Conceptual design of small modular reactor driven by natural circulation and study of design characteristics using CFD & RELAP5 code

Although the current Pressurized Water Reactors (PWRs) have significantly contributed to the global energy supply, PWRs have not been considered as a trustworthy energy solution owing to its several problems; spent nuclear fuels (SNFs), nuclear safety, and nuclear economy. In order to overcome these problems, lead-bismuth eutectic (LBE) fully passive cooling Small Modular Reactor (SMR) system is suggested. It is possible to not only provide the solution of the problem of SNFs through the transmutation feature of LBE coolant, but also increase the safety and economy through the concepts of the natural circulation cooling SMRs. It is necessary to maximize the advantages (safety and economy) of this type of Nuclear Power Plants for several applications in future. Accordingly, objective of the study is to maximize the reactor core power while the limitations of shipping size, materials endurance, long-burning criticality as well as safety under Beyond Design Basis Events must be satisfied. Design limitations of natural circulating LBE-cooling SMRs are researched and power maximization method is developed based on obtained design limitations. It is expected that the results are contributed to reactor design stage with providing several insights to designers as well as the methods for design optimization of other type of SMRs.

Download Full-text

Sensitivity Analysis of the SBLOCA Induced Severe Accident for a Natural Circulation Small Modular Reactors

Volume 6B: Thermal-Hydraulics and Safety Analyses ◽

10.1115/icone26-82267 ◽

2018 ◽

Author(s):

Longze Li ◽

Jue Wang ◽

Yapei Zhang ◽

G. H. Su

Keyword(s):

Sensitivity Analysis ◽

Heat Sink ◽

Natural Circulation ◽

Management Strategies ◽

Severe Accident ◽

Severe Accidents ◽

Small Modular Reactor ◽

Fraction Increase ◽

Crack Position

The natural circulation small modular reactor (NCSMR) is a 330 MW reactor which has no reactor coolant pumps (RCP) and no active safety injection systems at all. The reactor is mainly comprised of the reactor pressure vessel (RPV) with integral pressurize r and steam generator. RPV is enclosed by a vacuumed pressure containment vessel (PCV) and the PCV is submerged in the underground containment pool. A MELCOR model and corresponding input deck are developed for the RPV, PCV, and containment pool. The containment pool takes the role of ultimate heat sink (UHS) in accident situations. The containment pool may crack and leak in some critical accidents as the earthquake, leading to the severe accident of the reactor. A TMI-2 like SBLOCA in the RPV (stuck open RVVs) along with the containment pool crack (loss of ultimate heat sink) is simulated in the work. So me key parameters as the RRVs stuck open fraction, the PCV-SRVs open or not, the containment pool crack position would have large influence on the severe accident sequence. The sensitivity of these parameters to the accident sequence is analyzed in the work. According to the simulation results, the RPV pressure decreased with the RRVs stuck open. The depressurization of RPV accelerated with the RPV-SRV open fraction increase. The PCV pressure increased after that. Two cases as the PCV-SRV open after PCV pressure increase to 5 MPa, and PCV break while the RV d id not open, are analysis. The coolant discharge mass flo wrate in RPV and PCV were different in two cases, leading to the different degradation situation of the core. Since the containment pool is so important for the accident mitigation, sensitivity analysis is done for the containment pool crack position in the pool. The work will be meaningful in gaining an insight into the detailed process involved. One of the final goals of this work would be to identify appropriate accident management strategies and countermeasures for the potential extreme natural hazard induced severe accidents during the design process of NCSMR.

Download Full-text

Conceptual Design and Thermal-Hydraulic Characteristics of Natural Circulation Boiling Water Reactors

Nuclear Technology ◽

10.13182/nt88-a34103 ◽

1988 ◽

Vol 82 (2) ◽

pp. 147-156 ◽

Cited By ~ 17

Author(s):

Yoshiyuki Kataoka ◽

Hiroaki Suzuki ◽

Michio Murase ◽

Isao Sumida ◽

Tetsuo Horiuchi ◽

...

Keyword(s):

Conceptual Design ◽

Natural Circulation ◽

Boiling Water ◽

Boiling Water Reactors ◽

Hydraulic Characteristics ◽

Water Reactors

Download Full-text

Numerical Study of the Gas-Steam Transient Behavior in the Integrated Pressurizer

Volume 2: Plant Systems, Construction, Structures and Components; Next Generation Reactors and Advanced Reactors ◽

10.1115/icone21-15660 ◽

2013 ◽

Author(s):

Lei Wu ◽

Haijun Jia ◽

Yang Liu

Keyword(s):

Numerical Study ◽

Natural Circulation ◽

Transient Behavior ◽

Pressure Change ◽

Liquid Volume ◽

Liquid Temperature ◽

Analysis Model ◽

Transient Characteristics ◽

New Energy ◽

Relap5 Code

The integrated gas-steam pressurizer stabilizes the pressure by compressing the gas and steam mixture. It has attracted much attention because of its simple structure, eliminating heating and spraying of equipment, and preventing the liquid boiling. The NHR series developed by Institute of Nuclear and New Energy Technology in Tsinghua University uses the integrated gas-steam pressurizer. The major loop thermal parameters in NHR series increased progressively, which made it suitable for heating, industrial steam supply and seawater desalinization. In order to ensure the safety of the NHR series major loop system and guarantee the natural circulation capability of the system under high temperature and pressure, the researches on the gas-steam transient characteristics of the integrated gas-steam pressurizer is needed. This paper is mainly about study on transient characteristics of the gas-steam typed pressurizer using the Relap5 code. The classic experiment on the pressure behavior of gas-steam pressurizer during the in-surge performed at MIT is considered as reference objects, and the analysis model is established by using Relap5 code. By comparing the computing results with the MIT experiment data about pressure-time, the applicability of Relap5 code for forecasting the transient behavior of the gas-steam (nitrogen) pressurizer has been verified. The results show that Relap5 code can effectively track the transient behavior of the pressure in the gas-steam pressurizer. In addition, the transient characteristics of the integrated gas-steam pressurizer in the NHR series have been studied. It is founded that the pressure and the liquid temperature adjoining to the pressurizer lag behind the power change in natural circulation loop with integrated gas-steam pressurizer, and the liquid temperature adjoining to the pressurizer and the liquid volume under the pressurizer are the main factors determining the pressure change.

Download Full-text