[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Lead decay
>Content-Disposition: inline
>Date: Tue, 16 Jun 1998 12:30:59 +1000
>Reply-To: Medical Physics Mailing List <MEDPHYS@LISTS.WAYNE.EDU>
>Sender: Medical Physics Listserver <medphys@lists.wayne.edu>
>From: Daniel Schick <schickdk@HEALTH.QLD.GOV.AU>
>Subject: Re: Lead decay
>To: MEDPHYS@LISTS.WAYNE.EDU
>
>Hi,
>
>It was I (Danny Schick) that mentioned the corroding lead - sorry I
>didn't sign off properly.
>
>I have a paper accepted for publication in 'Australasian Radiology' - I
>don't know an issue number yet but if there is interest out there I will
>send details to the list when available.
>
>To answer some of the below questions:
>
>1. The lead was thought to have been installed some 30 years earlier
>however it is believed that much of the corrosion would have occured
>more rapidly after installation, then slowed.
>
>2. The corrosion occured primarily because of the existence of a
>relatively acidic timber (oregon) used in the wall construction. The
>acidic timber produced vapours that in the presence of a high humidity
>corroded the lead forming a lead carbonate (white/grey powder)
>bi-product. In some cases the lead had thinned in small localised areas
>only, however large chunks of lead carbonate literally fell out of the
>wall space in some circumstances (e.g. during building work). We
>performed a retrospective analysis of the radiation dose implications
>and (fortuitously) since the worst effected areas were designed for
>protection of low occupancy space, we don't expect personal doses to
>have exceeded relevant limits.
>
>3. I would not rule out the possibility of corrosion from sources such
>as formic acid (glues in plywood MDF etc.) or perhaps even some paints.
>However in the case of this hospital the high humidity (sub tropical
>climate) and probably the lack of air conditioning 30 or so years ago
>would have been integral to the process.
>
>4. If a number of the possible causative factors exist in your
>department it may be prudent to do some non-destructive testing with
>X-ray film as previously mentioned. Even minimally corroded areas will
>be obvious on the film.
>
>More questions/comments welcomed .
>
> ===================================
> Daniel Schick
> Senior Medical Physicist
> Biomedical Engineering and Health Technology Services
> Princess Alexandra Hospital
> Ipswich Road, Woolloongabba, QLD, Australia 4102
> ----------------------------------------------------
> Phone - 61 07 32402002
> Fax - 61 07 32405187
> EMail - schickdk@health.qld.gov.au
> ===================================
>
>>>> "Jesse H. Coleman" <radshoals@airnet.net> 15/June/1998 10:17pm >>>
>Michael Tkacik mentioned corroding lead found to exist through a
>large section of a radiology dept.
>
>Michael and others, what experience have you had with corroded
>lead shielding?
>
>How old was the lead?
>How much thickness (shielding) was lost?
>Was it "caused" by moisture? Other causes identified?
>What else?
>
>Might we need to recheck shielding each decade or such?
>
>One tends to think that lead is more or less inert and will just
>last "forever". Out of sight, out of mind.
>
> *****
>Frequently Asked Questions (FAQ) for Medphys at:
>http://www.mindspring.com/~sherouse/MPFAQ/
>
>Archives of recent Medphys postings at:
>http://www.escribe.com/medicine/medphys/
>