RELAP5 Code Analysis of LSTF Small Break LOCA Tests With Steam Generator Intentional Depressurization and its Uncertainty Quantification by Monte Carlo Method and Wilks Formula Approach

2016 ◽  
Author(s):  
Ikuo Kinoshita ◽  
Michio Murase
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Steam Generator ◽  
Tolerance Limit ◽  
Injection System ◽  
Test Facility ◽  
Statistical Fluctuation ◽  
Limit Values ◽  
Upper Limit ◽  
Secondary Side

The Best Estimate Plus Uncertainty (BEPU) method has been applied by the authors to analysis of the “intentional depressurization of steam generator secondary side” which is an accident management procedure in a small break loss-of-coolant accident with high pressure injection system failure. In the present study, experimental analyses using the RELAP5/MOD3.2 code were carried out for the ROSA/Large Scale Test Facility (LSTF) secondary-side depressurization tests. The two test cases were selected with different break sizes and different depressurization conditions to ensure the reliability for the accident scenario analyses. The uncertainty propagation analyses were performed through the random variations of input parameters whose uncertainty ranges and distributions were determined previously by the PIRT and the separate effects tests. One thousand random calculations were conducted to get the 95% upper limit values of the peak cladding temperature (PCT) by the Monte Carlo method. Furthermore, the 95%/95% tolerance limits for the PCT were obtained according to Wilks formula. It was confirmed that the code predicted well the major event progressions such as rod surface temperature and the 95% uncertainty bands included the measured values. Furthermore, the 95% upper limit values of the PCT are below the 95%/95% tolerance limit values. However, the statistical fluctuation of the tolerance limit values by Wilks first order formula is as large as the uncertainty value itself. The statistical fluctuation decreases with increasing order of Wilk formula. It is desirable to increase the order of Wilks formula to more than the second order to get the reliable safety margin.

scholarly journals ROSA/LSTF Tests and RELAP5 Posttest Analyses for PWR Safety System Using Steam Generator Secondary-Side Depressurization against Effects of Release of Nitrogen Gas Dissolved in Accumulator Water

2016 ◽  
Vol 2016 ◽  
pp. 1-15
Author(s):  
Takeshi Takeda ◽  
Akira Ohnuki ◽  
Daisuke Kanamori ◽  
Iwao Ohtsu
Keyword(s):  
Steam Generator ◽  
Safety System ◽  
Injection System ◽  
Test Facility ◽  
Gas Release ◽  
Dissolved Gas ◽  
Nitrogen Gas ◽  
Two Phase ◽  
Pressurized Water ◽  
Secondary Side

Two tests related to a new safety system for a pressurized water reactor were performed with the ROSA/LSTF (rig of safety assessment/large scale test facility). The tests simulated cold leg small-break loss-of-coolant accidents with 2-inch diameter break using an early steam generator (SG) secondary-side depressurization with or without release of nitrogen gas dissolved in accumulator (ACC) water. The SG depressurization was initiated by fully opening the depressurization valves in both SGs immediately after a safety injection signal. The pressure difference between the primary and SG secondary sides after the actuation of ACC system was larger in the test with the dissolved gas release than that in the test without the dissolved gas release. No core uncovery and heatup took place because of the ACC coolant injection and two-phase natural circulation. Long-term core cooling was ensured by the actuation of low-pressure injection system. The RELAP5 code predicted most of the overall trends of the major thermal-hydraulic responses after adjusting a break discharge coefficient for two-phase discharge flow under the assumption of releasing all the dissolved gas at the vessel upper plenum.

RELAP5 Code Uncertainty Analysis of LSTF Small Break LOCA Tests With Steam Generator Intentional Depressurization as an Accident Management Procedure

2016 ◽  
Author(s):  
Ikuo Kinoshita ◽  
Toshihide Torige
Keyword(s):  
Steam Generator ◽  
Injection System ◽  
Test Facility ◽  
Test Cases ◽  
Input Uncertainty ◽  
Accident Scenario ◽  
Management Procedure ◽  
Accident Management ◽  
Uncertainty Parameters ◽  
Secondary Side

The Best Estimate Plus Uncertainty (BEPU) method is applied to analysis of the “intentional depressurization of steam generator secondary side” which is an accident management procedure in a small break loss-of-coolant accident with high pressure injection system failure. In the present study, experimental analyses using the RELAP5/MOD3.2 code were carried out for the ROSA/Large Scale Test Facility (LSTF) secondary-side depressurization tests. The two test cases were selected with different break sizes and different depressurization conditions to ensure the reliability for the accident scenario analyses. The input parameter uncertainty propagation analyses were performed to get 95%/95% tolerance limit values of the output parameters. It was confirmed that the code predicted well the major event progressions of the accident for both test cases and the 95%/95% uncertainty bounds of the peak cladding temperatures included the measured values. On the other hand, the same ranges of some input uncertainty parameters could lead to different influences on the output uncertainties between the test cases. The dominating input uncertainty parameters could be different depending on the break sizes and depressurization conditions of the accident scenario.

RELAP5 Code Analysis of LSTF Small Break LOCA Tests With Steam Generator Intentional Depressurization as an Accident Management Procedure: Investigation on Base Case Result Appropriate for the Best Estimate Plus Uncertainty (BEPU) Application

2014 ◽  
Author(s):  
Ikuo Kinoshita ◽  
Toshihide Torige ◽  
Michio Murase ◽  
Yoshitaka Yoshida ◽  
Takeshi Takeda ◽  
...  
Keyword(s):  
Steam Generator ◽  
Large Scale ◽  
Model Simulation ◽  
Test Facility ◽  
Base Case ◽  
Best Estimate ◽  
Management Procedure ◽  
Accident Management ◽  
Characteristic Features ◽  
Secondary Side

The application of the Best Estimate Plus Uncertainty (BEPU) method is made to analysis of the “Intentional depressurization of steam generator secondary side” which is an accident management procedure in a small-break loss-of-coolant accident (SBLOCA) with high pressure injection (HPI) system failure. RELAP5/MOD3.2 is used as the analysis code. By applying the BEPU method, the uncertainties of the analysis results can be estimated quantitatively. However, the accuracy of the analysis results depends primarily on the base case result predicted by the best estimate code. In this study, in order to investigate the appropriate base case model, simulation analyses using the RELAP5/MOD3.2 were carried out for the ROSA Large Scale Test Facility (ROSA/LSTF) secondary-side depressurization tests. It was found that the code predicted well the major event progressions such as pressure responses, core liquid level responses, and rod surface temperatures, as well as important phenomena such as formation and clearing of loop seals, accumulation of water from condensation, and countercurrent flow limitation (CCFL) at the inlet of the U-tubes, which are characteristic features of this accident scenario.

Probability of Burst in Steam Generator Tubes Using Monte Carlo Method

2006 ◽  
Author(s):  
Jae Bong Lee ◽  
Jai Hak Park ◽  
Hong-Deok Kim ◽  
Han-Sub Chung ◽  
Tae Ryong Kim
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Steam Generator ◽  
Flaw Size ◽  
Assessment Model ◽  
Statistical Approaches ◽  
Inspection Data ◽  
Steam Generator Tubes ◽  
Non Destructive ◽  
Service Inspection

A statistical assessment model for structural integrity of steam generator tubes was proposed using Monte Carlo method. The growth of flaws in steam generator tubes was predicted using statistical approaches. The statistical parameters that represent the characteristics of flaw growth and initiation were derived from in-service inspection (ISI) non-destructive evaluation (NDE) data. Based on the statistical approaches, flaw growth models were proposed and applied to predict distribution of flaw size at the end of cycle (EOC). Because NDE measurement results differ from that of real ones in steam generator tubes, a simple method for predicting the physical number of flaws from periodic in-service inspection data was proposed. The probabilistic flaw growth rate was calculated from the in-service non-destructive inspection data. And the statistical growth of flaw was simulated using the Monte Carlo method. Probabilistic distributions of the flaw size and the probability of burst were obtained from numerously repeated simulations using the proposed assessment model.

Statistical Assessment of Integrity in Steam Generator Tubes Considering Uncertainty of NDE

2006 ◽  
Vol 326-328 ◽  
pp. 545-548
Author(s):  
Jae Bong Lee ◽  
Jai Hak Park ◽  
Hong Deok Kim ◽  
Han Sub Chung ◽  
Tae Ryong Kim
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Steam Generator ◽  
Structural Integrity ◽  
Assessment Model ◽  
Statistical Assessment ◽  
The Monte Carlo Method ◽  
Proposed Model ◽  
Inspection Data ◽  
Steam Generator Tubes

A statistical assessment model for structural integrity of steam generator tubes with axial cracks at the top of the tubesheet was proposed using Monte Carlo method. In the model, a method for estimating the number of "real cracks" from in-situ inspection (ISI) data was used. Based on the estimated "real cracks", the number of newly detected cracks and growth of cracks during arbitrary operating period were simulated using the Monte Carlo method. The flaw growth rate used in the simulation was statistically calculated from the periodic in-service non-destructive inspection data. The number of cracks, the probabilistic distribution of crack sizes at the end of next operating interval and the probability of burst during operation were calculated from numerously repeated simulations using the proposed model.

scholarly journals ROSA/LSTF Tests and Posttest Analyses by RELAP5 Code for Accident Management Measures during PWR Station Blackout Transient with Loss of Primary Coolant and Gas Inflow

2018 ◽  
Vol 2018 ◽  
pp. 1-19 ◽  
Author(s):  
Takeshi Takeda ◽  
Iwao Ohtsu
Keyword(s):  
Flow Rate ◽  
Injection System ◽  
Test Facility ◽  
Relief Valve ◽  
Nitrogen Gas ◽  
Primary Coolant ◽  
Gas Accumulation ◽  
Accident Management ◽  
Station Blackout ◽  
Secondary Side

Three tests were carried out with the ROSA/LSTF (rig of safety assessment/large-scale test facility), which simulated accident management (AM) measures during station blackout transient with loss of primary coolant under assumptions of nitrogen gas inflow and total failure of high-pressure injection system in a pressurized water reactor. As the AM measures, steam generator (SG) secondary-side depressurization was done by fully opening the relief valves in both SGs, and auxiliary feedwater was injected into the secondary-side of both SGs simultaneously. Conditions for the break size and the onset timing of the AM measures were different among the three LSTF tests. In the three LSTF tests, the primary pressure decreased to a certain low pressure of below 1 MPa with or without the primary depressurization by fully opening the relief valve in a pressurizer as an optional AM measure, while no core uncovery took place through the whole transient. Nonuniform flow behaviors were observed in the SG U-tubes under natural circulation (NC) with nitrogen gas depending probably on the gas accumulation rate in the two LSTF tests that the gas accumulated remarkably. The RELAP5/MOD3.3 code predicted most of the overall trends of the major thermal hydraulic responses observed in the three LSTF tests. The code, however, indicated remaining problems in the predictions of the primary pressure, the SG U-tube collapsed liquid levels, and the NC mass flow rate after the nitrogen gas ingress as well as the accumulator flow rate through the analyses for the two LSTF tests, where the remarkable gas accumulation occurred.

Search for an Admixture of a 17 keV Neutrino in the β Decay of 35S

1994 ◽  
Vol 49 (9) ◽  
pp. 874-884 ◽  
Author(s):  
S. Müller ◽  
Chen Shiping ◽  
H. Daniel ◽  
O. Dragoun ◽  
N. Dragounová ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Electron Scattering ◽  
Small Volume ◽  
Adjustable Parameter ◽  
Β Decay ◽  
Upper Limit ◽  
The Monte Carlo Method ◽  
Set Up ◽  
Energy Dependent

Abstract The β spectrum of a mass-separated thin 35S source has been measured with a small-volume Si photodiode. The energy-dependent response function of the total experimental set-up was calculated by the Monte Carlo method without any adjustable parameter. For an admixture of the hypothetical 17 keV neutrino, an upper limit of 0.59% (95% CL) was determined. Neglecting electron scattering on the spectrometer diaphragm was shown to generate a false 17 keV neutrino admixture of 0.3%.

Outbursts of comet Schwassmann-Wachmann 1, and the cloud of interplanetary boulders

1974 ◽  
Vol 22 ◽  
pp. 307 ◽  
Author(s):  
Zdenek Sekanina
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Method ◽  
Interplanetary Space ◽  
Porous Matrix ◽  
Maximum Diameter ◽  
Expansion Velocity ◽  
Solid Constituent ◽  
Meteoric Material ◽  
Periodic Comet

AbstractIt is suggested that the outbursts of Periodic Comet Schwassmann-Wachmann 1 are triggered by impacts of interplanetary boulders on the surface of the comet’s nucleus. The existence of a cloud of such boulders in interplanetary space was predicted by Harwit (1967). We have used the hypothesis to calculate the characteristics of the outbursts – such as their mean rate, optically important dimensions of ejected debris, expansion velocity of the ejecta, maximum diameter of the expanding cloud before it fades out, and the magnitude of the accompanying orbital impulse – and found them reasonably consistent with observations, if the solid constituent of the comet is assumed in the form of a porous matrix of lowstrength meteoric material. A Monte Carlo method was applied to simulate the distributions of impacts, their directions and impact velocities.

Structures and crystallization of vacuum-deposited amorphous Se and Sb films

1990 ◽  
Vol 48 (4) ◽  
pp. 140-141
Author(s):  
Makoto Shiojiri ◽  
Toshiyuki Isshiki ◽  
Tetsuya Fudaba ◽  
Yoshihiro Hirota
Keyword(s):  
Monte Carlo ◽  
Electron Microscope ◽  
Monte Carlo Method ◽  
Computer Program ◽  
Radial Distribution ◽  
Film Formation ◽  
Amorphous State ◽  
Two Dimensional ◽  
Amorphous Films ◽  
Binding Condition

In hexagonal Se crystal each atom is covalently bound to two others to form an endless spiral chain, and in Sb crystal each atom to three others to form an extended puckered sheet. Such chains and sheets may be regarded as one- and two- dimensional molecules, respectively. In this paper we investigate the structures in amorphous state of these elements and the crystallization.HRTEM and ED images of vacuum-deposited amorphous Se and Sb films were taken with a JEM-200CX electron microscope (Cs=1.2 mm). The structure models of amorphous films were constructed on a computer by Monte Carlo method. Generated atoms were subsequently deposited on a space of 2 nm×2 nm as they fulfiled the binding condition, to form a film 5 nm thick (Fig. 1a-1c). An improvement on a previous computer program has been made as to realize the actual film formation. Radial distribution fuction (RDF) curves, ED intensities and HRTEM images for the constructed structure models were calculated, and compared with the observed ones.

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