Βeff Values Research Articles

Neutronic examination of the U–Mo accident tolerant fuel for VVER-1200 reactors

In this study, we investigated the possibility of employing accident tolerant fuel (ATF) in VVER-1200/V491 assembly without gadolinium-containing fuel rods using the Monte Carlo code Serpent 1.1.7 with ENDF/B-VII cross-section library. The analysis involves assembly design with reflective boundary conditions. To compare the neutronic performances, U–5Mo, U-7.5Mo, U–10Mo, and U–15Mo fuels were chosen in addition to ordinary UO2 fuel. The concentration of 135Xe, 149Sm, fissile and fertile isotopes with burnup, reactivity feedback with fuel temperature variation, and βeff values were calculated. The results indicate that the fuel cycle length increases by 54.27% for U–5Mo, 32.6% for U-7.5Mo, and 13.8% for U–10Mo, while it decreases by 16.4% for U–15Mo fuel. Additionally, the effect of 95Mo content in natural Mo was investigated by reducing the 95Mo concentration. According to the results, each proposed fuel's fuel cycle length extended when the depletion ratio of 95Mo increased. Additionally, the calculations for reactivity feedback guarantee safe operating conditions for all U-xMo fuels.

Defect assisted enhanced nonlinear optical performance and optical limiting of pure and doped BiVO4 powders and nanocomposite films

The linear and nonlinear absorption properties, photoluminescence and optical limiting properties of bismuth vanadate (BiVO4) powders and films were presented in this work. The structural, morphological and optical effects of different doping elements (M: Mo,W and Ni) were investigated (M: BiVO4). XRD and Raman results proved that BiVO4 and M: BiVO4 powders were synthesized in the monoclinic scheelite structure. Twhe powder morphology as found to be changed by Ni and W doping. The nonlinear optical responses of pure and M: BiVO4 were studied using the open aperture Z-scan experiment and a theoretical model was used to determine the nonlinear optical absorption performance. The nonlinear absorption coefficient (βeff) values were found to be 6.59 × 104, 8.86 × 104, 2.26 × 105 and 1.62 × 106 cm/GW for BiVO4, Mo: BiVO4, W: BiVO4 and Ni: BiVO4 nanocomposite films, respectively. The highest nonlinear absorption coefficients (βeff) and saturation intensity thresholds (ISAT) were obtained for Ni:BiVO4 film. Experimental results showed that the βeff value and band gap can be controlled by the dopant element, making doped BiVO4 a good candidate for nonlinear optical applications such as optical limiters, optical switches and modulators in integrated photonic devices.

Influence of structural and morphological features of zinc (II)-tetraphenylporphyrin thin film on its third order optical nonlinearity at pico and nano second regimes

Implications of laser pulse width on the third-order nonlinear optical properties of Zinc(II) 5, 10, 15, 20-Tetraphenyl-21H, 23H-Porphine (ZnTPP) thin films is investigated. Thin films of ZnTPP are developed on glass substrate by means of thermal vapor deposition technique. X-ray diffraction analysis illustrates polycrystalline nature of these films. Atomic force microscopy and field emission scanning electron microscope images confirm the homogeneous film surface with mean surface roughness value of 8.45 nm. UV–Visible absorption spectrum depicts signature peaks attributable to π-π* orbital transitions. Photoluminescence spectrum illustrates fluorescence emission in the wavelength range of 590 nm–650 nm from S1 state. Nonlinear optical investigations are carried out using single-beam Z-scan technique. ZnTPP thin-film at pico-second regime depicts saturable nonlinear absorption nature, attributable to the collective effect of singlet excited state absorption and filling effect of localized defect states. Whereas, at nanosecond timescale the film exhibits reverse saturable nonlinear absorption, sensitive to triplet excited state absorption. Closed aperture Z-scan measurements at pico and nano second regime highlight self-defocusing optical nonlinearity. Enhanced nonlinear optical coefficient (βeff and n2) values are strongly influenced by the heavy zinc metal ion and modified excited state dynamics due to the strong intermolecular interactions through J-aggregation.

Preliminary study on TRU transmutation in VVER-1000 fuel assembly using MCNP6

Abstract Transmutation technology has been developed to address the issue of long-term safety of nuclear waste disposal in geological repository. Transuranic (TRU) transmutation in thermal neutron spectrum can be considered more beneficial at the present time due to the larger fission cross section of TRU elements than in fast neutron spectrum. This paper discusses preliminary study on TRU transmutation in Vodo-Vodyanoi Energetichesky Reactor (VVER)-1000 fuel assembly using MCNP6 code. The fuel assembly is configured by 312 fuel cells consist of 300 UO2 fuel rods with 3.7 wt% 235U and 12 UGD fuel rods containing a mixture of UO2 with 3.6 wt% 235U and 4.0 wt% Gd2O3. The calculation results show that the k inf value is higher with the increase in the TRU thickness at the beginning of cycle and at the end of cycle, which means that the addition of TRU will increase the fuel cycle length. The total temperature coefficient of reactivity is negative for all fuel assemblies both without TRU and with TRU. In general, the computed β eff values of the assembly with and without TRU addition are not significantly different. It shows that the coating of the TRU layer in the UGD fuel cell will not complicate the reactor control. The transmutation of TRU recycled from spent nuclear fuel in the VVER-1000 fuel assembly can be considered feasible from the viewpoint of excess reactivity and control safety characteristics. The total transmutation rate of ∼55.73% can be achieved with 239Pu and 241Am isotopes are taking the largest portion of transmuted nuclides.

Ultrafast third-order nonlinear optical response of Ag modified ZnSe/ZnS core-shell structure quantum dots composite films

ZnSe/ZnS/Ag composite films were prepared on quartz substrates by magnetron sputtering and spin coating techniques.The morphology of Ag nanoparticles (NPs) with different sputtering powers and the dispersion of ZnSe/ZnS quantum dots (QDs) at different concentrations were observed by SEM and TEM. The linear absorption spectra shows the composite films which modified by Ag NPs had a blue shifted compared with the single ZnSe/ZnS QDs.The Z-scan results showed that the saturated absorption(SA) characteristics of the composite films modified by Ag NPs were significantly enhanced.The SA intensity of the composite films can be adjusted by appropriate increase the concentration of QDs, increasing the sputtering power of Ag NPs and incident laser power.By calculating the nonlinear absorption coefficients of the composite films under different conditions, it is found that increasing the excitation power is the most effective way to improve the SA property of the composite films. Compared with the single ZnSe/ZnS QDs, the βeff value of the composite films is increased by 104 orders of magnitude, which makes the ZnSe/ZnS QDs more widely used in the field of nonlinear optical devices.

Modeling and comparative analysis of changeover of homogeneous and heterogeneous core of BN-1200 reactor to equilibrium mode

Equilibrium reactor core operating in closed fuel cycle with breeding ratio close to 1 is one of the key features of reactor designs developed within the framework of «Proryv» project direction (PD). Equilibrium reactor core is characterized by the stable reactivity and power density pattern, as well as isotopic composition of recycled plutonium. When putting into operation fast reactor using plutonium extracted from thermal reactor spent fuel in bicomponent nuclear power, the reactor core would operate rather long (more than 10 years) in transient mode, which requires special studies and special measures for controlling reactivity coast down during reactor run.Virtual-digital modeling of fast reactor (FR) fuel cycle closure is an efficient tool in such study. In this paper, RTM-2 code package option is outlined and used. This option includes updated fuel cycle model allowing to simulate heterogeneous core layout, as well as to use radial and axial blankets.Analytical studies have been made on sodium cooled large size reactor (1200 MW). Reactivity stabilization in such reactor is slightly more difficult as compared to lead cooled reactors, and excess reactivity exceeds βeff value attributed to BREST type reactors. Owing to heterogeneity of the core, the required excess reactivity can be decreased in transient mode down to βeff level. In equilibrium mode of such core, its breeding ratio (BR) is overrated, and this would even cause reactivity increase (although relatively small). Fuel breeding can be used for assurance of equilibrium mode with high fuel burnup.Basically, there is no need to use blankets in the core designs under consideration. However, one should not discount the demand for fuel breeding, which is also one of the potential advantages of fast reactors. Modeling has shown the possibility of adaptable variation of BR of BN-1200 M reactor within the range of values from 1.05 to about 1.4 with the use of additional blankets (axial and radial) and enriched N15.

Giant Nonlinear Optical Absorption of Ion‐Intercalated Tin Disulfide Associated with Abundant In‐Gap Defects

AbstractHerein it is reported that electrochemical ion‐intercalation is a convenient and effective strategy toward materials with giant nonlinear optical (NLO) absorption. Alkali‐metal ions (i.e., Li+, Na+, K+) are electrochemically intercalated into SnS2 nanosheets. All ion‐intercalated samples exhibit remarkably enhanced optical nonlinearity compared with an untreated sample, and Li‐intercalated SnS2 (Li0.952SnII0.398SnIV0.563S2) possesses optimized strong NLO performance. Li0.952SnII0.398SnIV0.563S2 exhibits strong saturable absorption, and the corresponding nonlinear absorption coefficient (βeff) is ‐1.7 × 104 cm GW–1 for the laser excitation at 515 nm. Li0.952SnII0.398SnIV0.563S2 shows prominent reverse saturable absorption with the laser excitation at 800 nm (βeff: 2.8 × 104 cm GW–1) and 1030 nm (βeff: 1.4 × 104 cm GW–1). All βeff values are larger than most of the reported inorganic NLO materials at corresponding wavelengths. The optical limiting threshold of Li0.952SnII0.398SnIV0.563S2 is 8 × 10–4 J cm–2, two orders of magnitude smaller (better) than the bench‐mark composite (e.g., SWNT‐NH‐TPP). Ion intercalation introduces abundant in‐gap defects. The excitation of electrons in in‐gap states to conduction band intensifies the Pauli‐blocking effect and therefore promotes the saturable absorption under the 515 nm laser excitation, while the in‐gap defect states acting as effective excitation pathway facilitate excited‐state absorption for 800 and 1030 nm laser.

Neutronic analysis of the ALLEGRO fast reactor core with deterministic ERANOS code and Monte Carlo Serpent code

The Gas-cooled Fast Reactor is an advanced concept selected to be part of the fourth generation of nuclear reactors. Before its development, the construction of the experimental demonstration reactor ALLEGRO is planned. Given the current interest in this innovative system, a neutronic study of the ALLEGRO reactor core is performed using the Monte Carlo Serpent calculation code and the deterministic ERANOS code. A detailed description of the core design and ceramic fuel composition is provided. To reduce the computational cost of the simulations for future applications, different cases are analyzed using different computational options in the TGV/VARIANT module and a 7-group energy structure. To validate the ERANOS models, the results are compared with the three-dimensional heterogeneous reference model developed in Serpent. The main parameters of the core, at the beginning of life, are calculated, such as the k-eff value, flux and power distributions, Doppler constant, effect of helium density on reactivity and the β-eff value. The main discrepancies in the results correspond to the diffusion and simplified transport calculations, due to the low density of helium. By using the 7-group structure, it was possible to reduce the calculation time with a reduced penalty in the precision of the results. Furthermore, the best agreement was obtained, with respect to the Serpent model, for the transport calculation (P3) with the 7-energy group structure. The k-eff and fuel isotope mass evolution during burnup is analyzed assuming an operating time of 365 days. The relative fuel fraction at the beginning and end of cycle, the breeding ratio and the average burnup are also given.

Optical limiting properties of indium 5,10,15,20-tetrakis(4-aminophenyl) porphyrin covalently linked to semiconductor quantum dots

5,10,15,20-tetrakis(4-aminophenyl) porphyrin and it indium derivative were synthesised and characterized then covalently linked to CdTe/ZnSe/ZnO semiconductor quantum dots. The nonlinear absorption of the complexes was studied using the Z-scan technique at 532 nm and 10 ns pulse in dimethyl sulfoxide. Indium 5,10,15,20-tetrakis(4-aminophenyl) porphyrin (InTAPP) exhibited the strongest nonlinear optical behaviour in comparison with the metal free derivative. DFT calculations were carried out using SDD basis set at B3LYP level of theory. The nonlinear absorption coefficient (βeff) values were determined experimentally using Z-scan whereby the first static hyperpolarizability (βHRS) value were determined using DFT calcutions.

Determination of βeff for ININ's TRIGA Reactor

Abstract The value of βeff for Training Research Isotopes of General Atomics (TRIGA) Mark III reactor, belonging to the National Institute of Nuclear Researches (ININ), is reported. The TRIGA Mark III reactor core was simulated with MCNP6 to deduce the effective multiplication factor (keff) for critical state and after a small insertion of positive reactivity (∼0.20 $). To perform more realistic simulations, we had to incorporate in the composition of the low-enrichment uranium (LEU) fuel element the produced poisons in a time period of six years, considering the operation time in days, during which the reactor was operating at maximum power (1 MWth). The calculation of the βeff value was obtained with the keff results, calculated with the code, and the reactor periods measured experimentally. We also obtained directly the βeff value, through the card of MCNP6 to calculate keff (KOPTS) card of the MCNP6 code in order to compare both values.

Nonlinear optical response and electrocatalytic activity of cobalt phthalocyanine clicked zinc oxide nanoparticles

In this article, we report on the linking of cobalt tetrakis(4-pentyn-oxy) phthalocyanine (CoTPPc) to ZnO nanoparticles via click chemistry. Subsequently, electrocatalytic activity and nonlinear optical properties were investigated (the latter using an open Z-scan technique at 532 nm). The linking of CoTPPc with ZnO resulted in the lowest limiting intensity value of 0.27 J.Cm−2, the βeff (cmW−1) values were found to be 1.51 × 10-8 and 7.10 × 104 for ZnO and CoTPPc-ZnO respectively. The catalytic rate constants (M−1s−1) (and limits of detection) were 4.1 × 104 (12.87 µM), 5.7 × 104 (8.62 µM) and 7.36 × 104 (4.35 µM) for ZnO, CoTPPc and CoTPPc-ZnO. Hence linking ZnO nanoparticles to CoTPPc result in the enhancement of both nonlinear optical behaviour and catalytic activity.

Applying the continuous-energy Monte Carlo calculation code, MVP3, to analysis of kinetic parameters measured for light-water moderated UO2 and MOX cores of the TCA and EOLE critical facilities

ABSTRACT In order to evaluate the accuracies of the kinetics parameters predicted with the continuous-energy Monte Carlo calculation code, MVP3, core analysis was performed for light-water moderated UO2 and mixed oxide (MOX) fuel cores for which the ratios of effective delayed-neutron fraction (βeff ) to prompt-neutron life time (ℓ) – represented hereafter by βeff /ℓ – and βeff values were measured. The results obtained with the JENDL-4.0-based neutron library showed that (the calculation values (C)/the measurement values (E)−1) ranged from −1.0% to 4.0% for the βeff /ℓ values with an average of 1.0% and a standard deviation of 1.1% for the 17 cores (the UO2, and UO2-MOX mixed cores) tested in the Tank-Type Critical Assembly (TCA). With respect to the βeff of one UO2 core in TCA, C/E − 1 was 1.2%. For the βeff values of the UO2 and MOX cores tested in the EOLE critical facility, C/E − 1 was −1.5% for the former and −4.6% for the latter. The calculated βeff value of the MOX core using the JEFF-3.2-based neutron library was larger by 4% than that calculated using the JENDL-4.0-based neutron library and showed better agreement to the measurement.

2,3-di(2-furyl) quinoxaline bearing 3 -ethyl rhodanine and 1,3 indandione based heteroaromatic conjugated T-shaped push -pull chromophores: Design, synthesis, photophysical and non-linear optical investigations

The design, synthesis, computational, spectroscopic, and, the second and third order non-linear optical studies of a two new π-deficient cross-conjugated T-shaped push-pull molecules (QFR and QFI) consisting of 3-ethyl rhodanine and 1,3 indandione substituted with heterocyclic quinoxaline ring were synthesized by Knoevenagel condensation reaction of the precursor dialdehydes with active dye molecules were described in detail. In the as synthesized molecule, the electron donating thiophene moiety acts as an efficient π-bridge on either side to the quinoxaline core that permits good viability in fine-tuning the optical absorption spectrum with good solubility. The computational studies of these molecules show efficient intra molecular charge transfer (ICT) processes analyzed through their molecular orbital characteristics, excitation energy, absorption maxima, oscillator strength and Mulliken population analysis. The comparison study between the structures of these push-pull molecules were done by their photophysical characteristics including CIE coordinates; thermal characteristics, XRD studies and electrochemical analysis. The time-resolved fluorescence spectra with nanosecond time profile were measured to detect the delayed fluorescent performance of the push-pull molecules QFR and QFI. Hyper-Rayleigh scattering (HRS) in chloroform solution of varying concentrations, using a standard wavelength at 1064 nm was used to assess their first order hyperpolarizability. Optical non-linear property was again proved by open-aperture Z-scan technique investigated at 532 nm and the observed optical limiting behavior was originated from the reverse saturable absorption (RSA) process. The second and third order NLO studies reveals that 3-ethyl rhodanine substituted QFR molecule (β value from HRS, 84.64 × 10−30 esu and βeff from Z scan, 10 × 10−10 m/W) shows high non-linear optical properties and thermal stability compared with 1,3 indandione substituted QFI (β value from HRS, 48.00 × 10−30 esu and βeff value from Z scan, 2 × 10−10m/W).

Fabrication of efficient nonlinear optical absorber using Zn phthalocyanine-semiconductor quantum dots conjugates

In this paper, we report on the synthesis of Zn(II) phthalocyanine derivatives and their conjugates with core/shell and core/shell/shell semiconductor quantum dots (SQDs). Zn(II) mono amino-carboxyethylphenoxy phthalocyanine (1), Zn(II) mono 3-carboxyphenoxy-tris(pyridin-2-yloxy) phthalocyanine (2) and Zn(II) mono aminophenoxy-tris(benzothiazole) phthalocyanine (3) were synthesized. The photophysical and optical limiting properties of the phthalocyanine (Pc) complexes and their conjugates with SQDs were investigated in dimethyl sulfoxide. The optical limiting behaviour of the Pc complexes and their conjugates were measured by the open aperture Z-scan technique at laser excitation wavelength of 532 nm with 10 ns pulse. The conjugates outperformed the Pc complexes alone with the conjugates of 2-SQDs affording highest nonlinear absorption coefficient (βeff) value of ∼80 cm/GW and lowest limiting threshold (Ilim) value of ∼0.27 J·cm−2 as compared to other samples while complex 1 gave low βeff and high Ilim values of 42.2 cm/GW and 1.39 J·cm−2, respectively.

Donor-acceptor substituted thiophene dyes for enhanced nonlinear optical limiting

Designed, synthesized and characterized here two thiophene dyes 3-(4-(diethylamino)phenyl)-2-(thiophen-2-yl)acrylonitrile (ET), 3-(4-(diphenylamino)phenyl)-2-(thiophen-2-yl)acrylonitrile (PT) along with their -CHO substituted derivatives 3-(4-(diethylamino)phenyl)-2-(5-formylthiophen-2-yl)acrylonitrile (ET-CHO) and 3-(4-((4-formylphenyl) (phenyl)amino)phenyl)-2-(5-formylthiophen-2-yl)acrylonitrile (PT-2CHO) for optoelectronic devices towards protecting human eyes and optical sensors, as well as for stabilizing light sources in optical communications. Using the open aperture Z-scan method in tandem with linear absorption spectroscopy, emission spectroscopy and density functional theory (DFT) calculations, the nonlinear absorption and optical limiting behavior under nanosecond (5 ns) Nd: YAG laser excitation at 532 nm wavelength was demonstrated. The observed nonlinearity in all the samples was found to be arising from two-photon absorption process. The DFT calculations at a B3LYP/6-31G(d) level for the geometry optimization have shown that the HOMO levels of ET and PT dyes are delocalized throughout the molecule, while for ET-CHO and PT-2CHO dyes, they occupy all over the molecule except -CHO group present on thiophene ring. Also, LUMO levels are delocalized through the aromatic bridge and shift towards thiophene ring for all dyes. This change in the band structure has tuned the effective nonlinear absorption coefficients (βeff) and PT-CHO possesses a maximum value of βeff = 2.9 × 10−11 m/W. The excellent optical limiting performance of these chromophores makes them useful in photonic or optoelectronic devices for protecting human eyes and optical sensors, as well as for stabilizing light sources in optical communications.

Effects of the carboxylic acid substituents on the photophysical and nonlinear optical properties of asymmetrical Zn(II) phthalocyanines–quantum dots conjugates

This work reports on three asymmetrical Zn(II) phthalocyanines, namely: zinc(II) 3–(4-phenoxy)propanoic acid) phthalocyanine(1), zinc(II) 3–(4-phenoxy carboxylic acid) phthalocyanine (2) and zinc(II) 3–(4–oxy)phenoxy)acetic acid phthalocyanine (3) when covalently linked to glutathione(GSH) capped CdTe/ZnSe and CdTe/ZnSe/ZnO quantum dots (QDs). Of the Pc complexes alone, 1 afforded the highest triplet quantum yield (ΦT) value of 0.67 with corresponding largest nonlinear absorption coefficient (βeff) value of 14.0 cm/GW compared to 2 and 3. The conjugates afforded improved triplet quantum yield and nonlinear optical behavior in comparison to the Pc complexes alone.

Optical nonlinearity of pentadecylphenoxyl substituted sandwich–type metallophthalocyanines in the presence of Ag–CdSeTe/ZnTeSe nanocrystals: Effects of conjugation and central metals

Novel pentadecylphenoxyl substituted homoleptic sandwich–type metallophthalocyanines: bis (complexes 2 and 4 containing Eu and Dy, respectively) and tris (complexes 3 and 5 containing Eu and Dy, respectively) 2,9,16,23–tetrakis–(3–pentadecylphenoxyl) phthalocyanines and cadmium based (Ag–CdSeTe/ZnTeSe) nanocrystals (NCs) were synthesized. The nonlinear optical (NLO) behavior of the metallophthalocyanines and their composites with NCs were investigated using the open aperture Z–scan technique at excitation wavelength of 532 nm with 10 ns pulse. All of the samples exhibited interesting NLO attributes: among all the sandwich–type complexes, complex 5 afforded the most efficient NLO features accounting for large nonlinear absorption coefficient (βeff) value of 3500 cm/GW and limiting threshold (Ilim) value of 0.43 J cm−2. Overall, the composites of the triple decker sandwich–type complexes with Ag–CdSeTe/ZnTeSe yielded the best NLO characteristics with 3 and 5 accounting for the largest βeff value of 5500 cm/GW and Ilim value of 0.09 J cm−2. The synthesized complexes and their composites with NCs could be viable and efficient NLO absorber due to their interesting NLO activities.

Photophysical and strong optical limiting properties of ball-type phthalocyanines dimers and their monomeric analogues

Abstract The nonlinear optical behaviors of ball-type phthalocyanine complexes: 1′,11,’15′,25′-tetrakis-[4,4′-((4-formyl-1,2-bisphenoxyl))bis(phthalocyaninato zinc (II)] (5), 1′,11,’15′,25′-tetrakis-[4,4′-((4-formyl-1,2-bisphenoxyl) bis(phthalocyaninato gallium (III) chloride)] (6), and 1′, 11,’15′,25′-tetrakis-4,4′-((4-formyl-1,2-phenoxyl)bis(phthalocyaninato indium (III) chloride)] (7) and the corresponding monomeric derivatives 8–10 were investigated using nanosecond pulse open aperture Z-scan technique at 532 nm. The nonlinear response showed strong reverse saturable absorption for all the complexes both in solution and when embedded in polymer matrix. The dimeric complexes showed better optical limiting properties compared to the monomeric derivatives. The βeff values for the dimeric complexes 5–7 were found to be 48.5, 55.2, and 60.1 cm/GW for 5, 6A, and 7 respectively, higher than the corresponding monomeric derivatives 8–10. Enhanced optical limiting properties were observed when the complexes were formulated in thin films. The second order hyperpolarizability values were in order of 10−28–10−26 esu in solution and 10−27–10−26 in films.

Effective delayed neutron fraction by Rossi-α method in accelerator-driven system experiments with 100 MeV protons at kyoto university critical assembly

ABSTRACTIn the accelerator-driven system (ADS), the effective delayed neutron fraction (βeff) is a requisite for converting the subcriticality from dollar units to pcm units. To evaluate the accurate βeff value in ADS, measurement of βeff complements its calculation methodology and the nuclear data on delayed neutrons. Subcriticality measurements are carried out by the pulsed neutron source method in the Kyoto University Critical Assembly, and the neutron noise analyses are conducted by the Rossi-α method with the pulsed shape of the spallation neutron source. The value of βeff is deduced with the combined use of measured subcriticality in dollar units and correction parameters by MCNP6.1 together with JENDL-4.0 and JENDL/HE-2007. A comparison between the calculated and the measured βeff represents the acceptable accuracy within the subcriticality range of around keff = 0.93 in the ADS operations. Here, the applicability of the measurement methodology based on the Rossi-α method is demonstrated by varying the subcriticality.

Understanding kinetic behaviour of TRIGA reactor core

The kinetic parameters govern the transient behaviour of a nuclear reactor. Estimation of these parameters has great importance for the safe design and operation of a nuclear reactor. In order to understand the kinetic behaviour of TRIGA core, the influence of graphite dummy elements, absorber materials and beam ports on kinetic parameters has been studied. To do so, the effective delayed neutron fraction (βeff), prompt removal lifetime (e) and mean neutron generation time (Λ) have been calculated for an infinite system of LEU fuel cells. The investigation has been extended to four different cases of TRIGA reactor core. Monte Carlo simulation has been carried out to compute the kinetic parameters by Monte Carlo code MCNP5. The βeff value remains unchanged but the e and Λ values are found to be sensitive to the local perturbations of core components.