摘要:

AbstractThis study considers a fast-reactor concept in which the recirculating molten plutonium alloy fuel is externally cooled by direct contact with an immiscible coolant fluid. An example of one such design is given using sodium as the coolant and Pu/Co/Ce ternary as the fuel. Operational characteristics are discussed showing the self-regulating features of the system. Some fission-product-removal mechanisms are considered together with their effect on core life and system safety. The principal problem areas are fuel pumping, phase separation, and containment-materials compatability.

ISSN:0029-5639    

DOI:10.13182/NSE64-A18759

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractChemical behavior of fission products is predicted for a“dynamic core”fast reactor, where the fuel is pumped through an outside loop by the coolant. For a 7.5 at % Pu/25 at % Co/67.5 at % Ce alloy, the various fission products are classified as sodium-extractable, fuel-soluble, precipitating, and rare gases. Evidence predicting the behavior of each class is presented. The rates of extraction of removable fission products are estimated for different modes of operation. Extractable fission product atoms are expected to remain in the fuel phase for only a few seconds. Sixty percent of all of the fission product atoms formed remain in solution in the fuel phase, and occupy a volume (∼35% of that of all fission products) roughly equal to that of the Pu consumed. The consumption of the initial inventory of Pu would require the gradual addition of 110% of the original amount of Pu, of which 3% is required to compensate for poisoning. The effective chemical composition of the fuel would be little changed during“100% burn-up.”A dynamic-core fast reactor can be operated for several years as a continuous chemical system at an economic burn-up rate.

ISSN:0029-5639    

DOI:10.13182/NSE64-A18760

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractLosses of delayed-neutron precursors are estimated for liquid-metal-fueled reactor models in which the coolant is in direct contact with the flowing fuel. It is shown that as much as 90% of the precursors may be extracted by the coolant before decaying to supply neutrons. As a result, the excess reactivity corresponding to prompt critical can decrease by a factor of 10, leading to a considerable shortening of the reactor period corresponding to a givenΔk. These conditions will, in actual operation at power, be alleviated by the contribution of the blanket's delayed neutrons and by the large negative temperature coefficient characteristic of liquid systems. The effects of mixing and reduced flow on delayed-neutron economy and resulting reactor period are evaluated. The benefits of reducing the flow are shown to be by far the greater, and a slower flow is recommended if enhanced control through delayed neutrons is needed at start-up.

ISSN:0029-5639    

DOI:10.13182/NSE64-A18761

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractThe standard analytical approaches to calculating the maximum temperature and surface -heat-flow rate in nuclear reactor fuel plates over-estimates both of these quantities due to the omission of conduction along the axis of the plate. The more general problem, including axial conduction, has been solved for fuel plates in which the clad and meat can be assumed to have the same thermal properties. Calculations made for a natural-circulation reactor show over-estimates of the maximum surface heat flow rate of 4.5 percent and of the maximum temperature rise of 4.8 percent. The error is minimized for systems having a large convection heat-transfer coefficient and will be less than 0.5 percent for most power reactor systems.

ISSN:0029-5639    

DOI:10.13182/NSE64-A18762

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractAn experimental comparison has been made in a hollow fuel element in PLUTO of a number of possible fast-neutron flux monitors with the object of providing such a flux monitor for irradiations in very high flux materials-testing reactors. If 107 mb is adopted as the reference fast-neutron activation cross section of Ni58, the fast-neutron activation cross sections for the reactions Fe54(n,p) Mn54and Ti46(n,p) Sc46are found to be 73 mb and 8 mb respectively. It is concluded from this experiment that the Fe54(n,p) Mn54reaction using iron enriched to 95% Fe54will be an adequate long-half-life fast-neutron flux monitor for irradiation in the high-flux facilities such as those likely to be used in, for example, BR-2.

ISSN:0029-5639    

DOI:10.13182/NSE64-A18763

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractA method is formulated for numerical integration of the spherical-harmonics equations in the case of cylindrical geometry. This method avoids many of the difficulties of the usual analytical techniques and allows space-varying sources as well as regions of low neutron cross section and large physical size. The usual spherical-harmonic equations (truncated) are presented in cylindrical geometry. To obtain a set of equations which (because they are more intuitive in form) lead to readily manageable numerical solution, the equations are converted to the discrete ordinate form in cylindrical geometry. From the discrete-ordinate equations, one may readily discuss inward- and outward-going neutrons. Based on this, reflection matrices are introduced at each radiusr, one describing the reflection of inwardly directed neutrons by the medium inward ofrand the other describing the reflection of outwardly directed neutrons by the medium outward ofr. The complete source-independent properties of the medium are described by these reflection matrices. Furthermore, the matrices can be obtained by numerical integration in a single pass, one by integrating from the center out and the other by integrating from the outside in. The source can be treated by considering at each radiusrthe flux that escapes outward due to sources inward ofrand by considering separately the flux that goes inward due to sources outward ofr. The first of these escape fluxes is obtained by integration outward from the origin, using the corresponding reflection matrix, the second by integration inwards. Once the above quantities have been found, the fluxes are obtained by solution of simultaneous algebraic equations (no further integrations). Numerical results necessary for the use of this method in theP3approximation are also given.

ISSN:0029-5639    

DOI:10.13182/NSE64-A18764

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractFast-neutron dose measurement by the activation of nickel foils involves a correction for thermal-neutron burnup of Co58, the daughter product of the (n,p) reaction. Fast-neutron irradiation of nickel produces Co58in its ground and excited isomeric states, and recently the isomer has been shown to have a high thermal-neutron-absorption cross section. This paper considers how the determination of fast-neutron dose by nickel activation should be corrected for thermal-neutron burn-up of both ground and isomeric states of Co58. Results, which have been fully corrected, are compared with results obtained at low reactor power where the thermal-neutron burn-up of Co58and Co58mis negligible. All the data considered were obtained from foils irradiated in rigs in hollow fuel elements in reactors of the DIDO type. The data demonstrate that accurate fast-neutron dose measurements, using nickel activation, in high-flux facilities can only be made if the thermal-neutron cross sections of Co58and Co58mand the branching ratio of the Ni58(n,p) reaction have previously been determined in the neutron spectrum being utilised.

ISSN:0029-5639    

DOI:10.13182/NSE64-A18765

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractEnergy spectra of neutrons leaking from the core tank of the Massachusetts Institute of Technology heavy-water-moderated reactor have been measured with a“fast”neutron chopper. The energy range 2×10-3eV to 2×105eV was examined for three different fuel configurations. The spectra are fairly well described as the sum of a Maxwell-Boltzman distribution and adE/Eslowing-down distribution. The energy resolution,ΔE/E, is less than 5% at energies below 100 eV and varies as E½above 100 eV, while the probable error in current,ΔJ/J, is less than 10% at all energies.

ISSN:0029-5639    

DOI:10.13182/NSE64-A18766

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractSolutions of the reactor kinetics equations for the reactivity variation required to achieve specified power responses are presented. This inverse approach is shown to extend the physical understanding of reactor behavior, to have utility in reactor operations, and to admit closed solutions for many otherwise non-linear problems. The inverse method is demonstrated by several examples: heating of a reactor at constant power, a ramp power rise followed by a constant level or by a linear drop, an oscillatory power, and a smooth transition betwen levels. Effects of a negative temperature coefficient may be described in terms of an additional fictitious delayed group. The constant-period response is shown to be optimum for a transition between two power levels.

ISSN:0029-5639    

DOI:10.13182/NSE64-A18767

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor

摘要:

AbstractA calculational method for Boltzmann's one-velocity, isotropic scattering transport equation is developed for cylindrical rods. The starting point is Peierls' integral equation, and the technique may be interpreted as a moments method or a variational method. Numerical results in the form of graphs are given for a set of standard problems. These problems include volume sources, surface sources, and the critical rod problem. For arbitrary, axially symmetric sources inside or outside the rod, a knowledge of the uncollided flux is sufficient to determine the escape probability from the rod in terms of these standard problems.

ISSN:0029-5639    

DOI:10.13182/NSE64-A18768

出版商:Taylor&Francis    

年代:1964

数据来源: Taylor