SM-3 Reactor Research Articles

Evaluation of Sn-117m Production in the SM-3 High-Flux Reactor

Due to its electron emission, the 117mSn isotope is an important radionuclide for therapeutic applications, showing promise in the palliative treatment of painful metastases in bone cancers. Also, 117mSn emits a specific 158.6 keV gamma ray which allows imaging for targeting and also for dosimetric purposes. The SM-3 reactor is a 100 MWth high flux reactor able to produce a wide range of radioisotopes for various applications in nuclear medicine and industry. In this work, we investigated the modeling of 117mSn production in the SM-3 high flux reactor. Calculations are performed using the ChainSolver 2.34 code. The calculations showed that the specific activity of 117mSn was about 10 Ci.g-1 during 5 full power irradiation days.

Simulation of the Antineutrino Detector for the Second Neutrino Laboratory at the SM-3 Reactor

An experiment aimed at searching for a sterile neutrino using a new detector of the second neutrino laboratory at the SM-3 reactor (Dimitrovgrad, Russia) has been simulated. This detector is a scintillation detector of reactor antineutrinos with a multisection structure and horizontal arrangement of sections. Distributions of counts from prompt and delayed signals, as well as the dependence of detector efficiency on the selected thresholds, have been obtained by simulation. The antineutrino flux has been simulated with an allowance for the dimensions of the reactor core and its spatial location with respect to the detector. This simulation has been used as a basis to calculate the effect that should be obtained by measurements for the specified parameters of oscillations and energy resolution of the detector.

Creation of the second neutrino laboratory at the SM-3 reactor in order to increase the accuracy of the "Neutrino-4" experiment

In the experiment "Neutrino-4" on the search for a sterile neutrino, the effect of oscillations was found at a confidence level of 3 standard deviations. In order to significantly increase the accuracy of the experiment, a second neutrino laboratory is created at the SM-3 reactor (Dimitrovgrad, Russia) and a new neutrino detector is developed. The scintillation-type detector consists of 4 modules having a multi-sectional structure with a horizontal arrangement of 100 sections with PMTs located on both sides of the section. The possibility of increasing the accuracy of the experiment by a factor of 2.7 is shown, which will make it possible to achieve a confidence level of more than 5 standard deviations and answer the question of the existence of a sterile neutrino. Keywords: sterile neutrino, reactor antineutrino.

Создание второй нейтринной лаборатории на реакторе СМ-3 с целью увеличения точности эксперимента "Нейтрино-4"

In the experiment "Neutrino-4" on the search for a sterile neutrino, the effect of oscillations was found at a confidence level of 3 standard deviations. In order to significantly increase the accuracy of the experiment, a second neutrino laboratory is created at the SM-3 reactor (Dimitrovgrad, Russia) and a new neutrino detector is developed. The scintillation-type detector consists of 4 modules having a multi-sectional structure with a horizontal arrangement of 100 sections with PMTs located on both sides of the section. The possibility of increasing the accuracy of the experiment by a factor of 2.7 is shown, which will make it possible to achieve a confidence level of more than 5 standard deviations and answer the question of the existence of a sterile neutrino.

Low Enrichment Nuclear Fuel Based on Uranium-Zirconium Carbonitride: Reactor Tests and Preparation for Studies at Critical Assemblies

Uranium-zirconium carbonitride has been developed at the Federal State Unitarian Enterprise Scientific Research Institute the Scientific Industrial Association "Luch" (LUCH FSUE) and is a high-density high-temperature fuel with high heat conductivity capable of being used in various types of reactors, including fast reactors. The main problem hindering wide application of this fuel is insufficient knowledge of its behavior under irradiation, especially at high burnup. In the USSR, HEU UZrCN (96% by U-235) fuel underwent reactor testing to a low burnup of approximately 1%. However, to confirm practical applicability of this fuel, the fuel needs to be reactor tested at a high burnup. In the framework of a joint Belarussian-American-Russian effort, LEU (19.75% by U-235) UZrCN fuel will undergo reactor testing to a burnup of approximately 40% in the SM-3 reactor at the Joint Stock Company "State Scientific Center Research Institute of Atomic Reactors" (JSC "SSC RIAR"). To conduct the prolonged reactor experiment, an irradiating device with an experimental capsule containing UZrCN pellets has been made, neutronic analysis and thermophysical analysis have been carried out and a programme of pre-irradiation experiments has been implemented. In June 2019 a methodical experiment was carried out in the SM-3 reactor at the JSC "SSC RIAR" in order to confirm operability of the irradiating device developed. Testing of the irradiating device and refinement of the prolonged irradiation experiment procedure were carried out at cell 11 of the reflector of the SM-3 reactor at the JSC "SSC RIAR". The period of irradiation equaled 23.3 effective days. The mean power density in the tested pellets throughout the methodical reactor testing was 516 W=cm3. Burnup achieved for the pellets studied was 0.63% FIFA. The "Giacint" and "Kristal", critical facilities of the State Scientific Institution "The Joint Institute for Power and Nuclear Research - Sosny" (the Scientific Institution "JIPNR - Sosny") will be used for studying neutronic characteristics of critical and subcritical fast assemblies simulating the physical particulars of the cores of advanced gas- or liquid metal cooled fast reactor systems and accelerator driven systems. This paper provides a detailed description of the results of preparatory works for conducting the reactor testing and the results of the methodical reactor experiment. Also the experimental programme and the descriptions of the design and composition of the fast critical assemblies with UZrCN fuel are presented.

ПРОГРАММА СПЕКТРОМЕТРИИ НЕЙТРОННЫХ ПОЛЕЙ В РЕАКТОРЕ СМ ПОСЛЕ МОДЕРНИЗАЦИИ

A program for refining the energy spectra of neutron radiation in the neutron trap, core and reflector of the SM-3 reactor after modernization using the certified equipment and verified methods is presented in the article. The relevance of the article lies in familiarization with the experimental implementation of the methods in order to compare the experimental neutron-physical characteristics of the reactor before and after the last reconstruction. During the program creation, the previous experience of spectrometric measurements was taken into account, as well as experiments were carried out under conditions close to those of spectrometry after reconstruction. The results of the research are necessary for the planning of irradiation experiments and verification of calculation methods for determining the neutron-physical characteristics. The results of the described researches cover most science and technology areas, many aspects of human practice, including healthcare. The authors presented results of accompanying experiments, which made it possible to work out the regulations and features of short-term measurements. The developed and optimized program of neutron spectrometry in the SM-3 reactor channels will allow to obtain reliable information on the density of neutron fluxes for the first time after modernization to verify analytical data and to optimize the use of the SM-3 reactor facility to increase the production of transplutonium elements and radionuclide products.

Search for sterile neutrinos with the Neutrino-4 experiment and measurement results

The experiment Neutrino-4 started in 2014 with a detector model and continued with a full-scale detector in 2016--2021. In this article, we describe all the steps of the preparatory work on this experiment. We present all results of the Neutrino-4 experiment with increased statistical accuracy provided to date. The experimental setup is constructed to measure the flux and spectrum of the reactor antineutrinos as a function of distance to the center of the active zone of the SM-3 reactor (Dimitrovgrad, Russia) in the range of 6--12 meters. Using all the collected data, we performed a model-independent analysis to determine the oscillation parameters $\mathrm{\ensuremath{\Delta}}{\mathrm{m}}_{14}^{2}$ and ${\mathrm{sin}}^{2}2{\ensuremath{\theta}}_{14}$. The method of coherent summation of measurement results allows us to directly demonstrate the oscillation effect. We present the analysis of possible systematic errors and the MC model of the experiment, which considers the possibility of the effect manifestation at the present precision level. As a result of the analysis, we can conclude that at currently available statistical accuracy, we observe the oscillations at the $2.9\ensuremath{\sigma}$ level with the parameters $\mathrm{\ensuremath{\Delta}}{m}_{14}^{2}=(7.3\ifmmode\pm\else\textpm\fi{}{0.13}_{\mathrm{st}}\ifmmode\pm\else\textpm\fi{}{1.16}_{\mathrm{syst}})\text{ }\text{ }{\mathrm{eV}}^{2}=(7.3\ifmmode\pm\else\textpm\fi{}1.17)\text{ }\text{ }{\mathrm{eV}}^{2}$ and ${\mathrm{sin}}^{2}2\ensuremath{\theta}=0.36\ifmmode\pm\else\textpm\fi{}{0.12}_{\mathrm{stat}}(2.9\ensuremath{\sigma})$. Monte Carlo based statistical analysis gave an estimation of the confidence level at $2.7\ensuremath{\sigma}$. We plan to improve the currently working experimental setup and create a completely new setup in order to increase the accuracy of the experiment by 3 times. We also provide a brief analysis of the general experimental situation in the search for sterile neutrinos.

Analysis of the Results of the Neutrino-4 Experiment on the Search for the Sterile Neutrino and Comparison with Results of Other Experiments

We present new results of measurements of reactor antineutrino flux and spectrum dependence on the distance in the range 6-12 meters from the center of the reactor core at SM-3 reactor (Dimitrovgrad, Russia). Additional measurements were carried out and set of data to perform statistical analysis was almost doubled since the previous report. Using all collected data we performed the model independent analysis on the oscillation parameters $\Delta m^2_{14}$ and $\sin^2(2\theta_{14})$. The method of coherent summation of results of measurements allows us to directly observe the effect of oscillations. We observed an oscillation effect in vicinity of $\Delta m^2_{14} = (7.25\pm0.13_{st}\pm1.08_{sys}) \text{eV}^2$ and $\sin^2(2\theta_{14}) =0.26\pm0.08_{st}\pm 0.05_{sys}$. We provide a comparison of our results with results of other experiments on search for sterile neutrino. Combining the result of the Neutrino-4 and the results of measurements of the gallium anomaly and reactor anomaly we obtained value $\sin^2(2\theta_{14})\approx 0.19\pm0.04(4.6\sigma)$. Also was performed comparison of Neutrino-4 experimental results with results of other reactor experiments NEOS, DANSS, STEREO, PROSPECT and accelerator experiments MiniBooNE, LSND and the IceCube experiment also. Sterile neutrino mass which can be calculated using the Neutrino-4 data in assumption that $m^2_4 \approx \Delta m^2_{14}$ is $m_4 = (2.68 \pm 0.13)\text{eV}$. Considering estimations of mixing angles obtained in other experiments we can calculate masses of electron neutrino, muon neutrino and tau neutrino: $m^{\text{eff}}_{\nu_e} = (0.58 \pm 0.09)\text{eV}, m^{\text{eff}}_{\nu_{\mu}} = (0.42 \pm 0.24)\text{eV}, m^{\text{eff}}_{\nu_{\tau}} \leq 0.65\text{eV}$. Extended PMNS matrix for (3 + 1) model with one sterile neutrino is provided, neutrino flavor mixing scheme with sterile neutrino and global fit of reactor experiments.

Simulating the Effects of Nuclear Transmutation when Studying the Physical Properties of Zirconium Alloys

The nuclear transmutation effects in zirconium alloys are analyzed in this work. The molybdenum content in zirconium alloys of various compositions are numerically estimated under irradiation in research (SM-3) and power (WWER-1000) nuclear reactors. The dynamics of molybdenum accumulation under irradiation in the SM-3 reactor and subsequent one-year aging of samples is estimated in the Zr–1% Nb and Zr–2.5% Nb standard zirconium alloys and the proposed Zr–1% Nb–0.5% Mo and Zr–2.5% Nb–0.5% Mo starting compositions.

First Observation of the Oscillation Effect in the Neutrino-4 Experiment on the Search for the Sterile Neutrino

We present the results of the Neutrino-4 experiment on search for a sterile neutrino. The experiment has been carried out on the SM-3 reactor having a compact active zone of $42\times42\times35\textrm{cm}^3$ and operating on the highly enriched uranium-235 at 90 MW thermal power. We report the results of the Neutrino-4 experiment of measurements of reactor antineutrino flux and spectrum dependence on the distance in the range 6-12 meters from the center of the reactor core. Using the measured spectrum and the distance dependence of antineutrino flux, we performed the model independent analysis of restrictions on the oscillation parameters $\Delta m^2_{14}$ and $\sin^2 2\theta_{14}$. The method of coherent addition of results of measurements is proposed. It allows us to directly observe the effect of oscillations. We observed the oscillation effect at CL $3.5\sigma$ in the vicinity of $\Delta m^2_{14} \approx 7.26\textrm{eV}^2$ and $\sin^2 2\theta_{14} \approx 0.38$. Combining the result of the Neutrino-4 experiment and the result of the gallium anomaly effect we obtained value $\sin^2 2\theta_{14} \approx 0.35 \pm 0.07 (5\sigma)$. The analysis of systematics effects is presented. Comparison with results of other experiments is presented. Future prospect of the experiment is discussed. It is necessary to notice that obtained values $\sin^2 2\theta_{14} \approx 0.35 \pm 0.07 (5\sigma)$ and $\Delta m^2_{14} \approx (7.3 \pm 0.7)\textrm{eV}^2$ allow make assessment on the mass of a neutrino: $m_{\beta} \approx 0.8\textrm{eV}$.

Regulation of the temperature in the ampoule channel with natural circulation of coolant

It has been shown by calculations that it is possible to extend considerably the capabilities for control of temperature conditions in an ampoule channel with natural coolant circulation, using the proposed hydraulic circuit layout, on samples during irradiation in the SM-3 reactor reflector cell by changing the circulation circuit geometry through the arrangement of a bypass heat removal line formed in the upper part above the flow limiter as compared to control only by changing the thermal conductivity of the gas gap in the channel body (through changing the gas pressure or composition). The ampoule channel test conditions, layout and simulation model for thermal-hydraulic analysis using the RELAP5/MOD3.2 code are presented. An investigation was conducted to study the effects of the bypass cooling circuit on the temperature conditions during irradiation of samples in an ampoule channel. The bypass flow rate change is achieved by varying the passage area of the flow limiter orifice. Options have been considered for filling the channel body gas gap with helium and a helium mixture. The calculation showed that the heat removed by the bypass line could reach 40% of the total heat released in the channel. With helium used in the channel body gap, the temperature conditions during irradiation are adjusted in a broader range (200–330 °С) than with a gas mixture of a lower thermal conductivity (279–330 °С), the major temperature variation taking place with the flow limiter orifice area being less than 0.2–0.3 cm2. Any further increase in the flow limiter orifice area does not lead to a major temperature change in the coolant flowing about the samples.

Neutrino-4 experiment on search for sterile neutrino with multi-section model of detector

In order to carry out research in the field of possible existence of a sterile neutrino the laboratory based on SM-3 reactor (Dimitrovgrad, Russia) was created to search for oscillations of reactor antineutrino. The prototype of a multi-section neutrino detector with liquid scintillator volume of 350 l was installed in the middle of 2015. It is a moveable inside the passive shielding detector, which can be set at distance range from 6 to 11 meters from the reactor core. Measurements of antineutrino flux at such small distances from the reactor core are carried out with moveable detector for the first time. The measurements carried out with detector prototype demonstrated a possibility of measuring a reactor antineutrino flux in difficult conditions of cosmic background at Earth surface.

Experiment neutrino-4 on searching for a sterile neutrino with multisection detector model

A laboratory for searching for oscillations of reactor antineutrinos has been created based on the SM-3 reactor in order to approach the problem of the possible existence of a sterile neutrino. The multisection detector prototype with a liquid scintillator volume of 350 L was installed in mid-2015. This detector can move inside the passive shield in a range of 6–11 m from the active core of the reactor. The antineutrino flux was measured for the first time at these short distances from the active core of the reactor by the movable detector. The measurements with the multisection detector prototype demonstrated that it is possible to measure the antineutrino flux from the reactor in the complicated conditions of cosmic background on the Earth’s surface.

Status of Experiment NEUTRINO-4 Search for Sterile Neutrino

In order to carry out research in the field of possible existence of a sterile neutrino the laboratory based on SM-3 reactor (Dimitrovgrad, Russia) was created to search for oscillations of reactor antineutrino. The prototype of a multi-section neutrino detector with liquid scintillator volume of 350 l was installed in the middle of 2015. It is a moveable inside the passive shielding detector, which can be set at distance range from 6 to 11 meters from the reactor core. Measurements of antineutrino flux at such short distances from the reactor core are carried out with moveable detector for the first time. The measurements with full-scale detector with liquid scintillator volume of 3m3 (5x10 sections) was started only in June, 2016. The today available data is presented in the article.

Investigation of a Possibility of Chromium-51 Accumulation in the SM-3 Reactor to Fabricate a Neutrino Source

Compact high intensity neutrino sources based on 51Cr isotope are demanded for very short baseline neutrino experiments. In particular, a 3 MCi 51Cr neutrino source is needed for the experiment BEST on search for transitions of electron neutrinos to sterile states. The paper presents the results of the analysis of options of the irradiation of highly enriched 50Cr in the existing trap of thermal neutrons of high-flux reactor SM–3, as well as using the most promising variants of the trap after upcoming reconstruction of the reactor. It is shown that it is possible to to obtain the intensity of 51Cr up to 3.85 MCi at the end of irradiation of 50Cr enriched to 97% in the high-flux reactor SM–3 of the JSC “SSC NIIAR”.

Experiment for search for sterile neutrino at SM-3 reactor

In connection with the question of possible existence of sterile neutrino the laboratory on the basis of SM-3 reactor was created to search for oscillations of reactor antineutrino. A prototype of a neutrino detector with scintillator volume of 400 l can be moved at the distance of 6–11 m from the reactor core. The measurements of background conditions have been made. It is shown that the main experimental problem is associated with cosmic radiation background. Test measurements of dependence of a reactor antineutrino flux on the distance from a reactor core have been made. The prospects of search for oscillations of reactor antineutrino at short distances are discussed.

Evaluation of the Americium transmutation performance in high flux reactors

The numerical transmutation of Americium heterogeneous loaded for one cycle in thermal high flux reactor category was realized. The transmutation calculations are performed based on ChainSolver 2.34 code. A comparison with the measurement and calculation results of the burn up of 241Am irradiated in HFR at Petten was examined to evaluate the accuracy of current available numerical tool. To reach the Am destruction with a short irradiation time, a high flux SM3 reactor having a flux density of thermal neutrons higher than 1015cm−2s−1 was proposed. To obtain transmutation rate of 99.75%, the Am samples needed only 90 exposure days in full power for SM3 reactor. The effectiveness results suggested an effective use of SM3 as compared to Petten HFR. Finally, the results have been discussed in order to propose a new concept of high flux reactor destined for the destruction of actinide minors, in particular 241Am.

Creation of neutrino laboratory for carrying out experiment on search for a sterile neutrino at the SM-3 reactor

To check the existence of a sterile neutrino, a neutrino laboratory aimed at searching reactor antineutrino oscillations is created at the SM-3 reactor. A prototype of a neutrino detector with a scintillator volume of 400 L is moved at distances 6–11 m from the core of the reactor. Background conditions are measured. It is shown that the cosmic rays background is the main problem in the experiment. The prospects of the search for reactor antineutrino oscillations at short distances are discussed.

Neutrino-4 experiment on the search for a sterile neutrino at the SM-3 reactor

In view of the possibility of the existence of a sterile neutrino, test measurements of the dependence of the reactor antineutrino flux on the distance from the reactor core has been performed on SM-2 reactor with the Neutrino-2 detector model in the range of 6–11 m. Prospects of the search for reactor antineutrinos at short distances have been discussed.

On the possibility of performing an experiment in the search for a sterile neutrino

At present, the possible existence of a sterile neutrino having a significantly smaller cross section of interaction with a substance than, for example, electronic antineutrinos from a reactor is being widely discussed. It has been suggested that, due to reactor antineutrino transition into a sterile state, one can observe both the oscillation effect at short distances (5–15 m) from the reactor and a deficiency of the reactor antineutrino flux at large distances. We have investigated the possibility of performing experiments in search for reactor antineutrino oscillations into a sterile state on research reactors. A model experiment has been carried out on a 16-MW WWR-M reactor at the Petersburg Nuclear Physics Institute with a view to implementing a full-scale experiment using a 100-MW SM-3 reactor at the Research Institute of Atomic Reactors (RIAR). Background conditions of these experiments have been studied for both reactors. It is concluded that the implementation of a full-scale Neutrino-4 experiment on the SM-3 reactor at the RIAR is possible.