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1.1 This test method covers the determination of ⁵⁵Fe in the presence of ⁵⁹Fe by liquid scintillation counting. The a-priori minimum detectable concentration for this test method is 7.4 Bq/L.2

1.2 This test method was developed principally for the quantitative determination of ⁵⁵Fe. However, after proper calibration of the liquid scintillation counter with reference standards of each nuclide, ⁵⁹Fe may also be quantified.

1.3 This test method was used successfully with Type III reagent water conforming to Specification D1193. It is the responsibility of the user to ensure the validity of this test method for waters of untested matrices.

1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For a specific hazard statement, see Section 9.

1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

5.1 Fe-55 is formed in reactor coolant systems of nuclear reactors by activation of stable iron. The ⁵⁵Fe is not completely removed by waste processing systems and some is released to the environment by means of normal waste liquid discharges. Power plants are required to monitor these discharges for ⁵⁵Fe as well as other radionuclides.

5.2 This technique effectively removes other activation and fission products such as isotopes of iodine, zinc, manganese, cobalt, and cesium by the addition of hold-back carriers and an anion exchange technique. The fission products (zirconium-95 and niobium-95) are selectively eluted with hydrochloric-hydrofluoric acid washes. The iron is finally separated from Zn⁺² by precipitation of FePO₄ at a pH of 3.0.