Hi Simon,
My colleague Prof David Sanderson at SUERC offers the following advice:
The query raises interesting and potentially complex issues.
One relates to the difference between legally radioactive materials, and
the radiation which they emit, and exempt materials. These are dealt with
through the Radioactive Substances Acts, and their 2011 amendments (the
Scottish part of which is attached). Another relates to control of
occupational exposure to ionising radiation, which in Europe is defined by
the EC Basic safety Directive, and in the UK by the Ionising Radiation
Regulations (for which there is HSE guidance). Finally there are the
overarching principles of radiation protection where regardless of
statutary limitations it is expect6ed that work with radioactive or
ionising material will be (i) justified, (ii) optimised and (iii) limited.
A. Issues for these naturally occurring materials include whether the
material is, from a legal (as opposed to practical) perspective considered
to be radioactive. RSA 93 and its 2011 amendments are the key here, and do
carry implicat6ions for the ways in which they need tobe handled and
associated work such as preparation of thin sections) would need to be
conducted. In Scotland SEPA would be the authority to consult, and in
England the environment agency. Taking their advice on the material would
be a starting point. If itıs not formally radioactive, then the regulatory
issues turn on radiation protection and occupational exposure. So my first
advise would be to determine whether the material is to be treated as
radioactive.
B. In terms of ionising radiation exposure the IRRıs require practices
involving occupational exposure to be risk assessed, and for the
organisation to have a radiation protection adviser in place (RPA). First
step here would be to consider whether the thin section lab has an RPA,
and seek their formal advice on how to manage such activities. There is a
paradox in that natural radioactivity is not considered as part of the
controlled radiation exposure. Radioactive minerals where the radiation
arises from natural sources are arguably anomalous. Although common sense
suggests that additional doses should be treated in the same way as if
they came from an x-ray source or a synthetic radioactive material. In
England there is case law against the Natural History Museum concerning
public exposure to radioactive minerals on display. Whether this was a
sensible verdict, and also whether it sets precedent in other parts of the
UK is open to question. But in effect this could be taken to imply that it
would be foolish to rely on exemption orders for natural materials in
defining how to deal with such situations
http://news.bbc.co.uk/1/hi/uk/1173070.stm
C. If therefore we put aside the question as to whether the material is
legally radioactive, and also whether its radiation and radioactivity
risks fall within IRRıs, we are left with the overarching principles of
radiation protection. Which start with the working assumption that all
radiation exposure (above background) has potential harm associated with
it. The first stage would be to justify the activity which might lead to
exposure (ie balance the value of the thin sections against the detriment
of the radiation dose received to produce them). This should be recorded
in a risk assessment. The second stage would be to optimise the process.
Which would involve consideration of what physical and procedural means
could be used to minimise the radiation exposure (taking account in the UK
of the 10-20 microSievert per year limit of optimisation, and the dose
constraint concept of 300 microSieverts per year from a single
activities). Taking precautions to avoid ingestion of radionuclides as
well as minimising direct radiation exposure would also seem sensible. The
final stage would be to demonstrate that statutory dose limits (which is
where the 1 mSv per year comes in) are not being breached.
I can imagine that thin section laboratories might prefer to avoid
confronting this potentially confusing and onerous system. If it were
Glasgow I would suggest that the correct approach is to start with the
RPA, and if necessary consult SEPA. Are there any other hazards associated
with preparation of thin sections or mineral samples containing
radioactivity? For example toxicity? These presumably should also be risk
assessment and appropriate measures put in place.
Hoping this helps.
David
David C.W. Sanderson
Professor of Environmental Physics,
SUERC,
Rankine Avenue,
East Kilbride G75 OQF
Tel 01355 270110
Fax 01355 223332
A further take on it would be to talk to BGS, as they will undoubtedly
have worked with monazite a lot (especially in their isotope labs at
NIGL). An initial contact would be Ian Millar ([log in to unmask]). Clearly
talking to Exeterıs RPA and the EA is also warranted.
Hope this all helps.
Adrian
Adrian Boyce
Professor of Applied Geology
Scottish Universities Environmental Research Centre
East Kilbride
Glasgow
G75 0QF
Tel direct: 44 (0)1355 270 143
Mobile: 44 (0)791 252 1434
http://www.gla.ac.uk/research/az/suerc/ourstaff/boyceadrian/
https://www.researchgate.net/profile/Adrian_Boyce
-----Original Message-----
From: The Mineral Deposits Studies Group listserver
<[log in to unmask]> on behalf of Sam Broom-Fendley
<[log in to unmask]>
Reply-To: The Mineral Deposits Studies Group listserver
<[log in to unmask]>
Date: Wednesday, 27 January 2016 at 16:45
To: "[log in to unmask]" <[log in to unmask]>
Subject: Radioactive sample preparation
>Dear all,
>
>We are having some hiccups preparing some naturally occurring radioactive
>samples in our thin section lab, such as monazite-bearing carbonatites
>and some alkaline granite samples (dose rate of 0.6--5 uSv/hr). I was
>wondering if any members of the community could impart some advice?
>
>Firstly, when assessing samples for radioactivity, what 'cut-off' levels
>do you have in your labs, and how are they calculated? We work from the
>UK HSE 1999 guidelines where no member of the public can obtain 1 mSv of
>radiation, above their normal background dose, over the course of a year.
>To assess the potential impact of an individual sample, we therefore
>measure the dose-rate in uSv/hr and multiply this by 1650 hours. From
>this we obtain the equivalent dose if the sample was worked with every
>working day in a year. If this value is above 1 mSv, currently, we do not
>proceed with any sample preparation (thin sectioning, crushing, etc.).
>This cut-off works out at around 0.65 uSv/hr for any sample.
>
>This cut-off has the advantage that a user of the thin-section lab will
>never receive >1 mSv in a year. However, it has the downside that many
>samples simply cannot be prepared in-house. Any advice on how you assess
>the radioactivity of samples, and the levels above which these samples
>cannot be worked on, would be helpful.
>
>Secondly, if you do prepare radioactive samples, what control measures do
>you put in place? For example, do you have completely separate equipment
>and dust filters for naturally-occurring radioactive samples? Do you
>apply a varying range of control measures depending on the activity of
>the sample? Any advice here would be very welcome.
>
>Lastly, do any of you know any thin-section labs which will prepare
>material in the range of 0.6-5 uSv/hr?
>
>Many Thanks,
>
>Sam Broom-Fendley
>
>_________________________________________
>
>Dr. Sam Broom-Fendley,
>Research fellow in geology,
>University of Exeter, Camborne School of Mines.
>
>Room 3129,
>University of Exeter, Penryn Campus,
>Cornwall,
>TR10 9FE
>
>https://emps.exeter.ac.uk/csm/staff/slb241
>http://www.bgs.ac.uk/sosRare/home.html
>
>Twitter: @SoSRare
>
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>-----
>Geo-mineralisation is administered by the Mineral Deposits Studies Group
>(UK)
>(www.mdsg.or.uk)
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