• Title/Summary/Keyword: Nuclear Fuels

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DISCUSSION ABOUT HBS TRANSFORMATION IN HIGH BURN-UP FUELS

  • Baron, Daniel;Kinoshita, Motoyasu;Thevenin, Philippe;Largenton, Rodrigue
    • Nuclear Engineering and Technology
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    • v.41 no.2
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    • pp.199-214
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    • 2009
  • High burn-up transformation process in low temperature nuclear fuel oxides material was observed in the early sixties in LWR $UO_2$ fuels, but not studied in depth. Increasing progressively the fuel discharge burn-up in PWR power plants, this material transformation was again observed in 1985 and identified as an important process to be accounted for in the fuel simulations due to its expected consequence on fuel heat transfer and therefore on the fission gas release. Fission gas release was one of the major concerns in PWR fuels, mainly during transient or accidents events. The behaviour of such a material in case of rod failure was also an important aspect to analyse. Therefore several national and international programs were launched during the last 25 years to understand the mechanisms leading to the high burn-up structure formation and to evaluate the physical properties of the final material. A large observations database has been acquired, using the more sophisticated techniques available in hot cells. This large database is discussed in this paper, providing basis to build an engineering-model, which is based on phenomenological description data and information accumulated. In addition this paper has the ambition to construct the best logical model to understand restructuring.

Analysis of loss of cooling accident in VVER-1000/V446 spent fuel pool using RELAP5 and MELCOR codes

  • Seyed Khalil Mousavian;Amir Saeed Shirani;Francesco D'Auria
    • Nuclear Engineering and Technology
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    • v.55 no.8
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    • pp.3102-3113
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    • 2023
  • Following the Fukushima nuclear disaster, the simulation of accidents in the spent fuel pool has become more noticeable. Despite the low amount of decay heat power, the consequences of the accidents in a spent fuel pool (SFP) can be severe due to the high content of long-lived radionuclides and lack of protection by the pressure vessel. In this study, the loss-of-cooling accident (LOFA) for the VVER-1000/V446 spent fuel pool is simulated by employing RELAP5 and MELCOR 1.8.6 as the best estimate and severe accident analysis codes, respectively. For two cases with different total power levels, decay heat of spent fuels is calculated by ORIGEN-II code. For modeling SFP of a VVER-1000, a qualified nodalizations are considered in both codes. During LOFA in SFP, the key sequences such as heating up of the pool water, boiling and reducing the water level, uncovering the spent fuels, increasing the temperature of the spent fuels, starting oxidation process (generating Hydrogen and extra power), the onset of fuel melting, and finally releasing radionuclides are studied for both cases. The obtained results show a reasonable consistency between the RELAP5 and MELCOR codes, especially before starting the oxidation process.

A Study on Relationship between Fuel Characteristics and Combustion Characteristics of Reformed Diesel Fuels by Ultrasonic Energy Irradiation (II) - Relationship between Chemical Structure and Cetane Number - (초음파 개질 경유의 연료특성과 연소특성의 상관관계에 관한 연구 (II) -화학구조와 세탄가의 상관성-)

  • 이병오;류정인
    • Transactions of the Korean Society of Automotive Engineers
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    • v.11 no.1
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    • pp.64-71
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    • 2003
  • In order to analyze the effect of the chemical structure and the cetane number of reformed diesel fuels by ultrasonic energy irradiation, proton nuclear magnetic resonance spectrometer$(^1H-NMR)$ was used. From the study, following conclusive remarks can be made. 1) Branch Index(BI), aromatics percentages, and alpha methyl radical$(H_{\alpha})$ of the reformed diesel fuels by ultrasonic energy irradiation decreased more than the conventional ones. 2) All the cetane numbers which were calculated from carbon type structure and hydrogen type distribution of the reformed diesel fuels increased more than the conventional ones. 3) It is more reasonable to predict cetane number equation from carbon type structure than from hydrogen type distribution. 4) BI, aromatics percentages, and $H_{\alpha}$ on both for conventional fuel and reformed diesel fuels by ultrasonic energy irradiation are inversely proportional to cetane number fur these fuels.

A new burn-up module for application in fuel performance calculations targeting the helium production rate in (U,Pu)O2 for fast reactors

  • Cechet, A.;Altieri, S.;Barani, T.;Cognini, L.;Lorenzi, S.;Magni, A.;Pizzocri, D.;Luzzi, L.
    • Nuclear Engineering and Technology
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    • v.53 no.6
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    • pp.1893-1908
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    • 2021
  • In light of the importance of helium production in influencing the behaviour of fast reactor fuels, in this work we present a burn-up module with the objective to calculate the production of helium in both in-pile and out-of-pile conditions tracking the evolution of 23 alpha-decaying actinides. This burn-up module relies on average microscopic cross-section look-up tables generated via SERPENT high-fidelity calculations and involves the solution of the system of Bateman equations for the selected set of actinide nuclides. The results of the burn-up module are verified in terms of evolution of actinide and helium concentrations by comparing them with the high-fidelity ones from SERPENT, considering two representative test cases of (U,Pu)O2 fuel in fast reactor conditions. In addition, a code-to-code comparison is made with the independent state-of-the-art module TUBRNP (implemented in the TRANSURANUS fuel performance code) for the same test cases. The herein presented burn-up module is available in the SCIANTIX code, designed for coupling with fuel performance codes.

A comparative study on the impact of Gd2O3 burnable neutron absorber in UO2 and (U, Th)O2 fuels

  • Uguru, Edwin Humphrey;Sani, S.F.Abdul;Khandaker, Mayeen Uddin;Rabir, Mohamad Hairie;Karim, Julia Abdul
    • Nuclear Engineering and Technology
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    • v.52 no.6
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    • pp.1099-1109
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    • 2020
  • The performance of gadolinium burnable absorber (GdBA) for reactivity control in UO2 and (U, Th)O2 fuels and its impact on spent fuel characteristics was performed. Five fuel assemblies: one without GdBA fuel rod and four each containing 16, 24, 34 and 44 GdBA fuel rods in both fuels were investigated. Reactivity swing in all the FAs with GdBA rods in UO2 fuel was higher than their counterparts with similar GdBA fuel rods in (U, Th)O2 fuel. The excess reactivity in all FAs with (U, Th)O2 fuel was higher than UO2 fuel. At the end of single discharge burn-up (~ 49.64 GWd/tHM), the excess reactivity of (U, Th) O2 fuel remained positive (16,000 pcm) while UO2 fuel shows a negative value (-6,000 pcm), which suggest a longer discharge burn-up in (U, Th)O2 fuel. The concentration of plutonium isotopes and minor actinides were significantly higher in UO2 fuel than in (U, Th)O2 fuel except for 236Np. However, the concentration of non-actinides (gadolinium and iodine isotopes) except for 135Xe were respectively smaller in (U, Th)O2 fuel than in UO2 fuel but may be two times higher in (U, Th)O2 fuel due to its potential longer discharge burn-up.

Extraction Chromatographic Separation of Technetium-99 from Spent Nuclear Fuels for Its Determination by Inductively Coupled Plasma-Mass Spectrometry (유도결합플라스마 질량분석을 위한 사용후핵연료 중 테크네튬-99의 추출크로마토그래피 분리)

  • Suh, Moo-Yul;Lee, Chang-Heon;Han, Sun-Ho;Park, Yeong-Jae;Jee, Kwang-Yong;Kim, Won-Ho
    • Analytical Science and Technology
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    • v.17 no.5
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    • pp.438-442
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    • 2004
  • To determine the contents of $^{99}Tc$ in the spent PWR (pressurized water reactor) nuclear fuels by ICP-MS (inductively coupled plasma-mass spectrometry), a technetium separation method using an extraction chromatographic resin (TEVA Spec resin) has been established. $^{99}Tc$ was separated from a spent PWR nuclear fuel solution by this separation procedure and its concentration was determined by ICP-MS. The result agrees well with the value calculated by the program ORIGEN 2 and also the value measured by AG MP-1 resin/ICP-MS method described in our previous paper. It can be concluded that the present separation procedure is superior to the AG MP-1 resin procedure with respect to the time required for technetium separation as well as the efficiency of decontamination from other radioactive nuclides.

HIGH BURNUP CHANGES IN UO2 FUELS IRRADIATED UP TO 83 GWD/T IN M5(R) CLADDINGS

  • Noirot, J.;Aubrun, I.;Desgranges, L.;Hanifi, K.;Lamontagne, J.;Pasquet, B.;Valot, C.;Blanpain, P.;Cognon, H.
    • Nuclear Engineering and Technology
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    • v.41 no.2
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    • pp.155-162
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    • 2009
  • Since the 90's, EDF and AREVA-NP have irradiated, up to very high burnups, lead assemblies housing $M5^{(R)}$ cladded fuels. Post-irradiation examination of high burnup $UO_2$ pellets show an increase in the fission-gas release rate, an increase in fuel swelling, and formation of fission-gas bubbles throughout the pellets. Xenon abundances were quantified, and phenomena leading to this bubble formation were identified. All examinations provided valuable data on the complex state of the fuel during irradiation. They show the good behavior of these fuels, exhibiting various microstructures at very high burnups, none of which is likely to lead to problems during irradiation.