Nuclear data sheets for A = 100

The 1960 version of the Nuclear Data Sheets for A = 100 has been revised on the basis of experimental data received prior to December 1, 1973. Information from approximately 100 papers and communications has been included in the present evaluation.Data on nine A = 100 nuclei are presented. The assignment of a 7.1-s activity to the decay of the ¹⁰⁰Zr ground state and the assignment of 1.5-s and 3.1-s activities to the decay of ¹⁰⁰Nb isomers adopted by the compilers differ from assignments proposed in the published literature. The decay scheme for ¹⁰⁰Zr is not known, and the separate decay schemes for the two ¹⁰⁰Nb isomers have not yet been determined. Many spin assignments have been made for the stable nuclei ¹⁰⁰Mo and ¹⁰⁰Ru. The decay scheme for ¹⁰⁰Tc is well established, but no excited levels in this nucleus are known. The decay of ¹⁰⁰Rh has been extensively studied. From an evaluation of all data, the compilers propose decay branching ratios to low-lying levels in ¹⁰⁰Ru which differ somewhat from those given in the literature. The spins of a few low-lying lying levels in ¹⁰⁰Rh are known. Details of the ¹⁰⁰Pd decay scheme are uncertain since the decay energy and the decay branching ratio to the ¹⁰⁰Rh ground state have not been measured and relative photon intensities for some transitions in the decay are not accurately known. The first level scheme for ¹⁰⁰Pd, which has recently been proposed, is presented. The assignment of a 2.3-m activity to ¹⁰⁰Ag decay appears well established, but the compilers regard the assignment of an 8-m activity to ¹⁰⁰Ag decay as uncertain. The half-life of the ¹⁰⁰Cd ground state has been measured, but no decay scheme has been proposed.     

Dysprosium as a resonance absorber and its effect on the coolant void reactivity in Advanced Heavy Water Reactor (AHWR)

Dysprosium has been used as a slow neutron absorber in the fuel assembly of Advanced Heavy Water Reactor (AHWR) to achieve a negative coolant void reactivity. Dysprosium as occurring in nature has as many as seven isotopes namely, ¹⁵⁶Dy, ¹⁵⁸Dy, ¹⁶⁰Dy, ¹⁶¹Dy, ¹⁶²Dy, ¹⁶³Dy, and ¹⁶⁴Dy. Of these, the isotope ¹⁶⁴Dy has the largest absorption cross section for thermal neutrons. In the past, nuclear data libraries used in our studies have considered only ¹⁶⁴Dy isotope and this was sufficient for performing foil activation studies of Dy. The other isotopes of Dy have significant resonances and could affect the design. The treatment of the dysprosium isotopes with resonance tabulations is required for a more accurate estimation of the lattice characteristics like the coolant void reactivity. The use of resonance tabulations for the dysprosium isotopes and its effect on the coolant void reactivity of AHWR fuel cluster has been studied in this paper. Also, the treatment of the stand-alone structural rod with dysprosium as burnable absorber having resonance tabulations has been done for the first time.     

Modelling the activity of I in the primary coolant of a CANDU reactor

A mathematical treatment has been developed to describe the activity levels of ¹²⁹I as a function of time in the primary heat transport system during constant power operation and for a reactor shutdown situation. The model accounts for a release of fission-product iodine from defective fuel rods and tramp uranium contamination on in-core surfaces. The physical transport constants of the model are derived from a coolant activity analysis of the short-lived radioiodine species. An estimate of 3×10⁻⁹ has been determined for the coolant activity ratio of ¹²⁹I/¹³¹I in a CANDU Nuclear Generating Station (NGS), which is in reasonable agreement with that observed in the primary coolant and for plant test resin columns from pressurized and boiling water reactor plants. The model has been further applied to a CANDU NGS, by fitting it to the observed short-lived iodine and long-lived cesium data, to yield a coolant activity ratio of ∼2×10⁻⁸ for ¹²⁹I/¹³⁷Cs. This ratio can be used to estimate the levels of ¹²⁹I in reactor waste based on a measurement of the activity of ¹³⁷Cs.     

Separation of the alpha-emitting radioisotopes actinium-225 and bismuth-213 from thorium-229 using alpha recoil methods

An innovative method has been demonstrated for separating alpha-emitting isotopes for medical radiotherapy applications. The method relies on recoil-ion separation rather than on conventional wet chemistry techniques to separate medical isotopes from their precursor sources. The isotopes ²²⁵Ac and ²¹³Bi have been separated from electro-deposited sources of ²²⁹ThO₂. Separations of ²²⁵Ac were carried out by placing nickel recoil collector foils in firm contact with the ²²⁹ThO₂ sources. One-stage recoil-ion separations of ²²⁵Ac from ²²⁹Th have been performed as well as two-stage separations of ²¹³Bi from previously recoil separated ²²⁵Ac. In addition, a direct recoil separation of ²¹³Bi from ²²⁹Th has been demonstrated. The ²¹³Bi from the one-stage direct separation has a high isotopic purity, but contains small amounts of long-lived ²²⁵Ac alpha activity. The two-stage separations of ²¹³Bi produce high isotopic purity material (>99.9999%), but result in lower isotopic yields. Range-energy calculations have been carried out to determine the yields of recoil ions as a function of alpha-particle energy and ThO₂ thickness. The results of the calculations have been benchmarked with recoil separation measurements carried out using ThO₂ electro-deposits over a range of thickness. A computer code based on the generalized Bateman equations has been developed to allow calculations of the amounts of any isotope in the ²²⁹Th decay chain as a function of recoil separation exposure time and elapsed time after the separation. An excellent match has been obtained between the predictions of the Bateman calculations and the results of recoil separation measurements. The recoil separation method has proven to be a simple and effective way of separating medically useful isotopes such as ²¹³Bi. In addition, the method has been shown to produce no chemical or radioactive wastes, in contrast to radiochemical separation methods, which generate mixed (chemical and radioactive) waste.     

Nuclear data sheets for A = 78

The 1966 version of Nuclear Data Sheets for A = 78 has been revised on the basis of all experimental data received before September 1, 1974. Experimental data, detailed level schemes, and arguments for J^π-assignments are presented. Two new isotopes, ⁷⁸Ga and ⁷⁸Rb, are now known to exist and a third, ⁷⁸Sr, has been tentatively identified. A significant amount of new information is given for the ⁷⁸Se, ⁷⁸Br, and ⁷⁸Kr level schemes, while very little new information is available for the level schemes of ⁷⁸Ge and ⁷⁸As.     

Nuclear Data Sheets for A=75

The experimental nuclear data for mass=75 have been reviewed, superceding 1981 evaluation by Ekstrom (81Ek02). Detailed level and decay schemes together with summary (adopted), arguments for Jπ assignments and experimental data of the known nuclei (Cu, Zn, Ga, Ge, As, Se, Br, Kr, Rb) are presented. ⁷⁵Cu has been identified as a β⁻ delayed neutron emission precursor while ⁷⁵Ga has been studied in detail in ⁷⁵Zn β⁻ decay recently. In ⁷⁵Ge, there are quite a few new data available, specially on particle-transfer reactions. Not much new information is known for ⁷⁵As except for a particle transfer reaction and ⁷⁵Se ε decay. The same is true for ⁷⁵Se except for a neutron capture study. New data have been reported for ⁷⁵Kr and ⁷⁵Br.     

Radioisotope detection with tandem electrostatic accelerators

An MP tandem Van de Graaff accelerator at the University of Rochester has been employed since May 1977 to detect ¹⁴C in terrestrial samples, ³⁶Cl in terrestrial and extraterrestrial samples and ¹⁰Be and ²⁶Al in samples produced by reactor and accelerator irradiation. The sample sizes ranged from about 10 to less than 1 mg and the ratio of the radioisotope to the stable isotopes approached one part in 10¹⁶ for ¹⁴C and ³⁶Cl and one part in 10¹⁴ for ¹⁰Be and ²⁶Al. ¹⁴C has been measured in a number of samples of geological and archaeological interest. ³⁶Cl has been measured in various groundwater samples as well as samples at Antarctic meteorites and ice. Dedicated systems for ¹⁴C dating and geological measurements based on the tandem electrostatic accelerator principle are presently under construction for laboratories in the U.S.A., U.K. and Canada.     

Nuclear data sheets for A = 79

The 1966 version of Nuclear Data Sheets for A = 79 has been revised on the basis of experimental data received prior to December 1, 1974. Information from approximately 85 papers and communications has been included in the present evaluation.Data on eight A = 79 nuclei are presented. The half-life and decay energy for ⁷⁹Ga have been proposed, but the compilers do not regard the nuclidic assignment as firmly established. The existence of two isomers in ⁷⁹Ge has recently been proposed. The compilers tentatively assign a 42-s activity to the ⁷⁹Ge ground state, and a partial decay scheme is given. The compilers do not regard the assignment of a 19.1-s activity to ⁷⁹Ge as firmly established. The spin of the ⁷⁹As ground state is known from its decay to levels in ⁷⁹Se. Many levels from ⁷⁹Se are known from ⁷⁹As decay, single-nucleon transfer, and a level scheme for ⁷⁸Se(th n,γ) proposed by the compilers. Only an upper limit for the half-life of long-lived ⁷⁹Se has been determined; this nucleus decays directly to the ⁷⁹Br ground state. Levels in stable ⁷⁹Br up to 2 MeV are known from ⁷⁹Kr decay, Coulomb excitation and resonance fluorescence, and (n,n′γ). Most of the information on excited levels in ⁷⁹Kr is regarded by the compilers as tentative, since the ⁷⁹Rb decay scheme is not well established and all reaction studies are unpublished. Only the ground state of ⁷⁹Rb is known, and its spin cannot be determined since the intensity of the decay to the ⁷⁹Kr ground state is not accurately known. The compilers tentatively assign as 8.1-m activity to the ⁷⁹Sr ground state, but no decay scheme has been proposed. The compilers regard the assignment of a 4.4-m activity to ⁷⁹Sr as not firmly established. The only data on excited levels of ⁷⁹Sr are unpublished.     

Nuclear data sheets for A = 157

Nuclear data for the mass 157 isobars is presented on the basis of new experimental information. Every effort has been made to include all available data prior to July 1, 1972.With the exception of Tm and Lu, A = 157 nuclei have been reported for all elements with 62?Z?72. For ¹⁵⁷Hf and ¹⁵⁷Yb the only information known is their half-life and α-decay energies. The ground-state spin but not the parity of ¹⁵⁷Er is known with certainty; its level structure has been studied through heavy-ion reactions, and a tentative level scheme is given. The decay of the ¹⁵⁷Ho ground state has recently been studied in detail but there is no information available on its excited states. In ¹⁵⁷Dy, energy levels up to 1.2 MeV have been well established through β/ε-decay; the J^π assignments for E_x > 0.5 MeV are, however, less certain. The higher members of various rotational bands in ¹⁵⁷Dy have recently been reported in (α,xn) reaction studies. The ¹⁵⁷Tb level scheme has been studied through the decay of ¹⁵⁷Dy and the (p,t) reaction. As have other Gd isotopes, ¹⁵⁷Gd has been studied extensively. Its level scheme has been constructed on the basis of β-decay and various reaction studies. The J^π assignments for most levels above 0.5 MeV are from reaction studies and are based upon model-dependent arguments. A new activity (T_1/2 = 83 s) has recently been assigned to ¹⁵⁷Sm; it has been proposed that the 30-s activity previously identified is an isomer in ¹⁶⁰Eu.     

Proton backscattering as a technique for light ion surface interaction studies in CTR materials investigations

Analysis of near-surface helium and hydrogen isotope depth profiles by a specialized proton backscattering technique has been demonstrated as a means to characterize the concentration, initial position, and subsequent migration behavior of all $\text{Z}$ atom species (except ¹H) in metals. The projected range $\text{(R}{}_{\mathrm{<mtext>p</mtext>}}\text{)}$ of helium implanted at 50 keV in Nb, V Ti and Cu has been measured and, for the latter two metals, has been found to agree with theoretical calculations within 100 Å (3%). Deuterium has also been detected and profiled (in Ti) using this technique. Detection sensitivity has been demonstrated at the 7 at % level for D in Ti and at the 0.5 at % level for ⁴He in Cu. In addition, surface and bulk distributions of carbon, oxygen and ³He have been profiled and, in principle, the depth distributions of tritium, ⁶Li, ⁷Li, Be, B, N, and F are also simultaneously resolvable if contained within the foil samples. The technique has been used to investigate the effect of radiation damage and in situ annealing on implanted helium profiles in copper. From these observations the mechanism for helium release from the end-of-range location has been delineated.     

Nuclear data sheets for A = 77

The 1966 version of the Nuclear Data Sheets for A = 77 has been revised on the basis of all experimental data received before January 1, 1973. Experimental data, detailed level schemes, and arguments for J^π assignments are presented. Two new isotopes, ⁷⁷Ga and ⁷⁷Rb, are now known to exist while a third, ⁷⁷Zn, has been tentatively identified. A significant amount of new information is now available on the ⁷⁷Ge, ⁷⁷As, ⁷⁷Se, and ⁷⁷Br level schemes.     

Nuclear data sheets for A = 55

The 1970 version of Nuclear Data Sheets for A = 55 has been revised on the basis of experimental data received prior to March 1, 1976. Results from approximately 220 papers and communications have been included in the present evaluation.Data on five A = 55 nuclei are presented. The decay schemes for ⁵⁵Cr, ⁵⁵Fe, and ⁵⁵Co are well established. Many excited levels are known in ⁵⁵Cr, ⁵⁵Mn, ⁵⁵Fe, and ⁵⁵Co from a variety of decay and reaction experiments. Many firm or tentative spin assignments are made, and many half-lives for excited levels in ⁵⁵Mn, ⁵⁵Fe, and ⁵⁵Co have been measured. An uncertainty in the level scheme for ⁵⁵Mn occurs near 1290 keV, where the number of distinct levels and their spins cannot be unambiguously determined. The nucleus ⁵⁵Ni has been observed for the first time in the (³He, ⁶He) reaction, but the decay of ⁵⁵Ni has not yet been observed.     

Accelerator mass spectrometry II: Background reduction with a Wien (velocity) filter; 10Be contents of Central American basalts

Our limit of detection for ¹⁰Be by accelerator mass spectrometry has been lowered to a few million atoms by the installation of a Wien filter which screens out co-transmitted ⁹Be. Analyses of six Central American basalts gave ¹⁰Be contents ranging from 1 × 10⁶ to 60 × 10⁶ atom/g. The sample richest in ¹⁰Be has been contaminated by sediments. The other samples have ¹⁰Be contents in the range reported in the literature by Brown and co-workers.     

Accelerator mass spectrometry for heavy isotopes at Oxford (OSIRIS)

The isotopic ratios ¹⁹⁴Pt/¹⁹⁵Pt/¹⁹⁶Pt and ¹⁹³Ir/¹⁹⁴Pt/¹⁹⁵Pt have been measured for samples from the Cretaceous-Tertiary boundary at Stevns Klint, Dania, Nye Kløv in Denmark and at Hor Har Har in Israel, for iron meteorites Odessa and Buenaventura and for the carbonaceous chondrite Allende. Determination of the indium ratio $\text{193}\text{191}$ in a standard and in a sample from the Cretaceous-Tertiary boundary at Stevns Klint has also been made. Preliminary measurements of the ratio ¹⁸⁸Os/¹⁸⁹Os in laboratory prepared Os samples (abundance approximately 10 ppm), in the Odessa and Allende meteorites and in the Stevns Klint Cretaceous-Tertiary boundary have been carried out. An anomalous abundance of ¹⁹³Ir, ¹⁹⁴Pt, ¹⁹⁵Pt and ¹⁸⁹Os at the Cretaceous-Tertiary boundary at Stevns Klint has also been established.     

U measurement with accelerator mass spectrometry at CIAE

²³⁶U is a long-lived radioactive isotope which is produced principally by thermal neutron capture on ²³⁵U. ²³⁶U may be potentially applied in geological research and nuclear safeguards. Accelerator mass spectrometry is presently the most sensitive technique for the measurement of ²³⁶U and a measurement method for long-lived heavy ion ²³⁶U has been developed. The set-up uses a dedicated injector and the newly proposed ²⁰⁸Pb¹⁶ molecular ions for the simulation of ²³⁶U ion transport. A sensitivity of lower than 10⁻¹⁰ has been achieved for the isotopic ratio ²³⁶U/²³⁸U in present work.     

Modeling and simulation of corrosion product activity in pressurized water reactors under power perturbations

An improved methodology is presented for simulation of coolant activation due to corrosion products and impurities in a typical pressurized water reactor (PWR) under power perturbations. Using time dependent production and losses of corrosion products in the primary coolant path an approach has been developed to calculate the coolant specific activity. Results for ²⁴Na, ⁵⁶Mn, ⁵⁹Fe, ⁶⁰Co and ⁹⁹Mo show that the specific activity in primary loop approaches equilibrium value under normal operating conditions fairly rapidly. Predominant corrosion product activity is due to ⁵⁶Mn. Flow rate has been assumed to follow power changes and different types of power perturbations are introduced after the equilibrium activity has been achieved. In particular the effects of linear changes in reactor operating power and power peaking on the corrosion product activity of the primary coolant have been studied.     

Determination of 14N(n,2n)13N Reaction Cross Section for 14.7 MeV Neutrons

The cross section for the ¹⁴N(n, 2n)¹³N reaction in respect of 14.7 MeV neutrons has been determined. In this experiment, the ²⁷Al(n,p)²⁷Mg reaction was selected as reference standard, for its generation of the nuclide ²⁷Mg which has a half-life very close to that of ¹³N. The full-energy peaks of the γ-ray spectrum obtained by multi-channel pulse height spectrometer was analyzed with γ-ray energy resolution determined by means of normal probability plots.

The resulting value for the cross section is 8.2±1.1 mb, which is in remarkably good agreement with the value reported in literature.     

Nuclear Data Sheets for A=76

The 1976 version of A=76 mass chain (76Be41) has been revised. Nuclear spectroscopic information for known nuclides of mass number 76 (Zn, Ga, Ge, As, Se, Br, Kr, Rb) has been evaluated and presented together with adopted level energies, level Jπ's and γ-rays in these nuclei. No data are yet available for excited states in ⁷⁶Zn and ⁷⁶Rb. Levels in ⁷⁶Ga are known only from a tentative level scheme from ⁷⁶Zn decay.High spin levels and band structures are known for ⁷⁶Se, ⁷⁶Br, and ⁷⁶Kr from (HI,xnγ) reactions.     

Progress in 14C and 10Be dating at SFU

Since early 1982, a substantial upgrading of the Simon Fraser University radioisotope dating system at the McMaster FN accelerator has taken place. The accelerator itself was equipped with a new charging system and beam tubes, resulting in excellent stability and beam transmission. A new isotope filtering system of two magnets and a Wien filter has removed previously troublesome backgrounds: our carbon background from graphite is now ～ 47 ka BP, and is due to real ¹⁴C rather than scattered ¹³C. Measurement of ¹⁰Be in natural samples is now routine, with several hundred samples processed. Other work on ¹⁰Be has included studies which showed for the first time that ¹⁰Be could be measured at low energies (3 MV). We have also started work on ²⁶Al detection as a preliminary to the investigation of ²⁶Al/¹⁰Be dating. Finally, we present examples of our applications of this facility to studies in oceanography and archaeology.     

Ion-implanted S targets for astrophysics studies

The fabrication of isotopically pure 10.4 μg/cm² targets of ³²S by the implantation of 60-100 keV negative ions into a 61 μg/cm² pure ¹²C thin foil is described. The process has been accomplished in rather shorter times than has been achieved previously by implanting the as-prepared carbon foil while still mounted on the underlying glass slide, thereby allowing for the use of much larger beam current intensities. The target has been assayed for absolute composition as a function of depth using Rutherford backscattering spectrometry and excellent agreement between the measured and nominal ³²S fluences was observed. The implanted targets exhibit excellent stability with regard to subsequent 34.5 MeV proton beam irradiation.