## ISOGEOCHEM@LIST.UVM.EDU

#### View:

 Message: [ First | Previous | Next | Last ] By Topic: [ First | Previous | Next | Last ] By Author: [ First | Previous | Next | Last ] Font: Proportional Font

Subject:

Re: errata

From:

Date:

Wed, 31 Jan 2001 11:28:28 -0800

Content-Type:

text/plain

Parts/Attachments:

 text/plain (113 lines)
 ```Bhaskar, The 2.09E7 atoms/L is for 1 pCi of tritium, not 1 TU. The error came when I mixed up pCi and TU in my first message (we agree now that 1 TU = 3.2 pCi/L). You can come by this number couple different ways: 1 pCi = 3.7E-2 dps and the tritium decay constant (lambda) = 1.767 E-9 s-1 So, for the decay eqn: -dN/dt = (lambda)N 3.7E-2 = (1.767E-9)*N N = 2.09 E7 atoms (multiply by 3.2 to get the number of 3H atoms per TU = 6.69 E7 atoms) Alternatively, use the definition for 1 TU as noted by Axel Suckow. 1 TU = (1 atom 3H/ 1E18 atoms H)*(6.022 E23 atoms H / mol H)*(2 mol H /18 g H2O)*1000 g/L = 6.69 E7 atoms 3H per L. Converting to g/L, I obtain 1 TU = 3.3 E-16 g tritium per liter, or a factor of two different from the number Axel reported. You should check this yourself - clearly I've been wrong before. If you want values in Bq, then 1 pCi = 37 mBq (or 1 Bq = 27 pCi). I am not a modeler, and cannot appropriately respond to Axel's comment about what units you should use in your model. However, I hope this helps clarify the "units" issue. - Tim At 09:14 AM 1/31/01 -0800, you wrote: >Hello Tim: > >I shall be very grateful if you can review the following calculation for me. >It is based on the input received from you > >3.2 pCi/L =1 TU = 2.09E7 atoms/L (Am I right here?? How do you get >the atoms/L) > >Now 3g Tritium = 6.023E23 atoms > >So 1 atom of Tritium = (3/6.023E23) g > >So 1TU = (2.09E7*3/6.023E23) g/L = 1.04E-16 g/L > >Now 1 TU = 0.118 Bq/ L (from Clark & Fritz pp. 175) > >so 1 TU = 1.04E-16 g/L = 0.118 Bq/L > >Can we then say that > > >1.04E-16 g of Tritium = 0.118 Bq ???? > >Even though Bq is a frequency unit (dps)it appears that it can be >equivalenced to mass of tritium. > I have to convert TU into a mass unit for a contaminant transport >simulation and this is the way I found > >But is this valid?? > >I shall be very grateful for your help > >Regards > >Bhaskar Joshi > > > > > > > >: > > > >-----Original Message----- >From: Timothy P. Rose [mailto:[log in to unmask]] >Sent: Tuesday, January 30, 2001 10:21 AM >To: [log in to unmask] >Subject: [ISOGEOCHEM] errata > > >Bhaskar, >You are correct that 1 TU = 3.2 pCi/L, not the other way around. Sorry for >the misinformation. I'll go a little slower before I hit the reply button >next time. >- Tim > > >***************************************************************** >Timothy P. Rose >Analytical and Nuclear Chemistry Division, L-231 >Lawrence Livermore National Laboratory >Livermore, CA 94550 >Phone: 925-422-6611 >Fax: 925-422-3160 >email: [log in to unmask] >***************************************************************** > > ***************************************************************** Timothy P. Rose Analytical and Nuclear Chemistry Division, L-231 Lawrence Livermore National Laboratory Livermore, CA 94550 Phone: 925-422-6611 Fax: 925-422-3160 email: [log in to unmask] ***************************************************************** ```