28 Matching Results

Search Results

Advanced search parameters have been applied.

Transfer reactions for the /sup 50/Ti + /sup 90/Zr system below the coulomb barrier

Description: Experimentally observed enhancements of fusion cross sections are often attributed to result from coupling interactions between fusion and transfer channels. Existing experimental results indicate that large fusion enhancement generally goes with large neutron-transfer cross section and thus supports this attribute, but observations of more specific relations between these quasielastic channels have not yet been reported. Here we present some experimental results that pertain to fusion-transfer coupling interactions. 21 refs., 6 figs.
Date: January 1, 1988
Creator: Kim, H.J.
Partner: UNT Libraries Government Documents Department

CRAB Cavity in CERN SPS

Description: Beam collisions with a crossing angle at the interaction point are often necessary in colliders to reduce the effects of parasitic collisions which induce emittance growth and decrease beam lifetime. The crossing angle reduces the geometrical overlap of the beams and hence the luminosity. Crab cavity offer a promising way to compensate the crossing angle and to realize effective head-on collisions. Moreover, the crab crossing mitigates the synchro-betatron resonances due to the crossing angle. A crab cavity experiment in SPS is proposed as a proof of principle before deciding on a full crab-cavity implementation in the LHC. In this paper, we investigate the effects of a single crab cavity on beam dynamics in the SPS and life time.
Date: May 1, 2010
Creator: Kim, H.J.; Sen, T. & /Fermilab
Partner: UNT Libraries Government Documents Department

Reactions between medium-mass nuclei at subbarrier energies

Description: A number of diverse theories can account, to a similar extent, for experimentally observed large enhancements in subbarrier fusion cross sections. For example, coupled-channels, neck-formation, distributed-barrier, and direct absorption theories have been used with comparable degrees of success to analyze the enhancement in {sup 58}Ni + {sup 58}Ni fusion cross sections at subbarrier energies. This example illustrates that, although necessary, fusion cross sections alone are not sufficient to assess what really is the underlying enhancement mechanism. Although their details vary, these theories share a reliance on interactions between the incident and one or more outgoing reaction channels to produce the enhancement. Being microscopic, the coupled-channels approach requires interactions with specific individual exit channels, such as inelastic and nucleon transfer. On the other hand, being macroscopic in nature, the neck-formation and distributed-barrier theories treat the interactions in a more global way. Thus, in addition to fusion, detailed studies of exit channels in general at subbarrier energies are very much needed in order to develop a good theoretical understanding of how the enhancement really comes about. We present results from our study of transfer reactions between {sup 50}Ti and {sup 93}Nb that pertain to the subbarrier neck. Since the experimental arrangement used is the same as that of our previous study, only a brief description is given. Target and target-like ejectiles emitted forward from the bombardment of thin {sup 50}Ti targets by {sup 93}Nb beams were first magnetically analyzed and then detected by a hybrid position-sensitive gas detector system, which was placed at the nominal focal plane of the magent; ejectiles emitted at 10{degree} {le} {theta} {le} 20{degree} angular range were investigated at bombarding energies of 283.1, 291.2, 273.2, 302.0, and 306.9 MeV.
Date: November 1, 1990
Creator: Kim, H.J.
Partner: UNT Libraries Government Documents Department

Liquid Drop Effects in Subbarrier Transfer Reactions

Description: Reaction products from a multitude of binary channels are observed to emerge at large c.m. angles at subbarrier energies for the {sup 50}Ti {plus} {sup 93}Nb system. The energy spectra of these products and the distance where they first emerge indicate that these reaction products result from the neck which is formed outside the Coulomb barrier. 9 refs., 5 figs.
Date: August 1990
Creator: Kim, H. J.
Partner: UNT Libraries Government Documents Department

Nuclear structure effects on alpha reduced widths

Description: A review of ..cap alpha.. widths for s-wave transitions is presented together with a discussion of the following topics: (1) a new determination of the /sup 218/Ra half-life and its relation to reflection asymmetry in nuclei near N = 130, (2) a measurement of the /sup 194/Pb ..cap alpha..-decay rate and the influence of the Z = 82 gap on neutron-deficient Pb nuclei, and (3) an up-date of ..cap alpha..-decay-rate systematics for isotopes in the rare earth and medium-weight mass regions. 16 refs., 6 figs.
Date: January 1, 1987
Creator: Toth, K.S.; Ellis-Akovali, Y.A.; Kim, H.J. & McConnell, J.W.
Partner: UNT Libraries Government Documents Department

Assessment of RELAP5/MOD3.1 with the LSTF SB-SG-06 experiment simulating a steam generator tube rupture transient

Description: The objective of the present work is to identify the predictability of RELAP5/MOD3.1 regarding thermal-hydraulic behavior during a steam generator tube rupture (SGTR). To evaluate the computed results, LSTF SB-SG-06 test data simulating the SGTR that occurred at the Mihama Unit 2 in 1991 are used. Also, some sensitivity studies of the code change in RELAP5, the break simulation model, and the break valve discharge coefficient are performed. The calculation results indicate that the RELAP5/MOD3.1 code predicted well the sequence of events and the major phenomena during the transient, such as the asymmetric loop behavior, reactor coolant system (RCS) cooldown and heat transfer by natural circulation, the primary and secondary system depressurization by the pressurizer auxiliary spray and the steam dump using the intact loop steam generator (SG) relief valve, and so on. However, there are some differences from the experimental data in the number of the relief valve cycling in the affected SG, and the flow regime of the hot leg with the pressurizer, and the break flow rates. Finally, the calculation also indicates that the coolant in the core could remain in a subcooled state as a result of the heat transfer caused by the natural circulation flow even if the reactor coolant pumps (RCPs) turned off and that the affected SG could be properly isolated to minimize the radiological release after the SGTR.
Date: September 1, 1996
Creator: Seul, K. W.; Bang, Y. S.; Lee, S. & Kim, H. J.
Partner: UNT Libraries Government Documents Department

Electromagnetic method for analyzing the property of steel casing

Description: It has been shown that electromagnetic (EM) imaging, in particular in borehole applications, can be effective in characterizing and monitoring subsurface processes involved in improved oil recovery operations and production management. In this report the authors present an innovative EM method for extracting information about a steel casing in terms of its electrical conductivity, magnetic permeability, and the casing thickness. The method is based on accurate evaluation of magnetic fields near the transmitting loop in a steel-cased borehole, and the least squares inversion of thus measured data. The need to make measurements close to the source stems from the two related considerations. One reason is that by making measurements close to the transmitter one can keep the formation response from entering the measurement to a minimum. The other reason concerns with the practical consideration involved in fabricating a borehole tool. The measurement accuracy in terms of PPM to the primary field can best be achieved when the transmitter and receiver are close to each other. To facilitate this requirement one can consider a single loop acting as the source and the receiver operating in time domain, or a closely coupled frequency-domain system with the source-receiver separation of just a few inches apart. Results are discussed.
Date: February 1, 1998
Creator: Lee, K.H.; Kim, H.J. & Song, Y.
Partner: UNT Libraries Government Documents Department

Three-dimensional transient electromagnetic modeling in the Laplace Domain

Description: In modeling electromagnetic responses, Maxwell's equations in the frequency domain are popular and have been widely used (Nabighian, 1994; Newman and Alumbaugh, 1995; Smith, 1996, to list a few). Recently, electromagnetic modeling in the time domain using the finite difference (FDTD) method (Wang and Hohmann, 1993) has also been used to study transient electromagnetic interactions in the conductive medium. This paper presents a new technique to compute the electromagnetic response of three-dimensional (3-D) structures. The proposed new method is based on transforming Maxwell's equations to the Laplace domain. For each discrete Laplace variable, Maxwell's equations are discretized in 3-D using the staggered grid and the finite difference method (FDM). The resulting system of equations is then solved for the fields using the incomplete Cholesky conjugate gradient (ICCG) method. The new method is particularly effective in saving computer memory since all the operations are carried out in real numbers. For the same reason, the computing speed is faster than frequency domain modeling. The proposed approach can be an extremely useful tool in developing an inversion algorithm using the time domain data.
Date: September 1, 1998
Creator: Mizunaga, H.; Lee, Ki Ha & Kim, H.J.
Partner: UNT Libraries Government Documents Department

Assessment of RELAP5/MOD3 with the LOFT L9-1/L3-3 experiment simulating an anticipated transient with multiple failures

Description: The RELAP5/MOD3 5m5 code is assessed using the L9-1/L3-3 test carried out in the LOFT facility, a 1/60-scaled experimental reactor, simulating a loss of feedwater accident with multiple failures and the sequentially-induced small break loss-of-coolant accident. The code predictability is evaluated for the four separated sub-periods with respect to the system response; initial heatup phase, spray and power operated relief valve (PORV) cycling phase, blowdown phase and recovery phase. Based on the comparisons of the results from the calculation with the experiment data, it is shown that the overall thermal-hydraulic behavior important to the scenario such as a heat removal between the primary side and the secondary side and a system depressurization can be well-predicted and that the code could be applied to the full-scale nuclear power plant for an anticipated transient with multiple failures within a reasonable accuracy. The minor discrepancies between the prediction and the experiment are identified in reactor scram time, post-scram behavior in the initial heatup phase, excessive heatup rate in the cycling phase, insufficient energy convected out the PORV under the hot leg stratified condition in the saturated blowdown phase and void distribution in secondary side in the recovery phase. This may come from the code uncertainties in predicting the spray mass flow rate, the associated condensation in pressurizer and junction fluid density under stratified condition.
Date: February 1, 1994
Creator: Bang, Y. S.; Seul, K. W. & Kim, H. J.
Partner: UNT Libraries Government Documents Department

Assessment of BETHSY Test 9.1.b using RELAP5/MOD3. International Agreement Report

Description: The 2`` cold leg break test 9.l.b, conducted at the BETHSY facility was analyzed using the RELAP5/MOD3 Version 5m5 code. The test 9.l.b was conducted with the main objective being the investigation of the thermal-hydraulic mechanisms responsible for the large core uncovery and fuel heat-up, requiring the implementation of an ultimate procedure. The present analysis demonstrates the code`s capability to predict, with sufficient accuracy, the main phenomena occurring in the depressurization transient, both from a qualitative and quantitative point of view. Nevertheless, several differences regarding the evolution of phenomena and affecting the timing order have to be pointed out in the base calculation. Three calculations were carried out to study the sensitivity to change of the nodalization in the components of the loop seal cross-over legs, and of the auxiliary feedwater control logics, and of the break discharge coefficient.
Date: June 1, 1993
Creator: Lee, S.; Chung, B. D. & Kim, H. J.
Partner: UNT Libraries Government Documents Department

RELAP5 assessment using semiscale SBLOCA test S-NH-1. International Agreement Report

Description: 2-inch cold leg break test S-NH-1, conducted at the 1/1705 volume scaled facility Semiscale was analyzed using RELAP5/MOD2 Cycle 36.04 and MOD3 Version 5m5. Loss of HPIS was assumed, and reactor trip occurred on a low PZR pressure signal (13.1 MPa), and pumps began an unpowered coastdown on SI signal (12.5 MPa). The system was recovered by opening ADV`s when the PCT became higher than 811 K. Accumulator was finally injected into the system when the primary system pressure was less than 4.0 MPa. The experiment was terminated when the pressure reached the LPIS actuation set point RELAP5/MOD2 analysis demonstrated its capability to predict, with a sufficient accuracy, the main phenomena occurring in the depressurization transient, both from a qualitative and quantitative points of view. Nevertheless, several differences were noted regarding the break flow rate and inventory distribution due to deficiencies in two-phase choked flow model, horizontal stratification interfacial drag, and a CCFL model. The main reason for the core to remain nearly fully covered with the liquid was the under-prediction of the break flow by the code. Several sensitivity calculations were tried using the MOD2 to improve the results by using the different options of break flow modeling (downward, homogeneous, and area increase). The break area compensating concept based on ``the integrated break flow matching`` gave the best results than downward junction and homogeneous options. And the MOD3 showed improvement in predicting a CCFL in SG and a heatup in the core.
Date: June 1, 1993
Creator: Lee, E. J.; Chung, B. D. & Kim, H. J.
Partner: UNT Libraries Government Documents Department

RELAP5/MOD3 assessment using the Semiscale 50% Feed Line Break test S-FS-11

Description: The RELAP5/MOD3 5m5 code was assessed using the 1/1705 volume scaled Semiscale 50% Feed Line Break (FLB) test S-FS-11. Test S-FS-11 was designed in three phases: (a) blowdown phase, (b) stabilization phase, and (c) refill phase. The first objective was to assess the code applicability to 50% FLB situation, the second was to evaluate the FSAR conservatisms regarding SG heat transfer degradation, steam line check valve failure, break flow state, and peak primary system pressure, and the third was to validate the EOP effectiveness. The code was able to simulate the major T/H parameters except for the two-phase break flow and the secondary convective heat transfer rate. The two-phase break flow had still deficiencies. The current boiling heat transfer rate was developed from the data for flow inside of a heated tube, not for flow around heated tubes in a tube bundle. Results indicated that the assumption of 100% heat transfer until the liquid inventory depletion was not conservative, the failed affected steam generator main steam line check valve assumption was not either conservative, the measured break flow experienced all types of flow conditions, the relative proximity to the 110% design pressure limit was conservative. The automatic actions during the blowdown phase were effective in mitigating the consequences. The stabilization operation performed by operator actions were effective to permit natural circulation cooldown and depressurization. The voided secondary refill operations also verified the effectiveness of the operations while recovering the inventory in a voided steam generator.
Date: June 1, 1993
Creator: Lee, E. J.; Chung, B. D. & Kim, H. J.
Partner: UNT Libraries Government Documents Department

RELAP5 assessment using LSTF test data SB-CL-18

Description: A 5 % cold leg break test, run SB-CL-18, conducted at the Large Scale Test Facility (LSTF) was analyzed using the RELAP5/MOD2 Cycle 36.04 and the RELAP5/MOD3 Version 5m5 codes. The test SB-CL-18 was conducted with the main objective being the investigation of the thermal-hydraulic mechanisms responsible for the early core uncovery, including the manometric effect due to an asymmetric coolant holdup in the steam generator upflow and downflow side. The present analysis, carried out with the RELAP5/MOD2 and MOD3 codes, demonstrates the code`s capability to predict, with sufficient accuracy, the main phenomena occurring in the depressurization transient, both from a qualitative and quantitative point of view. Nevertheless, several differences regarding the evolution of phenomena and affecting the timing order have been pointed out in the base calculations. The sensitivity study on the break flow and the nodalization study in the components of the steam generator U-tubes and the cross-over legs were also carried out. The RELAP5/MOD3 calculation with the nodalization change resulted in good predictions of the major thermal-hydraulic phenomena and their timing order.
Date: May 1, 1993
Creator: Lee, S.; Chung, B. D. & Kim, H. J.
Partner: UNT Libraries Government Documents Department

Assessment of RELAP5/MOD3.1 for gravity-driven injection experiment in the core makeup tank of the CARR Passive Reactor (CP-1300)

Description: The objective of the present work is to improve the analysis capability of RELAP5/MOD3.1 on the direct contact condensation in the core makeup tank (CMT) of passive high-pressure injection system (PHPIS) in the CARR Passive Reactor (CP-1300). The gravity-driven injection experiment is conducted by using a small scale test facility to identify the parameters having significant effects on the gravity-driven injection and the major condensation modes. It turns out that the larger the water subcooling is, the more initiation of injection is delayed, and the sparger and the natural circulation of the hot water from the steam generator accelerate the gravity-driven injection. The condensation modes are divided into three modes: sonic jet, subsonic jet, and steam cavity. RELAP5/MOD3.1 is chosen to evaluate the cod predictability on the direct contact condensation in the CMT. It is found that the predictions of MOD3.1 are in better agreement with the experimental data than those of MOD3.0. From the nodalization study of the test section, the 1-node model shows better agreement with the experimental data than the multi-node models. RELAP5/MOD3.1 identifies the flow regime of the test section as vertical stratification. However, the flow regime observed in the experiment is the subsonic jet with the bubble having the vertical cone shape. To accurately predict the direct contact condensation in the CMT with RELAP5/MOD3.1, it is essential that a new set of the interfacial heat transfer coefficients and a new flow regime map for direct contact condensation in the CMT be developed.
Date: October 1, 1996
Creator: Lee, S. I.; No, H. C.; Bang, Y. S. & Kim, H. J.
Partner: UNT Libraries Government Documents Department

Assessment of CCFL model of RELAP5/MOD3 against simple vertical tubes and rod bundle tests. International Agreement Report

Description: The CCFL model used in RELAP5/MOD3 version 5m5 has been assessed against simple vertical tubes and bundle tests performed at a facility of Korea Atomic Energy Research Institute. The effect of changes in tube diameter and nodalization of tube section were investigated. The roles of interfacial drags on the flooding characteristics are discussed. Differences between the calculation and the experiment are also discussed. A comparison between model assessment results and the test data showed that the calculated value lay well on the experimental flooding curve specified by user, but the pressure jump before onset of flooding was not calculated.
Date: June 1, 1993
Creator: Cho, S.; Arne, N.; Chung, B. D. & Kim, H. J.
Partner: UNT Libraries Government Documents Department

Implications of heavy-ion-induced satellite x-ray emission. II. Production of K and L x rays by 0. 9 to 2. 6 MeV/u Ar ions in thick targets of V, Cu, Nb, Ta, and Pt

Description: Cross sections are reported for x-ray production in targets of /sup 23/V, /sup 29/Cu, /sup 41/Nb, /sup 73/Ta, and /sup 78/Pt by /sup 40/Ar ions of 36.0, 56.4, 76.6, and 103 MeV. Because the targets were relatively thick, approx. 1 mg/cm/sup 2/, the data were corrected, using a novel approach, for projectile energy loss and x-ray attenuation in the targets. The cross sections so analyzed are compared with the predictions of the first Born approximation as well as with those of a more extensive treatment which includes energy loss, Coulomb deflection, perturbed stationary-state, and relativistic effects. The significant discrepancies between the data and this latter theory are atrributed primarily to the influence of multiple ionization on the x-ray emission probabilities.
Date: January 1, 1983
Creator: O'Kelley, G.D.; Auble, R.L.; Hulett, L.D.; Kim, H.J.; Milner, W.T.; Raman, S. et al.
Partner: UNT Libraries Government Documents Department

Washing of Cloth Contaminated with Radionuclides Using A Detergent-Free Laundry System

Description: In this study, we describe a new laundry system to wash clothes, including those contaminated with radionuclides, without using detergent. The main part of this system is electrolytic cell that consists of a cathode with a special coating of nickel, an anode of nickel, and a cation exchange membrane between the two electrodes. The electrolyte is supplied to the anode and the tap-water to the cathode. When an electricity of 5 volts and 25 amperes is applied to the electrodes, the processed water is produced from the cathode. This processed water containing no detergent was investigated experimentally with regard to its decontamination efficiency of radionuclides and detergency of soil as compared to the conventional washing using detergent. It was found that the processed water from this system has an ability to simultaneously remove radionuclides and soil from the cloth with good efficiency.
Date: February 25, 2003
Creator: Yim, S. P.; Ahn, B. G.; Lee, H. J.; Shon, J. S.; Chung, H.; Kim, K. J. et al.
Partner: UNT Libraries Government Documents Department

Far-infrared carrier dynamics in superconducting MgB[sub 2]

Description: We have performed optical-pump terahertz-probe measurements in transmission on MgB{sub 2} thin films in the superconducting state. The initial optical perturbation of the superconducting condensate and subsequent pair recovery display a strong fluence dependence. In conclusion, we have performed the first time-resolved far-infrared studies on the new superconductor MgB{sub 2}. We have observed a strongly fluence dependent pair recovery time that, at the lowest fluences used, is approximately 500 ps. In addition, at the lower excitation fluences where superconductivity is not destroyed, a risetime in the dynamics is observed that may be due to photoinduced gap fluctuations.
Date: January 1, 2002
Creator: Averitt, R. D. (Richard D.); Demsar, J. (Jure); Taylor, Antoinette J.,; Kang, W. N. (Won-Nam); Kim, H. J. (Hoen-Jung); Choi, E. M. (Eun-Mi) et al.
Partner: UNT Libraries Government Documents Department

Long-range and head-on beam-beam compensation studies in RHIC with lessons for the LHC

Description: Long-range as well as head-on beam-beam effects are expected to limit the LHC performance with design parameters. They are also important consideration for the LHC upgrades. To mitigate long-range effects current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the compensation of a single long-range interaction. The tests provide benchmark data for simulations and analytical treatments. To reduce the head-on beam-beam effect electron lenses were proposed for both RIDC and the LHC. We present the experimental long-range beam-beam program at RHIC and report on head-on compensations studies based on simulations.
Date: November 24, 2008
Creator: Fischer,W.; Luo, Y.; Abreu, N.; Calaga, R.; Montag, C.; Robert-Demolaize, G. et al.
Partner: UNT Libraries Government Documents Department

Long-range and head-on beam-beam compensation studies in RHIC with lessons for the LHC

Description: Long-range as well as head-on beam-beam effects are expected to limit the LHC performance with design parameters. They are also important consideration for the LHC upgrades. To mitigate long-range effects, current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the compensation of a single long-range interaction. The tests provide benchmark data for simulations and analytical treatments. Electron lenses were proposed for both RHIC and the LHC to reduce the head-on beam-beam effect. We present the experimental long-range beam-beam program at RHIC and report on head-on compensations studies based on simulations.
Date: January 12, 2009
Creator: Fischer, W.; Luo, Y.; Abreu, N.; Calaga, R.; Montag, C.; Robert-Demolaize, G. et al.
Partner: UNT Libraries Government Documents Department

Magnetism as a main origin for the diverse magnetotransport.

Description: Magnetotransport properties of pure Mg metal and MgB{sub 2} samples with varying amounts of unreacted Mg are systematically studied in magnetic fields up to 18 T. With increasing quantity of Mg, the inhomogeneous MgB{sub 2} samples show greatly decreased residual resistivity, enhanced residual resistance ratio (RRR) and enhanced magnetoresistance (MR), gradually approaching the transport behaviors of pure Mg metal. We use the generalized effective medium theory to show that the large RRR and MR of the inhomogeneous MgB{sub 2} samples can be quantitatively explained by a two-phase model in which the two phases are MgB{sub 2} and pure Mg.
Date: January 1, 2001
Creator: Betts, J. B. (Jonathan B.); Jaime, M. (Marcello); Lacerda, A. H. (Alex H.); Boebinger, G. S. (Gregory S.); Jung, C. U. (Chang Uk); Kim, H. J. (Hoen-Jung) et al.
Partner: UNT Libraries Government Documents Department

Long-Range And Head-On Beam-Beam Compensation Studies in RHIC With Lessons for the LHC

Description: Long-range as well as head-on beam-beam effects are expected to limit the LHC performance with design parameters. They are are also important consideration for the LHC upgrades. To mitigate long-range effects, current carrying wires parallel to the beam were proposed. Two such wires are installed in RHIC where they allow studying the effect of strong long-range beam-beam effects, as well as the compensation of a single long-range interaction. The tests provide benchmark data for simulations and analytical treatments. Electron lenses were proposed for both RHIC and the LHC to reduce the head-on beam-beam effect. We present the experimental long-range beam-beam program at RHIC and report on head-on compensations studies based on simulations.
Date: November 28, 2011
Creator: Fischer, W.; Luo, Y.; Abreu, N.; Calaga, R.; Montag, C.; Robert-Demolaize, G. et al.
Partner: UNT Libraries Government Documents Department