Pairing effects on the fragment mass distribution of Th,U, Pu,and Cm isotopes

In this article, a comprehensive study of the fission process of Th, U, Pu, and Cm isotopes using a Yukawa-folded meanfield plus standard pairing model is presented. The study focused on analyzing the effects of the pairing interaction on the fragment mass distribution and its dependence on nuclear elongation. The significant role of pairing interactions in the fragment mass distributions of ²³⁰Th, ²³⁴U, ²⁴⁰Pu, and ²⁴⁶Cm was demonstrated. Numerical ana...     

Use of the (α, n) reaction for the quantitative determination of the beryllium,boron and fluorine content of concentration products

A rapid method for the quantitative analysis of the beryllium, boron and fluorine contents in concentration products, based on the use of the (α,n) reaction, is described. Po²¹⁰ with an activity of 250 μ Cwas used as the α-radiation source. The number of neutrons in the concentration products knocked out by α-particles is recorded by a neutron counter and serves as a measure of the beryllium, boron, and fluorine content in the product analyzed. The method makes it possible to check the concentration products of beryllium, fluorite and boron ores, and also rich ores containing fluorine and boron, with an accuracy up to 1.5–2%. The content of the element checked can be determined in the presence of a constant amount of admixtures of other elements with a high(α,n) reaction yield.     

On the problem of the metabolic exchange of cesium,strontium, and a mixture of α-emitters in cows

The results are presented of an Investigation of the distribution and excretion of the radioactive isotopes Cs¹³⁷, sr^89,90, and of a mixture of ß -emitters in 6 cows after peroral administration. It is shown that cesium and strontium are resorbed well from the intestines and that a considerable portion of the amount of emitters resorbed is excreted into milk. Resorbed cesium is almost exclusively deposited in the muscles, while strontium is in the skeleton. The results of the work indicate the danger of widespread application of radioactive fertilizers and of the maintenance of cows in pastures contaminated by the radioactive particles resulting from fission. The results can be used in calculating the maximum permissible contents of cesium, strontium, and mixtures of ß-emitters in products intended for feeding cows.     

Mechanisms of DNA Damage and Repair Implications for Carcinogenesis and Risk Assessment June 2-7, 1985 DNA is the Beginning and the End

Program Sessions Monday,June 3,19859:00 a.m.-WelcomeIntroduction.Sanford A.Miller,Ph.D.,Director Center for Food Safety and Applied Nutrition Food and Drug Administration,Washington, D.C..David P.Rall,M.D.,Ph.D.Director National Institute of Environmental Health     

Design,Analysis and R＆D of the EAST In-Vessel Components

In-vessel components are important parts of the EAST superconducting tokamak. They include the plasma facing components, passive plates, cryo-pumps, in-vessel coils, etc. The structural design, analysis and related R＆D have been completed. The divertor is designed in an up-down symmetric configuration to accommodate both double null and single null plasma operation. Passive plates are used for plasma movement control. In-vessel coils are used for the active control of plasma vertical movements. Each cryo-pump can provide an approximately 45 m^3/s pumping rate at a pressure of 10^-1 Pa for particle exhaust. Analysis shows that, when a plasma current of 1 MA disrupts in 3 ms, the EM loads caused by the eddy current and the halo current in a vertical displacement event （VDE） will not generate an unacceptable stress on the divertor structure. The bolted divertor thermal structure with an active cooling system can sustain a load of 2 MW/m^2 up to a 60 s operation if the plasma facing surface temperature is limited to 1500 ℃. Thermal testing and structural optimization testing were conducted to demonstrate the analysis results.     

Neutron spectra emitted in the fission of U235 at 0, 45, and 90 ° to the direction of motion of the fragments

Neutron spectra emitted at 0, 45, and 90 ° to the direction of motion of the fragments in the fission of U²³⁵ by 14.3 Mev neutrons have been measured. The angular distribution of the fission neutrons was found to be N(0 °): N(45 °): N(90 °) = (3.23 ± 0.12): (1.75 ± 0.07): 1.00. The experimental data are compared with spectra calculated on the assumption of an isotropic Maxwellianneutron distribution in the center-of-mass system of the fragment.     

Calculation of the spectra of fission neutrons emitted at angles of 0, 45, and 90° to the direction of flight of the fragments

The evaporation model is used to solve the problem of the spectrum of neutrons emitted by fission Fragments at angIes of 0, 45, and 90° to the direction of flight of the fragments. It is assumed that the neutrons are emitted isotropically in a coordinate system associated with the fragment. The spectra calculated are in good agreement with the experimental data.Translated from Atomnaya Énergiya, Vol. 13, No. 6, pp. 530–533, December, 1962     

Cross-section measurements for the (n,p) and (n,α) reactions on 23Na and for the (n,p) reaction on 26Mg at the neutron energies from 13.6 to 14.9 MeV

Cross sections were measured at neutron energies from 13.6 to 14.9 MeV for the reactions ²³Na(n,p)²³Ne and ²³Na(n,α)²⁰F, and ²⁶Mg(n,p)²⁶Na leading to short-lived products. The production of short-lived nuclei and the spectra accumulation have been carried out by cyclic activation method. Corrections were made for the effects of gamma ray attenuation, coincidence summing, pulse pile-up, dead time, neutron flux fluctuations and scattered low energy neutrons.     

Uncertainties for the Kalimer Sodium Fast Reactor: Void Reactivity Coefficient,k eff, βeff,Depletion and Radiotoxicity

In this paper, we present the effect of nuclear data and its uncertainties on the core design of the KALIMER-600 Sodium Fast Reactor. The void reactivity coefficient, k _eff, and β_eff are calculated with uncertainties due to the nuclear data of the main components of the reactor: ²³⁸U, ^239;240Pu, ²³Na, ⁵⁶Fe, and ⁹⁰Zr. Two methods are used: the “Total Monte Carlo” method involving many identical calculations with different sets of randomized nuclear data, and the perturbation method using MCNP. In a second step, the depletion is calculated together with radiotoxicity components after irradiation. By the Total Monte Carlo method, uncertainties due to nuclear data are propagated to the fuel composition and radiotoxicity curves.     

Direct measurement of the energy variation of η for U233, U235, and Pu239

A technique is described that measures directly the energy variation of , the number of fission neutrons produced per neutron absorbed. When combined with total cross sections, the method is capable of giving fission cross sections as well. Results are presented in the energy region near thermal, of importance to reactor design, for U²³³, U²³⁵, and Pu²³⁹. Comparison with computed from total and fission cross sections shows good agreement for U²³³ and U²³⁵ but a disagreement outside experimental error for Pu²³⁹. An auxiliary experiment demonstrates that , the number of neutrons per fission, is constant with energy in the region of interest for Pu²³⁹, hence that the discrepancy cannot be ascribed to a variation.Work performed under contract with U. S. Atomic Energy Commission.[The following is a reproduction of the original American paper, and not a re-translation from Russian — Publisher's note].     

Radionuclide inventories in the discharged fuels of PHWR-220, BWR-160, VVER-1000 and the conceptual ATBR-600 reactors – A case study

Radionuclides content in the discharged fuel of the conceptual thorium breeder reactor ATBR-600 has been assessed and compared against other thermal power reactors considered in Indian nuclear power programme. The contribution of actinides and the fission products inventories in the discharged fuels are separately estimated and assessed. The ATBR-600 reactor is suggested for closed fuel cycle option. The relatively large presence of the unspent plutonium would in fact be recycled. Nonetheless, the data has been presented in the event of operating ATBR-600 like other present day power reactors in a once through fuel cycle mode.     

An Approximate Calculation Method of the λ, ω p and ω d Eigenvalue Problem of the Group Diffusion Equation

The approximate solutions of the, λ, ω _p and ω _d eigenvalue problems of the group-diffusion equation for a multi-region reactor are obtained by expanding neutron fluxes into finite numbers of eigenfunctions satisfying the Helmholtz equation and the boundary condition at the extrapolated boundary of the reactor. The original eigenvalue problem is reduced to that of an asymmetric real matrix for the vector whose components constitute the expansion coefficients. For the numerical calculation of the real matrix thus derived, to determine the higher λ, ω _p and ω _d modes, the QR iteration method based on numerically stable unitary transformation, in combination with inverse iteration is effective in saving computation time.

The λ, ω _p and ω _d modes obtained by the above method are expressed by a linear combination of a comparatively small number of simple elementary functions, and are thus of high practical value in the numerical calculation of higher order perturbations and for examining snace-deDendent reactor dynamics.     

Synthesis,labelling and animal experiments of the derivative of phenylpentadecanoic acid（CACPPA）

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Solubility studies,thermodynamics and electrical conductivity in the Th1−xSrxO2 system

A polymeric gel combustion method was employed for the lower temperature synthesis of 1, 2, 3, 5, 7.5, 10 and 15 mol.% SrO doped ThO₂ solid solutions. After final sintering of these samples at 1573 K in Ar, the solubility limit was found to be 1 mol.%, giving rise to a composition-independent value of (559.84±0.02) pm (at 300 K) for the CaF₂-type unit cell. AC impedance measurements carried out on discs of 1, 2, 3 and 5 mol.% SrO in ThO₂ discs in flowing Ar, yielded values of 116, 115, 128 and 96 kJ/mol, respectively as the activation energies for the bulk ionic conductivity. The thermodynamic activities of SrO in the 1, 2 and 3 mol.% solid solutions were measured using [SrO]_ThO2,SrF₂,O₂,Pt as the test electrodes and SrZrO₃,ZrO₂,SrF₂,O₂,Pt as the reference with sintered SrF₂ as the electrolyte over the range of approximately 650–800 K. The activity values differed marginally from each other, but were indicative of the combined (and not free) state of SrO. Hence, only a limiting value of a_SrO for the just saturated (mole fraction of SrO=0.01) thoria solid solution could be derived as log a_SrO=0.36−4602/T (K).     

Connection Between the Largest Lyapunov Exponent, Density Fluctuation and Multifragmentation in Excited Nuclear Systems

The largest Lyapunov exponent (LLE) has been widely used to measure the levelof chaos of a system     

A System for the γ-Production Data Intercomparison and the Intercomparison of γ-Production Data for Fe, Cr, Ni from Major Evaluated Data Libraries

The γ-production data are very important for the nuclear engineering, especially for radioactive shielding. There are γ-production data in the major evaluated nuclear data libraries, such as ENDF/B-6(B6), JENDL-3(J3),JEF-2(JE2), BROND-2(BR2) and CENDL-2.1(C2) for important nuclides, especially for structure and shielding materials. And meanwhile, quite lots of measured data have been compiled in EXFOR format. To intercompare the γ-production data from the major evaluated data libraries, a system has been developed and used to Fe, Cr, Ni data from C2, B6, J3, JE2 and BR2.