A Simulation of Small Break Loss of Coolant Accident in Nuclear Heating Reactor Based on RELAP5

2018 ◽  
Author(s):  
Meng Lu ◽  
Heng Xie
Keyword(s):  
Thermal Power ◽  
Heat Removal ◽  
Injection System ◽  
Water Volume ◽  
Nuclear Heating Reactor ◽  
Removal Capacity ◽  
Loss Of Coolant ◽  
Nuclear Heating ◽  
Residual Heat

Nuclear heating reactor is integrated designed without main pump and safety injection system. The loss of coolant accidents are mainly in the form of small break LOCA. As no safety injection system is designed for coolant makeup, the water volume in the reactor vessel is critical since it determines whether the reactor will be submerged during the whole scenario. Therefore, the study on coolant loss in this pool system is indispensable. The RELAP5 code has been developed for best-estimate transient simulation of light water reactor coolant systems during postulated accidents. The long term effect in nuclear heating reactor is important. In this paper we investigated the influential factors on SBLOCA scenario and found the long term residual heat removal capacity is decisive in determining the loss of coolant. The residual heat removal capacity should be greater than 2% of reactor thermal power if ensuring the core submerged in the long run.

scholarly journals Source Term Estimation under the SBLOCA-Induced Severe Accident Condition in the SMART

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Jaehyun Ham ◽  
Sang Ho Kim ◽  
Sung Il Kim ◽  
Byeonghee Lee ◽  
Jong-Hwa Park ◽  
...  
Keyword(s):  
Source Term ◽  
Thermal Power ◽  
Reactor Core ◽  
Heat Removal ◽  
Reactor Vessel ◽  
Severe Accident ◽  
Injection System ◽  
Spray System ◽  
Loss Of Coolant ◽  
Accident Condition

The SMART is a system-integrated modular reactor in which a nuclear steam supply system with a thermal power of 365 MW is contained inside of the reactor vessel. Although the probability is very low, the reactor core can be damaged during a small break loss-of-coolant accident when both the passive safety injection system and the passive residual heat removal system are completely unavailable. In this work, a total of five cases were analyzed considering the reactor vessel condition and the availability of the radioactivity removal tanks and the ancillary containment spray system as containment condition variables using MELCOR code. It was estimated that there is no containment failure based on pressure, hydrogen mole fraction, and ablation depth, so that the release fractions of the 12 classes of fission products in MELCOR were evaluated considering design leak only for all cases. The overall source term of the case in which the integrity of the reactor vessel is maintained by the early initiation of the cavity flooding system was similar to that of the reactor vessel failure case. While the release fraction of cesium to the environment was analyzed to increase when there is no water in the radioactivity removal tanks, the fraction is small enough at which the radioactivity of the released cesium-137 remains well below 100 TBq, a regulatory limit. Moreover, it was found that the source term can be cut in half if the ancillary containment spray system is available. The results of this study verify the safety performance of the SMART under the small break loss-of-coolant severe accident condition with respect to the source term of interest.

AP1000 Passive Residual Heat Removal Heat Exchanger Confirmatory Analysis

2006 ◽  
Author(s):  
Richard F. Wright ◽  
James R. Schwall ◽  
Creed Taylor ◽  
Naeem U. Karim ◽  
Jivan G. Thakkar ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Cooling System ◽  
Heat Removal ◽  
Passive Safety ◽  
Tube Heat Exchanger ◽  
Removal Capacity ◽  
Safety Margins ◽  
Final Design ◽  
Safety Features ◽  
Residual Heat

The AP1000 is an 1100 MWe advanced nuclear power plant that uses passive safety features to enhance plant safety and to provide significant and measurable improvements in plant simplification, reliability, investment protection and plant costs. The AP1000 received final design approval from the US-NRC in 2004. The AP1000 design is based on the AP600 design that received final design approval in 1999. Wherever possible, the AP1000 plant configuration and layout was kept the same as AP600 to take advantage of the maturity of the design and to minimize new design efforts. As a result, the two-loop configuration was maintained for AP1000, and the containment vessel diameter was kept the same. It was determined that this significant power uprate was well within the capability of the passive safety features, and that the safety margins for AP1000 were greater than those of operating PWRs. A key feature of the passive core cooling system is the passive residual heat removal heat exchanger (PRHR HX) that provides decay heat removal for postulated LOCA and non-LOCA events. The PRHR HX is a C-tube heat exchanger located in the in-containment refueling water storage tank (IRWST) above the core promoting natural circulation heat removal between the reactor cooling system and the tank. Component testing was performed for the AP600 PRHR HX to determine the heat transfer characteristics and to develop correlations to be used for the AP1000 safety analysis codes. The data from these tests were confirmed by subsequent integral tests at three separate facilities including the ROSA facility in Japan. Owing to the importance of this component, an independent analysis has been performed using the ATHOS-based computational fluid dynamics computer code PRHRCFD. Two separate models of the PRHR HX and IRWST have been developed representing the ROSA test geometry and the AP1000 plant geometry. Confirmation of the ROSA test results were used to validate PRHRCFD, and the AP1000 plant model was used to confirm the heat removal capacity for the full-sized heat exchanger. The results of these simulations show that the heat removal capacity of the PRHR HX is conservatively represented in the AP1000 safety analyses.

The Application of Heat Pipe Discharge Containment Heat Experimental Study: New Type of Passive Containment Heat Removal System Concept Design

2017 ◽  
Author(s):  
Haiqi Qin ◽  
Daogang Lu ◽  
Shengfei Wang
Keyword(s):  
Conceptual Design ◽  
Nuclear Power ◽  
Large Scale ◽  
Heat Removal ◽  
Operating Conditions ◽  
Concept Design ◽  
Heat Removal System ◽  
Removal System ◽  
Residual Heat

Practice has proved that nuclear power technology development and operation of nuclear power is a clean, safe and large-scale provided stable power. AP1000 uses a large number of passive safety technologies. Passive residual heat removal system is an important part, in the long-term cooling stage of nuclear reactor normal operating conditions or accident conditions, to prevent the core meltdown. The research of this paper is to solve the long-term discharge of residual heat of the containment in the accident condition of nuclear power plant. Based on the passive heat removal system of AP1000, combined with the heat transfer characteristics and advantages of heat pipes, the PRHR system is further improved on the basis of the present situation, and a conceptual design of passive containment residual heat removal system is proposed. In order to further verify the feasibility of the conceptual design, we make a simplified simulation of small containment test bench to carry out experimental verification and give a detailed experimental design.

Thermal Hydraulic Characteristics of the Integral Type Reactor, SMART-P for Validation of the Heat Removal Capability

2006 ◽  
Author(s):  
K. Y. Choi ◽  
S. Cho ◽  
S. J. Yi ◽  
H. S. Park ◽  
N. H. Choi ◽  
...  
Keyword(s):  
System Design ◽  
Heat Removal ◽  
Test Facility ◽  
Integral Type ◽  
Control Rod ◽  
Type Reactor ◽  
Loss Of Coolant ◽  
Heat Removal System ◽  
Removal System ◽  
Residual Heat

The SMART is an integral type reactor with new innovative design features aimed at achieving a highly enhanced safety and improved economics. This paper focuses on the thermal hydraulic experimental program for the development of SMART. Thermal hydraulic responses for the transient operations of the SMART-P are experimentally investigated by using an integral effect test facility. The test facility (VISTA) has been constructed to simulate the SMART-P, which is a pilot plant of the SMART. The VISTA facility is a full height and 1/96 volume scaled test facility with respect to the SMART-P with a power of 65MWt. In the present study, the VISTA facility was subjected to various transient conditions in order to understand the thermal-hydraulic responses following transients and finally to verify the system design of the SMART-P. Several experiments, including a heatup, a main coolant pump (MCP) speed change, and a power change, have been performed to investigate the heat transfer characteristics and the natural circulation performance of the primary system and the Passive Residual Heat Removal System (PRHRS) of the SMART-P by using the VISTA facility. Performance tests of a passive residual heat removal system (PRHRS) have also been carried out for its design optimization. Besides, several design basis accidents, such as an increase or a decrease of the feedwater flow, a loss of coolant flow, a control rod withdrawal, and a limited case of a loss of coolant accident (LOCA) on the line to the gas cylinder are under investigation in order to understand the thermal-hydraulic responses and finally to verify the system design of the SMART-P. Especially, the details of the experimental results for a loss of feedwater accident and a power increase accident due to a control rod withdrawal are explored in the present study.

Study on Measures During Loss of Normal Feedwater Accident for AP1000 NPP in Lower Power Operation

2020 ◽  
Author(s):  
Baisong Ma ◽  
Zhengqiang Miao ◽  
Yaping Zhuang ◽  
Weili Hou
Keyword(s):  
Heat Removal ◽  
Heat Sinks ◽  
Effective Measure ◽  
Lower Power ◽  
Removal Capacity ◽  
Feedwater Pump ◽  
Automatic Reactor ◽  
Power Operation ◽  
Loop 2 ◽  
Residual Heat

Abstract If an accident occurred in a plant in lower power operation, a series of problems could be caused by low residual heat and excessive removal capability of heat sinks. Taking a real accident as example, this paper discussed how to deal with loss of normal feedwater in AP1000 NPP during lower power operation. The level of Steam Generators (SG) will be rapidly reduced in case of Main Feedwater loss, and Startup Feedwater pump will start. If the reactor is not shut down immediately, the Startup Feedwater will not be enough to prevent SG level from falling, and automatic reactor trip will be inevitable. Therefore, in event of loss of Main Feedwater which cannot be recovered instantly, the reactor should be shut down manually to maintain SG level as high as possible. Appropriate measures should be taken to avoid excessive cooling after trip. Attention should be paid to SG level and feedwater flow to avoid Passive Residual Heat Removal Heat Exchanger (PRHR HX) actuation during regulating Startup Feedwater. Otherwise, PRHR HX may be actuated unexpectedly. With Reactor Coolant Pumps operating, PRHR HX heat removal capacity is strong. The Cold Leg temperature will drop rapidly because of PRHR HX and other heat sinks. In this case, the most effective measure to stabilize temperature of Cold legs is to isolate Streamline. Otherwise, structure integrity of the Reactor Pressure Vessel (RPV) will be challenged under Pressurized Thermal Shock (PTS) due to rapid drop of Cold leg temperature. In order to alleviate PTS, depressurization shall be performed and further cooling shall be suspended. Since PRHR HX is only connected to Loop 1, coolant in Hot Leg of Loop 2 is still kept at high temperature. Therefore, necessary measures shall be taken to prevent coolant flash in Loop 2 during the process of depressurization, which may fill the Pressurizer up with water. The RPV Head Vent valves perform safety-related function by preventing Pressurizer overfill in certain design basis events in AP1000 NPP. However, emergency letdown by opening the valves cannot effectively reduce Pressurizer level when coolant flashed in Loop 2. Because of mitigating PTS, opening RPV Head Vent valves, and steam condensation in Loop 2, the subcooling of the coolant at the core outlet is likely to drop below 6 °C or even 0 °C.

Experimental Research on Characteristics of Passive Residual Heat Removal System for Small Modular Reactors Under the Station Blackout Accident

2016 ◽  
Author(s):  
Xiaodong Lu ◽  
Chuanxin Peng ◽  
Yan Zhang ◽  
Xuesong Bai ◽  
Yuanfeng Zan ◽  
...  
Keyword(s):  
Experimental Research ◽  
Heat Removal ◽  
Injection System ◽  
Primary System ◽  
Water Tank ◽  
The Core ◽  
Station Blackout ◽  
Heat Removal System ◽  
Removal System ◽  
Residual Heat

An experimental research on performance characteristics of passive residual heat removal system (PRHRS) for the small modular reactor designed by Nuclear Power Institute of China (NPIC) under the station blackout accident was performed in the CREAS facility, which consists of the primary system, the secondary system, the passive safety injection system, the passive residual heat removal system, the overpressure protection system and the auxiliary system. The experimental results show that, after the station blackout accident, a stable two-phase natural circulation between the steam generators and the heat exchanger in the PRHRS was established with a mass flow of 0.4T/h, thus the heat from the primary system was removed to the water in the containment water tank (CWT). During this period, the core decay residual heat and the sensible heat were removed from the primary system by the PRHRS effectively. The cold water from the core makeup tanks was injected into the reactor pressure vessel for core cooling. The peaked primary pressure was 16.3MPa and less than relief valve opening pressure 16.9MPa. In addition, the average coolant temperature of the reactor core reduced below 483 K, and the reactor operated safely.

Sign in / Sign up

Export Citation Format

Share Document