[en] The decay data of radionuclides within the 4n series have been evaluated on the basis of specifications by staff within BNFL, Sellafield. Emphasis was placed on the beta-electron decay products of Np-236m and Np-236g through Pu-236 and U-232 to Tl-208 and stable Pb-208. Comprehensive evaluations were undertaken to determine the decay schemes for all of these radionuclides so that precise and definitive decay data could be recommended, including half-lives, branching fractions, alpha, beta and gamma-ray emission probabilities and their associated uncertainties. (author)

[en] Evaluated: July/August 2001. Re-evaluated: January 2004 and May 2010. Evaluation Procedures: Limitation of Relative Statistical Weight Method (LWM) was applied to average numbers throughout the evaluation. The uncertainty assigned to the average value was always greater than or equal to the smallest uncertainty of the values used to calculate the average. Decay Scheme: ²¹²Po is an extremely short-lived radionuclide populated via the beta decay of ²¹²Bi and the alpha decay of ²¹⁶Rn. 100% alpha decay of ²¹²Po occurs directly to the ground state of ²⁰⁸Pb (2005Br03)

[en] Evaluated: September 2010. Evaluation Procedure: Limitation of Relative Statistical Weight Method (LWM) was applied to average numbers throughout the evaluation. The uncertainty assigned to the average value was always greater than or equal to the smallest uncertainty of the values used to calculate the average. Decay Scheme: Very little of substance can be gleaned from the literature concerning the decay characteristics of ²¹⁹At (2001Br31). Although no γ or β^- emissions have been observed, an alpha group at 6.27 MeV was assigned to ²¹⁹At by Hyde and Ghiorso (1953Hy83). A simple decay scheme has been constructed with little confidence from this early study. Alpha and β^- feeding directly to the ground states of daughter ²¹⁵Bi and ²¹⁹Rn were assumed, but these processes were neither observed satisfactorily nor quantified experimentally. Spin and parity of 7/2^- were tentatively assigned to the ground state of ²¹⁹At to align with 5/2⁺ identified with the ground state of daughter ²¹⁹Rn (2001Br31), in order to define the proposed single beta-particle emission as first forbidden non-unique. Further spectral studies are required to assemble and quantify the decay scheme of ²¹⁹At with much greater confidence

[en] Evaluated: October 2010. Evaluation Procedure: Limitation of Relative Statistical Weight Method (LWM) was applied to average numbers throughout the evaluation. The uncertainty assigned to the average value was always greater than or equal to the smallest uncertainty of the values used to calculate the average. Decay Scheme A reasonably comprehensive decay scheme has been derived from the alpha-particle studies of 1962Wa18, 1991Ry01 and 1999Li05, and the gamma-ray measurements of 1967Da20, 1968Br17, 1970Da09, 1970Kr08 and 1999Li05

[en] Evaluated: January 2007/February 2009. Updated comments: Dec. 2010. Evaluation Procedure: Limitation of Relative Statistical Weight Method (LWM) was applied to average the decay data when appropriate (but see below). Decay Scheme: A relatively simple decay scheme was constructed from the gamma-ray studies of 1962Va08, 1963Ha29, 1967Sc34 and 1984Ho02. Only the gamma-ray measurements of Hoff et al. provide any estimates of the uncertainties in the gamma-ray probabilities expressed in terms of their relative intensity per 100 neutron captures in a high-flux reactor (1984Ho02). All other studies contained no information with respect to their overall uncertainties. Thus, no weighted mean data could be derived, and the data of 1984Ho02 were adopted wholesale and re-adjusted when deemed necessary (expressed in terms of the 743.977-keV gamma-ray emission probability (100%)). Further measurements are merited to quantify the gamma-ray emission probabilities and decay scheme with greater certainty

[en] An evaluation has been made of the decay of ²³⁵Np, a nuclide that has become popular for monitoring neptunium chemistry in the environment. Compared with other radioactive nuclides, ²³⁵Np produces few emissions that are suitable for quantitative analysis. A semi-theoretical study was undertaken, and it is recommended that four K-shell X rays are used to monitor ²³⁵Np. (U.K.)

[en] Evaluated: July/August 2001. Re-evaluated: January 2004 and April 2010. Evaluation Procedures: Limitation of Relative Statistical Weight Method (LWM) was applied to average numbers throughout the evaluation. The uncertainty assigned to the average value was always greater than or equal to the smallest uncertainty of the values used to calculate the average. Decay Scheme: A relatively simple decay scheme was constructed from the alpha-particle studies of 1962Wa28, 1969Pe17, 1971So15 and 1984Bo15, and the gamma-ray measurements of 1969Pe17, 1972DaZA, 1977Ku15, 1982Sa36, 1983Sc13, 1983Va22, 1984Bo15, 1984Ge07 and 1992Li05. Only the gamma-ray studies of 1977Ku15 provide any detail beyond the 240.986 keV gamma ray; all other measurements are dedicated to the determination of the absolute emission probability of the 240.986 keV gamma ray. A weighted mean emission probability was determined for this transition, and the other emission probabilities as measured by 1977Ku15 were subsequently adjusted. Cluster decay has been observed by 1985Pr01 and 1991Ho15, and reviewed by 1995Ar33 and 1997Tr17. ¹⁴C emissions were detected with a branching fraction of 5 (1) 10^-11. However, this decay mode has not been included in the decay-data summary section

[en] Evaluated: April 2007/April 2010. Evaluation Procedure: Limitation of Relative Statistical Weight Method (LWM) was applied to average the decay data when appropriate. Decay Scheme: A simple IT-decay mode dominates the decay scheme of ²⁴²Am^m. The small α branch is complex, and many features of this decay mode remain unresolved despite the extensive study of Hoff et al. (1990Ho02). Some confusion arose during the course of the 1950s as to the correct identity of the ground and metastable states of ²⁴²Am. This problem was resolved in 1960 by Asaro et al. (1960As05) when the 16-hour half-life activity was shown to be the ground state and the longer-lived 140-year isomer was defined as the metastable state. The α branch has been determined by Barnes et al. (1959Ba22) and Zelenkov et al. (1979Ze05) to be 0.46 (1)%. Hoff et al. have studied the emissions from the α-decay mode in considerable detail (1990Ho02), and the more modest measurements of Baranov et al. (1979Ba67) and Vylov et al. (1980VyZZ) show reasonable agreement with this extensive data set. A small spontaneous fission branch of 1.5 (6) x 10^-8% has been quantified by Caldwell et al. (1967Ca04), while an upper limit of 4.8 x 10^-9% has been specified by Zelenko et al. (1986Ze06)

[en] The decay data of various radionuclides have been evaluated on the basis of a series of well-defined specifications and the requirements of the UK nuclear power, fuel reprocessing and waste management programmes. These radionuclides are primarily activation products and standards that are commonly used in gamma-ray spectroscopy. Recommended data include half-life, branching fractions, alpha, beta and gamma-ray energies and emission probabilities, total decay energy, mean alpha, beta and gamma energies, internal conversion coefficients, and all associated uncertainties. Computer-based files have been generated in ENDF-6 format, including lists of the references used to produce the proposed decay scheme and comments that identify any inadequacies. (author)

[en] Evaluated: July/August 2001. Re-evaluated: January 2004 and July 2010. Evaluation Procedures: Limitation of Relative Statistical Weight Method (LWM) was applied to average numbers throughout the evaluation. The uncertainty assigned to the average value was always greater than or equal to the smallest uncertainty of the values used to calculate the average. Decay Scheme: The ground state of ²⁰⁸Tl (J^π = 5⁺) decays by beta minus emission to various excited levels of ²⁰⁸Pb. A consistent decay scheme has been derived, assuming no direct beta decay to both the 2614.55-keV nuclear level and ground state of ²⁰⁸Pb (based on spin-parity considerations). This decay scheme is primarily based on the gamma-ray measurements of 1960Em01, 1960Sc07, 1961Si11, 1969Au10, 1969La23, 1969Pa02, 1972DaZA/1973Da38, 1972Ja25, 1975Ko02, 1977Ge12, 1978Av01, 1982Sa36, 1983Sc13, 1983Va22, 1984Ge07, 1992Li05 and 1993El08