Standardization of tritiated water by the CIEMAT/NIST and TDCR methods

The activity of tritiated water has been standardized by two liquid scintillation counting methods： The CIEMAT/NIST method with the ^54Mn-standard efficiency tracing and the triple-to-double coincidence ratio（TDCR） method. The samples were prepared with Ultima Gold TM AB liquid scintillation cocktail in low-potassium glass vials. In the application of the CIEMAT/ NIST method, the computer program EMILIA was used to calculate the efficiency of ^3H and ^54 Mn according to the KL1L2L3 M atomic rearrangement model. And the detection efficiency of the TDCR counter was calculated using TDCR07 code, which makes it possible to allow for the potential asymmetry between the three photomultiplier tubes. The influence of stopping power and k B factor is discussed in the paper. When a power approach is adopted for the stopping power for electrons below 1 ke V and k B is chosen to be 0.0075 cm/Me V, the relative deviation will be only 0.3% between the two methods.