0000000001129378
AUTHOR
Kari Peräjärvi
Total absorption study of the \beta decay of 102,104,105Tc
The β-feeding probabilities for three important contributors to the decay heat in nuclear reactors, namely 102,104,105Tc, have been measured using the total absorption spectroscopy technique. For the measurements, sources of very high isobaric purity have been obtained using a Penning trap (JYFLTRAP). A detailed description of the data analysis is given and the results are compared with high-resolution measurements and theoretical calculations. peerReviewed
Production of pure samples of 131mXe and 135Xe
Pure samples of (131m)Xe, (133m)Xe, (133)Xe and (135)Xe facilitate the calibration and testing of noble gas sampler stations and related laboratory instrumentation. We have earlier reported a Penning trap-based production method for pure (133m)Xe and (133)Xe samples. Here we complete the work by reporting the successful production of pure (131m)Xe and (135)Xe samples using the same technique. In addition, we present data on xenon release from graphite.
β-decay data requirements for reactor decay heat calculations: study of the possible source of the gamma-ray discrepancy in reactor heat summation calculations
The decay heat of fission products plays an important role in predictions of the heat up of nuclear fuel in reactors. The released energy is calculated as the summation of the activities of allfission products P(t) = Ei λi Ni(t), where Ei is the decay energy of nuclide i (gamma and beta component), λi is the decay constant of nuclide i and Ni(t) is the number of nuclide i at cooling time t. Even though the reproduction of the measured decay heat has improved in recent years, there is still a long standing discrepancy in the t ∼ 1000s cooling time for some fuels. A possible explanation to this improper description has been found in the work of Yoshida et al. (1), where it has been shown that…
Improving the Confidence Associated with Passive Total Neutron Counting in the Nuclear Weapon Disarmament Verification Process
Passive total neutron counting is an important tool in the nuclear weapon disarmament monitoring and verification process proposed by the International Partnership for Nuclear Disarmament Verification (IPNDV). In the process, neutron measurements of given treaty accountable items (TAIs) are repeated multiple times in different locations and environments, and the measured neutron count rates are expected to remain unchanged. However, neutrons are heavily scattered in the environment, and the change in location or geometry of the environment can produce varying results in neutron measurements which can deteriorate the confidence of passive total neutron counting. In this paper, we have studie…
A position sensitive β−γ coincidence technique for sample analysis with the upgraded PANDA device
Abstract PANDA (Particles And Non-Destructive Analysis) is measuring system developed for non-destructive analysis of samples for safety, security and safeguards. The capabilities of the PANDA device were expanded by the addition of a thick silicon detector for β particle detection. The upgraded device can now be used for position-sensitive α − γ and β − γ coincidence measurements of various kinds of radioactive samples. The capability of the PANDA device in using the β − γ coincidence technique was tested using a mixed source of 134Cs and 226Ra. In addition, the ability of PANDA to locate nuclides emitting β particles from samples was tested using a combined sample containing a mixed 134Cs…
Reactor Decay Heat inPu239: Solving theγDiscrepancy in the 4–3000-s Cooling Period
The {beta} feeding probability of {sup 102,104,105,106,107}Tc, {sup 105}Mo, and {sup 101}Nb nuclei, which are important contributors to the decay heat in nuclear reactors, has been measured using the total absorption technique. We have coupled for the first time a total absorption spectrometer to a Penning trap in order to obtain sources of very high isobaric purity. Our results solve a significant part of a long-standing discrepancy in the {gamma} component of the decay heat for {sup 239}Pu in the 4-3000 s range.
Beta-decay strength and isospin mixing studies in the sd and fp-shells
We have studied beta decays of MT<0 nuclei in sd and fp shells. The decay of 41Ti shows a large, 10(8) %, isospin mixing of IAS and the Gamow-Teller strength is observed to be quenched by a factor of q2=0.64. These results can be reproduced qualitatively in our shell model calculations. We have observed for the first time proton and gamma decay of the isobaric analogue state in 23Mg. Our results on the isospin mixing of the isobaric analogue state agrees well with the shell model calculations. The obtained proton branch of the IAS is used to extract the transition strength for the reaction 22Na(p,γ)23Mg.
Energy loss measurement of protons in liquid water
The proton stopping power of liquid water was, for the first time, measured in the energy range 4.7-15.2 MeV. The proton energies were determined by the time-of-flight transmission technique with the microchannel plate detectors, which were especially developed for timing applications. The results are compared to the literature values (from ICRU Report 49 (1993) and Janni's tabulation (1982 At. Data Nucl. Data Tables 27 147-339)) which are based on Bethe's formula and an agreement is found within the experimental uncertainty of 4.6%. Thus, earlier reported discrepancy between the experimental and literature stopping power values at lower energies was not observed at the energies considered …
Improvements on Decay Heat Summation Calculations by Means of Total Absorption Gamma-ray Spectroscopy Measurements
The decay heat of fission products plays an important role in predictions of the heat released by nuclear fuel in reactors. In this contribution we present results of the analysis of the measurement of the beta decay of some refractory isotopes that were considered possible important contributors to the decay heat in reactors. The measurements presented here were performed at the IGISOL facility of the University of Jyvaeskylae, Finland. In our measurements we have combined for the first time a Penning trap (JYFLTRAP), which was used as a high resolution isobaric separator, with a total absorption spectrometer. The results of the measurements as well as their consequences for decay heat sum…
Comparison of gamma-ray coincidence and low-background gamma-ray singles spectrometry
Aerosol samples have been studied under different background conditions using gamma-ray coincidence and low-background gamma-ray singles spectrometric techniques with High-Purity Germanium detectors. Conventional low-background gamma-ray singles counting is a competitive technique when compared to the gamma-gamma coincidence approach in elevated background conditions. However, measurement of gamma-gamma coincidences can clearly make the identification of different nuclides more reliable and efficient than using singles spectrometry alone. The optimum solution would be a low-background counting station capable of both singles and gamma-gamma coincidence spectrometry.
Mass measurements of neutron-deficient nuclides close to A=80 with a Penning trap
The masses of 80,81,82,83Y, 83,84,85,86,88Zr and 85,86,87,88Nb have been measured with a typical precision of 7 keV by using the Penning trap setup at IGISOL. The mass of 84Zr has been measured for the first time. These precise mass measurements have improved Sp and QEC values for astrophysically important nuclides. peerReviewed
Ultra-high resolution mass separator—Application to detection of nuclear weapons tests
Abstract A Penning trap-based purification process having a resolution of about 1 ppm is reported. In this context, we present for the first time a production method for the most complicated and crucially important nuclear weapons test signature, 133mXe. These pure xenon samples are required by the Comprehensive Nuclear-Test-Ban Treaty Organization to standardize and calibrate the worldwide network of xenon detectors.
Total absorption study of theβdecay of102,104,105Tc
The $\ensuremath{\beta}$-feeding probabilities for three important contributors to the decay heat in nuclear reactors, namely ${}^{102,104,105}$Tc, have been measured using the total absorption spectroscopy technique. For the measurements, sources of very high isobaric purity have been obtained using a Penning trap (JYFLTRAP). A detailed description of the data analysis is given and the results are compared with high-resolution measurements and theoretical calculations.
Decays of T Z = − 3/2 nuclei 23Al, 31Cl, and 41Ti
This article gives an overview on the decay spectroscopy of T Z = − 3/2 nuclei 23Al, 31Cl, and 41Ti performed at the Ion Guide Isotope Separator On-Line (IGISOL) facility. The results of the IGISOL experiments are compared to the experimental results that have been published since. The isobaric multiplet mass equation (IMME) has been studied for the T = 3/2 quartets at A = 23 and A = 31. For 41Ti, a detailed comparison to the Gamow–Teller strengths obtained for the analog transitions via charge-exchange reactions has been done. Further improvements in the experimental instrumentation and methods and possible implementations for studying T Z = − 3/2 nuclei at the new IGISOL facility are di…
Beta decay of neutron-rich 118Ag and 120Ag isotopes
b decays of on-line mass-separated neutron-rich 118Ag and 120Ag isotopes have been studied by using b-g and g-g coincidence spectroscopy. Extended decay schemes to the 118,120Cd daughter nuclei have been constructed. The three-phonon quintuplet in 118Cd is completed by including a new level at 2023.0 keV, which is tentatively assigned the spin and parity of 24 1 . The intruder band in 118Cd is proposed up to the 41 level at 2322.4 keV. The measured b-decay half-life for the high-spin isomer of 120Ag is 0.4060.03 s. Candidates for the three-phonon states, as well as the lowest members of the intruder band in 120Cd, are also presented. These data support the coexistence of quadrupole anharmon…
b-decay of 116Agm and the vibrational structure of 116Cd
The structure of near neutron midshell 116 Cd has been investigated via β decay of 116 Ag m by β-γ and γ-γ coincidence spectroscopy. The 116 Ag m activity was produced by symmetric fission of natural uranium induced by 25 MeV protons. The ion guide technique has been employed to produce online mass separated sources. The decay scheme of 116 Ag m has been considerably extended by adding 19 new excited states of 116 Cd . The newly identified 116 Cd state at 1869.7 keV, along with other four levels near 2 MeV, are interpreted as forming the complete three-phonon quintuplet. The vibrational structure of 116 Cd is discussed in the context of an anharmonic vibrator. peerReviewed