Long-term performances of the 95ZR/95Nb chronometer for nuclear events dating.

The present work reports on a long-term analysis of the performances of the (95)Zr/(95)Nb chronometer for dating a nuclear event. Taking benefit of a recent Profiency Test Exercise, a sample containing a standardized mixture of fission products has been measured repeatedly with a low background HPGe spectrometer during a period extending up to one year with the aim of assessing the accuracy of the various zero-time determinations. Evaluation of the uncertainties associated to these evaluations was performed using a Monte Carlo approach. Input parameters sensitivity has been investigated, especially the influence of the (95m)Nb decay branch. The (95)Zr/(95)Nb chronometer was found to be accurate for zero-time determination within one day and one week for a decay of 3 months and 10 months respectively. Sub-day uncertainties are achievable for a two months old sample whereas sub-week uncertainties are reached after a decay of six months. Limitations of the technique for dating a real event are investigated.

Determination of weight distribution ratios of Pa(V) and Np(V) with some extraction chromatography resins and the AG1-X8 resin.

Literature data on distribution ratios (Dw) of Np(V) and Pa(V) for the AG1-X8 resin are scarce whereas those related on resin capacity factors (k') values for TEVA, TRU and U/TEVA resins are absent. Therefore, batch extraction experiments for Pa(V) and Np(V) from HCl and HNO3 media were realized, at tracer scale, with AG1-X8 and EIChroM resins (TEVA, TRU and U/TEVA). Based on the new Dw and k' values obtained in this study, a new protocol for Pa/Np separation has been developed leading to a better separation factor of 10(5) and a chemical yield of 97±3% and 99±1% for Pa and Np, respectively. A separation of (231)Pa from uranium matrix was successfully tested.

Low-level activity measurement of 131Xem, 133Xem, 135Xe and 133Xe in atmospheric air samples using high-resolution dual X-gamma spectrometry.

High-resolution dual X and gamma spectrometry has been optimized to improve the sensitivity in analyzing radioxenon from environmental samples, especially for the metastable isotopes (131Xem and 133Xem). The full-energy peak (FEP) efficiency curve in the 20-700 keV range has been established with a global uncertainty better than +/-3% using a Monte Carlo simulation. The minimum detectable activity concentrations (MDC) achievable at the laboratory for 131Xem, 133Xem, 133Xe and 135Xe are presented and the influence of 133Xe activity on the metastable radioxenon MDCs is evaluated.

Activity measurement of a 176Lu sample using coincidence peaks and Monte Carlo simulations.

We present the results of the activity measurement of a sample of the rare isotope 176Lu, obtained by gamma-ray spectrometry through the use of 22 peaks in an energy spectrum acquired with a 300 cc well-type HPGe detector located in the Modane underground facility below the French Alps. Of the above peaks, 17 are coincidence peaks between two or three gamma-rays or X-rays. True coincidence summing corrections were made using our Coincal code. Monte Carlo simulations were carried out for calibration purposes.

Measurement of the generalized polarizabilities of the proton in virtual Compton scattering at Q2=0.92 and 1.76 GeV2.

We report a virtual Compton scattering study of the proton at low c.m. energies. We have determined the structure functions P(LL)-P(TT)/epsilon and P(LT), and the electric and magnetic generalized polarizabilities (GPs) alpha(E)(Q2) and beta(M)(Q2) at momentum transfer Q(2)=0.92 and 1.76 GeV2. The electric GP shows a strong falloff with Q2, and its global behavior does not follow a simple dipole form. The magnetic GP shows a rise and then a falloff; this can be interpreted as the dominance of a long-distance diamagnetic pion cloud at low Q2, compensated at higher Q2 by a paramagnetic contribution from piN intermediate states.