Among the various international policies for the management of spent nuclear fuel and radioactive waste (RW), an important issue is the need to reprocess this waste. The aim of this work is to ...analyze current modern methods for transmutation of minor actinides (MA) in the reactor cores of thermal, fast (with homogeneous and heterogeneous placement) and in accelerated driven systems in order to identify factors limiting the efficiency of transmutation. This work is an analytical review and it defines the main methods for removing the limitations of the effectiveness of the transmutation process. On the basis of MA formation sources data and MA decay chains, namely americium, neptunium and curium, as well as transmutation methods in the latest reactor systems, factors limiting the efficiency of the transmutation process and methods of reducing their influence are investigated. The main factors are: an increased level of gassing during transmutation, industrial restrictions and the influence of the transmutation process on the processes occurring in the core during transient processes. The main current problem of transmutation is the high activity in terms of heat release level and neutron emission of irradiated assemblies due to the presence of curium isotopes.
The elongation of the fuel cycle period and the reactor reactivity control are crucial for all reactor suppliers. The traditional methods of boric acid, burnable absorbers, and control rods to ...control the reactor reactivity have their defects. A new method of the neutron spectral shift is studied to perform the reactor reactivity control and maintain the length of the fuel cycle. The neutron spectrum regulation can be achieved with different methods, including the Zr rods insertion in the fuel assemblies as water displacers. In this work, SERPENT2 version 2.1.30 was used to investigate a new fuel assembly design in the basics of Sierpinski carpet geometry to utilize the Zr rods as water displacers. The study of different fuel pitches of the Sierpinski fuel assembly is investigated to choose the reference fuel of the new design. The effect of boric acid concentration increasing and defining the maximum boric acid concentration in the Sierpinski fuel assembly are studied. The primary safety parameters of the Doppler effect and moderator temperature reactivity coefficients calculations approved the safety of the new Sierpinski fuel assembly design. The infinite multiplication factor at different steps of burnup showed the efficiency of the Sierpinski fuel assembly model to control the reactor reactivity. The average breeding factor to the burnup limit of 65 GWd/T is 0.68 in the Sierpinski fuel assembly with the presence of Zr rods.
The report reviews international organizations practices related to attraction of students and young researchers as trainees and participants of contests for implementation of large projects such as ...Mega-Science. Organizational frameworks are presented, which are used for these purposes in The Nuclear Energy Agency (NEA), the International Atomic Energy Agency (IAEA),European Nuclear Education Network (ENEN), European Nuclear Research Center (Conseil européen pour la recherche nucléaire (CERN)), The Generation IV International Forum (GIF), et. The role of international organizations in formation of scientific personnel with the great potential in arrangement of the international scientific cooperation has been determined. The classification of measures aimed at identification and development of scientific personnel was proposed: from studying at the university till working in the international organization.
Abstract
For the manufacture of high-precision parts for aviation and space technology, it is necessary to achieve high-quality work of metal-cutting machines. The accuracy of processing and the ...quality of the treated surface directly depends on the properties of the tool, as well as its wear. A number of devices and techniques for controlling cutting tools are known. However, many of them are not effective enough for precision machining on automated machines. For timely detection of defects and prevention of catastrophic wear of the cutting edge of the tool, recognition methods are necessary to ensure high quality control. The paper considers an algorithm for monitoring the condition of incisors, which makes it possible to increase the efficiency of active control on modern machines.
Due to the COVID-19 epidemic, the challenge of introducing methods for investigating patients reducing or eliminating the probability of infection of medical staff is currently relevant. This article ...provides an analytical review of new technological approaches to organizing the work of medical personnel in carrying out auscultation of patients with COVID-19. The development and approval of such technologies is shown to have started around the world. The ubiquitous and large-scale introduction of these methods into medical practice therefore seems expedient.
In 82 clinical strains of
Streptococcus pyogenes
(group A streptococci) isolated from patients with various manifestations of streptococcal infection,
emm
-typing revealed 27
emm
-types (
n
=77) with ...a predominance of
emm
-89 (
n
=15; 18%),
emm
-75 (
n
=9; 11%), and
emm
-1 (
n
=6; 7%); types
emm
-3,
emm
-12, and
emm
-58 (
n
=4; 5% each) were found with almost equal frequency; other types were less common. The superantigen genes
speC
,
speG
,
speH
,
speI
,
speJ
,
speK
,
speL
,
speM
,
smeZ
, and
SSA
were identified in
S. pyogenes
strains using multiprimer PCR; the genes of the superantigen SpeA and cysteine proteinase SpeB were detected using real-time PCR. All the studied
S. pyogenes
strains contained superantigen genes, and 98% of the strains had several (from 2 to 7) genes. The number of variants of these sets reached 37; 2% of the strains contained only one superantigen gene. The distribution frequencies of superantigen genes in the studied strains were:
speA
— 43%;
speC
— 38%;
speG
— 93%;
speH
— 13%;
speI
— 6%;
speJ
— 24%;
speK
— 13%;
speL
and
speM
— 11% each;
smeZ
— 98%;
SSA
— 15%. All studied
S. pyogenes
strains contained the
speB
gene. Our studies have demonstrated that the sets of superantigen genes of group A streptococci are characterized by pronounced diversity to some extent associated with
emm-
type.
•The transmutation performance of MAs in the critical SD-TMSR and SMSFR was investigated.•The transmutation ratio of long-lived MAs was calculated using the SERPENT-2 Monte-Carlo code.•The online ...reprocessing and refueling was applied during burnup.•The dynamics of keff, core reactivity, major isotopes inventory, and time evolution of MAs were investigated.•The neutron energy spectrum shift with different MAs loadings was calculated.
The long-lived Minor Actinides (MAs): 237Np, 241Am, 243Am, 243Cm, 244Cm, and 245Cm are responsible for the effective dose and heat generation after direct disposal in deep geological structures. Thus, long-lived MAs represent a major burden of nuclear power. The long-lived MAs have not yet been utilized as nuclear fuel. Therefore, the transmutation of these MAs is proposed as an alternative to the direct final disposal. In the current work, we analyze and compare the MAs transmutation performance in the critical Single-fluid Double-zone Thorium-based Molten Salt Reactor (SD-TMSR) and Small Molten Salt Fast Reactor (SMSFR). We study the variation of the Keff and core reactivity with different MAs loadings, the neutron spectrum shift, the time evolution of MAs and major nuclides inventories, and the transmutation ratio (TR). The TR of the long-lived MAs is calculated by using the SERPENT-2 Monte-Carlo code. The total neutron flux in the SD-TMSR and SMSFR can reach 4.1 × 1014 and 1.8 × 1015 n.cm−2.s−1, respectively. The results show that the SD-TMSR consumes about 50% of the generated Pu isotopes in the fuel salt, however, the SMSFR consumes about 86.5% of the generated Pu isotopes. During burnup, we apply the online reprocessing and refueling, therefore, the core is maintained critical and the total fuel mass in the core and blanket is almost constant. The results demonstrate that both reactors effectively transmute 237Np, 241Am,243Am, and 243Cm, meanwhile, the SMSFR has a higher TR than the SD-TMSR. The TR of the total MAs reaches 54.84% and 87.97% in the SD-TMSR and SMSFR, respectively.
Thermal-spectrum molten salt reactor (MSR) concepts usually adopt graphite as a neutron moderator. Although graphite as a moderator has many advantages, it also has drawbacks, including a relatively ...short lifespan (it has to be replaced), positive temperature feedback, and loss of impermeability due to expansion. Replacing graphite with heavy water in MSRs can effectively solve the problems introduced by graphite. The SD-HWMSR is a Single-fluid Double-zone Heavy Water-moderated Molten Salt Reactor. Optimization of SD-HWMSR’s fuel channel pitch and radius has been conducted in this work. As a result, the SD-HWMSR with a high breeding ratio (1.07465 ± 0.00060), low initial 233U loading (1.43 t), and negative temperature and void reactivity coefficients is put forward. The SERPENT-2 is used to analyze the neutronics parameters of the reactor design. The current work investigates the change in the multiplication factor, breeding ratio, and the accumulation of significant nuclides in the core. The suitable 232Th and 233U refill rates needed to maintain criticality and enable analysis of the whole core of SD-HMMSR are thoroughly determined in this study. Uranium-233 and thorium-232 both have a maximum refill rate of 3.49 and 3.20 kg/d, respectively. While the average refill rate for 233U and 232Th during the 60 years of operation is 1.90 and 2.35 kg/d, respectively. The net production of 233U rises with time, and by the end of the 60 years, it is around 1.98 t. The doubling time for the SD-HWMSR is 31 years, which is consistent with previous results.
•SD-HWMSR’s fuel channel pitch and radius have been optimized.•The SD-HWMSR with a relatively high breeding ratio has been introduced.•The feed rates of 232Th and 233U have been determined.•Breeding ratio and 233U doubling time have been estimated.•TCR evolution during SD-HWMSR operation has been investigated.
•University NRNU MEPhI works on testing of the Proryv codes.•The objectives of independent testing include assessment of the code quality.•Complexes were identified: CONSYST-RF, CORNER, DOLCE VITA, ...ODETTA, MCU-FR, BPSD.•The models of the BN-600, BN-1200, BR-1200 and BREST-OD-300 cores were used.
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