RADIATION DAMAGE AND DPA IN IRON USING MCNP5

EUROPEAN JOURNAL OF MATERIALS SCIENCE AND ENGINEERING Volume 5, Issue 3, 2020: 109-114 | www.ejmse.tuiasi.ro | ISSN: 2537-4338 DOI: 10.36868/ejmse.2020.05.03.109 RADIATION DAMAGE AND DPA IN IRON USING MCNP5 Hiwa Mohammad QADR Department of Physics, College of Science, University of Raparin, Sulaimanyah, Iraq Abstract A Monte Carlo simulation code is developed for the study of neutron induced radiation damage in the materials which results from nuclear collision as well as reactions that create energetic recoil atoms of the host material or reaction creates. The aim of this work is to investigate the impact of the radiation damage in the iron by the neutron energy irradiation. The damage parameter used in the evaluation is displacement per atom DPA in material as a function of neutron energy. For this purpose, the simulations were carried out using the Monte Carlo transport code MCNP to calculate the DPA cross section for iron. It was determined that the maximum number of displaced atoms was approximately 1.73E-03 DPA. Keywords: MCNP, Radiation damage, Neutron cross section, DPA, Iron. Introduction MCNP is general- purpose Monte Carlo N- particle Computer code which can be widely used in a number of different transport modes: neutron, proton and electron or coupled Monte Carlo transport Code : neutron/ photon/ electron transport [1, 2]. MCNP is usually a software package code that used for analysing nuclear techniques (the transport of gamma rays and neutron). It was first understood in 1970 as a proton and neutron transport. It was developed by the Monte Carlo staff at Los Alamos National Laboratory (LANL) [3-5]. It has been widely used as tool in many fields such as accelerator application, proton and neutron therapy, radiation shielding, radiation protection and dosimetry, fission and fusion reactor design, and other applications by several thousand users worldwide [6, 7]. The MCNP can deal with neutrons, gamma ray transport as well as coupled transport, such as secondary gamma rays as a result of the collision and also electron transport, both primary and secondary electron sources created resulting from gamma ray collision. The MCNP can provide geometry- independent mesh tallies for visualisation of does, flux and energy deposition over continuous space volume with no complicating particle transport over the geometry [8, 9]. The MCNP can use a surface card, cell card and data card or other physical property card that they are able to show the definition of the geometry. Furthermore, they are able to simulate the particle distribution [10]. The most common measure of the amount of radiation damage for displacement damage in a different type of particles is displacement per atom [11-15]. E521 ASTM standard particle for neutron radiation damage simulation by charged particle irradiation recommends the utilise of the NRT secondary displacement model that allows for calculating irradiation damage. Also it Corresponding author: H. M. Qadr allows DPA correlations from neutron damage [16]. The purpose of this paper is to investigate the effect of radiation damage in iron and demonstrate the DPA calculation model using MCNP. Calculation of displacement cross-section The Norgett-Robinson-Torrens was proposed NRT model as a mean of predicting the total number of displacements 𝑁𝑑 produced by a primary knock-on atom (PKA) with potential energy 𝐸𝑃𝐾𝐴 [17]. Based on the Athermal Recombination-Corrected (ARC-DPA) model, the number of stable defects produced under irradiation is given by the following equation. 𝑁𝑑 (𝑇) = 0 𝑇𝑑 < 𝐸𝑑 1 𝐸𝑑 ≤ 𝑇𝑑𝑎𝑚 < 2𝐸𝑑 𝛽 𝛽𝑇𝑑𝑎𝑚 (𝜉𝐴𝑅𝐶−𝐷𝑃𝐴 ) 2𝐸𝑑 ≤ 𝑇𝑑𝑎𝑚 < ∞ ( 2𝐸𝑑 𝛽 ) (1) Where 𝐸𝑑 is the threshold displacement energy and represented the minimum energy required to generate a stable Frankel pair. The damage energy denoted 𝑇𝑑𝑎𝑚 and represents the portion of the PKA energy which is lost by elastic collisions with the target atoms. Also, 𝛽 is equal to 0.8 factor which was determined from binary collision formula. Where the defect generation efficiency 𝜉𝐴𝑅𝐶−𝐷𝑃𝐴 is equal to the following equation [18]. 𝜉𝐴𝑅𝐶−𝐷𝑃𝐴 = 1 − 𝑐𝐴𝑅𝐶−𝐷𝑃𝐴 2𝐸 𝑏𝐴𝑅𝐶−𝐷𝑃𝐴 ( 𝑑) 𝛽 𝑏 𝐴𝑅𝐶−𝐷𝑃𝐴 𝑇𝑑𝑎𝑚 + 𝑐𝐴𝑅𝐶−𝐷𝑃𝐴 (2) Where 𝑐𝐴𝑅𝐶−𝐷𝑃𝐴 and 𝑏𝐴𝑅𝐶−𝐷𝑃𝐴 are parameters. Figure 1 shows an example of displacement cross-section for iron calculated using the ARC-DPA and NRT model. Values of displacement cross-section were calculated using nuclear data libraries from JEFF-3.3 [19]. In this figure, energy can depend on DPA-neutron cross section, which is multiplied with neutron incident energy spectrum to calculate displacement cross section. Fig. 1. Displacement cross section against neutron energy for iron 110 EUR J MATER SCI ENG 5, 3, 2020: 109-114 METHODOLOGY FOR THE PRODUCTION OF MAGNETIC COMPOSITES BASED ON... MCNP5 Method The Monte Carlo transport simulation code (MCNP5) has been used to model the interaction of neutrons within iron. The geometry modelled in MCNP5 consists of a 2 cm of length, 1 cm of high and 1 cm of thickness for slab target iron. The target iron slab was based on 5.9% Fe-54, 9.1% Fe-56, 2.1 Fe-57 and 0.28% Fe-58 which are surrounded by air as shown in figure 2. For the slab geometry, the model described a mono-directional source of 2 MeV neutrons which interact with the iron slab. Mono-directional source neutrons were emitted from a 1.5 cm x 1.5 cm square surface source, placed 1.5 cm far from the iron slab. Fig. 2. Schematic diagram showing the slab geometry by a monodirectional neutron source. The first simulation was started by running 2000000 histories for 2 MeV neutron source. And the graph was plotted between the number of histories and the statistical tests, which were found them from the output file. Once important thing is the reliability of the result of the test which can be determined either by passing all the ten statistical testes particularly the relative error. Also, it can be determined by considering on the figure of merit (fom). Figure 3. shows that the figure of merit tends to be fluctuating at the end of the way. However, the statistical tests were not passed, the value of that tally. Moreover, the total number of neutron flux was passed through the slab surface which was about 1.53891E-01 neutrons per cm2, with 0.0003 of error. MCNP5 calculation of DPA For the calculation of the DPA within iron, MCNPX was used. There are two kinds of methods which can calculate the DPA with model of specific geometry. The first method calculates flux and fold with DPA cross section. The second method calculates DPA directly with the MCNPX (HISTP/ HTAPE). Both methods produces radiation damage energy cross section http://www.ejmse.tuiasi.ro 111 H. M. Qadr [20, 21]. The DPA was calculated using the radiation damage cross sections that are not able to a part of the MCNPX cross section libraries. Cross section is developed by using NorgettRobinson-Torrens (NRT) model or new methods such as advanced models Molecular Dynamics (MD) simulation coupled with the binary (...truncated)