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Limit cycles and bifurcations in nuclear systems

Description: This work provides a basis for scoping calculations to determine the dynamic behavior - both linear and nonlinear - of BWRs. Additional work is now underway to establish the feasibility of routine operation of nuclear systems in the nonlinear (limit-cycle) regime.
Date: January 1, 1986
Creator: Cacuci, D.G.; March-Leuba, J. & Perez, R.B.
Partner: UNT Libraries Government Documents Department

Fuel performance improvement program: description and characterization of HBWR Series H-2, H-3, and H-4 test rods

Description: The fabrication process and as-built characteristics of the HBWR Series H-2 and H-3 test rods, as well as the three packed-particle (sphere-pac) rods in HBWR Series H-4 are described. The HBWR Series H-2, H-3, and H-4 tests are part of the irradiation test program of the Fuel Performance Improvement Program. Fifteen rods were fabricated for the three test series. Rod designs include: (1) a reference dished pellet design incorporating chamfered edges, (2) a chamfered, annular pellet design combined with graphite-coated cladding, and (3) a sphere-pac design. Both the annular-coated and sphere-pac designs include internal pressurization using helium.
Date: March 1, 1980
Creator: Guenther, R.J.; Barner, J.O. & Welty, R.K.
Partner: UNT Libraries Government Documents Department

Fuel Performance Improvement Program. Quarterly progress report, April-June 1979

Description: Two series of test rods are under irradiation in the Halden Boiling Water Reactor (HBWR Series H-1 and Series H-4). Fuel rods for Series H-2 and H-3 have been fabricated and delivered to Halden. Plans for the first series of demonstration fuel assemblies for irradiation in the Big Rock Point Reactor have been modified to substitute two BRPR Series S-2 assemblies containing segmented rods, some with sphere-pac fuel, for Series S-1 assemblies that will be irradiated later. These assemblies are in the current BRPR reload and reactor startup is scheduled for September-October. An effective method for applying graphite coating to the inside surface of cladding tubes has been demonstrated. Rod loading procedures for sphere-pac fuel that assure a uniform axial fuel density have been developed. Special hardware has been designed and tested that assures the spherical fuel can be retained in the fuel column during loading and handling operations. The measured centerline fuel temperature in the pressurized sphere-pac fuel rod (HBWR Series H-4) is lower (approx. 145/sup 0/C) than for the reference pellet fuel rod operating at comparable linear heat ratings.
Date: July 1, 1979
Creator: Crouthamel, C.E. (comp.)
Partner: UNT Libraries Government Documents Department

Development of an automated diagnostic system for BWR stability measurements

Description: An algorithm capable of automatically evaluating BWR stability has been developed. Main advantages are: Conservative estimate (asymptotic), adjusts to solve difficult conditions, confidence level, and error estimate. The apparent decay ratio (DR) is not a conservative estimate of the reactor stability. The asymptotic decay ratio must be used. Long enough record lengths must be used to reduce the uncertainty of the estimated DR.
Date: October 1, 1984
Creator: March-Leuba, J. & Smith, C.M.
Partner: UNT Libraries Government Documents Department

Identification of neutron noise sources in a boiling water reactor

Description: Measurements were made at Units 2 and 3 of the TVA Browns Ferry nuclear power plant in order to characterize the neutron and process signal noise signatures, to determine the degree of correlation between selected pairs of signals, and to assess the usefulness of such signatures for monitoring and anomaly detection in BWR-4s. Measurements were made in a power plant during normal operation at full power to determine the usefulness of the neutron and process signals from sensors and instrumentation in the plant which have been contaminated by plant electrical noise interference. It is concluded that the signals derived from existing plant sensors and instrumentation could be used to diagnose anomalies. The neutron signals could be used to monitor the stability of the core and to diagnose anomalies involving the reactor pressure, core flow, and steam flow.
Date: January 1, 1977
Creator: Sides, W.H. Jr. & Mathis, M.V.
Partner: UNT Libraries Government Documents Department

Numerical calculation of the global and local components of the neutron noise field in BWR's

Description: The calculation of the local and global components of the neutron noise field is illustrated. Agreement with experimental results is excellent above 6 H/sub 2/ frequency. The discrepancy at lower frequencies indicates the inadequacy of the point kinetics model to describe the global component of the neutron noise in large BWRs.
Date: January 1, 1979
Creator: Difilippo, F. C. & Otaduy, P. J.
Partner: UNT Libraries Government Documents Department

Report of the US Nuclear Regulatory Commission Piping Review Committee. Volume 1. Investigation and evaluation of stress corrosion cracking in piping of boiling water reactor plants

Description: IGSCC in BWR piping is occurring owing to a combination of material, environment, and stress factors, each of which can affect both the initiation of a stress-corrosion crack and the rate of its subsequent propagation. In evaluating long-term solutions to the problem, one needs to consider the effects of each of the proposed remedial actions. Mitigating actions to control IGSCC in BWR piping must be designed to alleviate one or more of the three synergistic factors: sensitized material, the convention BWR environment, and high tensile stresses. Because mitigating actions addressing each of these factors may not be fully effective under all anticipated operating conditions, mitigating actions should address two and preferably all three of the causative factors; e.g., material plus some control of water chemistry, or stress reversal plus controlled water chemistry.
Date: August 1, 1984
Partner: UNT Libraries Government Documents Department

Independent assessment of TRAC and RELAP5 codes through separate effects tests

Description: Independent assessment of TRAC-PF1 (Version 7.0), TRAC-BD1 (Version 12.0) and RELAP5/MOD1 (Cycle 14) that was initiated at BNL in FY 1982, has been completed in FY 1983. As in the previous years, emphasis at Brookhaven has been in simulating various separate-effects tests with these advanced codes and identifying the areas where further thermal-hydraulic modeling improvements are needed. The following six catetories of tests were simulated with the above codes: (1) critical flow tests (Moby-Dick nitrogen-water, BNL flashing flow, Marviken Test 24); (2) Counter-Current Flow Limiting (CCFL) tests (University of Houston, Dartmouth College single and parallel tube test); (3) level swell tests (G.E. large vessel test); (4) steam generator tests (B and W 19-tube model S.G. tests, FLECHT-SEASET U-tube S.G. tests); (5) natural circulation tests (FRIGG loop tests); and (6) post-CHF tests (Oak Ridge steady-state test).
Date: January 1, 1983
Creator: Saha, P.; Rohatgi, U.S.; Jo, J.H.; Neymotin, L.; Slovik, G.; Yuelys-Miksis, C. et al.
Partner: UNT Libraries Government Documents Department

Physical model of nonlinear noise with application to BWR stability

Description: Within the framework of the present model it is shown that the BWR reactor cannot be unstable in the linear sense, but rather it executes limited power oscillations of a magnitude that depends on the operating conditions. The onset of these oscillations can be diagnosed by the decrease in stochasticity in the power traces and by the appearance of harmonics in the PSD.
Date: January 1, 1983
Creator: March-Leuba, J. & Perez, R.B.
Partner: UNT Libraries Government Documents Department

Nonlinear dynamics of boiling water reactors

Description: Recent stability tests in Boiling Water Reactors (BWRs) have indicated that these reactors can exhibit the special nonlinear behavior of following a closed trajectory called limit cycle. The existence of a limit cycle corresponds to an oscillation of fixed amplitude and period. During these tests, such oscillations had their amplitudes limited to about +- 15% of the operating power. Since limit cycles are fairly insensitive to parameter variations, it is possible to operate a BWR under conditions that sustain a limit cycle (of fixed amplitude and period) over a finite range of reactor parameters.
Date: January 1, 1983
Creator: March-Leuba, J.; Cacuci, D.G. & Perez, R.B.
Partner: UNT Libraries Government Documents Department

Fuel utilization in a progressive conversion reactor (PCR)

Description: Preliminary studies indicate that for once-through fuel cycles, the PCR offers potential improvements over current LWRs in the following major areas: improved uranium utilization (reduced uranium demand), degraded plutonium product in spent fuel, reduced plutonium content of spent fuel, reduced amount of spent fuel, reduced fissile content of spent fuel, and reduced separative work.
Date: May 1, 1981
Creator: Leyse, C.F. & Judd, J.L.
Partner: UNT Libraries Government Documents Department

Existence of short and long range relaxation lengths in heterogeneous media

Description: Experimental data related to boiling water reactors show that the phase of the cross power spectra density between the detector response at two points in the system is described by a pure delay process above certain values of the frequency. For this to occur the adjoint flux (detector field of view) must be sharply peaked around each one of the detectors, which in turn implies the existence of a short range relaxation length. It is shown that the existence of this type of relaxation length is a direct consequence of the physical properties of heterogeneous systems and not a consequence of the number of groups used to describe the neutron field in the equivalent homogeneous system as it has been done traditionally. To show this point a one-group neutron diffusion model which accounts explicitly for the heterogeneities of the system is presented.
Date: January 1, 1980
Creator: Difilippo, F.C.
Partner: UNT Libraries Government Documents Department

Assessment of utilization of thorium in BWRs

Description: Performance characteristics and trends which could affect the incentives for and feasibility of use of thorium-based fuels in BWRs were investigated using preliminary scoping techniques. Benchmark comparisons with selected critical experiments and Monte Carlo calculations were made for simple geometries. Several fuel compositions, including uranium fissile isotopes diluted (''denatured'') with U-238 to reduce fissile enrichment below that suitable for weapon purposes, were evaluated. Emphasis was focused on design approaches which utilize unique BWR characteristics such as increased coolant boiling and nonuniform lattices. Thorium-based fuel material utilization efficiency in the BWR, without reprocessing and uranium recycle, shows no improvement in resource utilization relative to the UO/sub 2/ stowaway recycle. If plutonium recycle were restricted, then a major resource utilization incentive would exist for thorium use in LWRs with denatured uranium recycle and plutonium use in secured energy centers. The characteristics of hypothesized symbiotic systems involving secured plutonium burning sites are illustrated. However, the significant quantity of plutonium produced when ''denatured'' uranium is used raises question as to the nonproliferation effectiveness of the system. A distinctive incentive for thorium in the BWR appears to be its potential for favorable effects on power distribution, reactivity control, and margins for core dynamic response. The most promising designs are those which selectively locate thorium-bearing rods to most effectively utilize the unique heterogeneity of the BWR lattice, which is composed of individually channeled fuel assemblies separated by water spaces. Mixed lattice designs with only a few ThO/sub 2/ rods were found to significantly improve dynamic and control characteristics.
Date: January 1, 1978
Creator: Williamson, H.E.
Partner: UNT Libraries Government Documents Department

Application of noise-analysis methods to monitor stability of boiling water reactors

Description: The dynamic stability of Boiling Water Reactors (BWR's) is influenced by the reactor control system and its interaction with external load demand, channel thermal hydraulic properties, and coupled neutronic-thermal-hydraulic dynamics. The latter aspect of BWR stability which is affected by void reactivity feedback, coolant flow rate and fuel-to-coolant heat transfer characteristics is studied in this paper using the normal fluctuation data. The feasibility of overall core stability trend monitoring using neutron noise and the relatonship between stability and two-phase flow velocity in a fuel channel are studied. Time series modeling of the average power range monitor (APRM) detector signal, and bivariate analysis of adjacent local power range monitor (LPRM) detector signals are used to determine the neutron impulse response, spectral characteristics and two-phase flow velocity using data from an operating BWR. The results of analysis show that the APRM noise signal can be used to monitor changes in the closed-loop output stability of BWRs (but not the absolute stability as determined by the reactivity-to-neutron power transfer function), and that a positive correlation exists between stability and two-phase flow velocity in a fuel channel.
Date: January 1, 1981
Creator: Upadhyaya, B.R.; March-Leuba, J.; Fry, D.N. & Kitamura, M.
Partner: UNT Libraries Government Documents Department

Assessment of soil-structure interaction effects based on simple modes. [PWR; BWR]

Description: Soil-structure interaction effects are investigated using a simple mathematical model which employs three degrees-of-freedom. The foundation is approximated by a homogeneous, isotropic, elastic half-space. Harmonic functions and a recorded earthquake are used to represent the free-field input motion. Variations of the response characteristics due to structural and interaction parameters are demonstrated. Response spectra are presented that display the magnitude of the maximum structural response for a range of fixed-base structural frequencies, interaction frequencies and damping. Conclusions are obtained regarding the behavior of the response of the soil-structure system. The findings reported herein can be used for the interpretation of the results of soil-structure interaction analyses of nuclear plant structures that are performed with available computer codes.
Date: January 1, 1983
Creator: Philippacopoulos, A.J. & Miller, C.A.
Partner: UNT Libraries Government Documents Department

End effects on elbows subjected to moment loadings. [PWR; BWR]

Description: So-called end effects for moment loadings on short-radius and long-radius butt welding elbows of various arc lengths are investigated with a view toward providing more accurate design formulas for critical piping systems. Data developed in this study, along with published information, were used to develop relatively simple design equations for elbows attached at both ends to long sections of straight pipe. These formulas are the basis for an alternate ASME Code procedure for evaluating the bending moment stresses in Class 1 nuclear piping (ASME Code Case N-319). The more complicated problems of elbows with other end conditions, e.g., flanges at one or both ends, are also considered. Comparisons of recently published experimental and theoretical studies with current industrial code design rules for these situations indicate that these rules also need to be improved.
Date: January 1, 1982
Creator: Rodabaugh, E.C. & Moore, S.E.
Partner: UNT Libraries Government Documents Department

Workshop on data-acquisition and -display systems: directions after TMI. [PWR; BWR]

Description: The accident at Three Mile Island Unit-2 raised questions as to the adequacy of data acquisition and display systems in commercial nuclear power plants. A series of recommendations have developed from the various groups that have analyzed the accident in order to improve the oprator's overview of the plant safety conditions and to facilitate information transfer to technical support centers in emergency situations. This report is the result of an NSAC-sponsored workshop, where the various recommendations and emerging regulatory requirements were reviewed in an attempt to provide an integrated basis for their implementation.
Date: November 1, 1980
Partner: UNT Libraries Government Documents Department

Technical study for the chemical cleaning of Dresden-1 DNS-D1-016. Volume VII. Appendices IX thru XIV

Description: Appendices are presented which contain information concerning the decontamination of Dresden-1; consultant's opinions; proceedings of the American Power Conference, Volume 37, 1975; health physics reports; toxicological properties and industrial handling hazards of Dow solvent NS-1; and expected radiation dose rates in the new Dresden station radioactive waste processing building.
Date: June 15, 1977
Partner: UNT Libraries Government Documents Department

Technical study for the chemical cleaning of Dresden-1. Volume I, Section 1 and 2

Description: A feasibility study has been completed to decontaminate the primary system of the Dresden-1 Nuclear Power Unit operated by Commonwealth Edison Company of Illinois. Available data initially were searched to determine the state of the art. Solvents based on organic acids and chelates gave unsatisfactory deontamination factors or unacceptable corrosion rates when evaluated for cleaning of specimens from the Dresden-1 primary system, under static and dynamic conditions. A new proprietary cleaning solution, Dow Solvent NS-1, was successfully applied in these laboratory studies.
Date: June 15, 1977
Partner: UNT Libraries Government Documents Department

Evaluation of improved light water reactor core designs. Final progress report, September 1979. LWRCD-20

Description: The work conducted under this research project has developed information which supports in all respects the U.S. position evolved under the NASAP/INFCE programs with respect to the near and intermediate term potential for ore conservation in LWRs on the once-through fuel cycle. Moreover, in the even longer term, it has been confirmed that contention by Edlund and others that tight-pitch Pu/UO/sub 2/ PWR cores can achieve conversion ratios which may allow these reactors to provide a competitive energy source far into the ore-scarce post-2000 era.
Date: October 31, 1979
Partner: UNT Libraries Government Documents Department

Improving the safety of LWR power plants. Final report

Description: This report documents the results of the Study to identify current, potential research issues and efforts for improving the safety of Light Water Reactor (LWR) power plants. This final report describes the work accomplished, the results obtained, the problem areas, and the recommended solutions. Specifically, for each of the issues identified in this report for improving the safety of LWR power plants, a description is provided in detail of the safety significance, the current status (including information sources, status of technical knowledge, problem solution and current activities), and the suggestions for further research and development. Further, the issues are ranked for action into high, medium, and low priority with respect to primarily (a) improved safety (e.g. potential reduction in public risk and occupational exposure), and secondly (b) reduction in safety-related costs (improving or maintaining level of safety with simpler systems or in a more cost-effective manner).
Date: April 1, 1980
Partner: UNT Libraries Government Documents Department