Mehtap Günay

Three-dimensional neutronic calculations for the fusion breeder apex reactor

Three-dimensional analysis has been made using the MCNP Monte Carlo code and ENDF/B-VI nuclear data. The nuclear characteristics of a fusion-fission hybrid reactor such as tritium breeding ratio, energy multiplication factor, fissile fuel breeding, first wall radiation damage, and heat deposition have been investigated in a liquid first wall, blanket, and shield for the various mixture compositions of molten salt and heavy metals for blanket layer thicknesses of 20, 30, 40, and 50 cm. The neutron flux load at the first wall is assumed to be 10 MW/m2. The flowing molten salt wall is composed of flibe (Li2BeF4) as the main constituent with increased mole fractions of heavy metals, 2 to 10% ThF4 and UF4. In terms of all parameters, the mixtures with UF4 show better performance than the mixtures with ThF4. The atomic displacement and the helium, tritium production rates remain well below the presumable limits for all mixture compositions of molten salt and heavy metals and thicknesses of the blanket.

Comparisons of the Calculations Using Different Codes Implemented in MCNPX Monte Carlo Transport Code for Accelerator Driven System Target

The MCNPX code offers options based on physics packages; the Bertini, ISABEL, INCL4 intra-nuclear models, and Dresner, ABLA evaporation-fission models and CEM2k cascade-exciton model. The study analyzes the main quantities determining ADS performance, such as neutron yield, neutron leakage spectra, and neutron and proton spectrain the target andin the beam window calculated by the MCNPX-2.5.0 Monte Carlo transport code, which is a combination of LAHET and MCNP codes. The results obtained by simulating different models, cited above and implemented in MCNPX are compared with each other.The investigated system is composed of a natural lead cylindrical target and stainless steel (HT9) beam window. Target has been optimized to produce maximum number of neutrons with a radius of 20 cm and 70 cm of height. Target is bombarded with a high intensity linear accelerator by a 1 GeV, 1 mA proton beam. The protons are assumed uniformly distributed across the beam of radius 3 cm, and entering the target through a hole of 5.3 cm radius. The proton beam has an outer radius of 5.3 cm and an inner radius 5.0 cm. The maximum of the neutron flux in the target is observed on the axis ~ 10 cm below the beam window, where the maximum difference between 7 different models is ~ 15 %. The total neutron leakage out of the of the target calculated with the Bertini/ABLA is 1.83×1017 n/s, and is about 14 % higher than the value calculated by the INCL4/Dresner (1.60×1017 n/s). Bertini/ABLA calculates top, bottom and side neutron leakage fractions as 20 %, 2.3 %, 77.6 % of the total leakage, respectively, whereas, they become 18.6 %, 2.3 %, 79.4 % with INCL4/Dresner combination.

Hızlandırıcı Güdümlü Sistemlerde Nötronik Hesaplamalar

Bir kritikalti (k<1) sistemde Pb hedef, He, Na, Pb, Hg, W, PbBi sogutucular ve uzun yari omurlu bir nukleer atik, 99Tc, kullanilarak 6 farkli Hizlandirici Gudumlu Sistem (HGS) tasarimi yapilmistir. 1 GeV enerji, 10 mA akim siddeti ve 3 cm yaricapina sahip proton demeti dogal kursun hedefe gonderilmistir. Bu enerji icin proton basina uretilen parcacik sayisi (cogaltma faktoru), notron aki dagilimlari, isinma (heating) ve atik donusum miktarlari hesaplanmistir. Sistem; 200 cm yukseklik, 200 cm yaricap ve 2 cm duvar kalinlikli paslanmaz celikten yapilmis silindir seklinde bir celik kap, merkezinde 80 cm yukseklik ve 15 cm yaricapli bir silindirik dogal kursun hedef ve silindirik atik cubuklarindan olusmustur. Uc boyutlu nukleonik hesaplamalar, MCNPX bilgisayar programi ve ENDF/B-VI nukleer veri kutuphanesi kullanilarak gerceklestirilmistir.