Papers by Upendra Rohatgi
OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information), Jun 12, 2022
Nuclear Technology, 1995
Analysis has been performed for an anticipated transient without scram (ATWS) event in a simplifi... more Analysis has been performed for an anticipated transient without scram (ATWS) event in a simplified boiling water reactor. Loss of feedwater heating initiated this ATWS, which was mitigated by the insertion of fine-motion control rods. Calculations with RAMONA-4B code show that reactivity insertion, through increase in subcooling to the core, results in a rise in the core power to a new equilibrium condition. Insertion of fine-motion control rods from the bottom of the core is found to shift the peak of the axial power distribution to the upper part of the core until eventual shutdown of the reactor occurs.
Nuclear Technology, 1995
The purpose of isolation condensers (ICs) in a boiling water reactor (BWR) is to passively contro... more The purpose of isolation condensers (ICs) in a boiling water reactor (BWR) is to passively control the reactor pressure by removing heat from the system during abnormal reactor operation. This type of control is expected to reduce the frequency of opening and closing of the safety relief valves (SR Vs). In addition, the ICs are designed to remove the decay heat of the reactor system after reactor shutdown in case of a loss of coolant accident. Transient calculations of an anticipated transient without scram for a main steam isolation valve (MSIV) closure event were performed using the RAMONA-4B code with prescribed pressure set points for the SRVs and given time settings for the MSIV closure. It is demonstrated that the effect of the ICs is to reduce the rate of pressure rise and thereby decrease the cycling frequency of the SR Vs. The onset of high-pressure coolant injection is delayed if an IC is functional. An analysis for natural circulation flow in a BWR indicates that the effect of an IC on the transient performance is similar to that for the forced circulation system. In this case, the MSIV closure results in a lower peak pressure because of the lower power level.
Nuclear Technology, 1987
A 200% cold-leg break accident in a Westinghouse four-loop RESAR-3S plant has been analyzed using... more A 200% cold-leg break accident in a Westinghouse four-loop RESAR-3S plant has been analyzed using the best-estimate code TRAC-PD2/MODI /Version 27 with updates. Three TRAC calculations have been performed. The first calculation used the best-estimate or realistic initial and boundary conditions and scenarios and the other two calculations, one with and one without locked rotor resistance, used the licensing conditions. These calculations produced the peak cladding temperatures (PCTs) of 800.5, 1072, and 1153 K, respectively. Comparison of these results with the Westinghouse licensing calculations performed in accordance with the guidelines in Appendix K of 10CFR50 shows an overall safety margin of 663 K, of which 352.5 K is due to the conservative initial and boundary conditions and scenario. The remaining 310.5 K is due to conservative physical models. The locked rotor resistance contributed-81K to PCT.
Description/Abstract This report presents the results of independent code assessment conducted at... more Description/Abstract This report presents the results of independent code assessment conducted at BNL. The TRAC-PF1 (Version 7.0) and RELAP5/MOD1 (Cycle 14) codes were assessed using the critical flow tests, level swell test, countercurrent flow limitation (CCFL) ...
Volume 8B: Heat Transfer and Thermal Engineering, 2013
Lithium -ion batteries are used in electric cars, hybrid cars and Boeing 787 Dreamliner. There is... more Lithium -ion batteries are used in electric cars, hybrid cars and Boeing 787 Dreamliner. There is an issue with heat generation in these batteries that may cause fire and reduce performance. An experimental chamber has been setup that provides dynamic and static cooling/heating regimes for Li-ion batteries. Air flow is produced by air station with maximum output of 80 m3/h. The maximum possible pressure drop is 7000 Pa. Air station can work both in pumping and exhausting mode. This test setup will be used to study various surface topology to enhance heat transfer without increase weight. Experimental setup contains two-stage temperature stabilization system. During the first stage we use the preliminary heating or cooling of the inlet air in the air buffer. The aim is to achieve the air temperature close to required inlet temperature. During the next stage air passes through the chamber with temperature controller where eventually the flow temperature is set. This approach provides ...
Volume 2: Fora, Parts A and B, 2007
The cavitation erosion problem is not a new one; however, it is still important and even becomes ... more The cavitation erosion problem is not a new one; however, it is still important and even becomes more pressing. This is associated with requirements to justify and extend service life of power-generating plants while obviously seeking the maximum efficiency. Currently semiempirical correlation relations are typically used in pump designing for prediction of modes of operation that may be hazardous in terms of development of cavitation erosion [1, 2]. It appears, however, that a progress can be made in this field by introducing numerical modeling of flow with direct modeling of the cavitation erosion process. This optimism is based on an established fact that the major effect of erosion damage is observed in the mode of operation between the “NPSH-incipient” mode (mode of activation of vapor-phase formation centers) and the “NPSH-3%” mode (mode where a noticeable vapor volume content is produced in the near-wall layer), i.e. in the mode of operation where the vapor volume content is small and its effect on flow characteristics can be neglected.© 2007 ASME
Fluid Mechanics and Its Applications, 1993
The Emergency Core Coolant (ECC) is injected in the reactor cold legs to flow down the downcomer ... more The Emergency Core Coolant (ECC) is injected in the reactor cold legs to flow down the downcomer and to cool the hot core during a Large Break Loss of Coolant Accident. The ECC flows down in the downcomer before reaching the core entrance. The delivery of ECC to the core is critical to the safety. The portion of ECC not delivered to the core is bypassed to the break. Linearly scaled small test facilities have been designed to determine ECC delivery rates for the Nuclear Power Plants (NPP). However, based on the data, it is concluded that linearly scaled small facilities do not capture the phenomena of the NPP. In the small facilities the liquid distribution facilities is a combination of pure film and liquid slugs. In the full scale facilities the ECC flows as a column beneath the cold legs almost unaffected by the pressure of the gas. In addition, the correlation recommended by the USNRC for NPP based on scaled facilities underpredicts the ECC delivery rate when compared to the data from Upper Plenum Test facility which is a full scale test facility.It is recommended that the ECC bypass phenomena experiments be performed in full scale facilities.
As part of the U.S. Department of Energy's (DOE) Nuclear Energy Research Initiative (NERI), ... more As part of the U.S. Department of Energy's (DOE) Nuclear Energy Research Initiative (NERI), a 'Generation IV' high conversion Boiling Water Reactor design is being investigated at Purdue University and Brookhaven National Laboratory. One of the primary innovative design features of the core proposed here is the use of Thorium as fertile material. In addition to the advantageous nonproliferation and waste characteristics of thorium fuel cycles, the use of thorium is particularly important in a tight pitch, high conversion lattice in order to insure a negative void coefficient throughout the operating life of the reactor. The principal design objective of a high conversion light water reactor is to substantially increase the conversion ratio (fissile atoms produced per fissile atoms consumed) of the reactor without compromising the safety performance of the plant. Since existing LWRs have a relatively low conversion ratio they require relatively frequent refueling which...
Nuclear Engineering and Design, 1990
The Nuclear Regulatory Commission (NRC) has issued a revised Emergency Core Cooling System (ECCS)... more The Nuclear Regulatory Commission (NRC) has issued a revised Emergency Core Cooling System (ECCS) rule allowing the use of best estimate computer codes for safety analysis. The rule also requires an estimation of the uncertainty in the calculated system response and a comparison of the resulting bound with the acceptance limits of 10CFR Part 50. To support this revised rule the NRC and its consultants and contractors have developed and demonstrated the Code Scaling, Applicability and Uncertainty Methodology (CSAU). The last of the three elements of the methodology-Uncertainty Evaluation-is described in this paper.
Nuclear Engineering and Design, 2007
A quantitative methodology is developed to (a) scale time-dependent evolution processes involving... more A quantitative methodology is developed to (a) scale time-dependent evolution processes involving an aggregate of interacting modules and processes (such as a NPP) and (b) integrate and organize information and data of interest to NPP design and safety analyses. The methodology is based on two concepts: fractional scaling and hierarchy. Fractional scaling is used to provide a synthesis of experimental data to generate quantitative criteria for assessing the effects of various design and operating parameters on thermo-hydraulic processes in a NPP. The synthesis via fractional scaling is carried out at three hierarchical levels: process, component and system. The methodology is demonstrated by applying it to a LOCA. The fractional scaling analysis (FSA) identifies dominant processes, ranks them quantitatively according to their importance and provides thereby an objective basis for establishing phenomena identification and ranking tables (PIRT) as well as a basis for conducting uncertainty analyses. The paper also discusses the benefits to be realized by applying the methodology to presently operating NPP as well as to future design of NPP.
Journal of Fluids Engineering, 1995
A need to pump a mixture of two-phase fluid appears naturally in many situations. One example of ... more A need to pump a mixture of two-phase fluid appears naturally in many situations. One example of this situation is aircraft fuel systems, where the pump inlet may have two-phase mixture due to the desorption of the dissolved gases at low pressures at higher altitudes. A simple procedure of selecting proper design conditions for the inlet inducer and a method of sizing the inducer, impeller and volute to meet all the design requirements has been described. This procedure has also been applied to a typical fighter plane boost pump design.
Volume 14: New Developments in Simulation Methods and Software for Engineering Applications, 2008
Currently the cavitation erosion damage becomes a critical issue that limits the centrifugal pump... more Currently the cavitation erosion damage becomes a critical issue that limits the centrifugal pump life cycle extension. Despite of a long history of studying the cavitation erosion phenomenon in centrifugal pumps there are still no reliable assessment methods except semi-empirical formula having rather limited application and accuracy. The paper is presenting a novel method for assessment of centrifugal pump cavitation erosion combining 3D unsteady flow CFD modeling and numerical analysis of cavitation bubbles behavior. The Navier-Stokes equations are solved by a splitting method with the implicit algorithm and high-order numerical scheme for convective transfer terms. The 3D numerical procedure is based on non-staggered Cartesian grid with adaptive local refinement and a sub-grid geometry resolution method for description of curvilinear complex boundaries like blade surfaces. Rotation is accounted with implementation of “sliding-grid” technology. The method considers evolution of t...
Volume 4: Nuclear Safety, Security, and Cyber Security; Computer Code Verification and Validation
Nuclear reactor codes require validation with appropriate data representing the plant for specifi... more Nuclear reactor codes require validation with appropriate data representing the plant for specific scenarios. The thermal-hydraulic data is scattered in different locations and in different formats. Some of the data is in danger of being lost. A relational database is being developed to organize the international thermal hydraulic test data for various reactor concepts and different scenarios. At the reactor system level, that data is organized to include separate effect tests and integral effect tests for specific scenarios and corresponding phenomena. The database relies on the phenomena identification sections of expert developed PIRTs. The database will provide a summary of appropriate data, review of facility information, test description, instrumentation, references for the experimental data and some examples of application of the data for validation. The database has expandable platform and will accommodate different types of reactors and thermal-hydraulic tests. The current ...
The implementation of Super-Ultra Low Emission Vehicle standards requires more efficient exhaust ... more The implementation of Super-Ultra Low Emission Vehicle standards requires more efficient exhaust gas purification. To increase the efficiency of exhaust gas purification, an the adsorbent capable of holding hydrocarbons up to 250-300 ОС should be developed. The possibility to design such adsorbents by modification of zeolites of mordenite type, ZSM-5 and NaY, using different metals cations has been studied. It has been shown that introducing Cr, Cs, Zn, Ni, Co, Li, Mn in zeolites results in modification of the toluene TPD and toluene sorption capacity. 5%LiZSM-5 zeolite exhibits the most attractive TPD curve, with toluene desorption temperature ranging from 250 to 350ОС. The sorption capacity of 5%Li-ZSM-5 is 0.4 mmol/g. NaY zeolite has the highest sorption capacity, up to 2 mmol/g, and holds toluene up to 350ОС, but at 120ОС toluene desorption starts, which is not desirable, since the adsorbent of cold start hydrocarbons should retain them until 250-300ОС. Therefore 5%LiZSM-5 zeoli...
Fractional scaling analysis is demonstrated here at the component level for depressurization of n... more Fractional scaling analysis is demonstrated here at the component level for depressurization of nuclear reactor primary systems undergoing a large-break loss of coolant accident. This paper is the third of a three-part sequence. The first paper by Zuber et al. (2005, "Application of Fractional Scaling Analysis (FSA)
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Papers by Upendra Rohatgi