Comprehensive whole-body counter surveys of Miharu-town school children for three consecutive years after the Fukushima NPP accident

Comprehensive whole-body counter surveys covering over 93% of the school children between the ages of 6 and 15 in Miharu town, Fukushima Prefecture, have been conducted for three consecutive years, in 2011, 2012 and 2013. Although the results of a questionnaire indicate that approximately 60% of the children have been regularly eating local or home-grown rice, in 2012 and 2013 no child was found to exceed the ¹³⁷Cs detection limit of 300 Bq/body.     

Whole-body counter surveys of over 2700 babies and small children in and around Fukushima Prefecture 33 to 49 months after the Fukushima Daiichi NPP accident

BABYSCAN, a whole-body counter (WBC) for small children was developed in 2013, and units have been installed at three hospitals in Fukushima Prefecture. Between December, 2013 and March, 2015, 2707 children between the ages of 0 and 11 have been scanned, and none had detectable levels of radioactive cesium. The minimum detectable activities (MDAs) for ¹³⁷Cs were ≤3.5 Bq kg⁻¹ for ages 0–1, decreasing to ≤2 Bq kg⁻¹ for ages 10–11. Including the ¹³⁴Cs contribution, these translate to a maximum committed effective dose of ∼16 µSv y⁻¹ even for newborn babies, and therefore the internal exposure risks can be considered negligibly small.Analysis of the questionnaire filled out by the parents of the scanned children regarding their families’ food and water consumption revealed that the majority of children residing in the town of Miharu regularly consume local or home-grown rice and vegetables, while in Minamisoma, a majority avoid tap water and produce from Fukushima. The data show, however, no correlation between consumption of locally produced food and water and the children’s body burdens.     

Whole-body counter surveys of Miharu-town school children for four consecutive years after the Fukushima NPP accident

Comprehensive whole-body counter surveys of Miharu-town school children have been conducted for four consecutive years, in 2011–2014. This represents the only long-term sampling-bias-free study of its type conducted after the Fukushima Dai-ichi accident. For the first time in 2014, a new device called the Babyscan, which has a low ^134/137Cs MDA of <50 Bq/body, was used to screen the children shorter than 130 cm. No child in this group was found to have detectable level of radiocesium. Using the MDAs, upper limits of daily intake of radiocesium were estimated for each child. For those screened with the Babyscan, the upper intake limits were found to be ≲1 Bq/day for ¹³⁷Cs. Analysis of a questionnaire filled out by the children’s parents regarding their food and water consumption shows that the majority of Miharu children regularly consume local and/or home-grown rice and vegetables. This however does not increase the body burden.     

Discovery of radioactive silver (110mAg) in spiders and other fauna in the terrestrial environment after the meltdown of Fukushima Dai-ichi nuclear power plant

Six months after the explosion of TEPCO’s Fukushima Dai-ichi nuclear power plant, radioactive silver (^110mAg), was detected in concentrations of 3754 Bq/kg in Nephila clavata (the orb-web spider; Joro-gumo in Japanese) collected at Nimaibashi, Iitate village in Fukushima Prefecture, whereas ^110mAg in the soil was 43.1 Bq/kg. A survey of 35 faunal species in the terrestrial environment during the 3.5 years after the accident showed that most of Anthropoda had two orders higher ^110mAg in their tissues than soils, although silver is not an essential element for their life. However, tracing of the activity of ^110mAg detected in spider Atypus karschi collected regularly at a fixed location showed that it declined much faster than the physical half-life. These results suggest that ^110mAg was at once biologically concentrated by faunal species, especially Arthropoda, through food chain. The factors affecting the subsequent rapid decline of ^110mAg concentration in faunal species are discussed.     

Radioactive contamination of the atmosphere of Cairo,Egypt, from the Fukushima Dai-ichi nuclear plant accident

Radioactive contamination in air dust particles of Cairo atmosphere from the Fukushima accident was detected by the gamma-ray spectroscopy technique. Analysis of the spectra obtained by using an High-Purity Germanium detector showed that there were some traces of ¹³¹I and ^{134, 137}Cs. Estimate and study of concentration of those radionuclides were done over a period of about 5 months after the accident. Comparison with corresponding results in different countries all over the world has been performed.     

Continuously improving safety of nuclear installations: An approach to be reinforced after the Fukushima accident

After the Three Mile Island accident in 1979 and the Chernobyl accident in 1986, the Fukushima accident shows that the probability of a core meltdown accident in an LWR (Light Water Reactor) has been largely underestimated. The consequences of such an accident are unacceptable: except in the case of TMI2 (Three Mile Island 2) large areas around the damaged plants are contaminated for decades and populations have to be relocated for long periods. This article presents the French approach which consists in improving continuously the safety of the Nuclear Power Plants (NPP) on the basis of lessons learned from operating experience and from the progress in R&D (Research and Development). It details the key role played by IRSN (Institut de radioprotection et de sûreté nucléaire), the French TSO (Technical and scientific Safety Organization), and shows how the Fukushima accident contributes to this approach in improving NPP robustness. It concludes on the necessity to keep on networking TSOs, to share knowledge as well as R&D resources, with the ultimate goal of enhancing and harmonizing nuclear safety worldwide.     

Observation of fallout deposition in an outdoor swimming pool 50 km away from the Fukushima Daiichi nuclear power plant

After the accident at the Fukushima Daiichi nuclear power plant (NPP), outdoor school swimming pools at Fukushima were decontaminated to curb the redistribution of radioactivity into downstream farmlands. In the process, the radioactivity concentrations of the pool water and sediment substances (residue) were measured to estimate the deposition density of the fallout. At a pool situated 50 km away from the NPP, the average concentrations of radiocesium (^134+137Cs) for the water and residue were quantified as 170 Bq L⁻¹ and 3.6 × 10⁵ Bq kg⁻¹, respectively. Taking account of the radioactivity concentrations and of the water balance in and around the pool, the deposition density of radiocesium, as of August 2011, was precisely determined to be 0.32 ± 0.03 MBq m⁻² (k = 1). The density corroborated the previous results obtained by other methods, i.e., airborne surveys, in-situ Ge surveys and soil samplings at neighboring locations. Other than radiocesium, the only gamma-emitting nuclide detected was ^110mAg, with a concentration of 560 Bq kg⁻¹ in the residue. The radioactivity concentrations of ⁸⁹Sr, ⁹⁰Sr, ²³⁸Pu and ^239+240Pu in the water were all less than the minimum detectable activities – 2, 0.1, 0.002 and 0.002 Bq L⁻¹, respectively.     

Fission products from the damaged Fukushima reactor observed in Hungary

Fission products, especially ¹³¹I, ¹³⁴Cs and ¹³⁷Cs, from the damaged Fukushima Dai-ichi nuclear power plant (NPP) were detected in many places worldwide shortly after the accident caused by natural disaster. To observe the spatial and temporal variation of these isotopes in Hungary, aerosol samples were collected at five locations from late March to early May 2011: Institute of Nuclear Research, Hungarian Academy of Sciences (ATOMKI, Debrecen, East Hungary), Paks NPP (Paks, South-Central Hungary) as well as at the vicinity of Aggtelek (Northeast Hungary), Tapolca (West Hungary) and Bátaapáti (Southwest Hungary) settlements. In addition to the aerosol samples, dry/wet fallout samples were collected at ATOMKI, and airborne elemental iodine and organic iodide samples were collected at Paks NPP. The peak in the activity concentration of airborne ¹³¹I was observed around 30 March (1–3 mBq m^?3 both in aerosol samples and gaseous iodine traps) with a slow decline afterwards. Aerosol samples of several hundred cubic metres of air showed ¹³⁴Cs and ¹³⁷Cs in detectable amounts along with ¹³¹I. The decay-corrected inventory of ¹³¹I fallout at ATOMKI was 2.1±0.1 Bq m^?2 at maximum in the observation period. Dose-rate contribution calculations show that the radiological impact of this event at Hungarian locations was of no considerable concern.     

Decontamination of radioactivity from contaminated vegetables derived from the Fukushima nuclear accident

Many kinds of vegetables were contaminated by a huge amount of radioactivity, such as ¹³¹I or ¹³⁷Cs, derived from the Fukushima nuclear accident. The concentration of radioactivity in contaminated vegetables was higher than the value of the legal limit for shipment, therefore, we attempted to identify a simple and effective removal method for contaminated farm products to ensure the relief of farmers and the security of consumers. First, the radioactivity distribution and adhesion state of contaminated vegetables were investigated by an imaging plate (IP) image. As a result, there were two types of contamination, spot type or spread type, of vegetables. The removal of radioactivity by physical or chemical methods was investigated. As a result, radioactivity removal by water washing showed no significant difference between boiling water and cold water. There was no significant difference between hand washing and running water washing. The result of chemical removal showed that reducing agents removed radioactivity from vegetables by 70–80% for ¹³¹I and more than 80% for ¹³⁷Cs. In particular, ascorbic acid is promising as a safe and versatile option.     

Charged multiplicity distributions in pd and π+d interactions at 195 GeV/c

Topological inelastic cross-sections and average multiplicities for pd and π⁺d interactions at 195 GeV/c, are obtained from an exposure of the NAL 30″ proportional wire chamber-bubble chamber hybrid system to a positive π⁺/p beam. We find that 〈n_c〉_pn = 7.67 ± 0.25, and 〈n_c〉_π⁺n = 7.56 ± 0.30, yielding a negative multiplicity difference between pn and pp of 0.50 ± 0.14, and that σ_n(pp) is approximattely interleaved between σ_n?1(pn).     

从“福岛第一核电站事故”看我国核能利用的核安全

文章简要说明了福岛第一核电站事故的起因、发展和后果,并对核电站全厂断电、反应堆压力容器及安全壳超压、氢爆等导致事故恶化的原因作了分析.文章还就导致福岛核事故的相关因素与我国核电站的安全设计及防范对策进行了分析比较.在吸取福岛核事故的经验教训方面,文章提出了若干值得引发关注的启示,作为我国在建和在役核电站的改进,以及新设计核电站的参考.文章还就我国能源的状况,核能发展的必要性,以及核能发展的方针进行了探讨.     

Helium emission spectra—I. intermediate pressure studies

The apparent cross sections of the n¹P(n = 3,4,5,6) and n^1,3D(n = 4,5,6,7) levels have been measured as a function of pressure between 5 and 200 mTorr at 1·5KeV electron impact excitation energy. The 4¹S apparent cross section was measured under the same conditions to observe secondary electron effects. A detailed analysis is made on the mechanisms of excitation transfer out of the n¹P levels in terms of radiative and collision processes. Collisional n¹P?nF transfer cross sections are calculated for the n = 4 and n = 5 levels and the results are in agreement with the principle of detailed balance. An analysis of the 6¹P apparent cross section indicates that collision processes other than n¹P?nF become important at n = 6 level in determining collisional transfer out of n¹P. Evaluation of n^1,3D apparent cross sections show that direct collisional gain and loss become more important as n increases.     

K X-ray transition energies for first row atoms and ions

X-ray energies are computed using screened, hydrogenic Slater integrals for all configurations [(1s^l2s^m2pⁿ) with l = 0 and 1, m = 0, 1, and 2, and n = 1 through Z-4] of all ionization stages of the elements boron through neon. The results include diagram lines, satellite lines, hypersatellite lines, and two-electron, one-photon lines. Excellent agreement is found between these results and those found by the Hartree-Fock-Slater method. In addition, X-ray energies associated with the spin-orbit forbidden decay of n = 2 three-electron quartet terms and four-electron quintet terms are calculated for the elements beryllium through neon. These results agree closely with those found by 1/Z perturbation theory.     

On the 0<Superscript>+</Superscript> state with the energy of 681.3 keV in <Superscript>160</Superscript>Dy

A possibility that the 0⁺ state with the energy of 681.3 keV exists in the ¹⁶⁰Dy nucleus is discussed. Calculations based on the interacting vector boson model show that in addition to the known 0⁺ states with the number of bosons n = 2, 5, 6, and 7 there should exist other states with the number of bosons n = 1, 3, 4, and 8 in ¹⁶⁰Dy. It is shown that the peak at the energy 681.3 keV, which we experimentally observed in the ¹⁶⁰Dy internal conversion electron spectrum, can be ascribed to the 0⁺ state with the number of bosons n = 1 or n = 8.     

New data on (γ, n), (γ, 2n), and (γ, 3n) partial photoneutron reactions

Systematic discrepancies between the results of various experiments devoted to determining cross sections for total and partial photoneutron reactions are analyzed by using objective criteria of reliability of data in terms of the transitional photoneutron-multiplicity function F _i = σ(γ, in)/σ(γ, xn), whose values for i = 1, 2, 3, ... cannot exceed by definition 1.00, 0.50, 0.33, ..., respectively. It was found that the majority of experimental data on the cross sections obtained for (γ, n), (γ, 2n), and (γ, 3n) reactions with the aid of methods of photoneutron multiplicity sorting do not meet objective criteria (in particular, F ₂ > 0.50 for a vast body of data). New data on the cross sections for partial reactions on ¹⁸¹Ta and ²⁰⁸Pb nuclei were obtained within a new experimental-theoretical method that was proposed for the evaluation of cross sections for partial reactions and in which the experimental neutron yield cross section σ ^expt(γ, xn) = σ(γ, n) + 2σ(γ, 2n) + 3σ(γ, 3n) + ..., which is free from problems associated with determining neutron multiplicities, is used simultaneously with the functions F _i ^theor calculated within a combined model of photonuclear reactions.     

Estimation of the total population moving into and out of the 20 km evacuation zone during the Fukushima NPP accident as calculated using “Auto-GPS” mobile phone data

The first objective data showing the geographical locations of people in Fukushima after the Fukushima Dai-ichi nuclear power plant accident, obtained by an analysis of GPS (Global Positioning System)-enabled mobile phone logs, are presented. The method of estimation is explained, and the flow of people into and out of the 20 km evacuation zone during the accident is visualized.     

Kinetic-energy release distributions and stability of niobium-carbon clusters sputtered from the surface of niobium carbide by xenon ions

The results of studying the emission and fragmentation of niobium-carbon clusters Nb _m C _n ⁺ synthesized upon sputtering a niobium carbide surface with Xe⁺ ions are presented. The fragmentation channels of Nb _m C _n ⁺ clusters are studied. We present the values of the dissociation energy of some Nb _m C _n ⁺ clusters (m = 1–7, n = 2–8) calculated within the context of the “evaporation ensemble” model and theory of unimolecular reactions based on performed measurements of the kinetic-energy spectra of fragment ions. The obtained results are compared with published data.     

Cross-sections of isomeric state excitation of the 119Te and 121Te nuclei in (γ, n) reactions in an energy range of 9–20 MeV

The dependence of isomeric yield ratios upon the maximum bremsstrahlung gamma-quanta energy for the ¹²⁰Te(??, n)^119m,g Te and ¹²²Te(??, n)^121m,g Te reactions within an energy range of the giant dipole resonance is investigated. Cross-sections of excitation of metastable states with J ^?? = 11/2^? of the ¹¹⁹Te and ¹²¹Te nuclei are obtained. Experimental data are compared with computation results obtained using the TALYS-1.2 software package.     

Polarisation der durch Protonenstoß angeregten Singulett-Übergänge des Heliums

The polarization degree of then ¹ S-2¹ P(n=3, 5)-,n ¹ D-2¹P(n=3, 4, 5)- andn ¹ P-2¹ S(n=3, 4)-transitions of helium excited by proton impact has been measured in the energy range of 100 keV to 1 MeV. The results in connection with respective H ₂ ⁺ - ande ^?-impact values are used in a comparison with the principle statements of the 1. Born- and the Bethe-Born-approximation. The results are in a qualitative agreement with the theoretical calculations.     

The ground state of two-dimensional electrons in a nonuniform magnetic field

An exact solution to the Schrödinger equation for the ground state of two-dimensional Pauli electrons in a nonuniform transverse magnetic field H is presented for two cases. In the first case, the field H depends on a single variable, H = H(y), while in the second case, the field is axially symmetric, H = H(ρ), ρ²=x ²+y ². The electron density distributions n = n(y) and n = n(ρ) that correspond to a completely filled lower level are found. For quasiuniform fields of fixed sign, the functions n(y) and n(ρ) are locally related to the magnetic field: n(y) = H(y)/?₀ and n(ρ) = H(ρ)/?₀, where ?₀ = hc/|e| is a magnetic flux quantum. Magnetic fields are considered that are periodic, singular, and bounded in the plane xy. Finite electron objects in a nonuniform magnetic field are analyzed.