Sensitivity Studies of the Effect of Cladding Degradation on TSPA Results

2002 ◽  
Vol 713 ◽  
Author(s):  
Eric Siegmann ◽  
Eve Devonec
Keyword(s):  
Failure Rate ◽  
Localized Corrosion ◽  
Base Case ◽  
Driving Mechanism ◽  
Total System ◽  
Degradation Model ◽  
Large Computer ◽  
Peak Dose ◽  
Sensitivity Studies ◽  
Rock Overburden

ABSTRACTThe Commercial Spent Nuclear Fuel (CSNF) cladding directly influences the dose by reducing the release rate of radionuclides compared to bare fuel. A cladding degradation model was introduced in the Total System Performance Assessment – Viability Assessment (TSPA-VA) and has evolved into the TSPA-SR (Sight Recommendation), Rev 00 and most recently the Supplemental Science and Performance Analyses (SSPA) models. TSPAs are large computer models that predict how the radionuclides might escape through the various barriers and migrate through the different geological regions and predict the dose to the critical population. The major components in the cladding degradation model are initial cladding failure, creep, stress corrosion cracking (SCC), localized corrosion, mechanical failures (due to seismic events and rock overburden) and cladding unzipping. In the bare fuel case, the dose is controlled by the failure rate of the waste packages (WPs), the solubility limits for certain radionuclides, and the rate of diffusion of the radionuclides through the cracks in the WPs. The cladding degradation model involves two steps, perforation followed by unzipping. Sensitivity studies have shown that cladding limits dose primarily by preventing dissolution of the UO2 fuel (when the cladding is not perforated). If all the cladding is assumed to be perforated and cladding unzipping occurs, the peak dose would be within 4% of that of bare fuel. The UO2 dissolution rate (the driving mechanism for cladding unzipping) is sufficiently rapid that assuming instant dissolution increases the dose by only 12% from the base case. In the current cladding degradation model, cladding accounts for a reduction in dose for the first 100,000 years of a factor of 16 when compared with bare fuel. This is because of the low initial cladding failure rate (2.1% including SCC and creep) and few failures from localized corrosion (late WP breach and limited water entering the WPs). Failure of the cladding by rock overburden accounts for an increasing trend in dose at times greater than 100,500 years. This mechanism increases the peak dose and delays the peak from approximately 200,000 to 300,000 years. In conclusion, the cladding degradation model, mostly through preventing water from contacting the UO2, reduces the dose predicted in the TSPA analysis.

The Research on Rake-Car’s Driving System of Ore Reclaimer

2013 ◽  
Vol 300-301 ◽  
pp. 10-13
Author(s):  
Yuan Hui Li ◽  
Kui Sheng Chen ◽  
Jiang Hong Deng ◽  
Xin Yuan Chen
Keyword(s):  
Computer Simulation ◽  
System Design ◽  
Failure Rate ◽  
Hydraulic System ◽  
Driving Mechanism ◽  
Connecting Rod ◽  
Driving System ◽  
Final Design ◽  
Hydraulic System Design ◽  
Working Situation

Rake-car’s driving system of ore reclaimer originally used crank and connecting rod mechanism as driving mechanism. The driving mechanism got some trouble that parts got severe wear and failure rate of mechanism was high. The hydraulic system is used to drive rake car in view of hydraulic driving system’s advantage. By analysis on existing problem of crank and connecting rod mechanism, the actual working load of equipment is tested and the working situation is analysed. The working situation of the hydraulic system is also analysed by computer simulation. By optimization of the hydraulic system design, the final design is determined. The whole system is actually used. It works well.

scholarly journals Reliability Analysis of Load-SharingK-out-of-NSystem Considering Component Degradation

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Chunbo Yang ◽  
Shengkui Zeng ◽  
Jianbin Guo
Keyword(s):  
Reliability Analysis ◽  
Failure Rate ◽  
Load Sharing ◽  
Performance Degradation ◽  
Random Component ◽  
Rate Model ◽  
Successful Operation ◽  
Degradation Model ◽  
System Requirement ◽  
Degradation Effect

TheK-out-of-Nconfiguration is a typical form of redundancy techniques to improve system reliability, where at leastK-out-of-Ncomponents must work for successful operation of system. When the components are degraded, more components are needed to meet the system requirement, which means that the value ofKhas to increase. The current reliability analysis methods overestimate the reliability, because using constantKignores the degradation effect. In a load-sharing system with degrading components, the workload shared on each surviving component will increase after a random component failure, resulting in higher failure rate and increased performance degradation rate. This paper proposes a method combining a tampered failure rate model with a performance degradation model to analyze the reliability of load-sharingK-out-of-Nsystem with degrading components. The proposed method considers the value ofKas a variable which is derived by the performance degradation model. Also, the load-sharing effect is evaluated by the tampered failure rate model. Monte-Carlo simulation procedure is used to estimate the discrete probability distribution ofK. The case of a solar panel is studied in this paper, and the result shows that the reliability considering component degradation is less than that ignoring component degradation.

Instantaneous Probability of Uncontrolled External Leakage During the Production Phase of a Subsea Well

2013 ◽  
Author(s):  
Andre L. R. Alves ◽  
Theodoro A. Netto
Keyword(s):  
Failure Rate ◽  
Failure Modes ◽  
Probability Distributions ◽  
Base Case ◽  
Component Reliability ◽  
Production Phase ◽  
Common Cause Failures ◽  
Closed Position ◽  
The Impact

This work develops a methodology for evaluating the uncontrolled external leakage probability of a subsea well during the production phase. Based on a barrier diagram, an algorithm for possible leak paths identification is proposed, considering different operation modes: gas lift operation, free flowing or well closed at the subsea Xmas Tree. Considering the equivalency between these paths and the minimum cut sets from a fault tree modeling, the uncontrolled external leakage probability is calculated using the upper bound approximation. The effect of common cause failures is considered for the failure mode fail-to-close-valve. The instantaneous availability function of each component is modeled to represent the maintenance strategy applied. Non repairable, repairable and periodically tested items are used. For the latter, a nomenclature to distinguish two subtypes is introduced: the PT-R and PT-NR models, respectively Periodically Tested Repairable, and Periodically Tested Non Repairable. Probability distributions parameters are roughly estimated in order to make a case study. The failure rate functions determined are used as input for the proposed model, regarding the following failure modes: fail-to-close, external-leakage, and internal-leakage at the closed position. The objective of this section is to adjust a Weibull distribution, eliminate the usual assumption of constant failure rate and account for eventual wear-out effects. Finally, instantaneous probability results and sensitivity analysis are demonstrated for a base case study. Parameters like time between tests, inspections, and component reliability are varied in order to identify the impact on the uncontrolled external leakage probability. Therefore, the main objective is to propose a model that could support decision making on the well integrity management system during the production phase of a subsea well. To make this possible, reliable input data should be further considered.

Simulation-Based Analysis of Arctic LNG Transport Capacity, Cost and System Integrity

2014 ◽  
Author(s):  
Stein Ove Erikstad ◽  
Sören Ehlers
Keyword(s):  
Seasonal Variations ◽  
Storage Capacity ◽  
Continuous Production ◽  
Winter Season ◽  
Capacity Utilization ◽  
Utilization Rate ◽  
Base Case ◽  
Total System ◽  
Robust Solution ◽  
System Integrity

This paper presents a design case for arctic LNG transport, where liquefied gas is shipped from the Kharasevey terminal in Northern Russia to markets in US and Europe. Based on a fleet simulation model, the trade-off between the two main performance issues related to arctic transport are investigated; namely how to maintain transport system integrity in the harsh ice conditions, while maximizing the capacity utilization in a situation with considerable seasonal variations. The fixed contract, single destination base case shows that meeting the requirements for a robust solution implies a low degree of utilization in the summer season. To improve upon this situation, several mitigating strategies are evaluated, including vessel speed and size changes, fixed and seasonally varying contract and market mix schedules, revision stop rescheduling, storage capacity extensions and backhauling. The results indicate a high payoff from renegotiating the initial fixed schedule contract to allow for a higher degree of seasonal variations in the LNG deliveries. Further, increased storage capacity in loading port, combined with winter revision stops will have a significant impact on both fleet utilization and total system integrity. Flexible contracts that implies seasonal deliveries to the UK will help ensure continuous production and deliveries in winter season. Finally, surplus capacity gives opportunities for seasonal spot cargoes that could be exploited to increase fleet utilization rate.

Alternate Source Term Models for Yucca Mountain Performance Assessment Based on Natural Analog Data and Secondary Mineral Solubility

1999 ◽  
Vol 556 ◽  
Author(s):  
William M. Murphy ◽  
Richard B. Codell
Keyword(s):  
Performance Assessment ◽  
Release Rate ◽  
Source Term ◽  
Yucca Mountain ◽  
Solution Chemistry ◽  
Base Case ◽  
Total System ◽  
Spent Fuel ◽  
Natural Analog ◽  
Mineral Solubility

AbstractPerformance assessment calculations for the proposed high level radioactive waste repository at Yucca Mountain, Nevada, were conducted using the Nuclear Regulatory Commission Total-System Performance Assessment (TPA 3.2) code to test conceptual models and parameter values for the source term based on data from the Peña Blanca, Mexico, natural analog site and based on a model for coprecipitation and solubility of secondary schoepite. In previous studies the value for the maximum constant oxidative alteration rate of uraninite at the Nopal I uranium body at Peña Blanca was estimated. Scaling this rate to the mass of uranium for the proposed Yucca Mountain repository yields an oxidative alteration rate of 22 kg yr−1, which was assumed to be an upper limit on the release rate from the proposed repository. A second model was developed assuming releases of radionuclides are based on the solubility of secondary schoepite as a function of temperature and solution chemistry. Releases of uranium are given by the product of uranium concentrations at equilibrium with schoepite and the flow of water through the waste packages. For both models, radionuclides other than uranium and those in the cladding and gap fraction were modeled to be released at a rate proportional to the uranium release rate, with additional elemental solubility limits applied. Performance assessment results using the Peña Blanca oxidation rate and schoepite solubility models for Yucca Mountain were compared to the TPA 3.2 base case model, in which release was based on laboratory studies of spent fuel dissolution, cladding and gap release, and solubility limits. Doses calculated using the release rate based on natural analog data and the schoepite solubility models were smaller than doses generated using the base case model. These results provide a degree of confidence in safety predictions using the base case model and an indication of how conservatism in the base case model may be reduced in future analyses.

Effects of Iron and pH on Glass Dissolution Rate

2002 ◽  
Vol 757 ◽  
Author(s):  
Seung-Young Jeong ◽  
William L. Ebert
Keyword(s):  
Dissolution Rate ◽  
Ph Dependence ◽  
High Level Waste ◽  
Total System ◽  
Degradation Model ◽  
Static Tests ◽  
Dissolved Iron ◽  
Glass Dissolution ◽  
License Application ◽  
High Level

ABSTRACTShort-term static tests were conducted with a surrogate high-level waste glass to measure the effects of pH and dissolved iron on the glass dissolution rate. The tests were conducted to determine if a term to account for the effects of dissolved iron is needed in the glass degradation model developed for Total System Performance Assessment (TSPA) calculations for the Yucca Mountain disposal system license application. The glass degradation model includes terms for dependencies on temperature, pH, and chemical affinity. A series of tests was conducted at 90 °C in various pH solutions without iron and with added FeCl3, Fe2O3, Fe3O4, and FeOOH. Tests were conducted at glass surface area/solution volume (S/V) ratios about 2 and 10 m-1for between 2 and 21 days. Solution concentrations of boron were used to measure the extent of reaction and calculate the glass dissolution rates. Similar rates were measured in tests conducted with and without iron at each pH. Both the results of the tests with and without iron showed V-shaped pH dependence curves with minima at near-neutral pH values. The pH dependencies (η) are about 0.44 in basic solutions and –0.49 in acidic solutions, based on the combined results of tests with and without iron. These are within the range of values for the pH dependence in the TSPA model for site recommendation.

Effects of Uncertainty and Spatial Variability on Seepage Into Drifts in the Yucca Mountain Total System Performance Assessment Model

2001 ◽  
Author(s):  
Donald A. Kalinich ◽  
Michael L. Wilson
Keyword(s):  
Spatial Variability ◽  
Performance Assessment ◽  
System Performance ◽  
Seepage Flow ◽  
Yucca Mountain ◽  
Assessment Model ◽  
Base Case ◽  
Total System ◽  
Performance Uncertainty

Abstract Seepage into the repository drifts is an important factor in total-system performance. Uncertainty and spatial variability are considered in the seepage calculations. The base-case results show 13.6% of the waste packages (WPs) have seepage. For 5th percentile uncertainty, 4.5% of the WPs have seepage and the seepage flow decreased by a factor of 2. For 95th percentile uncertainty, 21.5% of the WPs have seepage and the seepage flow increased by a factor of 2. When seepage was forced on 100% of the WPs the seepage flow increased by a factor of 3.

Thermoeconomic Optimization of a LiBr/H2O Absorption Chiller Using Structural Method

2005 ◽  
Vol 127 (2) ◽  
pp. 119-124 ◽  
Author(s):  
R. D. Misra ◽  
P. K. Sahoo ◽  
A. Gupta
Keyword(s):  
Economic Cost ◽  
Vital Role ◽  
Base Case ◽  
Structural Method ◽  
Total System ◽  
Optimization Strategy ◽  
Absorption Chiller ◽  
Optimum Configuration ◽  
Optimization Methodology ◽  
Structural Coefficient

The optimization strategy for absorption chiller systems is generally based on thermodynamic analysis. However, the optimum, so obtained, does not always guarantee the economic optimum. In this regard, the thermoeconomics that combines the thermodynamic principles with economic parameters plays a vital role for achieving the cost effectiveness of these systems. In this paper, this technique is applied to optimize a single-effect LiBr/H2O absorption chiller system for air-conditioning applications aiming at achieving the minimum product cost. This optimization methodology is based on the relative interdependence between component irreversibility and the total system irreversibility. This relationship, known as structural coefficient, is used to evaluate the economic cost of the product of the system. The use of structural coefficient eliminates complex numerical procedures, and the optimization is achieved by sequential local optimization of the subsystems of the system. The analysis reveals that the capital cost of the optimum configuration is increased by about 33.3% from the base case, however, the additional cost is well compensated by reduced fuel cost. This is possible because of reduction of plant irreversibilities by about 47.2%.

scholarly journals The Key Parameter Effect Analysis Of Polymer Flooding On Oil Recovery Using Reservoir Simulation

2019 ◽  
Vol 4 (1) ◽  
pp. 49
Author(s):  
Tomi Erfando ◽  
Novia Rita ◽  
Romal Ramadhan
Keyword(s):  
Oil Recovery ◽  
Reservoir Simulation ◽  
Polymer Concentration ◽  
Polymer Flooding ◽  
Recovery Factor ◽  
Water Flooding ◽  
Base Case ◽  
Driving Mechanism ◽  
Geological Condition ◽  
Recovery Method

As time goes by, there will be decreasing of production rates of a field along with decreasing pressure. This led to the necessity for further efforts to increase oil production. Therefore, pressure support is required to improve the recovery factor. Supportable pressure that can be used can be either water flooding and polymer flooding. This study aims to compare recovery factor to scenarios carried out, such as polymer flooding with different concentrations modeled in the same reservoir model to see the most favorable scenario. The method used in this research is reservoir simulation method with Computer Modeling Group (CMG) STARS simulator. The study was carried out by observing at the pressure, injection rate, and polymer concentration on increasing field recovery factor. This study used cartesian grid with the assumption of homogeneous reservoir, there are no faults or other geological condition in the reservoir, and driving mechanism is only solution gas drive. This reservoir, oil type is light oil with API gravity 40.3˚API and layer of conglomerate rock. The simulation result performed with various scenarios provides a good result. Where the conditions case base case field recovery factor of 6.7%, and after water flooding produced 25.5% of oil, whereas with tertiary recovery method is polymer flooding was carried out with four concentrations of 640 ppm, 1,500 ppm, 3,000 ppm, and 4,000 ppm obtained optimum values at 4,000 ppm polymer concentration with recovery factor 28.9%, SOR reduction final value 0,5255, polymer adsorption of 818,700 ppm, reservoir final pressure 1,707 psi, and an increase in water viscosity to 0.94 cP.

Incorporation of “Corrosion-Time” and Effects of Corrosion-Product Spalling in Waste Package Degradation Simulation in the Potential Repository at Yucca Mountain

1996 ◽  
Vol 465 ◽  
Author(s):  
Joon H. Lee ◽  
Joel E. Atkins ◽  
Bryan Dunlap
Keyword(s):  
Carbon Steel ◽  
Yucca Mountain ◽  
Corrosion Products ◽  
Total System ◽  
General Corrosion ◽  
Degradation Model ◽  
Waste Package ◽  
Degradation Failure ◽  
Corrosion Time ◽  
Exposure Conditions

ABSTRACTA two-layer waste package (carbon steel outer barrier and Alloy 825 inner barrier) is specified to dispose of high-level nuclear waste at the potential repository at Yucca Mountain. A set of improvements and more realism have been added to a stochastic waste-package degradation model which was developed for a recent total system performance assessment of the potential repository [1]. The waste-package surface is divided into “patches” to better represent the general corrosion of the carbon-steel outer barrier. The “corrosion-time” concept is developed to represent the corrosion of the carbon-steel outer barrier in changing exposure conditions with time such as those expected in the potential repository. With the patches approach and the corrosion-time concept implemented into the waste-package degradation model, sensitivity of the waste package degradation (failure and pitting degradation) to different threshold spalling thicknesses of the corrosion products from the carbon-steel outer barrier is analyzed. The results show that the waste-package pitting degradation is sensitive to the corrosion-products spalling thickness of the carbon-steel outer barrier. A greater pitting degradation of the waste packages is predicted with a smaller spalling thickness. Further understanding of the corrosion-products spalling in different exposure conditions (i.e., water chemistry, water contact mode, etc.) and its effects on carbon steel corrosion is needed to enhance the confidence in the waste-package performance modeling in the potential repository.

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