[ RadSafe ] Pb-210 Accumulation on Supply Fan Filters and On
Conway Lowe Family
conlowe at bell.net
Wed Feb 17 12:29:33 CST 2016
Pb-210 accumulation on residues from gas pipelines cleaned by brush "pigs" is a common occurrence, although not all maintenance workers take the appropriate waste management options, such as suggested by Nick. I have seen Pb-210 concentrations on such "pigging wastes" up to 15,000 Bq/kg. Fairly conservative dose calculations suggest that doses (inhalation and ingestion) from exposure to such waste would be low, < 0.002 mSv for a working day. Actual doses under good industrial hygiene practices would be lower still.
From: Nick Tsurikov [mailto:nick.tsurikov at gmail.com]
Sent: Wednesday, February 17, 2016 8:06 AM
To: The International Radiation Protection (Health Physics) Mailing List <radsafe at health.phys.iit.edu>
Subject: Re: [ RadSafe ] Pb-210 Accumulation on Supply Fan Filters
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...
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
> -----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
> 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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