Nuclear Decay Data
The decay properties of radionuclides (for
example, half lives, gamma emission probabilities
and particle emission probabilities) are needed
for instrument calibration for environmental
monitoring, for patient dosimetry, for decayheat calculations for the nuclear industry and for
shielding calculations (amongst many applications).
NPL is contributing to international efforts to
evaluate decay data.
IFIN (Romania) and NPL is working on detailed
evaluations of decay data using an agreed common
methodology. These data are published periodically
as BIPM Monographie 5 and also on the LNHB
website http://www.nucleide.org/DDEP_WG/
DDEPdata.htm.
Cs-137 Half-Life Data Evaluations
11500
10500
LRSW
Normalised Residuals
Rajeval
Median
Measured data
Weighted Means
Bootstrap
10000
9500
9000
8500
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
No. of Measurement
A plot of the half-life evaluation data for 137Cs
NPL has recently provided evaluations of 228Ac,
Pa, 232Th and 232U as part of an IAEA Coordinated
Research Project “Updated Decay Data Library
for Actinides”. This work continues under the
Acoustics and Ionising Radiation NMO-funded
programme. NPL also maintains an enquiry service
for nuclear data.
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Contact details
Further information
National Physical Laboratory
Hampton Road
Teddington
Middlesex
United Kingdom
TW11 0LW
For further information on the Ionising Radiation
Programme please visit: http://www.npl.co.uk/ionrad
or contact one of our experts
via e-mail (radioactivity@npl.co.uk)
Switchboard: 020 8977 3222
Website: www.npl.co.uk
© Queen’s Printer and Controller of HMSO, 2011.
© Queen’s Printer and Controller of HMSO, 2011. 9860/1211
In order to gain international acceptance,
multinational team including staff from Laboratoire
National Henri Becquerel (France), Khlopin
Radium Institute (Russia), Argonne National
Laboratory (US), China Institute of Atomic Energy,
Half-Life in Days
11000
The decay properties of radionuclides have been
measured extensively over the last 50 years,
largely in order to study the fundamental physics
of nuclear structure. With a few exceptions where
the data are poorly known and further experimental
work is needed, much of the effort is now focused
on establishing a coherent data set that is accepted
internationally. The experimental studies are of
varying quality: information on the calculation of
uncertainties is often limited, and there is little
information on the experimental methods used.
Evaluation is the process of pulling data together
from the published measurements while taking into
account knowledge of the physical processes to
determine recommended values with uncertainties
for the key parameters.