Decay Scheme Data Research Articles

Specific absorbed fractions of energy from internal photon sources in brain tumor and cerebrospinal fluid

Transferrin, when injected intracranially into glioblastoma multiforme lesions, acts as a cytotoxic substance. Transferrin, radiolabeled with In-111, can be coinjected and subsequent scintigraphic imaging can demonstrate the biokinetics of the cytotoxic transferrin. The administration of 111In transferrin into a brain tumor results in distribution of radioactivity in the brain, brain tumor, and the cerebrospinal fluid (CSF). Information about absorbed radiation doses to these regions, as well as other nearby tissues and organs, is important for evaluating radiation-related risks from this procedure. The radiation dose is usually estimated for a mathematical representation of the human body. We have included source/target regions for the eye, lens of the eye, spinal column, spinal CSF, cranial CSF, and a 100-g tumor within the brain of an adult male phantom developed by Cristy and Eckerman. The mathematical models of the spinal column, spinal CSF, and the eyes were developed previously, however, these source/targets have not been routinely included in photon transport simulations. Specific absorbed fractions (SAFs) as a function of photon energy were calculated using the ALGAMP computer code, which utilizes Monte Carlo techniques for simulating photon transport. The ALGAMP code was run three times, with the source activity distributed uniformly within the tumor, cranial CSF, and the spinal CSF volumes. These SAFs, which were generated for 12 discrete photon energies ranging from 0.01 to 4.0 MeV, were used with decay scheme data to calculate S-values needed for estimating absorbed doses. S-values for 111In are given for three source regions (brain tumor, cranial CSF, and spinal CSF) and all standard target regions/organs, the eye and lens, as well as to tissues within these source regions. S-values for the skeletal regions containing active marrow are estimated. These results are useful in evaluating the radiation doses from intracranial administration of 111In transferrin. The SAFs are also generally useful for calculation of absorbed dose from any radionuclide in these source regions.

The standardization and measurement of decay scheme data of 124I

The increasing use of Positron Emission Tomography (PET) has highlighted the need to standardize and improve the quality of decay scheme data for some positron emitters. This paper presents the results of such work for 124I.

Activity measurement of 75Se using integral gamma-ray counting with a 4π-NaI(Tl) detector

In the high efficiency integral counting method the activity A is obtained from A = N/ϵN, where N is the integral countrate and ϵN the average detection efficiency per disintegration. This efficiency is calculated for 75Se using the energy-dependent calibration of the 4π-NaI(Tl) detector and 75Se decay scheme data. The calculation includes the decay via the isomeric state. An assumption in this calculation is the nonexistence of a direct EC decay to the ground state. The overall uncertainty of the 75Se activity obtained is 0.35% (standard deviation). Gamma-ray emission probabilities are determined by gamma spectrometry with germanium and Si(Li) detectors using the activity value measured.

Environmental radioactivity measurement intercomparisons in the UK

The results of two recent (1989 and 1990) nationwide radioactivity-measurement intercomparisons covering a range of pure β- and β/γ-emitting radionuclides are presented. Over fifty laboratories took part in the first exercise and, in general, the results were satisfactory although most laboratories confined themselves to γ-ray measurements only. There were some areas of concern, notably decay-scheme data, statements of uncertainty and cascade-summing effects. A follow-up meeting was held to discuss these points with the participants. As a result of this meeting, a second exercise was held, covering a different range of nuclides at lower-activity levels and seeking to discover how participants had improved their procedures in the light of the results from the first exercise. The overall results of the two exercises are reviewed in the light of i) UK radioactivity-monitoring arrangements and ii) the National Measurement Accreditation Scheme (NAMAS).

Specific activity of99mTcO4 − eluates from clinical99Mo/99mTc generators

Carrier-free99mTcO4− eluated from clinical99Mo/99mTc generators was examined to determine its specific activity. The observed specific activity was found to be always lower than the calculated value based on the99Mo−99mTc−99Tc decay scheme data. These results could be explained in terms of existence of excess Tc loaded onto generator column.

The structure of states at very high spin in 157Er

High spin states of 157Er have been populated using the 114Cd+48Ca reaction at a 48Ca bombarding energy of 200 MeV. Gamma rays were detected in an array (TESSA2) of six escape-suppressed Ge spectrometers and a 50-element BGO multiplicity and summed energy detector. Decay scheme and angular correlation data were obtained from the gamma - gamma BGO coincidence data The yrast band has been identified up to 65/2+ and two negative parity sidebands have been identified (one previously unobserved) up to 69/2- and 63/2-. An additional sideband of six transitions was also observed. The band structures are interpreted in terms of quasiparticles in the framework of the cranked shell model.

Near-yrast discrete line -ray spectroscopy of159Er and160Er to I or 40

High-spin states in 159Er and 160Er have been populated using the 116Cd+48Ca reaction at a 48Ca bombarding energy of 210 MeV. Gamma rays were detected in an array (TESSA2) of six escape suppressed germanium spectrometers and a 50 element BGO multiplicity and summed energy detector. Decay scheme and angular correlation data for these nuclei were deduced from the gamma - gamma -BGO coincidence data. In 159Er the yrast band has been identified up to Ipi =89/2+ and three side bands have been observed to 69/2-(77/2-), 43/2+ and 51/2-(59/2-). In 160Er the lowest energy positive-parity band has been observed up to 38+(40+) and the two lowest energy negative-parity side bands up to 40-(44-) and 39-(41-). The ground state level sequence has been observed up to (28+). The spin and parity of the low-lying states (I<20h(cross)) in the bands observed in 160Er were established by measuring gamma -ray angular distributions and internal conversion coefficients following the 148Nd(16O, 4n) reaction at a beam energy of 80 MeV. The band structures can be understood in terms of aligning quasiparticles using the cranked shell model. The alignment of the first pair of h11/2 protons is observed in the three lowest energy bands in each nucleus. The increase in crossing frequency of this alignment with neutron number is further evidence for the increase in deformation for the light Er isotopes. Evidence is presented for the competition of favoured single-particle configurations with the collective structures at the highest spins.

Nuclear data for biomedical applications

Abstract Needs for better nuclear data for biomedical applications are chiefly of two kinds: decay-scheme and production data for radionuclides used in nuclear medicine, and cross sections and spectral information for high-LET radiations used in radiation therapy of cancer, especially high-energy neutrons. Radiopharmaceuticals are used primarily for diagnostic and physiological function studies. Decay scheme information is important to establish the internal radiation dose received by the patient. Radionuclides for which better decay scheme data are needed are identified. Protons, alphas, pions, neutrons, and heavy nuclei such as Si-28 and A-40 are all being studied or used for radiation therapy of cancer. Of these, the most widely used is neutron radiation therapy at about 8 centers in the United States, 22 worldwide. The nuclear data needed are total and partial neutron cross sections for the elements that compose tissue and for dosimeter materials up to about 60 MeV.

Survey of standardization possibilities witha NaI(Tl) well-type detector

The standardization capabilities of a 12.7-cm × 12.7-cm NaI(Tl) well-type detector were investigated for a series of 27 radionuclides of practical interest with different complexity of the decay schemes. Total detection efficiencies and their uncertainties were calculated for low-mass point-like sources, for 1-cm 3 aqueous solutions, and also for the nuclides being homogenously incorporated in a 1-g solid sample with 20-mm diameter. Correlations amongst decay data and partial efficiencies for β- and γ-ray transitions were taken into account. The physical consistency of the chosen decay schemes was tested within their limits of uncertainty calculating the balance and its uncertainty for the β branches, which enabled tightening the efficiency - uncertainty limits taking a choice among different versions of the decay-scheme data. Special attention was paid to the possible calibration accuracy for multigamma-ray sources as 56Co, 75Se, 82Br, 110mAg, 124Sb, 134Cs, 133Ba, 152Eu, 182Ta and 192Ir achieving accuracies in the range ⩽ 0.1 % to 0.7% employing the special features of a 4 πγ-detector system.

The specific gamma-ray constant and exposure rate constant of 182Ta.

Reported values of the specific gamma-ray constant gamma for 182Ta range from the original value of 6.1 to 7.692 R cm2h-1mCi-1, recommended in NCRP Report No. 41. The original calculation of gamma was based on inadequate nuclear spectroscopy and decay scheme data. The higher value of gamma occurs because of a computational error in the relative intensity of the 1.2575-MeV gamma ray. Using nuclear spectroscopy data from the most recent Evaluated Nuclear Data File (ENSDF), gamma is calculated to be 6.71 +/- 0.06 R cm2h-1mCi-1 and the exposure rate constant gamma gamma is 6.87 +/- 0.06 R cm2h-1mCi-1. These new calculations are presented and previously reported values of gamma and gamma gamma are reviewed.

Experimental resolution of the 145Gd ϵ/ β-decay branching ratio anomalies

Previously reported large anomalies in 145Gd ϵ/β + decay branching ratios can be completely explained by improved experimental data. New, high-statistics decay-scheme data show conclusively that the anomalies resulted from numerous, formerly unobserved, weak transitions from levels in 145Eu fed primarily by ϵ-decay. In addition, the 145Gd β + endpoint is measured by β- γ coincidence techniques to be 240 keV lower than originally reported.

Theoretical Beta Spectrum from Uranium-235 Fission Fragments in Secular Equilibrium

The theoretical beta spectrum of the thermal fission fragments of /sup 235/U in secular equilibrium was calculated using recent fission yields, nuclear decay scheme data, and very recent semi-empirical mass formulas to predict beta Q values of nuclides with unknown energy level structure. Better agreement with experiment is achieved when these isotopes are assumed to contain all of the excited states of isotopes with known decay schemes with the same atomic number Z and with neutron numbers N differing by even integers. The beta branching ratios for the unknown isotopes were assumed to be the renormalized collection of branching ratios found in all known isotopes of the families described above. The results obtained with these narrower restrictions are in better general agreement with experiment than those that replace the excited states and branching ratios of the unknown nuclides with those obtained by taking broad averages over known isotopes. There still appears to be some disagreement between theory and experiment, particularly at the high-energy end of the spectrum.

Specific γ‐ray constant and exposure rate constant of 192Ir

Calculated values of the 192Ir specific gamma-ray constant, Gamma range from the low value of 3.948 R cm2h-1mCi-1 recommended in NCRP No. 41 to a high of 4.89 R cm2h-1mCi-1. Measured values of Gamma range only from 4.85 to 5.0 Rcm2h-1mCi-1. Discrepancies in reported calculated values exist because the isotope decay scheme and other nuclear spectroscopy data pertinent to these calculations were not well known. Using the 28 gamma rays and relative intensities from the most recent Evaluated Nuclear Structure Data File (ENSDF), Gamma is calculated to be 4.62 +/- 0.05 Rcm2h-1mCi-1 and the exposure rate constant Gamma delta is 4.69 +/- 0.05 Rcm2h-1mCi-1. These new calculations are presented and previously reported values of Gamma and Gamma delta are reviewed.

Weak neutral disintegration of the deuteron by reactor antineutrinos

The spectrum of antineutrinos emitted by beta decaying products of $^{235}\mathrm{U}$ in secular equilibrium has been recalculated using more recent experimental decay-scheme data. The new data involve 26 nuclides with $150 \ensuremath{\beta}$ branches and represent 22% of the total fission yield. The cross section for the reaction ${\overline{\ensuremath{\nu}}}_{e}+d\ensuremath{\rightarrow}p+n+{\overline{\ensuremath{\nu}}}_{e}$, which proceeds only via the weak neutral current, is shown to be predicted consistently by three theoretical treatments in the literature. The total cross section was calculated by weighting the cross section by the normalized antineutrino spectrum and is 7.4 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}45}$ ${\mathrm{cm}}^{2}$.

Calibration figures for the type 1383A ionization chamber

The increasing use of Positron Emission Tomography (PET) has highlighted the need to standardize and improve the quality of decay scheme data for some positron emitters. This paper presents the results of such work for 124I.

Gamma-ray energy release in the decay of fission products

Abstract Total disintegration rate, gamma-ray energy release rate and energy spectrum of the fission products of 235 U, 239 Pu, 241 Pu, and 233 U by thermal neutrons, and 235 U, 238 U, 239 Pu and 232 Th by fission spectrum neutrons have been reevaluated as a function of reactor operating times from 10 2 to 10 8 sec after shutdown. Decay scheme data were taken mainly from the Table of Isotopes [1] and fission yields from Meek and Rider's 1972 recommendations [2]. Gamma energy releases do not depend strongly on the incident neutron energy, and those for 239 Pu and 241 Pu are much different from that for 235 U. Soon after fission, the present values for burst fission are lower than those of Perkins [3], but agree after 10 4 sec and agree better with the experimental results of Sugarman et al. [4] and Borst [5]. The calculated data are tabulated in detail to facilitate interpolation.

Evaluated Decay Scheme Data

The Interlaboratory LMFBR Reaction Rates program involves the determination of rates of neutron-induced reactions by the measurement of gamma-ray spectra from the decay of radioactive reaction prod...

A Method for Absolute Determination of 238U Capture Rates in Fast Zero-Power Reactors

A method for the measurement of absolute 238U capture rates is described. The principle is based upon the fact that 243Am and 239U decay via 239Np into 239Pu. The α disintegration rate of 243Am is determined absolutely by low geometry α-particle counting. From this, the absolute 239Np disintegration rate follows directly, which is measured by the 106-keV γ-x-ray coincidence technique. Therefore, the explicit knowledge of detector efficiency and decay-scheme data is not necessary, and also radiochemical separation is avoided. The absolute 238U capture rate can then be obtained from the known 239Np activity. The γ-x-ray self-attenuation within thick uranium foils is treated quantitatively and an optimum foil thickness is derived. Special attention has been given to the reduction and correction of background due to fission-product γ activity. A detailed error analysis shows an overall accuracy of about 1% for the absolute 239Np disintegration rate including γ attenuation effects within the foils. To ascertain the reliability of low-geometry α calibration, comparison was made with the α-γ coincidence method. Agreement was found within the error limits of 1%.