Stewart, M.K.; Burnett, W.C.; Whitehead, N.E. 1993 Survey of some natural decay-series isotopes in the Wairakei geothermal area and possible residence-time applications. Lower Hutt: Institute of Geological & Nuclear Sciences Institute of Geological & Nuclear Sciences science report 93/38 16 p.
Abstract: Concentrations of selected isotopes in the uranium decay series were determined for samples collected from the Wairakei, Broadlands/Ohaaki and Waiotapu areas. 226Ra concentrations were found to be low (0.05-0.22 dpm/l), similar to values reported in neutral hot springs at Tatun geothermal area, Taiwan, but lower than other geothermal systems (Yellowstone, USA, and Latera, Central Italy) (up to 25 dpm/l). The potential of 226Ra/228Ra ratios for indicating water residence times could not be explored because 228Ra data was not available. 222Rn concentrations are higher and related to steam fractions and CO2 concentrations. The short half-life (3.8 days) makes 222Rn suitable for estimating residence times of radon in steam, and therefore the distance of travel of steam from its source (e.g., wells WK9 and 52). 210Pb and 210Po concentrations were very low and less than detection limits in many of the Wairakei waters; no residence time applications are apparent for these isotopes. (auth)