[ RadSafe ] Field determination of radon progeny

Tue Apr 13 16:16:46 CDT 2010

Group,

It is great that we can tell how radon moves out of soil or the air,
etc. but weren't we asked how to distinguish naturally occurring from
plant radionuclides on personnel that cannot make it out of an RCA
because they alarm a portal monitor?

Scott Davidson

On Tue, Apr 13, 2010 at 3:25 PM,  <Andycgeo at aol.com> wrote:
> Besides heavy sustained rainfall, frost and icy soil conditions prevent
> radon from escaping to the open air and the radon moves to dryer and more
> porous  parts of the soil pushing more radon indoors.
>
> Andy George
>
>
> In a message dated 4/13/2010 2:34:38 P.M. Eastern Daylight Time,
> hreynolds at energysolutions.com writes:
>
> Also as  the soil saturates with water, this will form a radon cap and
> inhibit  migration from the soil to the air above it.  This  can cause the
> radon to find its way into structures by below ground paths and increase  indoor
> levels.
>
>
> Harry  Reynolds
> ASRSO
> ENERGYSOLUTIONS
> 801-649-2219 Desk
> 801-349-9036 Cell
>
> -----Original Message-----
> From:  radsafe-bounces at health.phys.iit.edu
> [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Harry  Reynolds
> Sent: Tuesday, April 13, 2010 12:30 PM
> To: Stewart Farber;  radsafe at agni.phys.iit.edu; Eric.Goldin at sce.com
> Subject: Re: [ RadSafe ]  Field determination of radon progeny
>
> The onset of rain will be  accompanied by a drop in atmospheric pressure
> which will cause a pressure  differential between the soil and the air which
> will literally 'suck' the  radon out of the soil.  This is a relatively short
> term effect as the  pressure soon equalizes.
>
>
> Harry  Reynolds
> ASRSO
> ENERGYSOLUTIONS
> 801-649-2219 Desk
> 801-349-9036 Cell
>
> -----Original Message-----
> From:  radsafe-bounces at health.phys.iit.edu
> [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Stewart  Farber
> Sent: Tuesday, April 13, 2010 12:08 PM
> To:  radsafe at agni.phys.iit.edu; Eric.Goldin at sce.com
> Subject: Re: [ RadSafe ]  Field determination of radon progeny
>
> In terms of the effective  half-life of radon daughters on clothing, I
> believe the good working value is  just about 30 minutes. If clothing measured
> contamination drops by a factor of  2 in 30 min, and 4 in 1 hour, it is
> almost certainly Rn daughter  contamination.
>
> Bi-214 has a half-life of about 20 min, and Pb-214  about 27 min, with a
> rough overall effective half life for the Rn-daughter mix  of 30 min.
>
> Another interesting source of Rn-daughter  contamination  that might show
> up at a nuclear plant is that due to  rainfall.  I was involved with
> gathering and reviewing High Pressure  Ionization Chamber measurements of exposure
> rate  near an operating nuke  plant 30 years ago. Measurements were being
> made with a custom built  instrument [like the Reuter Stokes  RSS-111, which
> had a 10" diameter  sealed sphere, pressurized to 25 atm with Ar, so it was
> quite sensitive to  ionization from x rays  and gamma rays]. I had a custom
> unit built  because I needed to record data to a tape unit for long-term
> exposure rate  measurements at the site boundary a BWR nuclear plant [only 700'
> from the  turbine]. The State of VT had set an annual limit at the site
> boundary of only  5 mR/year  [0.05 milli-Sv/hr] from plant operations, with
> turbine shine  being the major factor at only 700'.
>
> I had plotted hourly average  radiation exposure rates. I also had gathered
> [for another purpose] concurrent  data of hourly rainfall rates in mm/hr.
> Putting the exposure rate data  together with the rainfall rate in mm/hr
> some very interesting things became  evident.
>
> During the start of initial hours of high rainfall, the  exposure rate
> increased from 8 uR/hr [0.08 uGy/hr] to  about 14  micro-R/hr [0.14 microGy/hr],
> an increase in background exposure rate of about  75%, due to ground-plane
> deposition of Rn-daughters around the HPIC system  located at the site
> boundary.
>
> Subsequently, after a few hours the  rainfall rate went to almost zero. The
> exposure increment began to drop with  about a half hour half life,
> returning toward 8 uR/hr. Then a few hours of  increase and drop of rainfall rate,
> and the total exposure rate went up  and down concurrent with the rainfal
> rate affecting the deposition of Rn  daughters. After about 10 hours the
> rainfall ended, and the 6 uR/hr [0.06  uSv/hr]  increase in background due to
> Rn-daughters decayed away, and the  total exposure rate returned [with about a
> 30 minute half-life] to the  background of about 8 uR/hr [0.08 uGy/hr] for
> that location. Of note, the  plant was not operating at the time, so there
> was no contribution from N-16  turbine shine, and no plant releases occurring.
>
> This 75% increase in  background measured at the time was due to rain
> washing ["scrubbing"]  Rn-daughter particulates from the air column and
> depositing them to the ground  where they caused an increase in exposure rate
> measured  by the fixed  HPIC.
>
> So, it is worth being aware that background exposure rates at or  near a
> nuclear facility [which might be monitored by HPIC or detectors able to
> measure slight increases in background] can increase by 75% [or who knows how
> much more depending on rainfall rate and average Rn-daughter concentration in
> the air mass at the location being measured at that time]. Then the
> increase  exposure rate above background, not due to plant releases, will decay
> away  with about a half hour half-life.
>
> Stewart Farber, MSPH
>
> Farber  Medical Solutions, LLC
>
> Bridgeport, CT 06604
>
>
>
> [203]  441-8433 [office]
>
> website:  http://www.farber-medical.com
> farber at farber.info
> =======================
>
> ---  On Tue, 4/13/10, Eric.Goldin at sce.com <Eric.Goldin at sce.com>  wrote:
>
> From: Eric.Goldin at sce.com  <Eric.Goldin at sce.com>
> Subject: [ RadSafe ] Field determination of  radon progeny
> To: radsafe at agni.phys.iit.edu
> Date: Tuesday, April 13,  2010, 10:46 AM
>
> I didn't ever see too much on the actual answer to Rick  Hansen's question
> on field determination of radon progeny:
>
> I have a  question for radsafe:
>
> What are some methods to use in the field to  determine if low levels of
> radiation detected on a person or clothing is due  to radon daughters rather
> than radioactive contamination from other  sources?
>
> Nuclear plants have a duty to not release people who are  contaminated with
>
> licensed radioactive  material
> (plant-related).  So to distinguish between naturally  occurring rad
> material (i.e. radon progeny) and plant-related noble gases  (typically Xe-133),
> the worker is typically asked to simply wait for  decay.  With most radon
> progeny having short half-lives (less than 20  minutes), a short decay period
> will usually drop the electrostatically bound  radon daughters to a
> sufficiently low level such that they will pass the whole  body contamination
> monitors.  Anything longer-lived is likely  plant-related and therefore requires
> documentation, decontamination,  investigation, . . . .     Of course an
> option is to take  the clothes and place them on a HpGe detector for a
> qualitative  evaluation
> - if the count room has the time.
>
>
> Eric M. Goldin,  CHP
> <Eric.Goldin at sce.com>
>
> _______________________________________________
> 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
> _______________________________________________
> 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
>