Half-life of radionuclides determined by the reference source method

Summary An approach for half-life determination using the reference source method associated with gamma-spectrometry with a Ge detector is presented. The method reduces the contribution of the type B component of the total uncertainty. The independence of the method regarding the instrumental interferences or radiochemical impurities was evidenced. However, there are some limitations when the method is applied for a genetically-related impurity with the same or very similar energy to that of the radionuclide to be measured, e.g., if ⁹⁹Mo in a ^99mTc sample is present. The measured half-life values are in good agreement with those of the literature and the associated uncertainties are lower than 0.1%.     

A rapid method for the determination of radionuclides in reactor coolant by ion exchange membranes

This paper deals with a rapid method to determine radionuclides in reactor coolant by anion, cation, and anion-cation exchange membranes. A high pressure filtration device was established to simulate the THOR cooling water sampling system by means of several membranes mentioned above. The experimental results indicate that the adsorption efficiency of each membrane for several radionuclides is /1/ >95% with cation exchange membrane for Zn, Co, Na, Mn, Cu, Cs, Ba, La, W etc., /2/ >98% with anion exchange membrane for I, and /3/ <98% with anion-cation exchange membranes for Fe and Cr. The results are obtained using cooling water of Tsing Hua Open-Pool Reactor and the following radionuclides were identified:^99mTc,¹⁴⁰Ba,¹⁴⁰La,⁵¹Cr,¹³¹I,⁵⁸Co,⁶⁰Co,⁵⁴Mn,⁴⁶Sc,⁵⁹Fe,²⁴Na, etc.     

Tables of gamma rays emitted by radionuclides produced through photonuclear reactions

The tables have been prepared as an auxiliary for the interpretation of results in photoactivation analysis. They include data concerning the disintegration of radionuclides produced by (γ, n) reactions on all stable isotopes with a relative abundance greater than 1% and by (γ, p) reactions on elements withZ≤39. The γ-rays are listed in ascending order of the energies; half-lives, intensities and other useful informations are also included.     

Kinetic energies of fragment ions produced by dissociative photoionization of NO

The kinetic energies of ions produced by dissociative photoionization of NO have been measured at the discrete resonance lines of He (584 Å) and Ne (736 Å), and with undispersed synchrotron radiation. O⁺ ions were identified with energies from 0 to approximately 0.5 eV and two groups of N⁺ ions one with energy of 0.36 eV and another with energies between 0.9 and 1.5 eV, apparently produced by predissociation of the c³Π and B′¹Σ states, respectively.     

Changes in poly-vinylidene fluoride produced by electron irradiation

A study was made of the effects of electron irradiation of poly-vinylidene fluoride, using the DSC, FTIR, and X-ray techniques, as well as determining the percent cross-linking. Changes in crystallinity and melting point of the sample as a function of dose were found, the latter due to competition between cross-linking and crystallinity. The cross-linking was observed to increase with radiation dose. Chemical changes observed include the formation of carbonyl groups and double bonding, associated with the loss of HF.     

ESR investigation of sucrose radicals produced by particle irradiation

We investigated sucrose radicals produced by heavy-ion irradiation with various linear energy transfer (LETs) and the possibility for a sucrose electron spin resonance (ESR) dosimeter. The impact of heavy ions on sucrose produced sucrose radicals, which were measured by ESR. The obtained spectral pattern was the same as that for helium (He) ions, carbon (C) ions, neon (Ne) ions, iron (Fe) ions, and gamma-ray irradiation. Identical spectra were measured after 1 year, but the initial intensities decreased by a few percent when the samples were kept in ESR tubes with the caps at ambient temperature. The total spin concentration obtained by heavy-ion irradiation had a linear relation with the absorbed dose, and correlated logarithmically with the LET. Qualitative ESR analyses showed that the production of sucrose radicals depended on both the particle identity and the LET at the same dose. The production of spin concentration by He ions was the most sensitive to LET. Empirical relations between the LET and the spin yield for various particles imply that the LET at a certain dose can be estimated by the spin concentration. Therefore, the present ESR results imply that sucrose can be used to monitor the absorbed dose and the LET of particle irradiation.     

Recoil properties of radionuclides formed in the photonuclear reactions onnatCu at intermediate energies

The recoil properties of 26 radionuclides produced in the photonuclear reactions on Cu at bremsstrahlung end-point energies (E ₀) of 250 to 1000 MeV have been investigated using the thick-target thick-catcher method. Kinematic properties of the product nuclei were calculated by the two-step vector velocity model. The calculated mean kinetic energies,T, of product nuclei increase with increase of the mass difference between products and target, reflecting the resonance natures and absorption mechanisms. TheT atE ₀≥600 MeV were well reproduced by a calculation performed by PICA code byGabriel andAlsmiller atE ₀=400 MeV, except for (γ,xn) products by giant-resonance.     

Liquid-solid extraction of high specific activity radionuclides from reactor irradiated metal phthalocyanines

Highly purified cobalt and zinc phthalocyanines were reactor irradiated and used in studies of the direct liquid-solid extraction procedure for obtaining high specific activity radionuclies. Hot dilute aqueous acid solutions, such as 0.1M HClO₄, were found to give useful yields />50%/ at moderate enrichments from -MPc targets. Dilute acid does not extract useful quantities of radionuclides from the irradiated -MPc targets examined.     

Regeneration of photocatalysts by in situ UV irradiation in photocatalytic membrane reactor

ZnO was successfully prepared by the conventional synthetic route. Polyvinylpyrrolidone was used as soft-template to synthesize ZnO with controllable size and shape. It was found that ZnO was synthesized with average crystal size of 49 nm, as reported by an X-ray diffraction experiment. Scanning electron microscopy and transmission electron microscopy confirmed the hexagonal shape of the as-synthesized ZnO. The thus prepared ZnO colloidal particles exhibited numerous opportunities for numerous applications.     

Modeling the dispersion of radionuclides released during reactor accidents aboard nuclear-powered vessels

Provenance determinations of pottery by chemical analysis is reviewed and shown to work well. Since pottery is produced from a well homogenized clay paste according to a certain recipe, sharp elemental patterns are expected for a series of products having the same origin. To obtain such patterns when forming compositional groups of pottery, a consideration of experimental errors, a correction for dilution and a choice of only stable elements is necessary. The patterns thus obtained will have low probability of overlap with groups of different origin. Examples for well defined groups of German stonewares and of Mycenaean wares from the Peloponnese are recorded.     

A compilation of resonance integrals

This section of the compilation is a continuation of Part I, Z=1–52 (Hydrogen-Tellurium) which appeared in this Journal.¹ This part lists the resonance integrals of reactor neutron capture and fission reactions for nuclides from Z=53 to Z=100; the thermal cross-sections of the corresponding nuclides are also included. The theoretical explanation and physical meaning of resonance integral obtained by different experimental approaches are discussed in Part I.     

Recovery and determination of tritium produced in lithium-aluminium alloy by neutron irradiation

Neutron-irradiated Li−Al alloy was heated at 800°C in He flow. The tritiated species released from the sample were oxidized to H₂O(T) by passing them through a CuO column heated at 800°C and completely trapped in water scrubbers. The tritium was determined by liquid scintillation counting. The amount of tritium determined by this method was consistent with that calculated by the method of WESTCOTT et al.     

INAA of human and animal whole blood samples by short term reactor irradiation

Instrumental Neutron Activation Analysis /INAA/ has been employed for the determination of 15 major, minor and trace elements in human and animal blood samples. Dry whole blood samples along with NBS and IAEA standards were irradiated for 5 min, 1 h, 5 h and 10 h with reactor thermal neutrons and counted using high resolution -spectrometry at successive intervals. Data for a new IAEA proposed CRM Mixed Human Diet /H-9/ is reported.     

Two-dimensional (half-life vs. energy) map of gamma-rays emitted by radionuclides produced through photonuclear reactions

Two-dimensional maps of half-life versus energy have been prepared for the radionuclides produced through photonuclear reactions at 30 MeV for assistance in the qualitative analysis of complex Ge(Li) spectra. The choice of nuclides for inclusion in the compilation is experimental, virtually all having been observed with a Ge(Li) detector after irradiation. Comprehensive data on relative yields at 30 MeV are also included. Senior U.S. Scientist Awardee of the Alexander von Humboldt Foundation.     

Comparison of radionuclides levels from the Chernobyl reactor accident and from global fallout

Studies on radioactive fallout from atmospheric nuclear weapons tests have been carried out at this laboratory since the mid-fifties. The data thus generated on the levels and composition of radioactive fallout in India has been published periodically. Consequent to the Chernobyl reactor accident in the USSR in April 1986, similar studies were carried out. A number of fairly active samples were collected from commercial aircraft which had flown over the USSR soon after the accident. Even though the levels of fallout from the Chernobyl reactor accident observed in India were not significant from a health hazard view point, the studies provided detailed information on differences in the composition of fallout from the accident and long term radiation exposures likely to accrue from the Chernobyl fallout as opposed to global fallout from atmospheric nuclear weapons tests. This paper presents the results and their interpretation on the above aspects.     

Determination of neutron temperature in irradiation channels of reactor

The neutron temperature is a characteristic parameter in irradiation channels of reactor. For nuclides which have resonances in the thermal neutron energy range, their Westcott g-factors are different from unity. The values of g-factors and cross-sections of (n, γ) reaction of these nuclides are temperature dependence. The standard energy for tabulation of thermal neutron cross-section (σ₀) is that of room temperature (293.59 K or 20.43 °C), corresponding to a neutron energy 0.0253 eV or to a neutron velocity of 2200 m/s. However, in the irradiation channels of reactor, the temperature is not exact at 20.43 °C. Thus, the temperature at the irradiation position must be known to convert σ₀ to σ(T). A method for determination of the neutron temperature in irradiation channels of Dalat reactor is presented by fitting the thermal neutron spectrum obtained from the calculation using MCNP code.