Is Tritium Really That "Nasty"?

[eh_carbaugh@ccmail.pnl.gov (Eugene H Carbaugh)]

     The thread identifying tritium as "nasty and HTO and particularly 
     nasty" disturbs me a bit. 
     
     In term of the risk posed per unit intake (i.e., Sv/Bq), tritium and 
     tritium oxide are among the least hazardous of radionuclides.  What 
     with all the expressed concerns of LD 50/30 and the various numbers of 
     7 and 8 curies calculated (for comparison with 25 curie sources), one 
     must remember that there is a very big difference between HT (or T2) 
     and HTO.  The exit signs that prompted the discussion may consist of 
     2-100 (ok, nominally 25) curies of tritium, however it is some 90+ 
     percent in the elemental gas form.  Actual experiences with the signs 
     has been that there is very little dose associated with routine use or 
     accidental breakage/leakage of these units.  Other applications of 
     tritium luminescence (e.g., watches, gun sights) also bear this out.
     
     I don't mean to underscore the nuisance that can be caused by 
     background tritium levels from these sources, nor the need for 
     vigilance in radiation protection programs associated with them.  
     However, it is recognized among those who routinely work with tritium 
     that absolute control of it is a myth because of its ease of 
     permeation and diffusion through barriers that would seem impenetrable 
     to most materials.  This nuisance factor becomes particularly apparent 
     when a zero-tolerance of contamination levels for workplaces is 
     applied by a well-meaning but naive authoritative or regulatory body.
     
     Referring to tritium as "nasty" and "particularly nasty" promulgates 
     unwarranted fears about the nuclide.  It raises a flaming torch to a 
     straw man and shouts "watch out for this extremely dangerous 
     situation."  
     
     Eugene H. Carbaugh
     Internal Dosimetry
     Pacific Northwest National Laboratory
     eh_carbaugh@pnl.gov