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                              QUANTITIES OF RADIONUCLIDES


The Ionising Radiations Regulations 1999 require that a prior radiological risk assessment
is undertaken for any work involving radioactive materials.        Much of the work with
radionuclides at the University of Hull involves the use of limited quantities of radioactive
materials. This assessment considers the generic radiation risks from all such work under
both normal and accidental conditions.

A “limited quantity” of radioactive material may be defined in relation to the Annual Limit
on Intake (ALI) for each radionuclide. For example, activity levels equivalent to up to 10
ALIs have previously been regarded as not requiring special precautions (controlled areas,
etc).     In some cases, however, routine work involves different levels of activity.
Consequently, for the purposes of this risk assessment, the following activity levels will be

                                                    Activity per procedure(MBq)

               Radionuclide                                       The limit for routine work
                                          Equivalent to 10 ALIs        assumed in this

     Tritium                                     4 800                      1000

     Carbon-14                                    340                        400

     Sulphur-35                                   150                        100

     Phosphorus-33                                140                        100

     Calcium-45                                    74                        100

     Phosphorus-32                                 63                         40

     Iodine-125                                    13                         10

It is also assumed that the work is inherently small-scale in nature, i.e. involves the
manipulation of small volumes of material, and that airborne contamination is not routinely


2.1       Radiation dose rates and external radiation risk to individuals

          Tritium, carbon-14, phosphorus-33, sulphur-35 and calcium-45

          These are all low energy beta-emitters readily shielded by normal laboratory
          containers, etc.    These are not expected to give rise to a significant external
          radiation hazard during normal use.

      Beta dose rates during normal procedures are usually negligible due to the
      (perspex) shielding provided.     The highest dose rates measured are above the
      open stock vial. For a typical stock vial, it is estimated that the dose rate at 10 cm
      above the open vial (ie where the fingers might be) is 1500 μSv/h.          Elsewhere,
      dose rates are all very low. A typical procedure will require no more than a few
      seconds exposure of the hands above the stock vial. Assuming 10 procedures a
      month gives an annual dose to the skin on the fingertips of less than 0.5 mSv
      (equivalent to 0.1% of the annual dose limit of 500 mSv).

      To ensure that doses remain low, the use of shielding around stock vials, pipettes,
      and on benches is very important, as is avoiding any direct handling of unshielded
      (or poorly shielded) activity.   Without such precautions, it is estimated that the
      skin dose could be very much higher.


      Is a gamma/x-ray emitter and is supplied in shielded stock vials. The following
      dose rates are expected during the normal use of 10 MBq:

              Body exposure:           1 μSv/h

              Finger exposure:         50 μSv/ h

      Exposure to the above dose rates is expected to be only a few minutes per day.
      Assuming an annual exposure time of 100 hours gives annual doses of 0.1 mSv
      (body) and 5 mSv (fingers). These represent 0.5% and 1% of the relevant dose
      limits, respectively.

2.2   Contamination levels and internal radiation risk to individuals

      In all cases, the work is small-scale in nature; typically involving limited quantities
      (a few ml) of radioactive solutions.     There is the potential for contamination to
      arise, for example through small spills or the handling of contaminated articles.
      Any contamination would be expected to be low level (major spills are considered
      later) and highly localised (e.g. a small “spot” on a workbench). Air contamination
      is not expected to occur from most procedures.        Ordinary laboratory procedures
      are considered sufficient to prevent the spread of contamination and intakes of
      radioactive materials.

      In summary, internal radiation doses from normal operations are expected to be
      negligible provided that:

         Good laboratory practice is observed

         Contamination routinely arising from the work is low-level and localised

         Airborne contamination is not expected.


3.1   Nature of accidents

      The most reasonably foreseeable accident is a spill, in the worst case this would
      involve all the activity from a single (stock) vial, i.e. containing the activity levels
described in section 1.   The radiation risks associated with this are considered
3.2   Potential external radiation risk

      Tritium, carbon-14, phosphorus-33, sulphur-35 and calcium-45

      Due to the low energy of the beta emissions these are not expected to give rise to
      a significant external radiation hazard even where there is a total loss of shielding
      (e.g. due to a spill).


      In the event of a spill of an entire stock vial, the following beta dose rates might

               1 cm distance:             1 000 000 μSv/h

               10 cm distance:            10 000 μSv/h

               50 cm distance:            40 μSv/h

      A person cleaning up a spill (hands at 1 cm distance) could receive a skin exposure
      of several mSv per minute. Therefore, a serious spill could quite conceivably give
      rise to skin doses of several tens of mSv, (for comparison, the annual dose limit is
      500 mSv). Distance and shielding should both be used to minimise skin exposures
      when cleaning spills. For example, tongs or tweezers should be used to remove
      gross activity when mopping up bench spills. Thereafter, thick rubber gloves will
      provide protection for the skin.


      In the event of a spill of an entire stock vial, the following gamma dose rates might

               1 cm distance:             30 000 μSv/h

               10 cm distance:            300 μSv/h

               50 cm distance:            14 μSv/h

      A person cleaning up a major spill (hands at 1 cm distance) could receive a
      skin/finger exposure of no more than few mSv (for comparison, the annual dose
      limit is 500 mSv).       The use of tongs or tweezers to remove gross activity when
      mopping up bench spills should ensure that doses are well below 1 mSv.

3.3   Potential internal radiation risk

      In case of a major spill, it is possible that a person could become contaminated
      and ingest some activity as a result.      The maximum activity in use in any one
      procedure is typically less than 10 ALIs and, in practice, it is unlikely that an
      activity equivalent to more than 1 ALI would be spilt, even in the worst case.
      Assuming that 1% of this is subsequently ingested (this is a very pessimistic
      scenario), an internal dose of 0.2 mSv (i.e. 1% of the annual dose limit) would be
      received.     In practice, simple emergency instructions in addition to the normal
      laboratory procedures should ensure that inadvertent ingestion           is all but

This is a specific type of accident involving radioactive material and is considered
separately in this section.

4.1     Nature of accident

        Radioactive materials do not normally need to be removed from the laboratory in
        which they are used, except for the disposal of radioactive waste from the
        premises.   It is, therefore considered unlikely that sources will be lost, although
        this cannot be ruled out altogether. A reasonably foreseeable incident might be
        the accidental disposal of a radioactive material to the waste bins, for example,
        because it was not properly labelled.    Theft is also considered possible although
        very unlikely.

        The worst scenario would be an entire stock solution being tampered with by a
        member of the public.       Although containers should be clearly marked, a person
        could still easily open such a container and become contaminated as a result.

4.2     Potential external radiation risk

        Persons could potentially be exposed for much longer times than those assumed
        for employees. Consequently, doses greater than those estimated in 3.1 could be
        received. The annual dose limit for the skin/extremities of 50 mSv could certainly
        be exceeded in the case of phosphorus-32, and this might be possible in the case
        of iodine-125.

4.3     Potential internal radiation risk

        Doses similar to those described in 3.2 (i.e. 0.2 mSv, equivalent to 20% of the
        annual dose limit for the public) might be expected. In the extreme case, a person
        (e.g. a child) could deliberately ingest the material and consequently receive an
        internal dose above this limit.

5       RECOMMENDED           ACTIONS     (requirements    of   the   Ionising   Radiations
        Regulations 1999 (IRR99))

5.1 Restriction of exposure

        Basic restrictions on the work

        This assessment applies to laboratory procedures that meet the following criteria:

           The maximum activity used in a single procedure does not exceed:

                 Tritium:                 1000 MBq

                 C-14:                     400 MBq

                 S-35, P-33 or Ca-45: 100 MBq

                 P-32:                      40 MBq

                 Iodine-125     :           10 MBq

           Contamination of work surfaces is not routinely expected (other than small
             “spots” of contamination in containment such as drip trays, etc).

           Airborne radioactive contamination is not expected.

      A checklist to ensure that the above criteria are met is given at the end of this

      Protection during normal operations

      The risk assessment indicates that radiation exposures (external and internal) from
      the laboratory use of small quantities of radioactive materials are likely to be very
      low. Notwithstanding this, the following precautions are recommended as a means
      of ensuring that radiation exposures are kept as low as reasonably practicable (as
      required by the Ionising Radiations Regulations 1999):

         All new procedures should be reviewed to determine whether the “routine
          work” criteria outlined above are applicable. A checklist is available for this,
          given at the end of this assessment.     Even where the work is “routine”, it
          should be (briefly) reviewed to determine whether any additional practical
          precautions are appropriate, and these should be given on the checklist.

         A separate risk assessment should be produced for any work that does not
          meet the above criteria.

         Good laboratory practice should be observed when handling radioactive
          materials.   This includes the use of drip trays and benchkote, where
          appropriate, and the wearing of laboratory coats and disposable gloves.

         Local shielding (Perspex bench shields, boxes, etc) should be used for all work
          involving phosphorus-32.

         Local shielding (e.g. lead shielded stock vials) and distance (e.g. the use of
          tongs or tweezers) should be used when handling stock solutions of iodine-

         Training should be provided to all persons that handle radioactive materials.
          This training should explain the conclusions of this risk assessment and the
          precautions expected.

      Accidents – prevention and mitigation

      In addition to the measures to avoid and restrict spills outlined above, the
      following precautions are also considered appropriate:

         Stores for radioactive materials should be designed to prevent unauthorised
          access and minimise the effects of fire. Stock solutions should be kept in
          closed non-combustible containers, and secondary containment should be
          provided to collect any leaks.    The store and containers should be suitably

         Procedures for cleaning up spills should be provided.            These should
          include the use of shielding and distance, as appropriate, when dealing
          with major spills of P-32 or gamma emitters.                Training in these
          emergency procedures should be provided for all relevant employees.

5.2   Designated Areas

      IRR99 require the designation of a controlled area where either:

      a) radiation doses are likely to exceed three-tenths of a dose limit; or
      b) special working procedures are required to restrict radiation exposures.

      For the routine work described in this risk assessment neither of these conditions
      is present, and the designation of controlled areas is not considered necessary.

      The Regulations also require that a supervised area should be designated where it
      is considered necessary to keep the radiological conditions under periodic review.
      This is considered appropriate and hence it is recommended that all areas where
      this work is undertaken be designated as Supervised Areas.

5.3   Classified persons and individual monitoring

      Internal radiation exposures are expected to be negligible and the designation of
      classified persons and individual monitoring for intakes of radioactive material are
      not considered appropriate. Provided that simple shielding precautions are taken
      when dispensing P-32 and I-125 materials from the stock vial, external radiation
      exposures are also expected to be very low. Consequently, classification and
      individual monitoring for external radiation are also considered unnecessary.

5.4   Working procedures and supervision

      Local rules are considered appropriate as a means of ensuring that good laboratory
      practice is observed. In particular, local rules should stress the importance of the
      precautions listed in sections 5.1 and 5.2.      The appointment of a Radiation
      Protection Supervisor (RPS) in each department is considered appropriate, as a
      means of confirming that the local rules are observed.

5.5   Personal protective equipment

      Standard laboratory coats and disposable gloves are considered appropriate.

5.6   Access restrictions and training

      Only laboratory workers are allowed to gain access to the area (visitors are always
      accompanied).   Further restrictions are not regarded as necessary.     All persons
      who work with unsealed radioactive materials should receive basic training in
      radiation protection and good laboratory practice.

5.7   Workplace monitoring

      It is considered appropriate for surface contamination monitoring to be carried out:

         in individual work areas during and after the work

         on individuals to check for personal contamination before leaving the area

      A formal monthly survey of each work area (with the results recorded) is also
      recommended. Routine surface contamination levels are expected to be negligible.
      Any reading above normal background will,            therefore, require action i.e.
                             Ionising Radiations Regulations 1999

             Prior Radiological Risk Assessment for work with radioactive materials

A generic risk assessment for routine work with radionuclides in laboratories has been
prepared. This risk assessment concludes that radiation exposures of employees are expected
to be minimal provided that certain criteria are met. The purpose of this checklist is to ensure
that the proposed work complies with these criteria.    The following should be completed
for all new protocols and procedures

Protocol description:                              Proposed by:

Nuclide and activity per procedure:                Department:
H-3 (max = 1000MBq)                   MBq
C-14 (max = 400 MBq)                  MBq          Location(s) of work:
S-35 (max = 100 MBq)                  MBq
P-33 (max = 100 MBq)                MBq
Ca-45 (max = 100 MBq)               MBq
P-32 (max = 40 MBq)                   MBq          RPS for work:
I-125 (max = 10 MBq)               MBq
Surface contamination: Please indicate whether surface contamination is expected to occur
on work surfaces as a result of normal operations, and also from any likely accidents. An
indication of the activity and spread of contamination should be given where applicable:

Air contamination: Please indicate whether airborne radioactivity (as a gas, dust or vapour)
might be expected at any stage during this work:

Waste: Provide estimates of the activity of waste expected to be disposed of by the following
Gaseous waste:        MBq per day =                            MBq per month =
Aqueous waste:        MBq per month =
Organic liquid waste: MBq per week =                           Litres per week =
Solid waste (to bins): Max kBq per item =                     Max kBq per 0.1 m3 =
Solid waste (for incineration) MBq per week =
Comments by RPS:
 Is the activity used and waste within departmental limits?
 Is the procedure consistent with the generic risk assessment?
Signature:                                         Date:
                           Additional precautions required
List below any additional precautions that should be taken during the work (e.g. any
additional containment, equipment for transferring radioactive materials, spill containment
measures, etc)

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