Re: Exposure from a spent fuel rod from the US supplied Rese

[Steven.Rima@DOEGJPO.COM (Steven Rima)]

     IF the reactor is U-235 based, the two highest yield fission products 
     are Cs-134 and Cs-137. Each of these accounts for between 7% and 8% of 
     all fission products from U-235. Cs-134 has about a two year 
     half-life, so the majority would be gone after 10 years, but Cs-137's 
     half-life of about 30 years means that most is still present after 10 
     years. Obviously, many fission and activation products contribute to 
     the exposure rate, but the majority of the external gamma exposure 
     rate from an older spent fuel bundle is due to the Cs-137. 
     (Personally, I'm somewhat surprised that the exposure rate is "only" 
     320 R/h; I'd have guessed somewhat higher.)
     
     Steven D. Rima, CHP
     Manager, Health Physics and Industrial Hygiene
     MACTEC-ERS, LLC
     steven.rima@doegjpo.com


______________________________ Reply Separator _________________________________
Subject: Exposure from a spent fuel rod from the US supplied Research
Author:  Myung Chul Jo <mjo@scs.unr.edu> at Internet
Date:    11/3/97 2:21 PM


I was a DOE sponsored training class. An instructor stated that the 
exposure rate would be 320 REM/hr at an arms length from a spent fuel rod. 
If this fuel has been in dry
storage for 10 years and not used, what causes that high exposure and 
what would be main fission or activation products causing the exposure. 
The fuel rod was 1.5 inch cylinder and about 3 feet long. I would 
appreciate any comments. Thank you in advance.
     
     
Myung Chul Jo <mjo@scs.unr.edu>
University of Nevada, Reno
Health Physics
EH&S/MS 328
Reno, NV 89557
(702) 784-4540(voice)
(702) 784-4553(fax)