Distribution characteristics of <Superscript>14</Superscript>C and <Superscript>3</Superscript>H in spent resins from the Canada deuterium uranium-pressurized heavy water reactors (CANDU-PHWRs) of Korea

It is regarded that the spent resins from the water purification systems of moderator (MOD) and the primary coolant of the Canada deuterium uranium-pressurized heavy water reactor (CANDU-PHWR) are a unique waste, owing to their high ¹⁴C and gamma-emitting nuclides. In this work, ¹⁴C and ³H contents, anion and cation fractions and the predominant gamma-emitting nuclides of the spent resins from 4 units of CANDUPHWRs, were investigated. Also the chemical species of ¹⁴C of the spent resins were determined. For a simultaneous separation of ¹⁴C and ³H from the spent resins, the wet oxidation-16 wt% H₂SO₄ stripping process was utilized. The ¹⁴C and ³H activity concentration range of the spent resins of the nuclear power plant (NPP), 4 units of all CANDU-PHWR types, was 2.48E5 Bq/g ∼5.33E6 Bq/g, 1.29E5 Bq/g and ∼2.33E5 Bq/g, respectively. Among the analyzed spent resins, the highest ¹⁴C and ³H activity concentration was detected in units 4 and 3, respectively. It was found that more than 92% of the ¹⁴C activity concentration was retained on the anion resin and the predominant chemical species was inorganic ¹⁴C. It was revealed that the anion resin fraction of the spent resins from unit 1 and unit 2, was about 40% and that of unit 3 and unit 4 was around 60%. More than 80% of the total gamma-radioactivity concentration was associated with the cation fraction of the spent resin. The predominant gamma-emitting nuclide of the spent resin for unit 2 was ¹³⁷Cs, a fission product, and that for unit 4 was ⁶⁰Co, a corrosion product.     

Determination of <Superscript>3</Superscript>H and <Superscript>14</Superscript>C in the Dry Active Wastes (DAW) generated from the Light Water Reactors (LWR) by a wet oxidation method

³H and ¹⁴C Measurements of the dry active waste (DAW), such as the cotton, paper, and vinyl, generated from a nuclear power plant (NPP) were conducted with wet oxidation using open vessel equipment based on simulation results. The recovery efficiency with the simulated samples was around 93% with a relative standard deviation (RSD) of 1–3%. A liquid scintillation counter (LSC) was used for counting and adjusted to a quenching correction curve. The counting value was evaluated for the minimum detectable activity (MDA), which was found to be about 4 × 10⁻¹ Bq/g for ³H and 2 × 10⁻² for ¹⁴C when approximately 5 g of the samples were measured. The measured DAW samples for the cotton, paper, and vinyl generated from NPP achieved of RSD values of 25, 25, and 60%, respectively, for ³H and 0–50% for ¹⁴C.     

Separation of 3H, 14C, 32P, 35S, 125I, and 131I in radioisotope waste

Measurement of ³H, ¹⁴C, ³²P, ³⁵S, ¹²⁵I, and ¹³¹I in radioisotope (RI) waste materials such as the vials, pipette tips, tubes, syringes, and paper generated from the industrial, medical, educational, and research organizations were conducted by a wet oxidation method. Counts were obtained by a liquid scintillation counter for ³H, ¹⁴C, and ³²P; a gas proportional counter for ³⁵S; a low energy photon spectroscopy for ¹²⁵I; and an HPGe detector for ¹³¹I. After the treatment of approximately 20 g of the sample, the counting value was determined to obtain a minimum detectable activity (MDA) of approximately 1 × 10^?3 ~ 5 × 10^?2 Bq/g. The specific activities of shor-half-life RIs (³²P, ³⁵S, ¹²⁵I, and ¹³¹I) were not detectable and/or resulted in a low value (<1 Bq/g). The waste containing ³H and ¹⁴C was observed to have the specific activities in the range of 10^?2–10⁵ and 10^?2–10⁴ Bq/g, respectively.     

A one-year study of the total air-borne14C effluents from two Swedish light-water reactors,one boiling water- and one pressurized water reactor

The results of a one-year study of the total air-borne¹⁴C effluents from two Swedish light-water reactors, one boiling water reactor (BWR) at Forsmark and one pressurized water reactor (PWR) at Ringhals, are presented. Air emitted from the stacks has been collected continuously over two-week periods and the¹⁴C content in the samples has been analysed using accelerator mass spectrometry (AMS). The¹⁴C activity concentration in the air issuing from the stack of the PWR varied between 2 and 1132 Bq/m³ with a mean value of 200 Bq/m³, while from the BWR the activity concentration varied between 4 and 146 Bq/m³, with a mean value of 95 Bq/m³. The corresponding¹⁴C release rate was 0.27 TBq/GW_el·year for the PWR and 0.48 TBq/GW_el·year for the BWR. During the same period of time, for comparison, the¹⁴C activity in continuously collected air from the stack of the PWR was also measured by liquid scintillation counting. In most cases the results of these measurements were in fair agreement with the corresponding AMS results.     

Solid Polymer Electrolytes Studied by NMR Spectroscopy and DFT Calculations

Summary: Results obtained recently on polymer electrolytes poly(ethylene oxide) (PEO)/LiCF₃SO₃ and poly(2-ethyl-2-oxazoline) (POZ)/AgCF₃SO₃ by a combination of solid-state ¹³C and ¹H NMR spectroscopy and DFT quantum-chemical calculations are discussed. Essentially the same local structure was found for the amorphous and crystalline phases of semicrystalline PEO/LiCF₃SO₃ polymer electrolyte. The amorphous POZ/AgCF₃SO₃ complex has a defined stoichiometry with two POZ monomeric units per one AgCF₃SO₃. A close contact between the metal salt and polymer was determined for both investigated systems from the Lee-Goldburg cross-polarization ¹H → ¹³C dynamics.     

The role of Cherenkov and liquid scintilation counting in evaluating the anion-exchange separation of210Pb−210Bi−210Po

Using as eluent a sequence of 3M HCl, 12M HCl, and 8M HNO₃, a mixture of²¹⁰Pb,²¹⁰Bi, and²¹⁰Po may be clearly separated on a column of Dowex 1×2−100 anion exchange resin. A Cherenkov count in H₂O and the variation in count rate with time confirm that the nuclides emerge in the order²¹⁰Pb→²¹⁰Bi→²¹⁰Po. If 12M HCl is replaced by 1.5M H₂SO₄/2.3 M Na₂SO₄, a clean separation also results, but recovery of²¹⁰Po becomes considerably more difficult. All three nuclides are readily detectable by liquid scintillation counting, with the efficiency for²¹⁰Pb in the 60–70% range. The Cherenkov aqueous counting efficiency for²¹⁰Bi is ∼14–15%.     

Gasification characteristics to <Superscript>14</Superscript>CO<Subscript>2</Subscript> of <Superscript>14</Superscript>C radionuclide desorbed from spent resin by phosphate solutions

The removal characteristics of H¹⁴CO₃ ⁻ ions from IRN-150 mixed resin contaminated with ¹⁴C radionuclide and the gasification effects of ¹⁴C radionuclide on ¹⁴CO₂ are investigated in this study. The stripping solutions used for the removal of ¹⁴C from spent resin are NaNO₃, Na₃PO₄, NH₄H₂PO₄, and H₃PO₄. The influence of the stripping solution concentration on the desorption characteristics of an inactive HCO₃ ion into a stripping solution from IRN-150 mixed resin and the gasification of this ion to CO₂ is analyzed. The gasification behavior to CO₂ using NaOH, HNO₃, and HCl was also compared to that of phosphate solution. Spent resin stored in Wolsong nuclear power plant is used to evaluate the gasification characteristics of ¹⁴C radionuclide to ¹⁴CO₂. Gamma radionuclides such as ¹³⁷Cs and ⁶⁰Co in residual striping solutions after desorption experiments are analyzed.     

Nitration and bromination of benzo-1,2,3,4-tetrazine 1,3-dioxides

Benzo-1,2,3,4-tetrazine 1,3-dioxide (BTDO) and its derivatives were nitrated with HNO₃/H₂SO₄ or HNO₃/oleum and brominated with dibromoisocyanuric acid in CF₃CO₂H/H₂SO₄ (5 : 1) or H₂SO₄. The reactivity of positions in the benzene ring of this heterocyclic system as regards electrophilic substitution was found to change in the following order: 5 7 > 8 > 6. Mono- and dinitro-BTDOs and mono- and polybromo-BTDOs were synthesized. Their structures were confirmed by ¹H, ¹³C, and ¹⁴N NMR spectra.     

A simple and reliable monitoring system for 3H and 14C in radioactive airborne effluent

Summary A simple and reliable sampling system for ³H and ¹⁴C in airborne release from nuclear facilities was designed. The sampling system can collect ³H and ¹⁴C simultaneously with a condensation technique using a commercially available cold trap equipment and a CO₂ absorption technique using an organic alkali monoethanolamine solution, respectively. In situ performance tests for the effluent from a reprocessing plant showed that the system has high and stable efficiencies for collecting ³H and ¹⁴C for a one-week batch sampling at a sampling flow rate of 0.4 l ^. min^-1. These collection techniques also provided a simple procedure of following sample preparation for activity measurements by liquid scintillation counting. The detectable concentrations of the proposed monitoring method were 3.0 Bq ^. m^-3 for ³H and 1.6 Bq ^. m^-3 for ¹⁴C, respectively. The sensitivity would be on an acceptable level for routine monitoring of airborne release at nuclear facilities.     

Generation of oxodiazonium ions 3. Synthesis of [1,2,5]oxadiazolo[3,4-c]cinnoline-1,5-dioxides

A reaction of 4-(N-nitramino)-3-phenylfuroxane with the Ac₂O/H₂SO₄ system leads to the formation of [1,2,5]oxadiazolo[3,4-c]cinnoline-1,5-dioxide, the first representative of furoxanocinnolines. The reaction presumably proceeds through the transformation of the nitramine fragment NHNO₂ to the oxodiazonium ion [N=N=O]⁺ with subsequent intramolecular attack by this cation on the phenyl ring. Furoxanocinnoline is also formed in the reaction of the 4-(N-nitramino)-3-phenylfuroxane O-methyl derivative with H₂SO₄. It is assumed that this reaction also proceeds with involvement of the intermediate cation [N=N=O]⁺ formed by the protonation of the N=N(O)OMe group and subsequent elimination of MeOH. 7-Nitro derivative is formed when furoxanocinnoline is nitrated with the concentrated HNO₃/H₂SO₄ mixture. The compounds obtained were characterized by ¹H, ¹³C, and ¹⁴N NMR spectroscopy.     

Cathodic stripping voltammetry of selenocystine,cystine, and cysteine in dilute aqueous acid

Selenocystine, cystine, and cysteine can be determined by cathodic stripping voltammetry (c.s.v.) in 0.1 M HClO₄ or 0.1 M H₂SO₄. The amino acids are accumulated at potentials more positive than —0.35 V, —0.20 V, and —0.10 V vs. s.c.e., respectively, and the stripping peak potentials are —0.45 V, —0.38 V and —0.15 V, respectively. Limiting coverage of the mercury electrode surface is observed for cysteine and selenocystine, but not for cystine. The detection limit for selenocystine is 5 × 10^-10 M in the presence of 100-fold amounts of cystine and cysteine. The detection limits for cystine and cysteine are 1 × 10^-5 M and 1 × 10^-9 M, respectively.     

Instrumentelle Kompensation des Quencheffektes bei der Bestimmung von 14C und 35S

Zusammenfassung Ein Quencheffekt tritt auch nach Oxydation der organischen Probe auf. Dieser ist bedingt durch gewisse Verbrennungsprodukte, wie NO₂, Halogene, SO₂ und SO₃. Es wurde gefunden, da\ man den Quencheffekt der Verbrennungsprodukte bei der Bestimmung von ¹⁴C und ³⁵S ausschalten kann, wenn man die Spannung des Data-Photomultipliers bis zu einem gewissen Punkt (Kompensationspunkt) erhöht und die Messung in einem ZÄhlfenster durchführt. Der Kompensationspunkt wird graphisch ermittelt; hierzu mi\t man die ZÄhlrate des reinen Absorbens sowie die ZÄhlrate des Absorbens, das die maximal zu erwartende Menge Verbrennungsprodukt enthÄlt, bei verschiedenen Data-Spannungen. Der Zusammenhang zwischen der instrumenteilen Kompensation und dem Energiespektrum von ¹⁴C wird aufgezeigt. Bei der Bestimmung von Tritium lÄ\t sich der Quencheffekt nicht kompensieren, denn das Energiespektrum von Tritium wird durch eine Quenchverbindung anders beeinflu\t als das Spektrum von ¹⁴C bzw. ³⁵S.

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Summary After combustion of the organic sample a quenching effect is observed, due to several combustion products as NO₂, halogens, SO₂, and SO₃. We found, that it is possible to eliminate quenching of the combustion products in the determination of ¹⁴C and ³⁵S, if the high voltage of the data-photomultiplier is raised to a certain level (compensation point) and if the counting is performed in a window. The compensation point is calculated graphically by determining the counting rate of the pure absorbant and the absorbant plus the highest expected amount of combustion products. The relation between instrumental compensation and the energy spectrum of ¹⁴C is elucidated. It is not possible to compensate quenching in the determination of tritium, because the energy spectrum of ³H is influenced in a different way than the spectrum of ¹⁴C and ³⁵S.

     

Catalytic decomposition of CFC‐12 on solid acids SO42‐/MxOy (M?Zr,Ti, Sn,Fe, Al)

The catalytic decomposition of dichlorodifluoromethane (CFC‐12) in the presence of water vapor on a series of SO₄^2?‐promoted solid adds was investigated. CFC‐12 was decomposed completely on SO₄^2?/ZrO₂, SO₄^2?/TiO₂, SO₄^2?/SnO₂, SO₄^2?/ Fe₂O₃ and SO₄^2–/Al₂O₃ at 265°C, 270°C, 325°C, 350°C and 325°C, respectively, and the selectivity to by‐products was neglectable. Obvious deactivation was found on SO₄^2?/ZrO₂ and SO₄^2?/Al₂O₃, during several hours on stream, while the catalytic activity was maintained on SO₄^2?/TiO₂, SO₄^2?/SnO₂ and SO₄^2?/Fe₂O₃ for 240 h on stream.     

Solid state NMR study of intercalate complexes of poly(ethylene oxide) and small molecules

From solid state NMR spectra, a lower shielding of poly(ethylene oxide) (PEO) protons, in contrast to higher shielding of PEO carbons, has been found for PEO/hydroxybenzene and PEO/LiCF₃SO₃ complexes in comparison with neat PEO. The same PEO chemical shifts were found both for crystalline and amorphous phase of PEO/LiCF₃SO₃ polymer electrolyte, confirming the same interaction in both phases. Measurements of 2D ¹H CRAMPS exchange NMR spectra have been used to characterize proton distances in complexes of PEO and benzene derivatives. A close contact (∼ 0.3 nm) between aromatic and PEO protons was detected in some cases. From the measurements of the cross polarization ¹H → ¹³C, using Lee-Goldburg irradiation of ¹H nuclei, the distance between LiCF₃SO₃ carbon and the nearest PEO protons in the PEO/LiCF₃SO₃ complex was determined.     

14C in spent ion-exchange resins and process water from nuclear reactors: A method for quantitative determination of organic and inorganic fractions

A method of separately quantifying organic and inorganic ¹⁴C compounds present in spent ion-exchange resins and process water from nuclear power reactors has been developed. Extraction of carbon compounds is accomplished by means of acid stripping (inorganic ¹⁴C) and subsequent wet oxidation (organic ¹⁴C) or by N₂ purging in combination with a catalytic furnace (oxidized and reduced gaseous compounds) with organic and inorganic ¹⁴C species collected separately. Recovery experiments on simulated samples spiked with ¹⁴C-labeled sodium carbonate, sodium acetate and sodium formate, showed extraction yields of 94–98%. The sample-specific procedures were also tested on authentic samples of spent resins and reactor water with good results. Validation and reliability of the procedures are presented and the method is compared to previous methods reported in the literature.     

Comparison of recoveries of inogranic and organic incorporated75Se by four mineralization methods of biological material

The recovery of selenium⁷⁵Se added as selenite to human blood and to mixed food, and the recovery of biologically incorporated⁷⁵Se from different rat tissues were determined by using four mineralization methods. The recoveries of⁷⁵Se after dry ashing /HNO₃, Mg/NO₃/₂/ and after three wet digestion methods — 1. HNO₃, HClO₄ 2. HNO₃, HClO₄, H₂SO₄ 3. HNO₃, HClO₄, MgCl₂ were as follows: 50–106%, 96–99%, 92–99% and 97–100%, resp. Losses of⁷⁵Se in wet digestion /HNO₃, HClO₄/ were observed at the end of the procedure, when an excess of acids was evaporated. The addition of MgCl₂ to the digestion mixture prevented the escape of⁷⁵Se and thus permitted the total evaporation of the digest without any loss of selenium.     

Generation of oxodiazonium ions 1. Synthesis of [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxides

Methods for the synthesis of [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxides, which include the reaction of 3-nitramino-4-(R-phenyl)furazans or their O-methyl derivatives with electrophilic agents, have been developed. Unsubstituted [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxide was synthesized from 3-nitramino-4-phenylfurazan upon the action of phosphorus anhydride or oleum, as well as from O-methyl derivative of 3-nitramino-4-phenylfurazan upon the action of H₂SO₄, MeSO₃H, CF₃CO₂H and BF₃·Et₂O, while 6-, 7-, 8-, and 9-nitro-substituted [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxides — from the corresponding 3-nitramino-4-(nitrophenyl)furazans upon the action of the H₂SO₄-HNO₃ nitrating mixture. A suggestion has been made that an oxodiazonium ion is formed in these reactions from nitramines or their O-methyl derivatives upon the action of electrophilic agents, which is further involved into the intra-molecular reaction of electrophilic aromatic substitution (S _EAr) with the aryl group. The structure of [1,2,5]oxadiazolo[3,4-c]cinnoline 5-N-oxides was confirmed by ¹H, ¹³C, and ¹⁴N NMR spectra. Theoretical studies by the B3LYP/6-311G(d,p) method of combined molecular system (O-methylated 3-nitramino-4-phenylfurazan + [H₃SO₄]⁺) resulted in calculation of thermodynamic parameters of the sequence of cascade elementary reactions leading to the formation of [1,2,5]oxadiazolo[3,4-c]cinnoline 5-oxide.     

A kinetic study of the chemistry of the SO2 (3B1) reactions with cis- and trans-2-butene

The chemical reactions of SO₂(³B₁) molecules with cis- and trans-2-butene have been studied in gaseous mixtures at 25°C by excitation of SO₂ within the SO₂(³B₁) → SO₂(+, ¹A₁) ‘forbidden’ band using 3500–4100-Å light. The initial quatum yields of olefin isomerization were determined as a function of the [SO₂]/[2-butene] ratio and added gases, He and O₂. The kinetic treatment of these data suggests that there is formed in the SO₂(³B₁) quenching step with either cis- or trans-2-butene, some common intermediate, probably a triplet addition complex between SO- and olefin. It decomposes very rapidly to form the 2-butene isomers in the ratio [trans-2-butene]/[cis-2-butene] = 1.8. In another series of experiments SO₂ was excited using a 3630 ± 1-Å laser pulse of short duration, and the SO₂(³B₁) quenching rate constants with the 2-butenes were determined from the SO₂(³B₁) lifetime measurements. The rate constants at 21°C are (1.29 ± 0.18) × 10¹¹ and (1.22 ± 0.15) × 10¹¹ l/mole·sec with cis-2-butene and trans-2-butene, respectively, as the quencher molecule. Within the experimental error these quenching constants equal those derived from the quantum yield data. Thus the rate-determining step in the isomerization reaction is suggested to be the quenching reaction, presumably the formation of the triplet SO₂-2-butene addition complex. In a third series of experiments using light scattering measurements, it was found that the aerosol formation probably originates largely from SO₃ and H₂SO₄ mist formed following the reaction SO₂(³B₁) + SO₂ → SO₃ + SO(³Σ^?). Aerosol formation from photochemically excited SO₂-olefin interaction is probably unimportant in these systems and must be unimportant in the atmosphere.     

Einbauversuche mit (3H und 14C)-doppelmarkiertem Farnesol in Cantharidin. 5. Mitteilung zur Biosynthese des Cantharidins

Incorporation experiments with (³H and ¹⁴C) doubly labelled farnesols into cantharidin After injection of 11′, 12-[³H]-7-[¹⁴C]-farnesol or 11′, 12-[³H]-5,6-[¹⁴C]-farnesol, the ³H-label is located specifically in the C(9)-methyl-group of cantharidin, whereas the ¹⁴C-labelling pattern follows an incorporation via acetic acid (Scheme 4). C-Atoms 5, 6 and 7 from the middle part of the farnesol molecule are utilized for cantharidin biosynthesis to an extent that is about 2.1–11% of the incorporation rate of the methyl groups C(11′) and C(12), depending on the position of the ¹⁴C-label in farnesol. These results confirm our earlier hypothesis [1] that the C₁₀-molecule cantharidin is biosynthesized from the C₁₅-precursor farnesol which is cleaved between C(1)–C(2), C(4)–C(5), and C(7)–C(8). The synthesis of 7-[¹⁴C]-farnesol and of 5,6-[¹⁴C]-farnesol is described.     

Biosynthesis of cytochalasins. II Building blocks of cytochalasun D

A number of potential ¹⁴C- and ³H-labelled precursors were fed to growing cultures of Zygosporium masonii after the rate of formation of cytochalasin D had been measured. By chemical degradation of [¹⁴C]- and [³H, ¹⁴C]-cytochalasin D the distribution of the radioactivity originating from incorporated [4′-3H, U-¹⁴C]-L -phenylalanine and [CH₃-¹⁴C]-L -methionine was determinated. The results demonstrate that the building blocks of cytochalasin D are 1 unit of pheylalanine, 3 units of methionine and acetate units.