Production of 11C and 7 Be by TRIGA-II Research Reactor

¹¹C has been produced by irradiating for 30 min in the pneumatic tube of a TRIGA-III research reactor about 700 mg of metaboric acid (HBO₂), using the ^11B (p,n) ¹¹C reaction initiated by neutron-hydrogen recoil. The fast neutron flux (>lMeV) was 9×10¹¹n/cm²·sec. The ¹¹C produced was separated from the irradiated target by distillation of CO₂. The yield of ¹¹C at the end of irradiation was 0.27 μ.Ci.

⁷Be also was produced by irradiating for 15 hr 1 g of lithium hydroxide in the central experimental tube of the reactor, through the ⁷Li(p,n) ⁷Be reaction initiated by neutron-hydrogen recoil. The fast neutron flux was 2.2×10¹² n/cm²·sec. Separation of carrier-free ⁷Be from the irradiated target was obtained by co-precipitation with ferric hydroxide. The yield of 7Be was 0.2 μCi.

For determining the influence on the ⁷Be yield brought by differences in the chemical composition of target, irradiations were carried out on lithium compounds containing hydrogen, such as lithium hydroxide, lithium hydroxide hydrate, lithium acetate and lithium citrate. Among these four lithium compounds, lithium hydroxide provided the highest yield of ⁷Be per gram of target.     

The 11B(p,α0)8Be nuclear reaction and 11B(p,p)11B backscattering cross sections for analytical purposes

The ¹¹B(p,α₀)⁸Be nuclear reaction and the ¹¹B(p,p)¹¹B backscattering cross sections were measured at a laboratory scattering angle of 165° in the energy range from 1700 to 2700 keV with an absolute accuracy of about 7%. The cross section values were derived by using the simultaneously measured RBS spectra of the protons backscattered from a thin gold layer. The measured cross section values are compared with X-ray photoelectron spectroscopy (XPS) and heavy ion elastic recoil detection analysis (HERDA) results of amorphous hydrogenated boron/carbon (a-B:C:H) layers. The cross section data are presented in graphical and tabular form.     

Tritium diffusion in zircaloy-2 in the temperature range −78 to 204° C

Tritium diffusion measurements in Zircaloy-2 were carried out over the temperature range ?78 to 204 °C by direct measurement of tritium diffusion gradients. The ⁶Li (n, α)³H reaction was used to inject tritium into the specimens and to produce initial tritium concentration in the range 0.0065 ppm to 0.013 ppm ³H by weight. Two diffusion components were identified from the concentration profiles: a surface trapping region approximately 5 μm thick and a normal diffusion profile characteristics of bulk diffusion. Surface release measurements of tritium verified the existence of a surface trapping layer. The bulk diffusion component was consistent with classical diffusion solutions and was given by: D = 0.00021_?0.00018^+0.005 exp?(8500 ± 200 cal/RT) cm² · sec^?1.The surface trapping was attributed to oxide films formed on the Zircaloy-2 at room temperature. The apparent diffusion coefficients for the surface region were consistent with: D = 4.0_?3.3^+19.7 × 10^?14 exp?(7200 ± 1500 cal/RT) cm² · sec^?1 over the temperature range 25 to 411°C.     

10Be annual fallout in rains in India

The ¹⁰Be concentrations of annual rainfall collections during 1979–1981, at eight stations in India, ranged from 0.43 × 10⁷ to 8.48 × 10⁷ atoms/l and the corresponding ¹⁰Be fallouts are in the range of 0.31 × 10 ⁶ to 2.73 × 10⁶ atoms cm^?2 a^?1. The estimated ¹⁰Be global fallout based on the presently available data is 1.55 × 10⁷ atoms^?2 a^?1 or 5 × 10^?2 atoms cm^?2 s^?1. Most of the measured rates of fallout and deep sea deposition of ¹⁰Be are a factor of 2–3 lower than the present estimate.     

Mass Transfer Model of Purex Process in Mixer-Settlers

The formation rate of ruthenium tetroxide (RuO₄) from nitrosyl ruthenium trinitrate (RuNO(NO₃)₃) was measured at temperatures of 70–115°C in 3–9 mol·dm^?3 nitric acid solutions. The gas-liquid equilibrium ratio was measured at temperatures of 40–80°C in 0.1–9 mol·dm^?3 nitric acid solutions. The gas-liquid equilibrium ratio of RuO₄ ranged about 60–260 under the experimental conditions. The reaction rate increased greatly with acid concentrations above 6 mol·dm^?3. The activation energy of the reaction was about 130 kJ·mol^?1 in 9 mol·dm^?3 nitric acid solution. It was concluded that the rate of RuO₄ formation dominated the distill-out phenomena of Ru in an evaporator as used in nuclear fuel reprocessing plants.     

Determination of the composition and instability constants of complex Pu+3oxalate ions

The solubility of Pu₂(C₂O₄)₃ · 9H₂O in aqueous solutions of K₂C₂O₄ of various concentrations (0.01–2.4 moles /liter) has been determined at constant ionic strength of the solution at 20. It was found that Pu⁺³ complexes are formed in these solutions. It was found from the results of Pu₂(C₂O₄)₃ · 9H₂O solubility determinations that in the region of K₂C₂O₄ concentrations studied the following complex ions are formed [Pu(C₂O₄)₂]^?, [Pu (C₂O₄)₃]^?3 and [Pu (C₂O₄)₄]^?5, the total instability constants of which are 4.9 · 10^?10; 4.10 · 10^?10 and 11.9 · 10^?11 respectively. The solubility of Pu₂(C₂O₄)₃ · 9H₂O in aqueous (NH₄)₂C₂O₄ solutions has also been determined in the range of ammonium oxalate concentrations from 0.07 to 0.7 mole/liter at 70 °. It is shown that the composition of the complex ions under these conditions corresponds to [Pu(C₂O₄)₂]^?, [Pu(C₂O₄)₃]^?3 and [Pu(C₂O₄)₄]^?5. The calculated total instability constants of these complex ions are 11.6 · 10^?9; 5.6 · 10^?9 and 2.5 · 10^?9 respectively. The heats of formation of complex Pu⁺³ oxalate ions have been calculated for the reaction Pu⁺³ + nC₂O₄ ^?2 ?[Pu(C₂O₄)_n]^3?2n Δ¯Q for the [Pu(C₂O₄)₂]^? ion is 1300 cal., for [Pu(C₂O₄)₃]^?3, 1200 cal., and for [Pu(C₂O₄)₄]^?5, 1300 cal.     

Chromatographic Study on Boron Isotopic Fractionation at High Pressure

Boron isotopic fractionation factor (S) between boron adsorbed onto kaolin clay and boron in aqueous solution was determined by break-through column chromatography at 25.0 MPa at 5 and 25°C. The S values obtained were 1.0021 at 5°C and 1.0011 at 25°C, and were smaller than those obtained by the batch method performed at the atmospheric pressure at room temperature. Theoretical calculations estimate that more than 90% of boron in the clay phase was taken up as B(OH)₃-form at high pressures. Combining the present S values with preliminarily obtained one at 12.0 MPa, it is likely that S value decreases with increasing pressure, which suggests that the difference of the partial isotopic molar volumes between ¹⁰B(OH)₃ and ¹¹B(OH)³ is larger than that of the volumes between ¹⁰B(OH)₄ ^? and ¹¹B(OH)₄ ^?.     

Implanted boron profiles in silicon

¹⁰B and ¹¹B implants into amorphous Si, with energies ranging from 50 keV to 2 MeV and 10 keV to 1 MeV respectively, were profiled by the nuclear reactions ¹⁰B(n, α)⁷Li and ¹¹B(p, γ)¹²C. The projected range R_p and straggling ΔR_p agree within a few percent with recent calculations due to Ziegler, Biersack and Littmark (ZBL). These results show that the ZBL electronic stopping power is adequate to reproduce range parameters resulting from MeV implantations.     

The 11B(p,α)8Be?→?α?+?α and the 11B(α,α)11B Reactions at Energies Below 5.4?MeV

Measurements of the absolute cross section and angular distributions for the $^{11} \hbox{B}(p,\alpha)^{8}{\text{Be}}\rightarrow\alpha+\alpha$ and the ¹¹B(α,α)¹¹B reactions have been performed from 0.15 to 3.8?MeV for the ¹¹B(p,α) study and from 2 to 5.4?MeV for the ¹¹B(α,α) reaction. The absolute cross sections are presented in terms of the total number of α-particles detected in order to avoid uncertainties due to ambiguities in the number of alpha particles emitted in the reaction at a particular energy. The angular distributions of the ¹¹B(p,α)⁸Be(2⁺) reaction were fit to a Legendre polynomial expansion and the coefficients are presented. Finally, the ¹¹B(α,α)¹¹B data were fit in terms of phase shifts (ignoring the spin of the target), providing a convenient representation of the elastic cross section data between 2 and 5.4?MeV.     

Nuclear reactions induced by deuterons and their applicability to skin tumor treatment through BNCT

In this work the D(d,n)³He and ⁹Be(d,n)¹⁰B reactions have been studied in a low-energy regime as neutron sources for skin tumor treatment in the frame of accelerator-based BNCT (AB-BNCT). The total neutron production and the energy and angular distributions for each reaction at different bombarding energies and for the thick targets considered (TiD₂, Be) have been determined using the available data in the literature. From this information, a feasibility study has been performed by means of MCNP simulations. The thermal, epithermal and fast neutron fluxes and doses at skin tumor positions (loaded with 40 ppm ¹⁰B) which are located on a whole-body human phantom have been simulated for different D₂O moderator depths. The best-case performance shows that a high tumor control probability (TCP) of 99% corresponding to a weighted dose in tumor of 40 Gy can be reached at the tumor position keeping the weighted dose in healthy tissue below 12.5 Gy, by means of the ⁹Be(d,n)¹⁰B reaction at 1.1 MeV for a deuteron current of 20 mA and a 30 cm D₂O moderator in 52 min. The availability of low-energy neutrons in the ⁹Be(d,n)¹⁰B reaction from the population of excited levels between 5.1 to 5.2 MeV in ¹⁰B and the convenience of a thin beryllium target are discussed.As a complement concerning alternatives to the Li(metal) + p reaction, the neutron yield of refractory lithium compounds (LiH, Li₃N and Li₂O) were calculated and compared with a Li metal target.     

Argon ion impact desorption cross sections of chlorine and carbon from molybdenum

Total desorption cross sections have been measured for Cl (σ_Cl) and C(σ_C) on molybdenum by argon ion bombardment for an incidence angle of 60° from the surface normal. For the bombardment an ion gun with low current density (i₀ ~ 1 × 10 ^?7 A cm^?2) at low system pressure (~10^?9 Torr) was used. The detection was performed by AES and the data were sensitivity factor corrected. The AES analysis of the surface after adsorption showed that Mo, C and Cl contributed to more than 94% of the atomic composition. With known i₀, it is possible to obtain σ from the adsorbate signal vs ion bombardment time curve. For ion energies between 0.2 keV to 1.0 keV the measured value for σ_Cl and σ_C are 0.5?3 × 10^?15 cm² and 0.2?4 × 10^?15 cm², respectively. The possible effects of the surface roughness due to prebombardment are discussed.     

PIGE analysis of magnesium and beryllium

In this work, we present an alternative method for PIGE analysis of magnesium and beryllium in thick samples. This method is based on the ERYA – Emitted Radiation Yield Analysis – code, which integrates the nuclear reaction excitation function along the depth of the sample. For this purpose, the excitations functions of the ²⁵Mg(p,p′γ)²⁵Mg (E_γ = 585 keV) and ⁹Be(p,γ)¹⁰B (E_γ = 718 keV) reactions were employed. Calculated gamma-ray yields were compared, at several proton energy values, with experimental yields for thick samples made of inorganic compounds containing magnesium or beryllium. The agreement is better than 5%. Taking into consideration the experimental uncertainty of the measured yields and the errors related to the stopping power values, this agreement shows that effects as the beam energy straggling, ignored in the calculation, seem to play a minor role.     

Distribution and Fixation of Cesium and Strontium in Zeolite A and Chabazite

The selective removal and fixation of Cs and Sr have been studied in zeolite A and chabazite. Cesium ion was preferentially distributed into chabazite with a high distribution coefficient (K _Cs>10³ cm³·g^?1) in the presence of NaCl (10^?1 mol·dm^?3). The K _Sr values for zeolite A attained about 10³ cm³·g^?1 in the pH range of 8～10, and they gradually decreased with an decrease in pH.

The initial rate of Cs adsorption was fairly fast in chabazite, and the adsorption ratio reached almost 100% within a few hours. The adsorption ratio of Sr in binderless A zeolite reached almost 100% after 15 h. The adsorption of Cs and Sr on these zeolites was followed by Langmuir-type isotherm. Cesium forms of these zeolites recrystallized to pollucite (CsAlSi₂O₆) above 900°C for zeolite A and above 1,200°C for chabazite. As for Sr forms, these zeolites changed to SrAl₂Si₂O₆ above 900°C.

These recrystallized phases were suitable hosts for the immobilization of Cs and Sr in the nuclear waste solutions.     

Diffusion of tritium in zircaloy-2

The dependency of the tritium diffusion in Zircaloy-2 on the temperature as well as on the oxygen and hydrogen concentration was investigated. From the determined diffusion coefficients the following values for the frequency factor d₀ and the activation energy E_a were obtained: D₀ = (1.04^+0.28_?0.17 ) 10^?3 [cm² · s^?1 ], E_a = -42.1 ± 1.1 [kJ · mol^?1 ]. In the concentration range from 1350 to 11300 ppm oxygen and 15 to 1000 ppm hydrogen no systematic influence of these elements on the tritium diffusion coefficients was observed.     

Preparation of potassium iron(III) hexacyanoferrate(II) supported on activated carbon and Cs uptake performance of the adsorbent

Synthesis of potassium iron(III) hexacyanoferrate(II) (K/Fe-Fe(CN)₆) in the pores of activated carbon (AC) was attempted by impregnating AC with K₄[Fe(CN)₆] and FeCl₃, and the Cs uptake performance of the resulting adsorbent was examined. K/Fe-Fe(CN)₆ supported on AC was prepared by varying the reaction conditions such as the supplied amounts and molar ratios of the reagents, and the Cs uptake performance was optimized. The impregnated product was characterized by XRD, EPMA, and porosimetry to elucidate the condition to which Fe₄[Fe(CN)₆]₃ was filled in the AC pores. The K/Fe-Fe(CN)₆-on-AC was immersed in seawater containing 0.075 mmol · dm^?3 Cs and agitated for 1 day to obtain the Cs uptake. The Cs uptake was large at pH < 10 but decreased abruptly at pH > 10.5. The maximum Cs uptake was 10.4 μmol · g^?1 at the equilibrium Cs concentration of 49 μmol · dm^?3 and the distribution coefficient was 45.5 dm³ · g^?1 at the equilibrium concentration of 0.015 μmol · dm^?3, respectively. When K/Fe-Fe(CN)₆-on-AC was immersed in Cs-containing seawater, K⁺ ions in the adsorbent were completely exchanged for Na⁺ ions in seawater, and the added Cs⁺ ions were then substituted for the Na⁺ ions in the adsorbent.     

Measurement of Be-profiles by the 9Be(p,α)6Li reaction

The use of the ⁹Be(p,α)⁶Li (E_p = 330 keV) reaction as a tool for the profiling of implanted Be is described.Pile-up problems, caused by elastically scattered particles, requires a mylar foil to be introduced in front of the particle detector. This causes severe straggling and thus loss of depth resolution. A deconvolution technique, which is based on an iterative procedure, is described. With it, profiles are reconstructed with a depth resolution of 300 Å.The present technique was used to assess the diffusion of Be implanted into InSb and GaAs during annealing. Pronounced diffusion accompanied by Be loss was found for GaAs (T_ann = 1113 K, T_melt = 1511 K), while hardly any changes in Be profiles for InSb (T_ann = 670 K, T_melt = 798 K) could be detected.     

An X-ray diffraction study of the formation of β-UO2.33 on UO2 pellet surfaces in air at 229 to 275°C

The surface oxidation of UO₂ fuel pellets at 229 to 275°C has been monitored by X-ray diffractometiy. The existence of β-UO_2.33 as a significant intermediate product of oxidation was confirmed, and a method for its quantitative estimation on the pellet surface was derived. The initial formation of gb-UO_2.33 occurs primarily in a uniform surface layer, but its subsequent growth appears to occur preferentially at microcracks and grain boundaries. Two values of the activation energy for the transformation of UO₂ to β-UO_2.33. derived from X-ray diffraction data for the initial and later stages of reaction, are 112 ± 14 kJ · mol^?1 and 107 ± 24 kJ · mol^?1 respectively, in good agreement with the literature. The conversion of UO₂ to β-UO_2.33 has been monitored up to at least 97% conversion of the upper 3 μm of a pellet surface.     

Cross-sections of B(p,α)Be reaction for boron analysis

Nuclear reaction, ¹¹B(p,α)⁸Be, shows great potentials in boron characterization of materials due to its large cross-section at the broad resonance at 660 keV. Unfortunately, the existing cross-section data on this reaction show errors of up to 30% and inconsistency as high as 50%. All previously published cross-sections of this reaction were based on assumptions or on more or less arbitrary convention. We present an accurate measurement of the cross-sections of nuclear reaction ¹¹B(p,α₁)⁸Be^* using self-supported ¹¹B foil target, high resolution detection and careful analysis of the α-spectra. An accurate cross-section with α₁ was obtained with careful spectrum stripping of α₁ from the α₁₂ continuum. Cross-section with α₁+α₁₂ under more definite and realistic convention is also given for practical applications. Cross-sections are given in graphical form for θ_lab=150°.     

Differential cross sections for the B(p,αo)Be and B(p,p0)B reactions, suitable for ion beam analysis

Boron depth profiling presents strong analytical challenges for all Ion Beam Analysis (IBA) techniques. In the past, both the ¹¹B(p,α_o)⁸Be (NRA) and the ¹¹B(p,p₀)¹¹B (EBS) reactions have been proposed and they seem to be quite suitable for analytical purposes. Nonetheless, both reactions have not been adequately studied in literature (as far as data suitable for material analysis in the backscattering geometry are concerned). Moreover, the existing datasets are relatively discrepant. In an attempt to clarify the situation, both reactions were studied in the present work between 135° and 160°, in steps of 5°, for the proton beam energy range between 2.2 and 4.2 MeV, in steps of 50 keV. An attempt to explain the occurring results in the framework of the resonance mechanism is also presented, along with a comparison with previously published data.