[en] The report on hand includes the experiments on criticality published from 1975 till 1980. About 90 experiments with the most important related data are listed. They are capable of being called up, with the data base system KRITEXP, by 14 different descriptors or printed in any arrangement or order. This is the basis for a global or purposeful verification of the calculating method for criticality safety. The proof of reliability of the calculations for the criticality analysis are immediately relevant for the licencing procedure under atomic law for all plants of the nuclear fuel cycle where nuclear fuels are handled. Since no criticality experiments are being carried out in the Federal Republic of Germany, the data collection on hand will help to fill this gap with regard to the assessment of experiments carried out in other countries. (orig.)

[en] Published in summary form only

[en] The physics parameters of a bare sphere of metallic ²³⁷Np have been investigated. The calculations indicate that a chain reaction can be sustained with fast neutrons. The predicted critical radius is 8.86 cm, and the corresponding critical mass is 59.7 kg. Kinetic parameters such as the prompt neutron lifetime, l, the prompt neutron decay constant at delayed criticality, α/sub c/, and the effective delayed neutron fraction, β/sub eff/, were also calculated. With respect to the last quantity, the phenomenon of the so-called vanishing dollar in systems consisting of even-neutron nuclei is discussed. Some remarks concern the possible utilization of ²³⁷Np, which is produced in nuclear power reactors as a by-product

[en] An examination is made of the various parameters acting on the neutron balance: mass, moderation, density, geometry, interactions, absorption and poisoning. The monitoring methods are deduced from this. Using two examples, it is shown how the various parameters act together and in different ways so that it is difficult to predict the results and that it is necessary to have calculation codes well qualified on experience

[en] The era of near-room-temperature superconductivity started after experimental discovery by Drozdov et al (2015 Nature 525 73) who found that compressed H₃S exhibits superconducting transition at T _c = 203 K. To date, the record near-room-temperature superconductivity stands with another hydrogen-rich highly compressed compound, LaH₁₀ (Somayazulu et al 2019 Phys. Rev. Lett. 122 027001), which has critical temperature of $T_c><!--\; >\; -->240K.$ In this paper, we analyse available upper critical field, B _c2(T), data for LaH₁₀ (Drozdov et al 2019 Nature 569 528) and report that this compound in all considered scenarios has the ratio of T _c to the Fermi temperature, T _F, 0.009 < T _c/T _F < 0.038, which is typical range for unconventional superconductors. In attempt to extend our finding, we examined experimental B _c2(T) data for superconductors in the palladium-hydrogen system and surprisingly find that PdH_x compounds have the ratio of 0.008 < T _c/T _F < 0.012. Taking in account that H₃S has the ratio of 0.012 < T _c/T _F < 0.039 (Talantsev 2019 Modern Phys. Lett. B 33 1950195) we come to conclusion that in the Uemura plot all discovered to date hydrogen-rich superconductors, i.e. PdH_x, H₃S and LaH₁₀, lie in same band as all unconventional superconductors, particularly heavy fermions, fullerenes, pnictides, and cuprates, and former should be classified as a new class of unconventional superconductors. (paper)

[en] The critical mass of the reactor RP-0 of the Peruvian Institute of Nuclear Energy is determined by using the Fermi model of diffusion and age in connection with an experimental subcritical neutron population. A desk computer HP9825 is used with a program in HP4. The observed discrepancy between the calculated and the measured mass is 5%

[en] The results of various conventional tests with this 1000kW experimental reactor (KSTR) are shown in diagrams. The comparatively high negative temperature coefficient of the reactivity was found to be a great advantage. Some inexplicable temperature differences and temperature changes in the reactor vessel were found. (J.S.)

[en] Less than two years after the discovery of high temperature superconductivity in oxypnictide LaFeAs(O, F) several families of superconductors based on Fe layers (1111, 122, 11, 111) are available. They share several characteristics with cuprate superconductors that compromise easy applications, such as the layered structure, the small coherence length and unconventional pairing. On the other hand, the Fe-based superconductors have metallic parent compounds and their electronic anisotropy is generally smaller and does not strongly depend on the level of doping, and the supposed order parameter symmetry is s-wave, thus in principle not so detrimental to current transmission across grain boundaries. From the application point of view, the main efforts are still devoted to investigate the superconducting properties, to distinguish intrinsic from extrinsic behaviors and to compare the different families in order to identify which one is the fittest for the quest for better and more practical superconductors. The 1111 family shows the highest T_c, huge but also the most anisotropic upper critical field and in-field, fan-shaped resistive transitions reminiscent of those of cuprates. On the other hand, the 122 family is much less anisotropic with sharper resistive transitions as in low temperature superconductors, but with about half the T_c of the 1111 compounds. An overview of the main superconducting properties relevant to applications will be presented. Upper critical field, electronic anisotropy parameter, and intragranular and intergranular critical current density will be discussed and compared, where possible, across the Fe-based superconductor families.

No abstract available

[en] Work accomplished in support of nonweapons programs by LASL Group Q-14 is described. Included are efforts in basic critical measurements, nuclear criticality safety, a plasma core critical assembly, and reactivity coefficient measurements