摘要:

AbstractRisk analysis of nuclear power generation often requires the use of expert opinion to provide probabilistic inputs where other sources of information are unavailable or are not cost effective. In the Reactor Risk Reference Document (NUREG-1150), a methodology for the collection of expert opinion was developed.Earlier criticisms pointed out the need to establish principles for the collection and use of expert opinion. These principles include selection of experts to promote diversity of opinion, the use of state-of-the-art methods of probability elicitation including debiasing training, communication of findings through complete and clear documentation, and the preservation of the inherent uncertainty in the findings.The resulting methodology involves a ten-step process: selection of experts, selection of issues, preparation of issue statements, elicitation training, preparation of expert analyses by panel members, discussion of analyses, elicitation, recomposition and aggregation, and review by the panel members. These steps were implemented in a multiple meeting format that brought together experts from a variety of work places. The elicitation of the experts’opinions was performed by teams versed in decision analysis and in the particular aspects of power plant safety being investigated.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23645

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractA zero-variance solution exists for any linear Monte Carlo problem, and this solution can be obtained by sampling the random numbers proportional to the expected score subsequently produced by using these random numbers in the random walk.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23646

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractThe light water breeder reactor (LWBR) operated at the Shippingport Atomic Power Station from 1977 to 1982, serving the electric power grid for the Greater Pittsburgh area. The LWBR was a pressurized water reactor (PWR) with several unique features: It was designed and proved to be a breeder with an end-of-life fissile fuel content∼1.3% greater than beginning of life; the reactor used the233U-Th fuel system; and it had a large Doppler coefficient, low reactivity worth of transient xenon, and a significant reactivity effect from transient233Pa. There were no control rods or soluble poison, and reactivity was controlled by movable fuel.Core operations went extremely well. The design lifetime of 18 000 effective full-power hours was exceeded by 60% by utilizing a gradual reduction in power level. The overall capacity factor was 65%.Physics experiments showed good agreement with predictions of movable fuel reactivity worth, most temperature coefficients, breeding, power distribution, and xenon stability. Unexpected results occurred in measurements of flow coefficient of reactivity, zero power temperature coefficients early in life, and bred fissile fuel distribution.The LWBR technology has demonstrated that water-cooled breeder reactors can operate in existing water power plants much like conventional PWRs.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23647

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractGeneralized perturbation theory for the coupled neutron/nuclide field is extended to the constrained equilibrium fuel cycle. A variational method is used to formulate the adjoint depletion equations for the two-point boundary value problem of the equilibrium cycle. The reactor operating constraints are treated using the methods of constrained sensitivity theory. A practical numerical algorithm is developed to solve the constrained equilibrium cycle adjoint equations and sensitivity coefficients are generated for several responses in a zero-dimensional, two-group example. In all cases, the sensitivities are in excellent agreement with the results of the direct subtraction of perturbed forward calculations.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23648

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractBy cell calculation with the SRAC code system, void reactivity is evaluated for a high conversion light water reactor tight lattice, with an emphasis on the breakdown of the void effect into component nuclides, nuclear reactions, and energy groups. The analysis is restricted to infinite lattices and deals with the consequence of neutron energy spectrum shifts caused by void.In a preliminary parameter survey over various fissile plutonium enrichments, a 7.5 % enrichment is found approximately to border the negative and the positive coefficients, when the moderator channel volume to fuel volume Vm/Vfis fixed at a typical value of 0.53. With this combination of the enrichment and Vm/Vfvalues fixed, the reactivity effect for an incremental void increase is analyzed in detail at low-void conditions (0 to 10%) and at high-void conditions (95 to 100%).At low-void conditions, the238U contribution is negative by the capture increase in the kilo-electron-volt range, whereas the240Pu and242Pu contributions proved to be positive by the capture decrease in the 0.1- to 10-eV range. At high-void conditions, on the other hand,239Pu makes a positive contribution, originating from (a) the fission increase in the 50-eV to 1-MeV range dominating over the fission decrease in the 10- to 50-eV range, and (b) the lower capture-to-fission ratio above 10 keV. Such a positive contribution of239Pu is in contrast to the negative contribution of235U in a highly voided pressurized water reactor lattice. Americium-241 generated by the decay of241Pu makes a positive contribution in both low- and high-void conditions. The breakdown of the void effect clearly illustrates the physical mechanism.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23649

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractA computer model is described that simulates the effects of releasing molten debris into a gas-filled container. This work is motivated by studies of direct containment heating due to the dispersal of debris produced in certain nuclear reactor accident scenarios. The model consists of a finite difference scheme for the gas flow coupled with a Lagrangian particle transport algorithm. It computes the transport of the debris through the gas and evaluates radiative and convective heat transfer effects. It also accounts for the chemical reaction of the debris with the oxygen in the atmosphere, including the concurrent heat release. The computer code is used to simulate experiments in the Surtsey Direct Heating Test Facility. Computational results are compared with those obtained from experiments with small and large debris input mass. It is shown that the simulation of configurations with large debris mass can be improved with better submodels to describe the debris behavior. The description of the interaction of the debris with the container walls is of particular importance.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23650

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractDescribing functions have traditionally been used to obtain the solutions of systems of ordinary differential equations. The describing function concept has been extended to include the nonlinear, distributed parameter solid heat conduction equation. A four-step solution algorithm is presented that may be applicable to many classes of nonlinear partial differential equations. As a specific application of the solution technique, the one-dimensional nonlinear transient heat conduction equation in an annular fuel pin is considered. A computer program was written to calculate one-dimensional transient heat conduction in annular cylindrical geometry. It is found that the quasi-linearization used in the describing function method is as accurate as and faster than true linearization methods.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23651

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractThe240Pu spontaneous fission half-life has been measured using neutron coincidence counting with an enriched source. The measurement was made using a large liquid scintillator tank, and a value of 1.12×1011yr±1.6% was obtained.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23652

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

AbstractAt 24.5-keV neutron energy, the radiative capture of neutrons proceeds with only a few parts per million compared to the scattering and (n,p) reactions. Nevertheless, the radiative capture is of interest in the study of fusion reactions, which occur in the sun or in fusion reactors. This reaction yields very high energy (20.6-MeV) gamma rays, which are outstanding above any background and therefore may be of diagnostic value in fusion reactor research. A cross-section valueσnγ(24.5 keV) = 9.2±2.0µb is obtained, which is in good agreement with the value 12±6µb from earlier literature.

ISSN:0029-5639    

DOI:10.13182/NSE89-A23653

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor