PART 3Radioactive substances parameters

TABLE DParametric values for radon, tritium and ID of water intended for human consumption

Parameters	Maximum concentration or value		Units of measurement
Indicative dose (for radioactivity)	0,10		mSv
Radon1	100		Bq/1
Tritium (for radioactivity)2	100		Bq/l
1 Enforcement action by the local authority is deemed justified on radiological protection grounds without further consideration where radon concentrations exceed 1,000 Bq/1.
2 If tritium concentration exceeds its parametric value, an investigation (which may include analysis) of the presence of artificial radionuclides must be carried out.

SCHEDULE 2AMonitoring of radioactive substances

Regulation 10A

Radon1

1

In relation to the radon parameter in the radioactive substances parameters table, a local authority—

a

must ensure that a representative survey is carried out in accordance with sub-paragraph (2) to determine the likelihood of a supply failing to comply with the relevant parametric concentration or value specified in the radioactive substances parameters table; and

b

must carry out monitoring where there is reason to believe, on the basis of the results of the representative surveys or other reliable information, including any risk assessment carried out in accordance with regulation 6, that the parametric value for the radon parameter laid down in the radioactive substances parameters table might be exceeded.

2

A representative survey must be designed in such a way—

a

as to be capable of determining the scale and nature of likely exposure to radon in water intended for human consumption originating from different types of groundwater sources and wells in different geological areas; and

b

that underlying parameters, especially the geology and hydrology of the area, radioactivity of rock or soil, and well type, can be identified and used to direct further action to areas of likely high exposure.

Tritium2

1

In relation to the tritium parameter in the radioactive substances parameters table, a local authority—

a

must carry out monitoring where an anthropogenic source of tritium or other artificial radionuclides is present within the catchment area and it cannot be shown on the basis of other surveillance programmes or investigations, including any risk assessment carried out in accordance with regulation 6, that the level of tritium is below the parametric value listed in the radioactive substances parameters table; and

b

must carry out an investigation of the presence of other artificial radionuclides if the concentration of tritium exceeds the parametric value listed in the radioactive substances parameters table.

2

Where monitoring is required by sub-paragraph (1)—

a

it must be carried out at the frequencies as set out for audit monitoring in Table 3 in Part 2 of Schedule 2; or

b

it must (in the case of a private water supply falling within the scope of regulation 10(1)) be carried out at least every five years or more frequently if the risk assessment referred to under sub-paragraph (1)(a) shows this to be necessary.

Indicative Dose3

1

In relation to the indicative dose (“ID”) parameter in the radioactive substances parameters table, a local authority must carry out monitoring where a source of artificial radioactivity or elevated natural radioactivity is present and it cannot be shown on the basis of other surveillance programmes or investigations, including any risk assessment carried out in accordance with regulation 6, that the level of ID is below the parametric value listed the radioactive substances parameters table.

2

Where monitoring is required by sub-paragraph (1) in relation to artificial radionuclides—

a

it must be carried out at the frequencies as set out for audit monitoring in Table 3 in Part 2 of Schedule 2;

b

it must (in the case of a private water supply falling within the scope of regulation 10(1)) be carried out at least every five years and more frequently if the risk assessment shows this to be necessary.

3

Where monitoring is required by sub-paragraph (1) in relation to a source of elevated natural radioactivity—

a

the local authority—

i

may decide the frequency of monitoring in its area depending on the screening strategy adopted by the authority; and

ii

must notify the Welsh Ministers in writing of its decision under sub-paragraph (i); and

b

the frequency of monitoring decided under sub-paragraph (a)(i) may vary from a single check measurement to the frequencies as set out for audit monitoring in Table 3 in Part 2 of Schedule 2.

4

Where a local authority decides under sub-paragraph (3) that a single check measurement for natural radioactivity is appropriate, the local authority must carry out a further check if any change occurs in relation to the supply which is likely to influence the concentrations of radionuclides in the supply.

Water treatment4

Where treatment to reduce the level of radionuclides in a private water supply has been undertaken, the local authority must monitor the supply for total indicative dose, radon and tritium in accordance the provisions of this Part and the frequencies as set out for audit monitoring in Table 3 in Part 2 of Schedule 2 to verify the continued efficacy of that treatment.

Averaging5

Where a parametric value in the radioactive substances parameters table is exceeded in relation to a particular sample taken by a local authority, the Welsh Ministers must specify, by notice in writing to the local authority, the extent of resampling necessary to ensure that the measured values are representative of an average activity concentration for a full year.

PART 3Monitoring for indicative dose and analytical performance characteristics

Monitoring for compliance with the indicative dose5

A local authority may use reliable screening strategies to indicate the presence of radioactivity in water intended for human consumption.

6

The strategies referred to in paragraph 5 may include screening for–

a

certain radionuclides or individual radionuclide; or

b

gross alpha activity or gross beta activity (where appropriate gross beta activity may be replaced by residual beta activity after subtraction of the K-40 activity concentration).

Screening for certain radionuclides, or screening for an individual radionuclide7

If one of the activity concentrations exceeds 20% of the corresponding derived value or the tritium concentration exceeds its parametric value listed in Part 3 of Schedule 1 an analysis of additional radionuclides is required.

8

A local authority must, in deciding which radionuclides require to be measured for each supply, take into account all relevant information about likely sources of radioactivity.

Screening strategies for gross alpha activity and gross beta activity9

Subject to paragraph 10 the recommended screening values are–

a

0,1Bq/l for gross alpha activity; and

b

1,0Bq/l for gross beta activity.

10

If the gross alpha activity exceeds 0,1Bq/l or the gross beta activity exceeds 1,0Bq/l, analysis for specific radionuclides is required.

11

The Welsh Ministers may set alternative screening levels for gross alpha activity and gross beta activity where it can be demonstrated by the local authority that the alternative levels are in compliance with an indicative dose of 0,1 mSv.

12

The radionuclides to be measured must be based on all relevant information about likely sources of radioactivity.

Calculation of the indicative dose12

The indicative dose must be calculated from–

a

the measured radionuclide concentrations and the dose coefficients laid down in Annex III, Table A of Directive 96/29/Euratom M1; or

b

more recent information recognised by the Welsh Ministers, on the basis of the annual intake of water (730 1 for adults).

13

Where the following formula is satisfied, it can be assumed that the indicative dose is less than the parametric value of 0,1 mSv and no further investigation is required–

$\underset{i=1}{\overset{n}{\sum }}\frac{Ci\left(obs\right)}{Ci\left(der\right)}\le 1$

where:

Ci(obs) = observed concentration of radionuclide i

Ci(der) = derived concentration of radionuclide i

n = number of radionuclides detected.

Derived concentrations for radioactivity in water intended for human consumption¹

Origin	Nuclide	Derived concentration
Natural	U-2382	3,0 Bq/1
	U-2342	2,8 Bq/1
	Ra-226	0,5 Bq/1
	Ra-228	0,2 Bq/1
	Pb-210	0,2 Bq/1
	Po-210	0,1 Bq/1
Artificial	C-14	240 Bq/1
	Sr-90	4,9 Bq/1
	Pu-239/Pu-240	0,6 Bq/1
	Am-241	0,7 Bq/1
	Co-60	40 Bq/1
	Cs-134	7,2 Bq/1
	Cs-137	11 Bq/1
	1-131	6,2 Bq/1
1 This table includes values for the most common natural and artificial radionuclides; these are precise values, calculated for a dose of 0,1 mSv, an annual intake of 730 litre and using the dose coefficients laid down in Annex III, Table A of Directive 96/29/ Euratom; derived concentrations for other radionuclides can be calculated on the same basis, and values can be updated on the basis of more recent information recognised by the Welsh Ministers.
2 This table allows only for the radiological properties of uranium, not for its chemical toxicity.

Performance characteristics and methods of analysis14

For the following parameters and radionuclides, the method of analysis used must, as a minimum, be capable of measuring activity concentrations with a limit of detection specified below:

Parameters and radionuclides	Limit of detection 12	Notes
Tritium	10 Bq/1	3
Radon	10 Bq/1	3
gross alpha	0,04 Bq/1	4
gross beta	0,4 Bq/1	4
U-238	0,02 Bq/1
U-234	0,02 Bq/1
Ra-226	0,04 Bq/1
Ra-228	0,02 Bq/1	5
Pb-210	0,02 Bq/1
Po-210	0,01 Bq/1
C-14	20 Bq/1
Sr-90	0,4 Bq/1
Pu-239/Pu-240	0,04 Bq/1
Am-241	0,06 Bq/1
Co-60	0,5 Bq/1
Cs-134	0,5 Bq/1
Cs-137	0,5 Bq/1
I-131	0,5 Bq/1
1 The limit of detection must be calculated according to the ISO standard 11929: Determination of the characteristic limits (decision threshold, detection limit, and limits of confidence interval) for measurements of ionising radiation – Fundamentals and application, with probabilities of errors of 1st and 2nd kind of 0,05 each.
2 Measurement uncertainties must be calculated and reported as complete standard uncertainties, or as expanded uncertainties with an expansion factor of 1,96 according the ISO Guide for the Expression of Uncertainty in Measurement.
3 The limit of detection for tritium and for radon is 10% of its parametric value of 100 Bq/1.
4 The limit of detection for gross alpha activity and gross beta activities are 40% of the screening values of 0,1 and 1,0 Bq/1 respectively.
5 This limit of detection applies only to initial screening for indicative dose for a new water source; if initial checking indicates that it is not plausible that Ra-228 exceeds 20% of the derived concentration, the limit of detection may be increased to 0,08 Bq/1 for routine Ra-228 nuclide specific measurements, until a subsequent re-check is required.