First -decay spectroscopy of and new -decay branches of

19 pags., 14 figs., 3 tabs.The  decay of the neutron-rich and was investigated experimentally in order to provide new insights into the nuclear structure of the tin isotopes with magic proton number above the shell. The -delayed -ray spectroscopy measurement was performed at the ISOLDE facility at CERN, where indium isotopes were selectively laser-ionized and on-line mass separated. Three -decay branches of were established, two of which were observed for the first time. Population of neutron-unbound states decaying via rays was identified in the two daughter nuclei of and , at excitation energies exceeding the neutron separation energy by 1 MeV. The -delayed one- and two-neutron emission branching ratios of were determined and compared with theoretical calculations. The -delayed one-neutron decay was observed to be dominant -decay branch of even though the Gamow-Teller resonance is located substantially above the two-neutron separation energy of . Transitions following the  decay of are reported for the first time, including rays tentatively attributed to . In total, six new levels were identified in on the basis of the coincidences observed in the and decays. A transition that might be a candidate for deexciting the missing neutron single-particle state in was observed in both  decays and its assignment is discussed. Experimental level schemes of and are compared with shell-model predictions. Using the fast timing technique, half-lives of the , and levels in were determined. From the lifetime of the state measured for the first time, an unexpectedly large transition strength was deduced, which is not reproduced by the shell-model calculations.M.P.-S. acknowledges the funding support from the Polish National Science Center under Grants No. 2019/33/N/ST2/03023 and No. 2020/36/T/ST2/00547 (Doctoral scholarship ETIUDA). J.B. acknowledges support from the Universidad Complutense de Madrid under the Predoctoral Grant No. CT27/16- CT28/16. This work was partially funded by the Polish National Science Center under Grants No. 2020/39/B/ST2/02346, No. 2015/18/E/ST2/00217, and No. 2015/18/M/ST2/00523, by the Spanish government via Projects No. FPA2017-87568-P, No. RTI2018-098868-B-I00, No. PID2019-104390GB-I00, and No. PID2019-104714GB-C21, by the U.K. Science and Technology Facilities Council (STFC), the German BMBF under Contract No. 05P18PKCIA, by the Portuguese FCT under the Projects No. CERN/FIS-PAR/0005/2017, and No. CERN/FIS-TEC/0003/2019, and by the Romanian IFA Grant CERN/ISOLDE. The research leading to these results has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 654002. M.Str. acknowledges the funding from the European Union’s Horizon 2020 research and innovation program under Grant Agreement No. 771036 (ERC CoG MAIDEN). J.P. acknowledges support from the Academy of Finland (Finland) with Grant No. 307685. Work at the University of York was supported under STFC Grants No. ST/L005727/1 and No. ST/P003885/1

First beta-decay spectroscopy of In-135 and new beta-decay branches of In-134

The beta decay of the neutron-rich In-134 and In-135 was investigated experimentally in order to provide new insights into the nuclear structure of the tin isotopes with magic proton number Z = 50 above the N = 82 shell. The beta-delayed gamma-ray spectroscopy measurement was performed at the ISOLDE facility at CERN, where indium isotopes were selectively laser-ionized and on-line mass separated. Three beta-decay branches of In-134 were established, two of which were observed for the first time. Population of neutron-unbound states decaying via. rays was identified in the two daughter nuclei of In-134, Sn-134 and Sn-133, at excitation energies exceeding the neutron separation energy by 1 MeV. The beta-delayed one- and two-neutron emission branching ratios of In-134 were determined and compared with theoretical calculations. The beta-delayed one-neutron decay was observed to be dominant beta-decay branch of In-134 even though the Gamow-Teller resonance is located substantially above the two-neutron separation energy of Sn-134. Transitions following the beta decay of In-135 are reported for the first time, including. rays tentatively attributed to Sn-135. In total, six new levels were identified in Sn-134 on the basis of the beta.. coincidences observed in the In-134 and In-135 beta decays. A transition that might be a candidate for deexciting the missing neutron single-particle 13/2(+) state in Sn-133 was observed in both beta decays and its assignment is discussed. Experimental level schemes of Sn-134 and Sn-135 are compared with shell-model predictions. Using the fast timing technique, half-lives of the 2(+), 4(+), and 6(+) levels in Sn-134 were determined. From the lifetime of the 4(+) state measured for the first time, an unexpectedly large B(E2; 4(+)-> 2(+)) transition strength was deduced, which is not reproduced by the shell-model calculations.Peer reviewe

Critical and subcritical assemblies – an important element of the didactic and training process of personnel for the nuclear power industry

Niezwykle istotne w procesie edukacyjnym fizyków i inżynierów jądrowych jest rozumienie zachowania reaktora poprzez prowadzenie własnych eksperymentów, pomiarów i jego obsługę. Najprostsze urządzenia, które idealnie spełniają cele dydaktyczne, ale zarazem stanowią narzędzia do badań naukowych w dziedzinie fizyki reaktorowej są to zestawy krytyczne i podkrytyczne. Są to układy składające się z paliwa jądrowego i moderatora. W przypadku zestawu krytycznego masa paliwa jest taka, że pozwala osiągnąć stan krytyczny dopiero po wprowadzeniu zewnętrznego źródła neutronów. Z kolei zestawy podkrytyczne mają wymiary i masę paliwa mniejsze od krytycznych wartości. W artykule analizujemy możliwości budowy prostej, niedrogiej instalacji jądrowej – zestawu podkrytycznego, przeznaczonego do celów kształcenia, szkolenia i badań eksperymentalnych w zakresie inżynierii reaktorowej, którą można zlokalizować na terenie kampusu uczelni wyższej.It is extremely important in the educational process of nuclear physicists and engineers to understand the behavior of the reactor by conducting their own experiments, measurements and its operation. The simplest devices that perfectly meet didactic goals, but at the same time are tools for scientific research in the field of reactor physics, are critical and subcritical assemblies. These are systems consisting of a nuclear fuel and a moderator. In the case of the critical assembly, the mass of the fuel is such that it allows to reach the critical state only after the introduction of an external neutron source. On the other hand, subcritical assembly has dimensions and mass of the fuel smaller than critical values. In the article, we analyze the possibilities of building a simple, inexpensive nuclear installation – a subcritical assembly, dedicated to the purposes of education, training and experimental research in the field of reactor engineering, which can be located on the campus of a University

Characteristics of selected types of generation III/III+ nuclear power plant

Energetyka jądrowa rozwija i doskonali technologię reaktorów już od sześciu dekad. Dlatego rozróżnia się kilka generacji reaktorów jądrowych, z których każda wyróżnia się innymi cechami związanymi z projektem, kwestiami bezpieczeństwa, czy wykorzystaniem paliwa jądrowego. Zdecydowana większość reaktorów obecnie eksploatowanych na świecie została zbudowana w latach 70. i 80. XX wieku. Są to reaktory II generacji. Program Polskiej Energetyki Jądrowej zakłada budowę elektrowni jądrowych generacji III/III+. Rynek oferuje kilka konkretnych technologii tej generacji. W niniejszym artykule prezentowane są informacje o czterech z nich – trzech reaktorach wodnych ciśnieniowych – AP1000, APR1400 oraz EPR, a także jednym reaktorze wodnym wrzącym – ABWR. Artykuł zawiera informacje zebrane na potrzeby jednego z tematów realizowanych przez autorów w Narodowym Centrum Badań Jądrowych.Nuclear Power Industry has been developing and improving reactor technology for six decades. The history of reactors development is divided into several generations that differ in their design, approach to safety issues, utilization of nuclear fuel and so on. The vast majority of reactors, currently in operation in the world, was built in the 1970s and 1980s. They are considered as the second generation reactors. The Polish Nuclear Power Programme assumes construction of NPP of III/III+ generation. Several technologies are available on the market. In the current paper the information on four of them is contained – three of PWR type – AP1000, APR1400 and EPR, and one of BWR type – ABWR. The information in this article has been compiled for the needs of one of the topics performed at National Centre for Nuclear Research

A Useful Synthesis of Diethyl 1-Substituted Vinylphosphonates

A variety of diethyl 1-substituted vinylphosphonates 8 has been conveniently synthesized by piperidine catalyzed decarboxylative condensation of 2-diethoxyphosphorylalkanoic acids and 2-diethoxyphosphorylalkenoic acids 7 with formaldehyde. The Knoevenagel-Doebner decarboxylative condensation of alkanoic acids bearing C-2 electron withdrawing substituents with aldehydes has long been recognized as a convenient route to various a,b-unsaturated compounds Herein, we wish to describe an alternative, convenient route to diethyl 1-substituted vinylphosphonates 8 by the decarboxylative condensation of 2-diethoxyphosphorylalkanoic acids and 2-diethoxphosphorylalkenoic acids 7 with formaldehyde