BS EN ISO 10704:2015 pdf free download Water quality — Measurement of gross alpha and gross beta activity in non-saline water — Thin source deposit method
1 Scope
This International Standard specifies a method for the determination of gross alpha and gross beta activity innon-saline waters for alpha-and beta-emitting radionuclides.
The method is applicable to raw and potable waters containing a small quantity of dissolved matter.Ilt can,after adaptation, apply to other kind of waters.
The range of application depends upon the amount of dissolved material in the water and on the perfomancecharacteristics of the measurement equipment (background count rate and counting efficiency).
2 Normative references
The following referenced documents are indispensable for the application of this document. For datedreferences,only the edition cited applies. For undated references,the latest edition of the referenceddocument (including any amendments) applies.
ISo 3696, Water for analytical laboratory use -Specification and test methods
ISO 5667-1,Water quality— Sampling — Part 1: Guidance on the design of sampling programmes andsampling techniques
ISO 5667-3,Water quality — Sampling—Part 3: Guidance on the preservation and handling of watersamples
ISO/IEC 17025,General requirements for the competence of testing and calibration laboratoriesISo 80000-10,Quantities and units — Part 10: Atomic and nuclear physics
ISo/IEC Guide 98-3:2008,Uncertainty of measurement — Part 3: Guide to the expression of uncertainty inmeasurement (GUM:1995)
3 Symbols, definitions and units
For the purposes of this document, the symbols, definitions, and abbreviations given in ISO 80000-10, and the following, apply.
A activity of the calibration source Bq
A a activity spiked in sample a, prepared for self-absorption estimation purposes Bq
c A activity concentration Bq l −1
f aα , f aβ self-absorption factor of sample a for α and β, respectively —
m d mass of the deposit mg
m p mass of the planchet mg
m pd mass of the planchet and the deposit mg
m pf mass of the planchet and the filter mg
m pfd mass of the planchet, the filter and the deposit mg
r 0α , r 0β background count rate from the α and β windows, respectively s −1
r aα , r aβ self-absorption sample a count rate from the α and β windows, respectively s −1
r gα , r gβ sample gross count rate from the α and β windows, respectively s −1
r sα , r sβ calibration count rate from the α and β windows, respectively s −1
t 0 background counting time s
t g sample counting time s
t s calibration counting time s
U expanded uncertainty calculated by U= k ⋅ u(c A ) with k = 1, 2,… Bq l −1
u(c A ) standard uncertainty associated with the measurement result Bq l −1
V volume of test sample l
ε α , ε β counting efficiency for α and β, respectively —
ε aα , ε aβ counting efficiency of sample a for α and β, respectively —
χ alpha-beta crosstalk
4Principle
IMPORTANT—Gross alpha and gross beta determinations are not absolute determinations of thesample alpha and beta radioactive contents, but relative determinations referred to specific alpha andbeta emitters that constitute the standard calibration sources.
In order to obtain a thin deposit directly on a planchet, the sample can be progressively evaporated to drynessat a temperature below about 85 °℃.Alternatively,for alpha determination,it can be concentrated via acoprecipitation, the filtered coprecipitate being measured on to the planchet (Reference [3]). The gross alphaand gross beta activity of the deposit is measured by counting in an alpha- and beta-particle detector orcounting system previously calibrated against alpha- and beta-emitting standards.
When suspended matter is present in a significant quantity, a filtration step is required and the gross alphaand gross beta activity can also be determined for the material retained on the filter.
IMPORTANT —Due to the ingrowth of radon daughters over time, the results are dependent on thetime elapsed between sample preparation and measurement. For comparison purposes,it isrecommended that the measurement be performed at the same time after the preparation of thesample.
5 Chemical reagents and equipment5.1 Reagents
All reagents shall be of recognised analytical grade and shall not contain any detectable alpha and betaactivity,except for radioactive standards solutions.
5.1.1Standard solutions
5.1.1.1Alpha standard
The choice of alpha standard depends on the knowledge of the type of radioactive contaminant likely to bepresent in the waters being tested. In general,this leads to a choice between naturally occurring andman-made alpha emitters.
Commonly used standards of artificial alpha-emitting radionuclides employed for this purpose are 241Amsolutions and 239pu solutions. When 239pu is used, the presence of 241Pu as an impurity shall be taken intoaccount as it leads to growth of 241Am in prepared standard solutions of sources. When 241Am is used, takeinto account the potential interferences of its gamma emission.
NOTE An uranium compound of certfied natural or known isotopic composition has one arguable advantage, in thatits specific activity can be calculated from established physical constants and isotopic abundance date which areindependent of the calibration procedures of a particular organisation. However, an uranium compound of known isotopiccomposition is difficult to obtain.Furthermore, since the energies of the alpha emissions from uranium isotopes are lessthan those from the artificial transuranic nuclides, the use of a uranium standard tends to give a high result for transuranicelements.