40 CFR § 141.25 - Analytical methods for radioactivity.

(a) Analysis for the following contaminants shall be conducted to determine compliance with § 141.66 (radioactivity) in accordance with the methods in the following table, or the alternative methods listed in appendix A to subpart C this part, or their equivalent determined by EPA in accordance with § 141.27.

Alternative Testing Methods for Contaminants Listed at 40 CFR 141.25(a)

Contaminant	Methodology	EPA method	SM 21st edition 1	SM 22nd edition, 28 SM 23rd edition, 49 SM 24th edition 66	ASTM 4	SM online 3
Naturally Occurring:
Gross alpha and beta	Evaporation	900.0, Rev. 1.0 50	7110 B	7110 B
	Liquid Scintillation			7110 D	D 7283–17	7110 D–17.
Gross alpha	Coprecipitation		7110 C	7110 C
Radium 226	Radon emanation	903.1, Rev. 1.0 53	7500-Ra C	7500-Ra C	D 3454–05, –18, D 3454–21
	Radiochemical	903.0, Rev. 1.0 54	7500-Ra B	7500-Ra B	D 2460–07
	Gamma Spectrometry			7500-Ra E		7500-Ra E–07.
Radium 228	Radiochemical	904.0, Rev. 1.0 62	7500-Ra D	7500-Ra D
	Gamma Spectrometry			7500-Ra E		7500-Ra E–07.
Uranium	Radiochemical		7500–U B	7500–U B
	ICP–MS		3125		D 5673–05, 10, 16
	Alpha spectrometry		7500–U C	7500–U C	D 3972–09
	Laser Phosphorimetry				D 5174–07
	Alpha Liquid Scintillation Spectrometry				D 6239–09
Man-Made:
Radioactive Cesium	Radiochemical		7500-Cs B	7500-Cs B
	Gamma Ray Spectrometry		7120	7120	D 3649–06
Radioactive Iodine	Radiochemical		7500–I B, 7500–I C, 7500–I D	7500–I B, 7500–I C, 7500–I D	D 3649–06
	Gamma Ray Spectrometry		7120	7120	D 4785–08, –20
Radioactive Strontium 89, 90	Radiochemical		7500-Sr B	7500-Sr B
Tritium	Liquid Scintillation		7500- 3H B	7500- 3H B	D 4107–08, –20
Gamma Emitters	Gamma Ray Spectrometry		7120, 7500-Cs B, 7500–I B	7120, 7500-Cs B, 7500–I B	D 3649–06, D 4785–08, –20

(b) When the identification and measurement of radionuclides other than those listed in paragraph (a) of this section is required, the following references are to be used, except in cases where alternative methods have been approved in accordance with § 141.27.

(1) Procedures for Radiochemical Analysis of Nuclear Reactor Aqueous Solutions, H. L. Krieger and S. Gold, EPA-R4–73–014. USEPA, Cincinnati, Ohio, May 1973.

(2) HASL Procedure Manual, Edited by John H. Harley. HASL 300, ERDA Health and Safety Laboratory, New York, NY., 1973.

(c) For the purpose of monitoring radioactivity concentrations in drinking water, the required sensitivity of the radioanalysis is defined in terms of a detection limit. The detection limit shall be that concentration which can be counted with a precision of plus or minus 100 percent at the 95 percent confidence level (1.96σ where σ is the standard deviation of the net counting rate of the sample).

(1) To determine compliance with § 141.66(b), (c), and (e) the detection limit shall not exceed the concentrations in Table B to this paragraph.

Table B—Detection Limits for Gross Alpha Particle Activity, Radium 226, Radium 228, and Uranium

Contaminant	Detection limit
Gross alpha particle activity	3 pCi/L.
Radium 226	1 pCi/L.
Radium 228	1 pCi/L.
Uranium	1 µg/L

(2) To determine compliance with § 141.66(d) the detection limits shall not exceed the concentrations listed in Table C to this paragraph.

Table C—Detection Limits for Man-made Beta Particle and Photon Emitters

Radionuclide	Detection limit
Tritium	1,000 pCi/1.
Strontium–89	10 pCi/1.
Strontium–90	2 pCi/1.
Iodine–131	1 pCi/1.
Cesium–134	10 pCi/1.
Gross beta	4 pCi/1.
Other radionuclides	1/10 of the applicable limit.

(d) To judge compliance with the maximum contaminant levels listed in § 141.66, averages of data shall be used and shall be rounded to the same number of significant figures as the maximum contaminant level for the substance in question.

(e) The State has the authority to determine compliance or initiate enforcement action based upon analytical results or other information compiled by their sanctioned representatives and agencies.

[41 FR 28404, July 9, 1976, as amended at 45 FR 57345, Aug. 27, 1980; 62 FR 10173, Mar. 5, 1997; 65 FR 76745, Dec. 7, 2000; 67 FR 65250, Oct. 23, 2002; 69 FR 38855, June 29, 2004; 69 FR 52180, Aug. 25, 2004; 72 FR 11245, Mar. 12, 2007; 74 FR 30958, June 29, 2009; 89 FR 5779, Jan. 30, 2024]