ISO 13162:2021 Water quality — Carbon 14 — Test method using liquid scintillation counting

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Water quality — Carbon 14 — Test method using liquid scintillation counting

WARNING — Persons using this document should be familiar with normal laboratory practice. This document does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user to establish appropriate safety and health practices and to determine the applicability of any other restrictions.

IMPORTANT — It is absolutely essential that tests conducted according to this document be carried out by suitably trained staff.

1 Scope

14

This document specifies a method for the measurement of C activity concentration in all types of water samples by liquid scintillation counting (LSC) either directly on the test sample or following a chemical separation.

The method is applicable to test samples of supply/drinking water, rainwater, surface and ground water, marine water, as well as cooling water, industrial water, domestic, and industrial wastewater.

The detection limit depends on the sample volume, the instrument used, the sample counting time, the background count rate, the detection efficiency and the chemical recovery. The method described in this document, using currently available liquid scintillation counters and suitable technical conditions, −1

has a detection limit as low as 1 Bq∙l , which is lower than the WHO criteria for safe consumption of -1 14 6 -1

drinking water (100 Bq·l ). C activity concentrations can be measured up to 10 Bq∙l without any sample dilution.

It is the user’s responsibility to ensure the validity of this test method for the water samples tested.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

ISO 5667-1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes and sampling techniques

ISO 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples

ISO 5667-10, Water quality — Sampling — Part 10: Guidance on sampling of waste water

ISO 11929-1, Determination of the characteristic limits (decision threshold, detection limit and limits of the coverage interval) for measurements of ionizing radiation — Fundamentals and application — Part 1: Elementary applications

ISO 19361, Measurement of radioactivity — Determination of beta emitters activities — Test method using liquid scintillation counting

ISO 80000-10, Quantities and units — Part 10: Atomic and nuclear physics

ISO/IEC 17025, General requirements for the competence of testing and calibration laboratories

ISO/IEC Guide 98-3:2008, Uncertainty of measurement — Part 3: Guide to the expression of uncertainty in measurement (GUM: 1995) — Part 3: Guide to the expression of uncertainty in measurement (GUM: 1995)

ISO/IEC Guide 99:2007, International vocabulary of metrology — Basic and general concepts and associated terms (VIM)

3 Terms, d efinitions , symbols and abbreviations

For the purposes of this document, the definitions, symbols and abbreviations given in ISO/IEC Guide 99:2007, ISO/IEC Guide 98-3:2008, ISO 80000-10, and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www. iso .org/o bp

— IEC Electropedia: available at http:// www .electropedia .org/ β Maximum energy for the beta emission keV

max

V

Volume of laboratory sample l

m

Mass of laboratory sample kg

-1

ρ

Density of the sample kg∙l

-1

c Activity concentration Bq∙l

A

-1

a

Activity per unit of mass Bq∙kg

A Activity of the calibration source Bq

A Activity of the internal standard solution Bq

s

n Number of counting -

N Number of the counted pulses for the background -

o

t Background counting time, in second s

0

N Number of the counted pulses for the sample -

g

t Sample counting time s

g

t Calibration counting time s

s

-1

r Background count rate s

0

-1

r Test sample count rate s

g

-1

r Calibration count rate s

s

ε

Detection efficiency -

Q Quench parameter -

f Quench factor -

q

ε Counting efficiency at quench parameter Q -

q

R Chemical recovery -

c

m Mass of total carbon in the sample kg

TC

m Mass of carbon in the precipitate kg

PC

m Mass of carbon in the carrier kg

CC

m Mass of sample carbon in the precipitate kg

SC

-1

Standard uncertainty associated with the measurement result Bq∙l

uc()

A

u Relative standard uncertainty -

rel

-1



c Possible or assumed true quantity values of the measurand Bq∙l

A

-1



  Standard uncertainty of c Bq∙l

uc()

A

A

α, β Probability of a false positive and false negative decision, respectively -

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