FW: Activation and dose rate in concrete in 40 years.

From: Thomas Otto <Thomas.Otto_at_cern.ch>
Date: Fri, 10 Aug 2012 06:49:54 +0000

Hello Mina,

Technically yes, it is just a matter of applying the Bateman (build-up and
decay) equations with t_decay =3D 40 y.
How reliable the estimate is, is another question. Three reasons for that:
1. the estimates of Fluka have been tested on short decay timescales
(order of a year, about). This is equivalent to say that the production cross
sections of radionuclides which contribute on these timescales (roughly, with
a half-live between 0.1 and 10 years AND a reasonable production cross
section) are predicted reasonably well. No rigorous tests for longer decay times
are available to my knowledge. With rigorous I mean that the irradiation =
conditions were under control.
2. after a long decay times some of the "usual contributors" have strongly
decayed. More exotic radionuclides produced on minor components of your
material are suddenly becoming dominant. The precision with which you know the=
  composition of the material will determine the accuracy of our activity estimate.
3. the irradiation pattern (beam intensity and time pattern) is not very important
in your case. It would be if you wanted to know the activity of short-lived
radionuclides shortly after beam-off. For the long lived ones a long time after
the shut-down of the facility an average beam intensity smeared out over its operational time will be sufficient.

To address point 2, sensitivity analysis is the key to assess the uncertainties:
vary the concentration of any component in your concrete mixture and look how
it influences the result. For point 1, get a second estimate with a different program and compare.

Best regards,

Thomas Otto
Safety Officer, Technology Department

-----Original Message-----
From: owner-fluka-discuss_at_mi.infn.it [mailto:owner-fluka-discuss_at_mi.infn.it] On Behalf Of Mina Nozar
Sent: 7 August 2012 19:57
To: fluka-discuss_at_fluka.org
Subject: Activation and dose rate in concrete in 40 years.

Hello everyone,

Will FLUKA be able to simulate activation and dose rates in concrete (of te vault walls)
40 years after end of beam, i.e. at the time of decommissioning of a cyclotron?
I have used FLUKA to look at activations as far as 5 years after EOB but not 40 years.

Thank you very much,
Received on Fri Aug 10 2012 - 10:02:32 CEST

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