pa-231 variation as burnable poison 0.2%-5%. In addition, analysis of changes in the volume fraction of fuel ranging from 40%-60%, with the type of cladding used in the form of Zirlo. The calculation system uses the SRAC computer code with PIJ and CITATION modules for cell and core calculations, using JENDL-4.0 nuclide data. Parameters analyzed from the fuel cell calculation results are reactor criticality, excess reactivity, and power density profile. The analysis results show that the best fuel performance is found in fuel volume fraction of 60%, U-233 configuration on the fuel of 4-5-6%, and the addition of 2.5% Pa-231. This fuel configuration can achieve cycles of up to 19 years with excess reactivity at BOL of 2.57% dk/k and excess reactivity at EOL of 0.87% dk/k.

Comparison of thorium nitride and uranium nitride fuel on small modular pressurized water reactor in neutronic analysis using SRAC code

Comparison of thorium nitride (ThN) and uranium nitride (UN) fuel on small modular PWR in neutronic analysis has been carried out. PWR in module is one type of reactor that can be utilized because of its small size so that it can be placed on demand. Neutronic calculations were performed using SRAC version 2006, the data library using JENDL 4.0. The first calculation was fuel pin (PIJ) calculation with hexagonal fuel pin cell type. And the second calculation was reactor core (CITATION) calculation using homogeneous and heterogeneous core configurations. ThN and UN fuels use heterogeneous configurations with 3 fuel variations. The reactor geometry was used in two fuels are the same, with diameter and height active core was 300 cm and 100 cm. In this research, Np-237 was added as a minor actinide in the UN fuel to reduce the amount of Np-237 in the world and also reduce the k-eff value. For ThN fuel, Pa-231 also added in the fuel to reduce the k-eff value. The optimum configuration of UN fuel reached when used heterogeneous core configuration case four with percentage of U-235 in F1=5.5 %, F2=7 % and F3=8.5 % also with the addition of Np-237 0.2 % and fuel fraction 56 %. It has a maximum excess reactivity value 12.56 % %∆k/k. And then, the optimum configuration of ThN fuel reached when used heterogeneous core configuration case three with percentage of U-233 in F1=2 %, F2=4 % and F3=6 % with the addition of Pa-231 0.5 % and fuel fraction 53 %. It has a maximum excess reactivity value 7.67 % %∆k/k. The comparison of optimum design of UN and ThN fuel shows that the ThN fuel has the k-eff value closer to critical than UN fuel. Therefore, in this study, ThN fuel is more suitable for use in PWR reactors because it has a small excess value and can operate for 10 years without refueling

The CANDLE burnup strategy applied to small modular pressurized water reactor loading with fully ceramic microencapsulated fuel

Abstract For post-Fukushima nuclear power plants, there has been interested in accident-tolerant fuel (ATF) since it has better tolerant in the event of a severe accident. The fully ceramic microencapsulated (FCM) fuel is one kind of the ATF materials. In this study, the small modular pressurized water reactor (PWR) loading with FCM fuels was investigated, and the modified Constant Axial shape of Neutron flux, nuclide number densities and power shape During Life of Energy producing reactor (CANDLE) burnup strategy was successfully applied to such compact reactor core. To obtain ideal CANDLE shape, it’s necessary to set the infinity or enough length of the core height, but that is impossible for small compact core setting infinity or enough length of the core height. Due to the compact and finite core, the equilibrium state can only be maintained short periods and is not obvious, other than infinitely long active core to reach the long equilibrium state for ideal CANDLE. Consequently, the modified CANDLE shape would be presented. The approximate characteristics of CANDLE burnup are observed in the finite and compact core, and the power density and fuel burnup are selected as main characteristic of modified CANDLE burnup. In this study, firstly, lots of optimization schemes were discussed, and one of optimization schemes was chosen at last to demonstrate the modified CANDLE burnup strategy. Secondly, for chosen compact small rector core, the modified CANDLE burnup strategy is applied and presented. Consequently, the new characteristics of this reactor core can be discovered both in ignition region and in fertile region. The results show that application of CANDLE burnup strategy to small modular PWR loading with FCM fuels suppresses the excess reactivity effectively and reduces the risk of small PWR reactivity-induced accidents during the whole core life, which makes the reactor control more safety and simple.

Development of a thermal-hydraulic analysis code for primary system of an integrated small modular pressurized water reactor

In this study, a thermal-hydraulic analysis code has been developed for primary system of the integrated small modular pressurized water reactor IRIS (International Reactor Innovative and Secure). Numerical model of the primary system has been established, and characteristics of equipment and layout are considered. The sub-channel model is used for performance analysis of hot channel in the core. In modeling of the helically coiled steam generator, effects of secondary flow inside coiled tubes are taken into account. Based on the model established, the simulation code THAS (Thermal-Hydraulic Analysis code of SMRs) has been developed. To benchmark this code, steady state performance of the system has been calculated and compared with design parameters as well as results obtained with RELAP5. Furthermore, transient performance of the system is also simulated and compared with RELAP5. The comparison presents a good agreement, which confirms simulation capacity and accuracy of the THAS code.

Conceptual design of long‐cycle boron‐free small modular pressurized water reactor with control rod operation

Conceptual design of long‐cycle boron‐free small modular pressurized water reactor with control rod operation

An Interval Approach to Nonlinear Controller Design for Load-Following Operation of a Small Modular Pressurized Water Reactor

A pressurized water reactor (PWR) is most suitable for load-following operation because of its self-regulating nature. However, rapid power maneuvering at an enhanced rate is heavily constrained by the overall power coefficient of reactivity which depends on both the reactor neutronics and thermal hydraulics. In this paper, a 100 MWe PWR module with an integrated steam generator, is modeled using the nonlinear equations representing both the neutronics and thermal hydraulics. Such a PWR is typically an integrated structure with a steam generator included in the same casing and can either be connected to the grid or connected with other such modules using a multimodular approach to constitute a Nuclear Steam Supply System (NSSS) driving a common turbine and an alternator. In this paper, Nonlinear Dynamic Inversion (NDI) technique is used to design a controller capable of controlling such a reactor for load-following with frequent changes in demand, in both the modes of operation, namely, reactor-follow-turbine and turbine-follow-reactor. With the assumption that the parameters of the reactor vary within intervals as the power varies, an interval approach coupled with NDI ensures that the controller satisfies the operating constraints. The methodology is established for both the modes with credible real-time Hardware-in-Loop (HiL) simulations.

Neutronic-thermal hydraulic coupling analysis of the fuel channel of a new generation of the small modular pressurized water reactor including hexagonal and square fuel assemblies using MCNP and CFX

The main purpose of this paper is neutronic-thermal hydraulics coupling analysis of the fuel channel of an advanced Small Modular Reactor (SMR), which is nominated as a near term option of the generation IV reactors. The CAREM25 is chosen as the reference SMR. By considering hexagonal and square lattices of the fuel assemblies in the SMR reactor core, neutronic-thermal hydraulic coupling of hot and average fuel channels were conducted via utilizing of the MCNPX and CFX codes. Central fuel assemblies are determined as the hottest fuel assembly in the proposed SMR cores with hexagonal and square fuel assemblies with power peaking factor of 1.778 and 1.674, respectively. The hottest fuel rod power peaking factor is calculated as 1.846 and 1.954 for hexagonal and square fuel channels, respectively. The calculated linear power densities of the hottest and the average fuel rod of hexagonal channels are 20.18(kWm)and10.77(kWm), respectively, as well as of square channels are24.75(kWm) and10.36(kWm), respectively. Results show that the maximum axial power along the fuel rods occurred below the mid-plane of the rod. The ratio of the hot to average rod axial power peaking factor as a safety parameter used to calculate the maximum heat flux in the hottest channel, is calculated close to 2 and 2.4 for the core with hexagonal and square fuel assemblies, respectively. The calculated power peaking factors and linear power densities of fuel rods are in suitable range and in good agreement with PWR safety issues.The maximum temperature of fuel centerline in both types of the proposed SMRs is much lower than that of large PWRs (e.g., 2156 K for hot rod in VVER-1000). Between hexagonal and square fuel assemblies, the hexagonal FAs are preferred because of the two reasons; first, the axial fuel centerline temperature in the hottest hexagonal channel is lower than that of hottest square channel, so it is a good feature with respect of safety margins. Second, the outlet temperatures of the channels in the SMR core with hexagonal FAs are higher than the outlet temperature of the channels in the SMR core with square FAs. Thus the thermal efficiency of the reactor core with hexagonal FAs is more than that of the core with square FAs.

New long-cycle small modular PWR cores using particle type burnable poisons for low boron operation

In this paper, new small long-cycle PWR (Pressurized Water Reactor) cores for low boron concentration operation are designed by employing advanced burnable poison rods (BPRs) in which the BISO (Bi-Isotropic) particles of burnable poison are distributed in a SiC matrix. The BPRs are designed by adjusting the kernel diameter, the kernel material and the packing fraction to effectively reduce the excess reactivity in order to reduce the boron concentration in the coolant and achieve a flat change in excess reactivity over a long operational cycle. In addition, axial zoning of the BPRs was suggested to improve the core performances, and it was shown that the suggested axial zoning of BPRs considerably extends the cycle length compared to a core with no BPR axial zoning. The results of the core physics analyses showed that the cores using BPRs with a B4C kernel have long cycle lengths of ∼4.5 EFPYs (Effective Full Power Years), small maximum CBCs (Critical Boron Concentration) lower than 370ppm, low power peaking factors, and large shutdown margins of control element assemblies.

Neutronic study of a new generation of the small modular pressurized water reactor using Monte-Carlo simulation

Small Modular Reactors (SMRs) are the innovative design of nuclear reactors making remarkable interest during recent years. Since there is not enough available operating experience on SMRs, it might be possible to initiate extensive investigations on these types of reactors for the purpose of improving the current performance level of these systems, significantly. The main purpose of this present study is neutronic study of a typical small modular pressurized water reactor via Monte-Carlo method using the MCNPX code. The CAREM25 is chosen as the reference SMR. The reactor core geometry is simulated and neutronic parameters are visualized and analyzed via high qualified 3-D figures. They are figure out neutronic nature of the chosen case study. They capture the simulation of the reactor core geometry, and skim the neutron flux and power distribution, radial and axial power peaking factors and the influence of the control rods on the thermal flux. Central fuel assembly is determined as the hottest fuel assembly with power peaking factor of 1.778. The hottest fuel rod power peaking factor is calculated as 1.846 in the hottest assembly. The maximum calculated axial power peaking factor of the hot rod is 2.85. Results show that the maximum axial power along the fuel rods occurred below the mid-plane of the rod. The ratio of the hot to average rod axial power peaking factor as a safety parameter used to calculate the maximum heat flux in the hottest channel, is calculated close to 2 in almost 70% of the core height.The core reactivity at cold and hot shut down without safety injections of boron acid is calculated as 0.09712(Δkk) and −0.00103(Δkk), respectively.Results show suitable neutronic behavior and responses during virtual tests and analyses.

Cutback sensitivity test for boron-free small modular PWR

A soluble boron-free small modular pressurized water reactor (SMPWR) uses burnable absorbers (BA) instead of soluble boron to reduce excess reactivity. As a consequence, the fuel cycle length can be shortened by the residual penalty of BA. This paper performs cutback sensitivity tests to extend the cycle length. The influence of the height of the cutback, of the 235U enrichment rate, and of the BA material on the power peaking factor (Fq), the axial offset (AO) and the fuel cycle length is analyzed with the reactor core design system, CASMO-4E/SIMULATE-3 code system.

Boron-free small modular pressurized water reactor design with new burnable absorber

Summary This paper presents a preliminary design of a Small Modular Pressurized Water Reactor (SMPWR) aimed at boron-free operation which can reduce the size of a nuclear power plant (NPP) and the amount of liquid radioactive waste, and also reduce the corrosion issues caused by boric acid in the coolant. The design parameter limits, such as reactivity swing, axial offset (AO), 3D pin peaking factor (Fq), and the required shutdown margin, have been established for the boron-free SMPWR. Furthermore, a new ring type of burnable absorber (R-BA) with Zr–167Er is adopted as a burnable absorber (BA) and HfB2 is adopted as a control rod material to satisfy those design limits without liquid boron. Optimal fuel assemblies (FAs) and loading patterns have been searched through a sensitivity study, and the excess reactivity control capacity and design requirements have been demonstrated to be satisfactory. Copyright © 2016 John Wiley & Sons, Ltd.

Technology Selection for Offshore Underwater Small Modular Reactors

Abstract This work examines the most viable nuclear technology options for future underwater designs that would meet high safety standards as well as good economic potential, for construction in the 2030–2040 timeframe. The top five concepts selected from a survey of 13 nuclear technologies were compared to a small modular pressurized water reactor (PWR) designed with a conventional layout. In order of smallest to largest primary system size where the reactor and all safety systems are contained, the top five designs were: (1) a lead–bismuth fast reactor based on the Russian SVBR-100; (2) a novel organic cooled reactor; (3) an innovative superheated water reactor; (4) a boiling water reactor based on Toshiba's LSBWR; and (5) an integral PWR featuring compact steam generators. A similar study on potential attractive power cycles was also performed. A condensing and recompression supercritical CO2 cycle and a compact steam Rankine cycle were designed. It was found that the hull size required by the reactor, safety systems and power cycle can be significantly reduced (50–80%) with the top five designs compared to the conventional PWR. Based on the qualitative economic consideration, the organic cooled reactor and boiling water reactor designs are expected to be the most cost effective options.

Analyses of the OSU-MASLWR Experimental Test Facility

Today, considering the sustainability of the nuclear technology in the energy mix policy of developing and developed countries, the international community starts the development of new advanced reactor designs. In this framework, Oregon State University (OSU) has constructed, a system level test facility to examine natural circulation phenomena of importance to multi-application small light water reactor (MASLWR) design, a small modular pressurized water reactor (PWR), relying on natural circulation during both steady-state and transient operation. The target of this paper is to give a review of the main characteristics of the experimental facility, to analyse the main phenomena characterizing the tests already performed, the potential transients that could be investigated in the facility, and to describe the current IAEA International Collaborative Standard Problem that is being hosted at OSU and the experimental data will be collected at the OSU-MASLWR test facility. A summary of the best estimate thermal hydraulic system code analyses, already performed, to analyze the codes capability in predicting the phenomena typical of the MASLWR prototype, thermal hydraulically characterized in the OSU-MASLWR facility, is presented as well.

Possible design improvements and a high power density fuel design for integral type small modular pressurized water reactors

The study evaluates potential weaknesses and possible improvements for integral type small modular pressurized water reactor designs. By taking International Reactor Innovative and Secure (IRIS) as the reference design and keeping the power output as the same, a new fuel and reactor design were proposed. The proposed design relocates the primary coolant pumps and the pressurizer outside the reactor pressure vessel (RPV). Three recirculation lines and jet pumps/centrifugal pumps are introduced to provide the coolant circulation similar to Boiling Water Reactor designs. The pressurizer component is expected to be similar to the AP600 design. It is located at one of the recirculation lines. The new fuel assembly adopts 264 solid cylindrical fuel pins with 10 mm diameter and 2.3 m height, arranged at a hexagonal tight lattice configuration. Large water rods are introduced to preserve the moderating power and to accommodate finger type control rods. The resulting fuel can operate with 104.5 kW/l power density while having substantially higher margin for boiling crisis compared to typical large PWRs. Full core neutronic analysis shows that 24-month cycle length and 50 MWd/kg burnup is achievable with a two-batch refueling scheme. Furthermore, the fuel behavior study shows that the new fuel with M5 type Zircaloy cladding show fairly acceptable steady state performance. A preliminary Loss of Coolant analysis shows that the new design could be advantageous over IRIS due to its low ratio of the water inventory below the top of the active fuel to total RPV water inventory. The proposed reactor pressure vessel height and the containment volume are 30% lower than the reference IRIS design.