Re: Bananas (K-40)

["Björn Cedervall" <bjorn_cedervall@hotmail.com>]

Dear Radsafers,

More details about the banana issue after a contact with some people 
involved in our spent nuclear fuel transports. First the ”Bq” on the 
surface: In principle this is Cs-137 (and I would assume a smaller 
amount Cs-134 also)and/or Co-60. As external radiation sources these are 
much more important than K-40.
Second, there is indeed a dose rate to speak about – from the nuclear 
material inside. At 1 m distance this contribution (from what is inside 
the casket) may be about 0.1 mSv/h – thus dominating here.

A friend of mine at Ringhals NPP used Microhield today for the banana 
”wall”: Infinite slab, 15 m thickness (”depth”), assumed density: 1 
g/cc. ICRP51 data, and one meter distance. He came to 4.5 nSv/h which
essentially confirms Tom’s previous calculation. So the nuclear waste 
caskets are worse. Thanks for the responses giving a perspective on the 
issue.

Bjorn
------------------------------------------------------------
>using ICRP 26 methodology (weighting factors) and FGR 12, I get around
>0.0003 mrem/hr to the person. Using ICRP 60, I get about the same 
answer.
>>
>Tom Johnson
bjorn_cedervall@hotmail.com
Depts. Medical Radiation Biology and Medical Radiation Physics,
Karolinska Institutet, Box 260,
S-171 76 Stockholm, Sweden
Ph/fax: Int + 468 343525 (Med. Radiation Physics)
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