[ RadSafe ] Pb-210 Accumulation on Supply Fan Filters

Wed Feb 17 12:29:11 CST 2016

Radsafe,

     I always liked when someone triggered the portal monitor at the
Brookhaven
Medical Research Reactor (BMRR) with whatever they had picked up in/on their
double-knit pants.  Unfortunately, due to a fuel storage pool overflow
problem at
BNL, the BMRR and HFBR (High Flux Beam Reactor) were shut down.

     Joe Preisig

On Wed, Feb 17, 2016 at 8:06 AM, Nick Tsurikov <nick.tsurikov at gmail.com>
wrote:

> Dear all,
> I've seen Pb-210 on several occasions in gas production/storage
> facilities.  Sure, there is large Pb-210 peak - but it is present in the
> form of a a rather thin film (1/16" is probably the most I've seen) and is
> relatively easy to remove. Clean the stuff with a "pig"/"plug", put it in a
> drum in the corner of the workshop/plant and signpost it (so it won't get
> lost), pipes are back - clean and good for re-use.
> With filters - one needs to look at the electrostatic precipitators and
> filters at different smelters (copper and nickel in particular, sometime
> iron/steel as well).  The "attached fraction" [to dust] of Rn-222 progeny
> tends to accumulate there, and the longest living progeny (Pb-210) is
> almost always detectable...
> Kind regards
> Nick Tsurikov
>
> On Tue, Feb 16, 2016 at 5:15 PM, Conway, Ken C <kcconway at bwxt.com> wrote:
>
> > I have seen this on outside metals. The Pb 210 rusts right into  the
> > metal.  The daughter Po-210 a strong alpha emitter should accompany it.
> > Lead 210 as you describe it is expected.
> >
> >
> > From the Multi-Agency Radiation Survey and Assessment of Material and
> > Equipment (MARSAME) manual (USEPA, 2009)
> > "
> > Radon progeny tend to become fixed to solid particles in the air. These
> > particles can become attached to surfaces as a result of electrostatic
> > charge or gravitational settling. Air flow through ventilation ducts can
> > produce an electrostatic charge that will attract these particles. A
> > decrease in atmospheric pressure often precedes a rainstorm, which
> > increases the radon emanation rate. Immediately prior to an electrical
> > storm, an electrostatic charge can build up on equipment resulting in
> > elevated radiation levels from radon progeny. Rainfall acts to scavenge
> > these particles from the air, potentially resulting in elevated dose
> rates
> > and surface activities during and immediately following rainfall.
> >
> > Pb-210 is a decay product of 222Rn and 238U. The 22-year half-life
> > provides opportunities for buildup 210Pb and progeny in sediments and
> > low-lying areas. As mentioned previously, rain acts to scavenge radon
> > progeny from the air. Areas where rain collects and concentrates can
> result
> > in elevated levels of 210Pb and progeny over time. In addition, lead is
> > easily oxidized and can become fixed to surfaces through corrosion
> > processes. Rust or oxide films on equipment can be indicators of
> locations
> > with a potential for elevated background radioactivity."
> >
> > NCRP 45 states that Pb-210 is present in ground level atmosphere at 1
> E-14
> > uCi/ml. I would expect that air handling devices constantly exposed to
> such
> > air would accumulate  Pb-210 as discussed in MARSAME. Similarly rain
> > contains ~ 3 pCi/l Pb-210 and is also a potential source( NCRP 77).
> >
> > This radon daughter washout process is a known and established natural
> > process.
> >
> >
> > -----Original Message-----
> > From: radsafe-bounces at health.phys.iit.edu [mailto:
> > radsafe-bounces at health.phys.iit.edu] On Behalf Of
> > Randy.Redmond at cns.doe.gov
> > Sent: Monday, February 15, 2016 4:42 PM
> > To: 'radsafe at health.phys.iit.edu'
> > Subject: EXTERNAL: [ RadSafe ] Pb-210 Accumulation on Supply Fan Filters
> >
> > Anyone else run across supply fan filters that have detectable beta-gamma
> > that will not decay away like typical short-lived radon progeny?  Gamma
> > spec shows a large Pb-210 peak.  Our thought process is there is an
> > accumulation of Pb-210 on the filters because of the amount of air being
> > moved and filtered;  the filters remain in use for several years; and the
> > Pb-210 has a 20.4 year half-life.
> >
> >
> > [cid:image001.png at 01CF9A97.E7064240]
> >
> > Randy Redmond
> > Y-12 Radiological Control
> > Radiological Engineering
> > Randy.Redmond at cns.doe.gov<mailto:Randy.Redmond at cns.doe.gov>
> > (865) 574-5640 Office
> > (865) 574-0117 Fax
> >
> >
> >
> >
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