[ RadSafe ] RadSafe Digest, Vol 1241, Issue 1

Wed Mar 20 12:52:27 CDT 2013

Radsafe:

     The real trick with models is to do good data  fitting.  Chi-Square 
tests or whatever, the whole shebang...
Figure out whether you are doing Gaussian or Poisson or whatever  fitting.  
Refer to books like Bevington,
Press, Teukolsky et al.,  Joan Westlake (Matrix Inversion  hints).  For 
really involved stochastic modeling, refer to books like  Jazwinski 
(linearization of non-linear problems).

    Pick a first model: linear with a slope and intercept,  then go from 
there.  Compare the actual measured data with the modeled  data.  The 
quantities you are measuring are not always the parameters you  are estimating.  See 
books by Gelb, R. Grover Brown, J.V. Candy etc.   Improve the model as 
needed.
You don't want too many fitted parameters, nor too few.

    A brief comment on the source terms available with the  computer 
program MCNP (Monte Carlo Neutral Particle Program).  Many  radiation source 
possibilities are available --- not just line or point  sources.
You can define the actual source geometry using MCNP's geometric shape  
definition language.  You can have spherical sources, cylindrical sources,  
etc.  You can input the mathematical form of the source
also --- isotropic and other varieties.  It's pretty neat.

    And sometimes you cannot make radiation measurements of  a new 
radiation facility, because it hasn't been built yet.  You can use  MCNP to design a 
new facility --- neutron, gamma/xray or perhaps even 
electron-based.  I did this once for a new Cesium source at the Long  
Island National Laboratory (USA).

   MCNP also has the capability to make repeated structures, such  as 
geometric elements such as fuel rods, moderating material etc.  So, you  just 
define the structure once and then put it anywhere else in the reactor or  
whatever, as needed.  I expect you could design a rudimentary power reactor  
using MCNP.  If the neutron cross-section data were available, one might  also 
design a crude nuclear device.

   If you get the chance to learn MCNP, perhaps you should do  so.  You'll 
never give anyone a straight answer again --- you'll end up  speaking to 
people in terms of probabilities...It pretty much changes the way  you think 
somewhat.

   Have a good week     Joe Preisig

PS  Sometimes hotspots are geological phenomena...

In a message dated 3/20/2013 1:25:09 P.M. Eastern Daylight Time,  
Mike.Brennan at DOH.WA.GOV writes:

The  trick with models is to be an engineer rather than an economist:

"The  difference between an engineer and an economist is that an engineer
sees  his models as potentially useful simplifications of reality, and  an
economist sees reality as a special case, albeit a potentially  important
one, of his model."

-----Original Message-----
From:  radsafe-bounces at health.phys.iit.edu
[mailto:radsafe-bounces at health.phys.iit.edu]  On Behalf Of Harrison -
CDPHE, Tony
Sent: Tuesday, March 19, 2013 10:12  AM
To: radsafe at health.phys.iit.edu
Subject: Re: [ RadSafe ] RadSafe  Digest, Vol 1241, Issue 1

LOL Remind me never to hire either of you to  do my modelling for me.

In my experience people who model, and people  who hire modelers are
after the same thing: the best estimate of  "truth."  Some models are
incomplete, but when all the models tend  toward the same result, as they
do in climate models, you'd best take the  results seriously.

Tony Harrison, MSPH

Inorganic &  Radiochemistry Supervisor

Laboratory Services Division

Colorado  Department of Public Health and Environment

8100 Lowry  Blvd.

Denver, CO  80230

303-692-3046 |  tony.harrison at state.co.us

Message: 9

> Date: Mon, 18 Mar  2013 21:03:13 -0600
> From: Maury Siskel  <maurysis at peoplepc.com>
> Subject: Re: [ RadSafe ] Teller and  Climate change - and radiophobia
> To: "The International Radiation  Protection (Health Physics) Mailing
>          List"   <radsafe at health.phys.iit.edu>
> Message-ID:  <5147D571.8090504 at peoplepc.com>
> Content-Type: text/plain;  charset=ISO-8859-1; format=flowed
>
> Thanks ffor voicing these  comments, Jerry.  I wish what you have said 
> would have no  application, but they are all too true. The organization

> and  pursuits of the IPCC is another prime example of this exact
>  process.   Sigh ...
> Best,
> Maury&Dog    [MaurySiskel maurysis at peoplepc.com]
>  ----------------------------------------------------------------
> On  3/18/2013 4:37 PM, Jerry Cohen wrote:
> > I reject the implication(s)  that calculation models showing the 
> >safety  of the Yucca  Mtn. project are sound while those predicting 
> >dire   consequences from climate change make  sense. Both are  designed

> >to  determine some predetermined outcome and are  therefore  nonsense.

> >Tell  me the answer you want  and I can easily develop a model to get 
> >that  answer. No  matter how you look at it, it isn't science! When 
> >doing   government sponsored research, you would be well-advise to 
> >first  learn  the desired answer, and then get it---assuming you wish 
>  >to get more  contracts in the future.
> > Jerry  Cohen
> >--
_______________________________________________
You  are currently subscribed to the RadSafe mailing list

Before posting a  message to RadSafe be sure to have read and understood
the RadSafe rules.  These can be found  at:
http://health.phys.iit.edu/radsaferules.html

For information on  how to subscribe or unsubscribe and other settings
visit:  http://health.phys.iit.edu
_______________________________________________
You  are currently subscribed to the RadSafe mailing list

Before posting a  message to RadSafe be sure to have read and understood 
the RadSafe rules.  These can be found at: 
http://health.phys.iit.edu/radsaferules.html

For  information on how to subscribe or unsubscribe and other settings 
visit:  http://health.phys.iit.edu