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1.
The aim of this work is to develop a short and cost-saving procedure for the determination of 241Am in sludge sample of the alkaline low-level radioactive waste (LL LRAW) collected from Nuclear Power Plant “Kozloduy”. The
determination of americium was a part of a complex analytical approach, where group actinide separation was achieved. An anion
exchange was used for separation of americium from uranium, plutonium and iron. For the separation of americium extraction
with diethylhexyl phosphoric acid (DEHPA) was studied. The final radioactive samples were prepared by micro co-precipitation
with NdF3, counted by alpha and gamma spectrometry. The procedure takes 2 hours. The recovery yield of the procedure amounts to (95
± 1.5)% and the detection limit is 53 mBq/kg 241Am (t=150 000 s). The analytical procedure was applied for actual liquid wastes and results were compared to standard procedure. 相似文献
2.
A 100 MWt reactor design has been conceived to support flux level of the order of 1015 n/cm2/s in selected flux trap zones. The physics design considers high enriched metallic alloy fuel in the form of annular plates
placed in a D2O moderator tank in a hexagonal lattice arrangement. By choosing a tight lattice pitch in the central region and double the
lattice pitch in the outer region, it is possible to have both high fast flux and thermal flux trap zones. By design the flux
level in the seed fuel has been kept lower than in the high flux trap zones so that the burning rate of the seed is reduced.
Another important objective of the design is to maximize the time interval of refueling. As against a typical refueling interval
of a few weeks in such high flux reactor cores, it is desired to maximize this period to as much as six months or even one
year. This is possible to achieve by eliminating the conventional control absorbers and replacing them with a suitable amount
of fertile material loading in the reactor. Requisite number of seedless thorium-aluminum alloy plates are placed at regular
lattice locations vacated by seed fuel in alternate fuel layers. It is seen that these thorium plates are capable of acquiring
asymptotic fissile content of 14 g/kg in about 100 days of irradiation at a flux level of 8 × 1014 n/cm2/s. In summary, the core has a relatively higher fast flux in the central region and high thermal flux in the outer region.
The present physics design envisages a flat core excess reactivity for the longest possible cycle length of 6 months to one
year. It is also possible to modify the design for constant subcriticality for about the same period or longer duration by
considering neutron spallation source at the centre and curtailing the power density in the inner core region by shielding
it with a layer of thoria fuel loading.
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3.
SEYED AMIR HOSSEIN FEGHHI MARZIEH REZAZADEH YACINE KADI CLAUDIO TENREIRO MORTEZA AREF ZOHREH GHOLAMZADEH 《Pramana》2013,80(1):105-120
The small reactor design for the remote and less developed areas of the user countries should have simple features in view of the lack of infra-structure and resources. Many researchers consider long core life with no on-site refuelling activity as a primary feature for the small reactor design. Long core life can be achieved by enhancing internal conversion rate of fertile to fissile materials. For that purpose, thorium cycle can be adopted because a high fissile production rate of 233U converted from 232Th can be expected in the thermal energy region. A simple nuclear reactor core arranged 19 assemblies in hexagonal structure, using thorium-based fuel and heavy water as coolant and moderator was simulated using MCNPX2.6 code, aiming an optimized critical assembly. Optimized reflector thickness and gap between assemblies were determined to achieve minimum neutron leakage and void reactivity. The result was a more compact core, where assemblies were designed having 19-fuel pins in 1.25 pitch-to-diameter ratio. Optimum reflector thickness of 15 cm resulted in minimal neutron leakage in view of economic limitations. A 0.5 cm gap between assembles achieved more safety and 2.2% enrichment requirements. The present feasibility study suggests a thermal core of acceptable neutronic parameters to achieve a simple and safe core. 相似文献
4.
This paper presents the results of calculations for CANDU reactor operation in thorium fuel cycle. Calculations are performed
to estimate the feasibility of operation of heavy-water thermal neutron power reactor in self-sufficient thorium cycle. Parameters
of active core and scheme of fuel reloading were considered to be the same as for standard operation in uranium cycle. Two
modes of operations are discussed in the paper: mode of preliminary accumulation of 233U and mode of operation in self-sufficient cycle. For the mode of accumulation of 233U it was assumed for calculations that plutonium can be used as additional fissile material to provide neutrons for 233U production. Plutonium was placed in fuel channels, while 232Th was located in target channels. Maximum content of 233U in target channels was estimated to be ∼13 kg/t of ThO2. This was achieved by irradiation for six years. The start of the reactor operation in the self-sufficient mode requires
233U content to be not less than 12 kg/t. For the mode of operation in self-sufficient cycle, it was assumed that all channels
were loaded with identical fuel assemblies containing ThO2 and certain amount of 233U. It is shown that nonuniform distribution of 233U in fuel assembly is preferable.
相似文献
5.
It is shown for a closed thorium–uranium–plutonium fuel cycle that, upon processing of one metric ton of irradiated fuel after each four-year campaign, the radioactive wastes contain ~54 kg of fission products, ~0.8 kg of thorium, ~0.10 kg of uranium isotopes, ~0.005 kg of plutonium isotopes, ~0.002 kg of neptunium, and “trace” amounts of americium and curium isotopes. This qualitatively simplifies the handling of high-level wastes in nuclear power engineering. 相似文献
6.
Polymer electrolyte membrane (PEM) fuel cells are susceptible to degradation due to the catalyst poisoning caused by CO present
in the fuel above certain limits. Although the amount of CO in the fuel may be within the permissible limit, the fuel composition
(% CO2, CH4, CO and H2O) and the operating conditions of the cell (level of gas humidification, cell temperature and pressure) can be such that
the equilibrium CO content inside the cell may exceed the permissible limit leading to a degradation of the fuel cell performance.
In this study, 50 cm2 active area PEM fuel cells were operated at 55–60 °C for periods up to 250 hours to study the effect of methane, carbon dioxide
and water in the hydrogen fuel mix on the cell performance (stability of voltage and power output). Furthermore, the stability
of fuel cells was also studied during operation of cells in a cyclic dead end / flow through configuration, both with and
without the presence of carbon dioxide in the hydrogen stream. The presence of methane up to 10% in the hydrogen stream showed
a negligible degradation in the cell performance. The presence of carbon dioxide in the hydrogen stream even at 1–2% level
was found to degrade the cell performance. However, this degradation was found to disappear by bleeding only about 0.2% oxygen
into the fuel stream. 相似文献
7.
A novel two-wavelength mid-infrared laser-absorption diagnostic has been developed for simultaneous measurements of vapor-phase
fuel mole fraction and liquid fuel film thickness. The diagnostic was demonstrated for time-resolved measurements of n-dodecane liquid films in the absence and presence of n-decane vapor at 25°C and 1 atm. Laser wavelengths were selected from FTIR measurements of the C–H stretching band of vapor
n-decane and liquid n-dodecane near 3.4 μm (3000 cm−1). n-Dodecane film thicknesses <20 μm were accurately measured in the absence of vapor, and simultaneous measurements of n-dodecane liquid film thickness and n-decane vapor mole fraction (300 ppm) were measured with <10% uncertainty for film thicknesses <10 μm. A potential application
of the measurement technique is to provide accurate values of vapor mole fraction in combustion environments where strong
absorption by liquid fuel or oil films on windows make conventional direct absorption measurements of the gas problematic. 相似文献
8.
V. S. Vorob’ev 《Journal of Experimental and Theoretical Physics》1999,89(4):740-745
The free energy of a crystal containing a given void fraction is derived in terms of the truncated interparticle Lennard-Jones
potential. The free energy is minimized over the void fraction at constant pressure and temperature. It is shown that for
all pressures the optimal void fraction remains less than 1% as the temperature is raised. However, at some temperature it
grows suddenly and reaches values of the order of the percolation level for voids in a crystal, ∼0.125. At this point, the
crystal transitions to the liquid state takes place. The derived dependence of the transition temperature on the pressure—the
melting curve—is in good agreement with experimental data on the melting of solidified inert gases.
Zh. éksp. Teor. Fiz. 116, 1375–1385 (October 1999) 相似文献
9.
I. I. Amelin N. N. Volkova A. A. Zhirnov A. P. Alekseev A. F. Zholudev E. V. Polianczyk G. B. Manelis 《Russian Journal of Physical Chemistry B, Focus on Physics》2010,4(2):265-270
For mixtures of carbon materials and an inert filler, dependences of the characteristics of the filtration combustion wave
on the gaseous oxidizer supply rate at a fuel content in the mixture of less than 7 wt % were obtained. The existence of a
lower concentration limit for a steady-state filtration combustion wave was established. It was demonstrated that at a given
intensity of heat loss, the concentration limits are determined by the reactivity of the carbon material and the oxidizer
supply rate. At the effective coefficient of heat loss α = 8 W/(m2 K), effective conductivity of mixture material λ = 2 W/(m K), and air supply rate G = 0.1 m/s, the lowest fraction of carbon in the mixture at which combustion is still possible was 4.5 wt % for carbon-carbon
composite, 2.5 wt % for activated birch coal, and 2.0 wt % for birch coal, the most reactive kind of carbon. 相似文献
10.
Accelerator-driven systems (ADS) have evoked lot of interest the world over because of their capability to incinerate the
MA (minor actinides) and LLFP (long-lived fission products) radiotoxic waste and their ability to utilize thorium as an alternative
nuclear fuel. One of the main subsystems of ADS is a high energy (∼1 GeV) and high current (∼30 mA) CW proton Linac. The accelerator
for ADS should have high efficiency and reliability and very low beam losses to allow hands-on maintenance. With these criteria,
the beam dynamics simulations for a 1 GeV, 30 mA proton Linac has been done. The Linac consists of normal-conducting radio-frequency
quadrupole (RFQ), drift tube linac (DTL) and coupled cavity drift tube Linac (CCDTL) structures that accelerate the beam to
about 100 MeV followed by superconducting (SC) elliptical cavities, which accelerate the beam from 100 MeV to 1 GeV. The details
of the design are presented in this paper. 相似文献
11.
Modified CMPO-PAN production was used and the resulting composite material was tested for purposes of extraction chromatography.
A commercially avaialble extraction agent octyl(phenyl)-N,N’-diisobutylcarbamoylmethylphosphine oxide (CMPO) and polyacrylonitrile
(PAN) were used. The europium uptake kinetics by composite material was studied in two different nitric acid solutions. The
dependences of weight distribution coefficients (Dg) of europium, americium, plutonium, uranium, and neptunium on nitric acid concentration (0.01–5 mol L−1) in the presence of sodium nitrate (0.1 mol L−1) were determined. High Dg-values were found in 0.1–5 M nitric acid for all elements tested. Increase in europium and americium Dg-values with decrease in nitric acid concentration (bellow 0.1 mol L−1) was observed. This behaviour in diluted nitric acid solutions differs from the behaviour of the similar materials with another
support. CMPO-PAN composite material was compared with commercially available TRU Resin. Dg-values of the tested elements in all solutions used were higher for CMPO-PAN than for TRU Resin. The retention of the studied
elements on CMPO-PAN in hydrochloric acid was made as a screening study. 相似文献
12.
It was found for the first time that the catalysis of yttrium doping of spinel LiMn2O4 can enhance the electrochemical activities of manganese, leading to both improvement of electrochemical capacity and reactivity with the electrolyte of manganese. A proper amount of doping was 0.5%, and such yttrium-doped sample, Li(Y0.005Mn0.995)2O4, had an initial capacity of 130 mAh g−1 over that of the undoped one with the capacity retention to reach 92.3% exceeding that of the undoped one at 100th cycle. 相似文献
13.
Two improved sample preparation methods for the determination of americium and plutonium (Method 1) and plutonium (Method
2) from environmental samples by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) and alpha spectrometry
are presented. Both procedures involve a rapid CaF2 co-precipitation step for pre-concentration and matrix removal followed by extraction chromatographic separations. The average
recovery after sample preparation was better than 85 % for both americium and plutonium. The method developed also focused
on the elimination of possible interferences in the mass spectrometric analysis caused by molecular ions (e.g. 208Pb16O
2
+
or 238U1H+) by employing suitable matrix separation prior to ICP-SFMS analysis of the desolvated sample. Isotopes with alpha energies
similar to the analytes that may cause interferences in alpha spectrometric analysis were also separated. For 239Pu, 240Pu, 241Pu and 241Am detection limits of 15, 9.2, 14 and 23 fg g−1, respectively were achieved by ICP-SFMS, and 0.1 mBq obtained by alpha spectrometry. The methods developed are especially
applicable for monitoring purposes of anthropogenic transuranium elements, as the analysis (sample preparation and ICP-SFMS
measurement) can be carried out within 6 hours for one batch of samples. 相似文献
14.
The role that could be played by liquid metal-cooled fast breeder reactors (LMFBRs) in the utilization of India’s considerable
thorium resources is reviewed in this article. Distinct advantages of thorium-based fuels over plutonium-uranium fuels in
LMFBRs pertain to a more favourable coolant voiding reactivity coefficient and better fuel element irradiation stability.
The poorer breeding capability of thorium-fuelled fast reactors can in principle be overcome by improved core design and development
of advanced fuel concepts. The technical feasibility of such advanced thorium fuels and core designs must be established by
sustained research and development. It is also necessary to efficiently close the thorium fuel cycle of fast breeder reactors
by appropriate development of the fuel reprocessing and refabrication stages. The Fast Breeder Test Reactor (FBTR) at Kalpakkam
is expected to be an important tool for development of thorium fuel and fuel cycle technology. A quick look at the economics
of the thorium cycle for fast reactors, vis-a-vis the more conventional uranium cycle indicates only a small and acceptable
cost disadvantage on account of the need for remote fabrication of recycled thorium fuel.
The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion. 相似文献
15.
A. C. Mueller 《The European physical journal. Special topics》2009,176(1):179-191
While a considerable and world-wide growth of the nuclear share in the global energy mix is desirable for many reasons, a
major concern or objection is the long-term burden that is constituted by the radiotoxic waste from the spent fuel. The concept
of Partitioning & Transmutation, a scientific and technological answer, is therefore of high interest. Its deployment may
use dedicated “Transmuter” or “Burner” reactors, using a fast neutron spectrum. For the transmutation of waste with a large
content (up to 50%) of (very long-lived) Minor Actinides, a sub-critical reactor, using an external neutron source is a solution
of high interest. It is constituted by coupling a proton accelerator, a spallation target and a subcritical core. This promising
new technology is named ADS, for accelerator-driven system. The present paper aims at an introduction into the field in order
to focus, in its later part, on the development of the required accelerator technology. 相似文献
16.
This study investigates the hybridization scenario of a single-flash geothermal power plant with a biomass-driven sCO2-steam Rankine combined cycle, where a solid local biomass source, olive residue, is used as a fuel. The hybrid power plant is modeled using the simulation software EBSILON®Professional. A topping sCO2 cycle is chosen due to its potential for flexible electricity generation. A synergy between the topping sCO2 and bottoming steam Rankine cycles is achieved by a good temperature match between the coupling heat exchanger, where the waste heat from the topping cycle is utilized in the bottoming cycle. The high-temperature heat addition problem, common in sCO2 cycles, is also eliminated by utilizing the heat in the flue gas in the bottoming cycle. Combined cycle thermal efficiency and a biomass-to-electricity conversion efficiency of 24.9% and 22.4% are achieved, respectively. The corresponding fuel consumption of the hybridized plant is found to be 2.2 kg/s. 相似文献
17.
An Otto cycle engine with internal and external irreversibilities of friction and heat leakage, in which the heat transfer between the working fluid and the environment obeys linear phenomenological heat transfer law [q ∝△(T -1)], is studied in this paper. The optimal piston motion trajectory for maximizing the work output per cycle is derived for the fixed total cycle time and fuel consumed per cycle. Optimal control theory is applied to determine the optimal piston trajectories for the cases of with and w... 相似文献
18.
Atmospheric plasma spray is a fast and economical process for deposition of yttria-stabilized zirconia (YSZ) electrolyte for
solid oxide fuel cells. YSZ powders have been used to prepare plasma-sprayed thin ceramic films on the metallic substrate
employing plasma spray technology at atmospheric pressure. Alumina doping was employed to improve the structural characteristics
and electrical properties of YSZ. The effect of alumina addition from 1 to 5 wt.% on the properties of plasma-sprayed YSZ
films was investigated. It was found that the gas permeability of the Al-doped YSZ electrolyte layer reached a level of 8.6 × 10−7 cm4 gf−1 s−1, which is a necessary value for the practical operation of solid oxide fuel cells. Alumina doping considerably increased
the ionic conductivity of plasma-sprayed YSZ. The open circuit voltage of the alumina-doped YSZ coating was approximately
equal to the theoretical value for dense YSZ material. 相似文献
19.
R. L. Thews 《The European Physical Journal A - Hadrons and Nuclei》2006,29(1):15-18
We examine the possibility to utilize in-medium charmonium formation in heavy-ion interactions at collider energy as a probe
of the properties of the medium. This is possible because the formation process involves recombination of charm quarks which
imprints a signal on the resulting normalized transverse momentum distribution containing information about the momentum distribution
of the quarks. We have contrasted the transverse momentum spectra of J/ψ, characterized by 〈p
T
2〉, which result from the formation process in which the charm quark distributions are taken at opposite limits with regard
to thermalization in the medium. The first uses charm quark distributions unchanged from their initial production in a pQCD
process, appropriate if their interaction with the medium is negligible. The second uses charm quark distributions which are
in complete thermal equilibrium with the transversely expanding medium, appropriate if a very strong interaction between charm
quarks and medium exists. We find that the resulting 〈p
T
2〉 of the formed J/ψ should allow one to differentiate between these extremes, and that this differentiation is not sensitive to variations
in the detailed dynamics of in-medium formation. We include a comparison of predictions of this model with preliminary PHENIX
measurements, which indicates compatibility with a substantial fraction of in-medium formation. 相似文献
20.
A. N. Shmelev G. G. Kulikov V. A. Kurnaev G. H. Salahutdinov E. G. Kulikov V. A. Apse 《Physics of Atomic Nuclei》2015,78(10):1100-1111
Discussions are currently going on as to whether it is suitable to employ thorium in the nuclear fuel cycle. This work demonstrates that the 231Pa–232U–233U–Th composition to be produced in the thorium blanket of a hybrid thermonuclear reactor (HTR) as a fuel for light-water reactors opens up the possibility of achieving high, up to 30% of heavy metals (HM), or even ultrahigh fuel burnup. This is because the above fuel composition is able to stabilize its neutron-multiplying properties in the process of high fuel burnup. In addition, it allows the nuclear fuel cycle (NFC) to be better protected against unauthorized proliferation of fissile materials owing to an unprecedentedly large fraction of 232U (several percent!) in the uranium bred from the Th blanket, which will substantially hamper the use of fissile materials in a closed NFC for purposes other than power production. 相似文献