Neutron emission from spent VVÉR-1000 fuel

Translated from Atomnaya Énergiya, Vol. 67, No. 3, pp. 219–220, September, 1989.     

Neutron emission spectrum from gold excited with 16.6 MeV linearly polarized monoenergetic photons

ABSTRACT

The neutron-emission spectrum from a 197Au target excited with a 16.6 ±0.2 MeV, monoenergetic, linearly polarized photon beam was measured using the time-of-flight method at the NewSUBARU-BL01. Two components were clearly detected in the neutron spectrum produced by photonuclear reactions. One component [component (A)] shows an evaporation-like spectrum with energies up to 4 MeV. The spectrum of the other component [component (B)] is shaped like a bump and energies ≥4 MeV. The intensity of the component (A) does not show any definite angular dependence, whereas, that of the component (B) follows the relation [a+ b cos(2Θ)] as a function of the angle Θ between the polarization and detector directions.     

Neutron spectrum from heterogeneous media

On the basis of transport theory, a determination was made of the neutron spectrum from a heavy-atom medium consisting of two neutron nonabsorbing components at different temperatures. The results are compared with data obtained by means of the Selengut group model. A comparison of numerical results is made in those cases where the neutron spectrum, obtained by exact solution of the initial equations, can be represented by closed expressions containing only tabulated functions. By this means, one can estimate the error in neutron temperature to be 10%, with it being less when the slowing-down capabilities and temperature difference of the components are smaller.VEB Atomkraftwerk Rheinsberg, Betriebsteil, Berlin, East Germany Translated from Atomnaya Énergiya, Vol. 19, No. 3, pp. 253–257, September, 1965     

Neutron emission and the tritium content associated with deuterium-loaded palladium and titanium metals

An experimental investigation has been conducted on samples of palladium and titanium metals which have been loaded with deuterium through the electrolysis of D₂O and by absorption of D₂ gas. In approximately 200 experiments on 25 cells, statistically significant evidence for neutron emission was obtained in three separate experiments from one palladium cathode. Observed rates are 3–4 times the background rate and correspond to source strengths up to 50 neutrons/min. The pulse height response of the NE213 liquid scintillator-based detectors corresponds to that expected for 2.45 MeV neutrons. Tritium has been identified in nine Pd−Ni electrolytic cells, at levels corresponding 10¹²–10¹⁶ atoms. Activity buildup curves indicate that the apparent production occurs over a time period as short as a few hours. This work supported by the Office of High Energy and Nuclear Physics of the U.S. Department of Energy under Grants DE-FG05-86ER40256 and DE-FG05-88ER40437     

Neutron Yield from Water-Cooled Lead Targets

A method is developed for calculating the neutron yield from heterogeneous water-cooled targets. Comparing the computed and experimentally measured values of the neutron yield for targets consisting of pure lead and tungsten shows that the method is correct. The neutron yield of a variant of a water-cooled target consisting of tin-doped lead and a target consisting of pure lead enclosed in a zirconium shield is calculated for a realistic model. It is shown that the doped lead target gives a higher neutron yield. It is established experimentally that the lead–tin alloy is corrosion-resistant in hot water and that this alloy does not undergo appreciable recrystallization under heat shocks.     

Neutron Scaling Laws from Numerical Experiments

Experimental data of neutron yield Y _n against pinch current I _pinch is assembled to produce a more global scaling law than available. From the data a mid-range point is obtained to calibrate the neutron production mechanism of the Lee Model code. This code is then used for numerical experiments on a range of focus devices to derive neutron scaling laws. The results are the following: Y _n = 2 × 10¹¹ I _pinch ^4.7 and Y _n = 9 × 10⁹ I _peak ^3.9. It is felt that the scaling law with respect to I _pinch is rigorously obtained by these numerical experiments when compared with that obtained from measured data, which suffers from inadequacies in the measurements of I _pinch.     

用金活化法测定加速器中子源中子注量及MCNP4C修正

在四川大学720所2.5MeV静电质子加速器上,由核反应7Li(p,n)7Be,T(p,n)3He产生中子,对中国工程物理研究院研制的新型中子探测器进行效率刻度实验中,需要知道探测器位置处的中子绝对注量,为此我们测量了0.165、0.352、0.576、1.400MeV四个能点的中子注量。测量方法采用的是金活化法,在实验测量中,由靶头材料、冷却水层和样品的包层材料等引起的多次散射效应及中子在样品中的自屏蔽效应等均对实验结果产生影响。这些因素在实验中不可避免,也难以通过实验方法扣除,因此用Monte Carlo程序MCNP4C对上述效应进行了修正计算。     

Neutron sources and spectra from cold fusion

Deterministic methods are used to calculate the neutron and photon sources and spectra that would develop if fusion reactions were occurring in cold fusion experimental devices. The results from the calculations give the neutron and gamma spectra resulting from a 2.45-MeV and a 14.1 MeV neutron source. The neutron source strength from certain (gamma,n) and (alpha,n) reactions are also determined.     

Secondary electron emission coefficient for fission fragments with a fixed mass and kinetic energy

Conclusions The experimentally obtained secondary emission coefficient of electrons from thin aluminum oxide films is described within the framework of effective-charge models and a velocity-dependent expression for fission-fragment energy losses. At the same time, it was shown that secondary emission is related to energy lost to electrons, and not to the ionic charge of the fragments. This semiempirical formula can be used to calculate energy losses from heavy ions in heavy-element materials. In our opinion, the work of Brunelle et al. [3] cannot serve as a basis for identifying ion charges that penetrate both surfaces of a target. Russian Federation State Science Center, A. I. Leipunskii Institute of Physics and Power Engineering, Obninsk. Translated from Atomnaya énergiya, Vol. 83, No. 4, pp. 266–273, October, 1997.     

Neutron production from polyethylene and common spacecraft materials

We report experimental measurements of neutron production from collisions of neutron beams with polyethylene blocks simulating tissue at the Los Alamos National Laboratory Neutron Science Center and 1 GeV/amu iron nuclei with spacecraft shielding materials at the Brookhaven National Laboratory AGS.     

Separation of Curium from Neutron Irradiated Am-241

The conditions under which curium can be separated from irradiated ²⁴¹Am target were elucidated. The isolation process consists of three steps: In the first step, Am(III) is oxidized to pentavalent state in a dilute nitric acid solution, and then plutonium and curium are extracted from the irradiated target by solvent extraction with HDEHP. Curium in the organic phase is back-extracted with 1 N nitric acid, and thereafter plutonium with a reducing solution containing ferrous sulfamate. The curium is finally purified by cation exchange, using α-hydroxy isobutyrate as the eluting solution. About 0.4 μg of ²⁴²Cm and 4×10^?3 μg of ²⁴³Cm were found in the curium fraction, which had been separated from 1 mg of irradiated ²⁴¹Am sample.