The role of natural rock filler in optimizing the radiation protection capacity of the intermediate-level radioactive waste containers

Tashlykov O.L.,Alqahtani M.S.,Mahmoud K.A. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.10

The present work aims to optimize the radiation protection efficiency for ion-selective containers used in the liquid treatment for the nuclear power plant (NPP) cooling cycle. Some naturally occurring rocks were examined as filler materials to reduce absorbed dose and equivalent dos received from the radioactive waste container. Thus, the absorbed dose and equivalent dose were simulated at a distance of 1 m from the surface of the radioactive waste container using the Monte Carlo simulation. Both absorbed dose and equivalent dose rate are reduced by raising the filler thickness. The total absorbed dose is reduced from 7.66E-20 to 1.03E-20 Gy, and the equivalent dose is rate reduced from 183.81 to 24.63 mSv/ h, raising the filler thickness between 0 and 17 cm, respectively. Also, the filler type significantly affects the equivalent dose rate, where the redorded equivalent dose rates are 24.63, 24.08, 27.63, 33.80, and 36.08 mSv/h for natural rocks basalt-1, basalt-2, basalt-sill, limestone, and rhyolite, respectively. The mentioned results show that the natural rocks, especially a thicker thickness (i.e., 17 cm thickness) of natural rocks basalt-1 and basalt-2, significantly reduce the gamma emissions from the radioactive wastes inside the modified container. Moreover, using an outer cementation concrete wall of 15 cm causes an additional decrease in the equivalent dose rate received from the container where the equivalent dose rate dropped to 6.63 mSv/h.

Analysis for the secondary gamma-ray emission for glasses irradiated with various doses of fast neutron: Case study borate and silicate glasses

O.L. Tashlykov,V. Yu. Litovchenko,N.M. Aristov,K.A. Mahmoud Korean Nuclear Society 2023 Nuclear Engineering and Technology Vol.55 No.7

Are borate and silicate glasses suitable for working as shieling materials against fast neutrons? To correctly answer the above question, some silicate, and borate-based glasses were fabricated and irradiated with various doses of fast neutrons varied between 1.73 and 12.10 MGy. The color and hardness of the fabricated glasses were affected by the fast neutron fluence where the transparent glasses turned colored as well as the hardness of the fabricated glasses was decreased. The gamma-ray spectrometric analysis shows a high activity concentration produced in the barium borate glasses due to the formation of radioisotopes Ba-131 and Ba-133 reaches to 5.92E+05 Bq and 4.25E+03 Bq, respectively for sample Cd-5 Batch 3. Additionally, the gamma-ray spectrometric analysis for the sodium silicate glasses shows low activity concentrations emitted from isotopes formed due to the activation of Y₂O₃-associated impurities. These activities are low compared to that emitted by barium borate-based glasses.

A novel barium oxide-based Iraqi sand glass to attenuate the low gamma-ray energies: Fabrication, mechanical, and radiation protection capacity evaluation

Al-Saeedi F.H.F.,Sayyed M.I.,Kapustin F.L.,Al-Ghamdi Hanan,Kolobkova E.V.,Tashlykov O.L.,Almuqrin Aljawhara H.,Mahmoud K.A. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.8

In the present work, untreated Iraqi sand with grain sizes varied between 100 and 200 mm was used to produce a colored glass sample that has shielding features against the low gamma-ray energy. Therefore, a weight of 70e60 wt % sand was mixed with 9e14 wt% B2O3, 8e10 wt% Na2O, 4e6 wt% of CaO, 3e6 wt% Al2O3, in addition to 0.3% of Co2O3. After melting and annealing the glass sample, the X-ray diffraction spectrometry was applied to affirm the amorphous phase of the fabricated glass samples. Moreover, the X-ray dispersive energy spectrometry was used to measure the chemical composition, and the MH-300A densimeter was applied to measure the fabricated sample's density. The Makishima-Makinzie model was applied to predict the mechanical properties of the fabricated glass. Besides, the Monte Carlo simulation was used to estimate the fabricated glass sample's radiation shielding capacity in the low-energy region between 22.1 and 160.6 keV. Therefore, the simulated linear attenuation coefficient changed between 10.725 and 0.484 cm1 , raising the gamma-ray energy between 22.1 and 160.6 keV. Also, other shielding parameters such as a half-value layer, pure lead equivalent thickness, and buildup factors were calculated

Experimental and theoretical justification of passive heat removal system for irradiated fuel assemblies of the nuclear research reactor in a spent fuel pool

Ta Van Thuong,O.L. Tashlykov,S.M. Glukhov,D.E. Shumkov,Yu.V. Volchikhina Korean Nuclear Society 2023 Nuclear Engineering and Technology Vol.55 No.6

The safety of nuclear installations is largely determined by the tightness of fuel elements cladding. As the Fukushima nuclear accident showed, the main task in case of loss of power supply is to ensure reliable removal of residual heat release from spent fuel pool (SFP) with irradiated fuel assemblies (IFAs). The paper presents the results of calculated-experimental studies and thermal-hydraulic modeling of temperature storage modes of IFAs in SFP. Experimental studies of SFP's temperature regime and calculated evaluation of residual heat removal due to the thermal conductivity of building structures surrounding the SFP were performed. To ensure the safe operation of research reactors, it's necessary to know the IFA's residual heat power (RHP) in the reactor and SFP, which is determined depending on the operating time of fuel assemblies (FAs) and the IFAs calculated holding time. The FAs operating time depends on the reactor energy output. The IFAs calculated holding time is determined by the fuel burnup, U-235 mass in the fuel, and reactor utilization factor. The IFAs fuel burnup was calculated using the MCU-PTR program. Also presented are the RHP's calculation results using some of the empirical dependencies. The concept of a passive heat removal system (PHRS) based on thermosyphon's operating principle was proposed.

Gamma ray shielding characteristics and exposure buildup factor for some natural rocks using MCNP-5 code

K.A. Mahmoud,M.I. Sayyed,O.L. Tashlykov 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.7

The mass attenuation coefficient for eight rock samples having different chemical composition was simulated using the MCNP 5 code in energy range . Moreover, the for the studied rock samples was computed theoretically using XCOM database. The comparison between simulated and computed data for all selected rock samples showed a good agreement with differences varied between 0.01 and 8%. The highest was found for basalt rocks M2 and M1 and the lowest one is reported for limestone rocks Dike. The simulated values of the then were used to calculate other important shielding parameters such as the mean free path, effective electron density and effective atomic number. The exposure buildup factor was also computed for the selected rocks with the contribution of G-P fitting parameters and the highest EBF attended by the basalt sample Sill and varied between 1.022 and 744 in the energy range between but the lowest EBF achieved by basalt sample M2 and varied between 1.017 and 491 in the same energy range.

The influence of BaO on the mechanical and gamma / fast neutron shielding properties of lead phosphate glasses

Mahmoud, K.A.,El-Agawany, F.I.,Tashlykov, O.L.,Ahmed, Emad M.,Rammah, Y.S. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.11

The mechanical features evaluated theoretically using Makishima-Mackenzie's model for glasses xBaO-(50-x) PbO-50P₂O₅ where x = 0, 5, 10, 15, 20, 30, 40, and 50 mol%. Wherefore, the elastic characteristics; Young's, bulk, shear, and longitudinal modulus calculated. The obtained result showed an increase in the calculated values of elastic moduli with the replacement of the PbO by BaO contents. Moreover, the Poisson ratio, micro-hardness, and the softening temperature calculated for the investigated glasses. Besides, gamma and neutron shielding ability evaluated for the barium doped lead phosphate glasses. Monte Caro code (MCNP-5) and the Phy-X/PSD program applied to estimate the mass attenuation coefficient of the studied glasses. The decrease in the PbO ratio has a negative effect on the MAC. The highest MAC decreased from 65.896 cm²/g to 32.711 cm²/g at 0.015 MeV for BPP0 and BPP7, respectively. The calculated values of EBF and EABF showed that replacement of PbO with BaO contents in the studied BPP glasses helps to reduce the number of photons accumulated inside the studied BPP glasses.

Gamma ray exposure buildup factor and shielding features for some binary alloys using MCNP-5 simulation code

Rammah, Y.S.,Mahmoud, K.A.,Mohammed, Faras Q.,Sayyed, M.I.,Tashlykov, O.L.,El-Mallawany, R. Korean Nuclear Society 2021 Nuclear Engineering and Technology Vol.53 No.8

Gamma radiation shielding features for three series of binary alloys identified as (Pb-Sn), (Pb-Zn), and (Zn-Sn) have been investigated. The mass attenuation coefficients (µ/ρ) for the selected alloys were simulated using the MCNP-5 code in the energy range between 0.01 and 15 MeV. Moreover, the (µ/ρ) values were computed using WinXCOM database in the same energy range to validate the simulation results. Results reveal a good agreement between the simulated and computed values. The half value layer (HVL), mean free path (MFP), effective atomic number (Z_eff) and exposure buildup factor (EBF) were evaluated for the selected binary alloys. Results showed that the PS1, PZ1, and ZS2 alloys have the best shielding parameters and better than the commercially standard and available radiation shielding materials. Therefore, the investigated alloys can be used as effective radiation shielding materials against gamma ray with energies between 0.01 and 15 MeV.