Appendix CRF - Part 3 - Northamptonshire County Council

Methodology
Job reference number
GAU1278 (Final)
Samples were received at the National Oceanography Centre, Southampton on 18 th
August 2008 in good condition.
Gamma spectrometry (Method GAU/RC/2032: Accredited to ISO/IEC 17025:2005)
100ml of the sample was evaporated down to less than 20ml and transferred to a
scintillation vial. The sample was then counted on a well-type HPGe detector
previously calibrated with a mixed nuclide standard of identical geometry. The
resulting spectrum was analysed using Fitzpeaks spectral analysis software. All
anthropogenic radionuclides were identified and quantified. In addition 60 Co, and
137 Cs were specifically searched for and limits of detection reported where no activity
was detected.
Gross alpha / beta in waters (Method GAU/RC/2034)
200 ml of the sample was acidified with H2SO4 and evaporated to dryness and the
residue ignited at 350 C. The ignited residue was ground and mounted onto a 47 mm
filter paper. The source was then counted on a gas flow proportional counter
previously calibrated against 241 Am (alpha) and 137 Cs (beta).
3 H in aqueous samples (Method GAU/RC/2004)
50ml of the sample was removed for 3 H analysis. The sub-sample was purified by
distillation. The 3 H content of the distillate was then measured using a Quantulus
ultra-low level liquid scintillation counter.
226 Ra in aqueous samples (Method GAU/RC/2038)
An aliquot of the aqueous sample is mixed with a water-immiscible scintillation
cocktail in a glass vial. The vial is sealed and immediately counted on a Perkin Elmer
Quantulus liquid scintillation counter with alpha-beta discrimination activated to
determine the total 222 Rn activity. The sample is then stored for two weeks and
recounted to determine the activity of supported 222 Rn/ 226 Ra.
Th isotopes by alpha spectrometry (Method GAU/RC/2027)
An aliquot of the sample is spiked with 229 Th and acidified. An iron hydroxide
precipitation followed by anion exchange chromatography is used to isolate Th from
the solution. The activities of 230 Th and 232 Th are then determined by alpha
spectrometry.
U by alpha spec & ICPMS (Method GAU/RC/2026)
An aliquot of the sample is spiked with 232 U and acidified. A combination of anion
exchange and extraction chromatography is used to isolate U from the solution. 238 U
and 234 U are determined by alpha spectrometry, and the 235 U content is determined
relative to 238 U by ICP-MS.
Geosciences Advisory Unit, National Oceanography Centre, Southampton, European Way, SO14 3ZH
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