[ RadSafe ] Pb-210 Accumulation on Supply Fan Filters

[Nick Tsurikov]

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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