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

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.

Offshore Small Modular Reactor (OSMR): An Innovative Plant Design for Societally Acceptable and Economically Attractive Nuclear Energy in a Post-Fukushima, Post-9/11 World

2014 ◽  
Author(s):  
Jacopo Buongiorno ◽  
Michael Golay ◽  
Neil Todreas ◽  
Angelo Briccetti ◽  
Jake Jurewicz ◽  
...  
Keyword(s):  
Transmission Line ◽  
Deep Water ◽  
Heat Sink ◽  
Nuclear Energy ◽  
Severe Accident ◽  
Plant Design ◽  
Cooling Systems ◽  
Physical Protection ◽  
Severe Accidents ◽  
Small Modular Reactor

The potential for major gains in safety, physical protection and economics of nuclear energy exists through the development of a floating Offshore Small Modular Reactor (OSMR). This is a plant that can be entirely built (and decommissioned) as a floating rig in a shipyard, floated to the operating site (within 8–15 km of the coast), anchored in relatively deep water (i.e., ∼100 m), and connected to the grid via an underwater transmission line. The OSMR design presented here features innovative passive and indefinite emergency core and containment cooling systems that eliminate the loss of ultimate heat sink accident, thus decreasing the likelihood of severe accidents. Furthermore, the OSMR containment design and back-up venting procedures effectively eliminate the threat of serious land contamination, should a severe accident actually occur.

Study on Cooling Process in a Reactor Vessel of Sodium-Cooled Fast Reactor Under Severe Accident: Velocity Measurement Experiments Simulating Operation of Decay Heat Removal Systems

2020 ◽  
Author(s):  
Mitsuyo Tsuji ◽  
Kosuke Aizawa ◽  
Jun Kobayashi ◽  
Akikazu Kurihara ◽  
Yasuhiro Miyake
Keyword(s):  
Natural Circulation ◽  
Heat Removal ◽  
Reactor Vessel ◽  
Severe Accident ◽  
Decay Heat ◽  
The Core ◽  
Severe Accidents ◽  
Piv Measurement ◽  
Image Velocimetry ◽  
Experimental Apparatus

Abstract In Sodium-cooled Fast Reactors (SFRs), it is important to optimize the design and operate decay heat removal systems for safety enhancement against severe accidents which could lead to core melting. It is necessary to remove the decay heat from the molten fuel which relocated in the reactor vessel after the severe accident. Thus, the water experiments using a 1/10 scale experimental apparatus (PHEASANT) simulating the reactor vessel of SFR were conducted to investigate the natural circulation phenomena in a reactor vessel. In this paper, the natural circulation flow field in the reactor vessel was measured by the Particle Image Velocimetry (PIV) method. The PIV measurement was carried out under the operation of the dipped-type direct heat exchanger (DHX) installed in the upper plenum when 20% of the core fuel fell to the lower plenum and accumulated on the core catcher. From the results of PIV measurement, it was quantitatively confirmed that the upward flow occurred at the center region of the lower and the upper plenums. In addition, the downward flows were confirmed near the reactor vessel wall in the upper plenum and through outermost layer of the simulated core in the lower plenum. Moreover, the relationship between the temperature field and the velocity field was investigated in order to understand the natural circulation phenomenon in the reactor vessel. From the above results, it was confirmed that the natural circulation cooling path was established under the dipped-type DHX operation.

scholarly journals RESULTS OF A PHENOMENA IDENTIFICATION AND RANKING TABLE (PIRT) EXERCISE FOR A SEVERE ACCIDENT IN A SMALL MODULAR HIGH-TEMPERATURE GAS-COOLED REACTOR

2019 ◽  
Vol 8 (2) ◽  
pp. 159-169
Author(s):  
David William Hummel ◽  
Yu-Shan Chin ◽  
Andrew Prudil ◽  
Anthony Williams ◽  
Eugene Masala ◽  
...  
Keyword(s):  
High Temperature ◽  
Current Knowledge ◽  
Safety Analysis ◽  
Severe Accident ◽  
Specific Interest ◽  
Worst Case ◽  
Severe Accidents ◽  
Small Modular Reactor ◽  
Physical Phenomena ◽  
High Temperature Gas

Canada has attracted specific interest from developers of nonwater-cooled small modular reactor (SMR) technologies, including concepts based on high-temperature gas-cooled reactors (HTGRs). It is anticipated that some research and development (R&D) will be necessary to support safety analysis and licensing of these reactors in Canada. The Phenomena Identification and Ranking Table (PIRT) process is a formalized method in which a panel of experts identifies which physical phenomena are most relevant to the reactor safety analysis and how well understood these phenomena are. The PIRT process is thus a tool to assess current knowledge levels and (or) predictive capabilities of models, thus providing direction to a focused R&D program. This paper summarizes the results of a PIRT process performed by a panel of experts at Canadian Nuclear Laboratories for a limiting or “worst-case” accident scenario at a generic HTGR-type SMR. Suggestions are given regarding the highest priority R&D items to support severe accidents analysis of these reactors.

Characteristics of Pressure Buildup From Local Fuel-Coolant Interactions in a Simulated Molten Fuel Pool

2014 ◽  
Author(s):  
Songbai Cheng ◽  
Ken-ichi Matsuba ◽  
Mikio Isozaki ◽  
Kenji Kamiyama ◽  
Tohru Suzuki ◽  
...  
Keyword(s):  
Severe Accident ◽  
Water Volume ◽  
Reactor Safety ◽  
Experimental Conditions ◽  
Melt Temperature ◽  
Pressure Buildup ◽  
Severe Accidents ◽  
Series Of Experiments ◽  
Boiling Mode

Studies on local fuel-coolant interactions (FCI) in a molten pool are important for severe accident analyses of sodium-cooled fast reactors (SFRs). To clarify the mechanisms underlying this interaction, in this study a series of experiments was conducted by delivering a given quantity of water into a simulated molten fuel pool (formed with a low-melting-point alloy). Based on the experimental data obtained from a variety of conditions, including difference in water volume, melt temperature and water subcooling, the characteristics of pressure-buildup during local FCIs was investigated. It is found that under our experimental conditions the water volume and melt temperature have remarkable impact on the interaction, while the role of water subcooling seems to be less prominent. The performed analyses also suggest that the pressurization from local FCIs should be intrinsically limited, due to a suppressing role caused by the increasing of coolant volume entrapped within the pool as well as the transition of boiling mode. Current work, which gives a palette of favorable data for a better understanding and an improved estimation of severe accidents in SFRs, is expected to benefit future analyses and verifications of computer models developed in advanced fast reactor safety analysis codes.

MELCOR severe accident analysis for a natural circulation small modular reactor

2017 ◽  
Vol 100 ◽  
pp. 197-208 ◽  
Author(s):  
Longze Li ◽  
Tae Woon Kim ◽  
Yapei Zhang ◽  
Shripad T. Revankar ◽  
Wenxi Tian ◽  
...  
Keyword(s):  
Natural Circulation ◽  
Severe Accident ◽  
Accident Analysis ◽  
Small Modular Reactor

Analysis of Flow Stability Boundaries of ERVC System

2013 ◽  
Author(s):  
Fei Li ◽  
Di Jin ◽  
Xiao Jing Liu ◽  
Xu Cheng
Keyword(s):  
Flow Instability ◽  
Natural Circulation ◽  
Thermal Power ◽  
Management Strategies ◽  
Density Wave ◽  
Flow Stability ◽  
Severe Accident ◽  
Two Phase ◽  
System Pressure ◽  
Calculation Results

ERVC is widely adopted as a part of in-vessel retention (IVR) in severe accident management strategies. In this paper, two-phase flow instability in natural circulation loops of external reactor vessel cooling (ERVC) system in a large size power PWR (CAP 1700 with a thermal power 5000 MWt) is simulated and evaluated by the RELAP5 code. Under certain conditions, flow instability of ERVC system are obtained. It is a kind of density wave oscillation that occurs in non-equilibrium boiling in the heat section and void flashing in the riser at low equilibrium quality and low system pressure. The calculation results show such oscillation course clearly. And several parameters affecting the flow stability are discussed.

Retention of Molten Corium in Calandria Vessel of PHWR With Moderator Drain Pipe

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Pradeep Pandey ◽  
Parimal P. Kulkarni ◽  
Arun Nayak ◽  
Sumit V. Prasad
Keyword(s):  
Thermal Load ◽  
Management Strategy ◽  
Severe Accident ◽  
Drain Pipe ◽  
Severe Accidents ◽  
External Cooling ◽  
Accident Management ◽  
Water Reactors ◽  
Containment Integrity

Abstract Retention of molten corium inside calandria vessel is crucial for arresting accident progression in pressurized heavy water reactors (PHWRs) during severe accidents. Our earlier tests have demonstrated corium retention and its cooling inside the calandria vessel of PHWRs through external cooling by vault water. However, the presence of nozzles and moderator drain pipe at the bottom of calandria vessel has not been considered in these studies. These nozzles and drain pipes used for moderator circulation can make the viability of corium retention even more challenging. Once the moderator has evaporated, debris reheating, compacting, and finally melting can cause the release of molten corium into the moderator recirculation system. This can lead to the relocation of corium beyond calandria vessel. The corium might reach the pump room or calandria vault after the failure of moderator drain pipe and/or moderator pump seals. This has severe consequences on containment integrity due to molten corium concrete interaction (MCCI). The risks posed by MCCI can be avoided if corium can be contained inside calandria vessel even with the presence of nozzles (at the bottom of the vessel) or if at all it enters into the drain line, does not cause its failure. Thus, it becomes crucial to evaluate the challenges faced by “in-vessel retention” (IVR) as a severe accident management strategy due to the presence of openings in the calandria vessel. Relatively colder debris present near the bottom of calandria vessel might help in obstructing the nozzles of the moderator drain line and can prevent the entry of hot molten corium into the moderator cooling line. The role of debris, therefore, becomes important under such scenarios for not just insulation of calandria vessel from hot corium but also for retention of corium within the vessel. In this article, these issues are addressed by conducting two sets of experiments for assessment of retention capability (IVR) of calandria vessel: (i) with the presence of debris and (ii) without debris at the bottom of calandria vessel. The moderator recirculation line was scaled to simulate the heat transfer from corium to vault water and solidification of corium simulant while flowing through the moderator drain pipe. It was observed that debris bed present at the bottom of the vessel helps in arresting the molten corium front and thus prevents corium from entering into moderator drain pipe. When experiments were conducted without debris, molten corium was found to be relocating in the moderator drain pipe. The drain pipe, however, did not fail under the thermal load.

Moderating Role of Learning Strategies Between Meta-Cognitive Awareness and Study Habits Among University Students

2019 ◽  
Vol 34 (Spring 2019) ◽  
pp. 215-231
Author(s):  
Mussarat J. Khan ◽  
Seemab Rasheed
Keyword(s):  
Regression Analysis ◽  
Resource Management ◽  
University Students ◽  
Learning Strategies ◽  
Management Strategies ◽  
Cognitive Strategies ◽  
Study Habits ◽  
Good Reliability ◽  
Cognitive Awareness

The purpose of present study is to examine the role of learning strategies as moderator between meta-cognitive awareness and study habits among university students. Sample comprises of 200 students (100 male students and 100 female students) of various universities of Islamabad and Rawalpindi with age ranging from 18-25 years. In order to assess study variables questionnaires were used included Meta-Cognitive Awareness Inventory (Schraw & Dennison, 1994) measuring two-components of meta-cognition that are knowledge and regulation of cognition. Study habits demonstrated by the students were measured by the Study Habits Inventory (Wrenn, 1941). Motivated Strategies for Learning Questionnaire (Pintrich, Smith, Garcia, & McKeachie, 1991) which includes motivation and learning strategies scales. In the present study, only the learning strategies section was utilized, which measures the cognitive strategies and resource management strategies. Results revealed positive correlation between research instruments and are also having good reliability. Regression analysis reflected that meta-cognitive awareness predicts study habits among university students. Regression analysis also suggested that learning strategies including resource management strategies and cognitive strategies significantly moderates the relationship between meta-cognitive awareness and study habits. It is also explored gender differences on learning strategies, meta-cognitive awareness and study habits. Future implications of the study were also discussed.

BİLGİ YÖNETİMİ UYGULAMALARI KAPSAMINDA İNSAN KAYNAKLARI YÖNETİMİNDE MEYDANA GELEN DEĞİŞİMLER

2013 ◽  
Vol 1 (1) ◽  
pp. 83
Author(s):  
Ozan Büyükyılmaz
Keyword(s):  
Knowledge Management ◽  
Human Resources ◽  
Performance Management ◽  
Management Practices ◽  
Human Resources Management ◽  
Management Strategies ◽  
Resources Management ◽  
Management Philosophy ◽  
Management Processes

The development and expansion of knowledge management as an important management philosophy has a significant impact on human resources management as well as on organization as a whole. In this context, knowledge management processes have been used as a strategic tool within human resources management.Therefore, functions of human resources management must adapt itself to this change. The purpose of this study is to determine the role of human resources management in the management of knowledge and to reveal the effects of knowledge management practices on the functions of human resources byexamining the relationship between human resources and knowledge management. In this context, a theoretical investigation was conducted. It has been determined that significant changes occurred on the functions of human resources management such as selection and recruitment, performance management, remuneration and reward, training and development within the framework of the knowledge management strategies.

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