– On tritium — excerpts from memorandum to NRC Chairman Allison Macfarlane

From Institute for Energy and Environmental Research
By Dr. Arjun Makhijani, President
June 2013 issue Science for Democratic Action

Tritium is likely to be a critical radionuclide for estimating fetal dose from nuclear power plant operation. IEER concluded some time ago that the ICRP’s method of attributing the mother’s uterine wall dose from tritium (and from alpha-emitting radionuclides) to the embryo during the first eight weeks of pregnancy is incorrect. Though I have not yet looked at it specifically, it seems to me that the problem also extends to carbon-14, which was also identified as a key radionuclide in the feasibility study. The issue of a scientifically defensible approach for fetal dose estimation, especially during the early part of pregnancy, needs to be addressed because it is very important for a credible children’s case control study that is geared (rightly so, in my opinion) to the mother’s place of residence at the time of the birth of the child. IEER’s report, Science for the Vulnerable, which briefly covers this issue (especially see pages 73 and 85) can be downloaded from the IEER website.3

I recommend that the NRC request the EPA’s Science Advisory Board or the National Academies Committee to Assess Health Risks from Exposure to Low Levels of Ionizing Radiation to provide it with scientific advice as expeditiously as possible on how fetal doses, including in the first eight weeks, from alpha emitters and relatively low-energy beta emitters, particularly tritium and carbon-14, should be calculated. This problem should also be addressed by the National Academies pilot study in the course of its work [which has now been cancelled by the NRC].

A related data problem is that the NRC does not require monitoring of tritium in rainwater, though this is recognized as a potential issue by at least some in industry. This could be a crucial exposure pathway especially during pregnancy, notably for people with private wells. In 2006, Ken Sejkora of Entergy Nuclear Northeast (Pilgrim Station) estimated that under adverse weather conditions, episodic releases could result in concentrations as high as 36 million pCi/L – 180 times the drinking water limit close to the stack (probably onsite, though this is not explicitly stated).  Sejkora used a source term of 1 Ci/day.4 While this choice is on the higher side of routine releases (for one sample year, 2004) I have looked at, even higher tritium source terms releases from US nuclear power plants have been measured. For instance, the Palo Verde plant reported 2,123 curies of tritium releases to the atmosphere in 2004 (all three reactors).

I recommend that the NRC require routine monitoring of
rainwater around commercial nuclear reactors. The NRC should also encourage nuclear power plant owners to consider making funds voluntarily available to private well owners nearby in case the well owners want to have their water tested for tritium and other radionuclides emitted from nuclear power plants.