Computational investigation of the formation of radiation fields behind the radiation shield of accelerators is an important problem. Interest in the development of standard methods employed in reactor physics for extending radiationtransfer calculations (the multigroup approach in the description of the energy dependence of the cross sections and the method of discrete ordinates for solving kinetic equation) to the high-energy range has increased substantially in connection with more stringent requirements for computational accuracy, especially in problems of deep penetration of particles, electronuclear power generation, transmutation of long-lived radionuclides, and minimization of background loads on detectors [1--3], This approach makes it possible to separate the mathematical and physical aspects of the calculation of particle transport in matter. The computational programs are universal with respect to the type of particles and their energy, and the main initial physical information --nuclear constants for different types of particles and energy --is contained in libraries, prepared beforehand, of group cross sections.Examples of libraries of group nuclear constants are the BND-400 [4], HILO [1], and Sadko-1 [5] libraries. However, the first two libraries contain data only for neutrons in the energy range below 400 MeV and the Sadko-1 system makes it possible to perform calculations for protons and neutrons with energies up to 600 MeV.The development of a new fast code [6] for calculating the yield of secondary hadrons in inelastic hA-interactions, which would make it possible to obtain much more accurate nuclear data, to expand the energy range, and to increase the number of particle types supported, was the basis for a new version of a library of group nuclear cross sections. The Sadko system (version 2), developed at the Institute of High-Energy Physics, of hadron constants provides the constants necessary for performing calculations by group methods for protons and r-mesons in the energy range from 20 MeV to 10 TeV, neutrons from thermal energy to 10 TeV, and photons from 0.01 to 15 MeV.In the present paper we describe the structure and basic parameters of the new version of the system of constants. Structure of Sadko-2 (Fig. 1). The constituent parts of the system consist of independent blocks of programs and algorithms which are unified by the problem of producing a file of group cross sections in a definite format. The structure of Sadko is determined by the steps required to solve this problem: calculation of the total and double-differential cross sections for the inelastic hA-interaction for a given isotope and energy range;choice of the optimal number of energy groups and a rational method for averaging the cross sections, calculation of group microsections and the scattering phase function for an isotope in the energy range of protons, neutrons, and pions > 20 MeV and probabilities of transitions in a group for neutron energy < 20 MeV; preparation of a low-energy file of group interaction cross...

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A large number of codes and program packages, for example, [1--4], have been developed to solve many radiationphysics probIems on charged-particle accelerators involving calculation of the transfer of high-energy radiation. However, no code or program is universal --each program is restricted with respect to energy, type of particles, size and geometry of the region computed, and so on. Outside their region of applicability the programs often lead to incorrect results. The possibilities of computational methods and their restrictions are not always clear to the user. For this reason, we feel that all codes must be verified. However, the programs cannot always be verified on experimental results: special experiments are expensive and the experimental data obtained are, as a rule, insufficient for comprehensive verification of the programs. The way out of this situation is to test the programs on computational results obtained with so-called exact codes, i.e., codes which are designed for definite conditions with a known and quite low methodological error. An example of such a code in a wide range of particle (n, p, x, K, 3') energies is the program-constants system ROZ-6N + Sadko [5--7], which is based on solving a kinetic equation by the method of discrete ordinates.Our objective in the present work is to make a comparative analysis of the computational results for radiation transfer with some known codes and program packages and with the use of the ROZ-6N+Sadko program system for a diverse range of primary-particle energies.Methods for calculating the transport of particles generated by high-energy hadrons. Almost all programs developed for calculating the transport of high-energy particles employ analog modeling of the particle trajectories by the Monte Carlo method. This method is chosen because of its advantages, such as the mathematical simplicity of the modeling algorithm, the possibility and simplicity of taking into account within the scope of the method any physical process, and the possibility of calculating radiation transfer in a complicated geometry. At the same time, the Monte Carlo method has a limitation that determines its region of application --the deep-penetration problem.The limit of applicability of the Monte Carlo analog method can be easily estimated on the basis of the following obvious considerations. The error in estimating the mathematical expectation of a functional N (for example, N can be the number of particles) behind a shield of thickness t by the method of random tests is determined by the formula ~ = 1/x/N. The functional N can be approximated by the well-known function N -N o exp (-fiX), where N o is the number of histories and X is the attenuation length. The computation time is related linearly to No: T = T0N o, where T O is the average time for analyzing one history. Combining the three expressions into one, we obtain an approximate exponential dependence of the computation time on the thickness of the shield T -T O exp(t/X)/e 2, whence it follows, for example, that 10 h of...