Prior Risk Assessment

‘Open / Unsealed Source’

Ionising Radiation Work Activity

A risk assessment must be prepared for all ionising radiation work activities. This assessment form should be completed for the use of ‘open / unsealed’ radioactive sources and be agreed by the Departmental Radiation Protection Supervisor and approved by the Radiation Protection Officerbefore the work starts. Additional guidance and information at the end of this form is provided to assist in the preparation of the assessment.

1. General Information

Activity Title:
Assessment Code:
(e.g. Group Leaders initials + 1, 2, etc)
Assessment Prepared by:
Name of Group Leader responsible for the safety of the work:
Department:
Location(s) of Work:
(area / room)

2. Activity Details and Hazard Identification

Activity Details
Why are you proposing to use radioactive material? If there is a safer alternative technique, why is it not being used?
Radioisotope and Molecule:
Radioisotope(s), principle emissions (i.e. ,β,) and energies (MeV) (see tables):
Form of Material:
(e.g. liquid / powder/gas)
Identify the hazardsusing information supplied by the supplier of the radioisotope together withguidance information at the end of this form:
External radiation hazard(i.e. medium-high energy isotopes)
Internal radiation hazard (Ingestion)(all isotopes could potentially be ingested)
Internal radiation hazard (Inhalation)(i.e. is it volatile?)
Internal radiation hazard (Absorption)(i.e. is the material easily absorbed through the skin) / Yes/No
Yes/No
Yes/No
Yes/No
Maximum amount of radioactive material (MBq) / Experiment:
Maximum Stock Activity to be Stored (MBq):
Brief Description of Work Activity:
Hazardous Procedures:
Identify and describe those stages of the work activity most likely to cause an exposure
Estimated Handling Time / Expt:
Estimated Frequency of Experiment (no. times per annum):
Persons at Risk
Identify all categories of people who may be directly or indirectly at risk:
Considere.g. laboratory staff / postgraduates, undergraduate students, cleaners / contractors
Waste Disposal Requirements
Waste Disposal Routes / Solid / Aqueous Liquid
(via designated sinks) / Organic Scintillant / Gas
Estimate % to each route
Estimate of Monthly Disposals (MBq) and % of local sink disposal limit (aqueous liquid only):

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Estimated External Radiation Exposures
1. Dose Rates:
Estimate the unshielded external radiation dose rate(mSv/min) to which anyone could be exposed during the work for high energy beta (includes 32P & 36Cl) and gamma emitting radioisotopes, using the formulae in the Guidance Notes at the back of this form. Calculations need to consider dose rate to hands (extremities) from a distance of 1 cm, and dose rate to the whole body from a distance of 30 cm. This shouldbe supported by actual radiation dose rate measurements whereavailable.
Note:External Dose rate calculations are not required for3H as the betas have insufficient energy to penetrate the dead layer of skin and do not present an external dose hazard. Other low energy Beta emitters (<0.3 MeV) (includes 14C, 45Ca, 33P, 35S) can penetrate the outer layer of skin and give a skin dose (these are calculated later in the ‘accident considerations’).
a)‘Extremity’ (hand accessible) dose rate (mSv/min) (D; calculated at 1cm):
  • Dose rate whendispensing radioactive material from stock container (assume first use of stock material): For example, dose rate from stock bottle containing 9.25 MBq P-32 when full

  • Dose rate from radioactive material used in a typical experiment: For example, dose rate from experiment that uses1.8 MBq P-32

b)‘Whole Body’ dose rate (mSv/min) (D; calculated at 30 cm) from radioactive material used in a typical experiment:
2. External Exposures:
The dose rates (calculated above) can now be used to estimate the annual exposures you and other laboratory workers would receive if work were carried out without local shielding. To estimate annual external exposures to the hands or whole body requires you to consider approximately how long you will be exposed to the radioactive material during the experiment, and approximately how many times a year you will be performing the experiment.
Unshielded Annual External Exposure=
Dose rate (D) X duration of exposure at each distance (mins.) X annual frequency of exp’t
a)Annual ‘extremity’ dose (calculated at 1 cm)(mSv):
  • Fromdispensing radioactive material removed from stock bottle:

  • From radioactive material used in a typical experiment (consider the main handling stages of the expt.):

  • Express total annual extremity dose (from dispensing & experimental work)as a % of annual ‘extremity’ dose limit(500mSv):

b)Unshielded annual ‘whole body’ dose:(calculated at 30 cm)(mSv):
Express dose as a % of annual ‘whole body’ dose limit (20mSv):

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Internal Radiation Exposure Risk
Establish if there is a significant risk of radioactive materials being inhaled, ingested or absorbed. Refer to the safety data provided by the supplier of the materials and the informationat the back of the document for guidance.
Ingestion:
Assume a worst case scenario (because ofvery poor working practices) of 5% of the total experimental activity being ingested.
Dose (mSv) / experiment:
Annual Dose (mSv):
Inhalation:
Is the radioisotope volatile or could the work activity generate gaseous emissions? / Yes/No
If yes, what is:
a) the dose (mSv) / experiment
b) annual dose (mSv)?
(Assume a worst case scenario of 5% of the total experimental activity being inhaled).
Skin absorption / penetration:
Is the radioisotope easily absorbed through skin? / Yes/No
If yes, what is:
a) the dose (mSv) / experiment
b) annual dose (mSv)?
(Assume a worst case scenario that 5% of the total experimental activity is absorbed through skin).
Total annual Internal whole body Dose (mSv):
(i.e. sum of ingested, inhaled and absorbed doses)
Express dose as a % of annual ‘whole body’ dose limit (20mSv):
Total Annual Whole Body Dose Summary(without controls)
a) External ‘whole body’dose estimate:
(see external ‘whole body’ dose (mSv / annum)calculation (2b) above)
b) Internal ‘whole body’dose estimate:
(see calculation above) (mSv / annum)
TOTAL (UNCONTROLLED) ANNUAL WHOLE BODY DOSE (a + b):(mSv / annum)
Identification of Control Measures
Potential doses must be reduced AsLowAsReasonablyPracticable
The hierarchy of control measures for restricting exposure:
1. Engineering controls, safety features and warning devices
2. Administrative controls
3. Finally, personal protective equipment.
Control Measure Considerations / Description of Control Measures
Assuming justification for the use of radiation has been made earlier, confirm that the amount of material has been optimised for your work.
Is radiation shielding required?
e.g. 1 cm Perspex for 32P or
lead impregnated Perspex for 125I
If yes, describe what shielding will be provided. The following should be available: screens, shielded storage / transport / waste boxes / microtube blocks.
What measures are being taken to minimise exposure to hands from high energy betas (>0.3 MeV)?
Consider minimising time exposed to radiation; maximising distance (e.g. use of tongs etc), and shielding (Perspex blocks for pipettes).
If volatile material has been identified, or if the work activity generates gaseous emissions, what measures will be taken to prevent inhalation?
Containment: how will the spread of contamination be controlled?
  • Describe access restrictions to radiation work areaand storage arrangements for stocks and waste material
  • Note:a basic workstation should be established consisting of Benchkote (absorbent side up); drip tray; warning tape, tissues, decontamination liquid, appropriate contamination monitor

Type of contamination / dose monitor to be used?e.g. Mini Instruments Type EP15
Note: since monitors are not sensitive to detect 3H, ‘wipe testing’ is used to detect 3H
Designation of radiation room / area:
Supervised or Controlled?
(most areas used for modest amounts of unsealed sources are designated a ‘Supervised’ area unless high risk activities are taking place- see Guidance Notes for further details)
Approved ‘Local Rules’ in place?
Written protocol in place?
A protocol briefly describing how the procedure will be performed safely (including key safety features to be applied) MUST be prepared for workers & attached to this report.
Is Personal Dosimetry required? (required for high energy betas (32P, 36Cl), & gammas)
Will radioactive material be transported outside the radiation room / area? If yes, describe arrangements for the safe transport of material.
Note: movement of radioactive materials in or between labs.Must be minimised. Where it is taken outside the lab.Work area, double containment must be used to reduce the risk of spillage.
Training:
  • Research Groups: confirm that all workers will receive formal University training + ‘local practical induction training’
  • Undergraduate Teaching Practicals: describe the training to be provided

Lone Working: does lone working (e.g. out of normal working hours) need to be avoided for this activity? Lone working restrictions should be applied to all activities involving stocks of 32P and 125I.
Identify any other measures that will be used to control exposure?
‘Personal Protective Equipment’ (PPE)What PPE will be used?
Note: all workers must wear a lab. coat, disposable gloves as a matter of course. Safety glassesmust also be used for splash protection when manipulating all liquid isotopes and for shielding eyes against high energy isotopes such as 32P and 125I
Are further measures still required to reduce a potential dose ‘as low as reasonably practicable’?
Estimate Effectiveness of Local Shielding
(if applicable) at reducing annual exposures:
Shielded annual ‘whole body’ dose:
(assume appropriate local shielding (e.g. from shields, Perspex blocks etc) reduces dose from0.3 MeV beta emitters by a factor of 1x106). Shielding should be used for all >0.3 MeV beta emitters, and gamma emitters if, a) accessible ‘whole body’ dose rate is > 2.5 µSv/h, and b) accessible extremity dose rate is >75 µSv/h
Express dose as a % of annual ‘whole body’ dose limit (20mSv):
Possible Accident situations
Skin contamination dose: assume 5% of total stock material(not experimental activity) is spilt uniformly on hand and left on skin for 1 hour (refer to Table 2, ‘External Exposures’ in Guidance Notes for dose from uniform deposit of 1kBq/cm2 on the skin)
Loss/theft of material: describe measures to prevent loss / theft of material e.g. storage facilities and any other security measures
Failure of fume cupboard: describe steps to be taken in the event of fume cupboard failure during use
Note: All ionising radiation workers should be familiar with the procedure for dealing with spillages of radioactive material. This procedure is documented in the ‘local rules’ of all radiation rooms / areas, and should be included as part of the ‘local practical induction training’ provided to all radiation workers.
Contamination Considerations
Estimate the surface contamination (Bq/cm2) that would occur if the whole aliquot of stock material (not experimental activity)was spilled over an area of 300 cm2
Estimate the airborne contamination that could occur if the whole aliquot of a volatile stock material was spilled
What (if any) equipment is expected to become contaminated during the course of the work activity? Describe the extent of any contamination and how this will be decontaminated.
Group Leader’s Declaration:
  1. I confirm that all the information contained in this assessment is correct.
  2. I will ensure that no work associated with this activity will be carried out until this assessment is approved and all necessary control measures are in place.
  3. I have considered ways of conducting this work using non-radioactive methods and I cannot find a suitable non-radioactive alternative. The amount of radioactive material will be kept to a minimum.
  4. I agree to provide or organise full and proper training for all persons involved in this specific activity to ensure they use radioactivity safely.
  5. I will monitor the work of all persons involved in this activity and ensure that both Local Rules and University of York rules / codes of practice are followed.

Name: / Date:
Signature:

SEND THE COMPLETED FORM TO YOUR RADIATION PROTECTION SUPERVISOR FOR APPROVAL BEFORE WORK STARTS

Assessment Review:
Review and update your assessment when significant change(s) in practice has occurred (e.g. activity limits, procedure, radiolabelled compound) or an inspection shows that a review is necessary.
Revised assessments to be sent to Biology RPS for approval.
RPO approval
Name: / Date:
Signature:

1

Guidance Notes

1. Estimation of Radiation Exposures

Simplified formulae for estimation of external and internal radiation exposures are provided below and should be suitable for most scenarios.

a) Estimation of External Dose Rates

(i) High Energy Beta-emitting Radioisotopes

Refer to Table 1, ‘Properties of Radioisotopes’, to determine the energy of the beta emitter(s) being used.

  • Beta particles having energies <0.3 MeV do not penetrate the skin, and are considered to present a negligible external dose risk. As such, there is no need to estimate external doses for low energy beta-emitting radioisotopes.
  • For beta-emitting radioisotopes with energies >0.3 MeV (e.g. 32P and 36Cl) calculate external dose rates using the following formulae

Extremity dose rates (@ 1 cm): D = 1.3 x A
For whole body dose rates (@ 30 cm): D = 1.5 10-3 x A
where:
D = dose rate in mSv/min
A = the experimental activity in MBq (1 mCi = 37 MBq, 1 MBq = 27 µCi)
  • 32P and 36Cl are both high energy beta-emitting radioisotopes that are capable of giving significant extremity (i.e. hand) doses.

32P / Experimental Activity / Extremity Dose Rate
37 MBq (1 mCi)
3.7 MBq (0.1 mCi)
1 MBq (27 µCi) / 2886 mSv/h (3Sv/h)
289 mSv/h
78 mSv/h
  • If you are handling high activities of 32P and 36Cl your risk assessment must carefully consider and identify how exposure will be minimised. You will need to consider:
  • dispensing material, especially stock material- a Perspex ‘pipette guard’ should be used
  • how you will manipulate radio-labelled materials in centrifuge tubes, eppendorf tubes etc
  • how you will transfer radioactive material onto chromatographic plates, gels etc, and how you will handle the plates and gels
  • A safety protocol should be written describing how you will handle radioactive materials so as to reduce exposure to a level that is as low as reasonably practicable.

(ii) Gamma-emitting radioisotopes

For gamma-emitting radioisotopes:

D= CA
where
D = dose rate in mSv/min
A = the experimental activity in MBq (1 mCi = 37 MBq, 1 MBq = 27 µCi)
C = gamma factor at either 1 or 30 cm
Radioisotope / Gamma Factor (C) for ‘Extremity’ Dose Rates (1 cm) / Gamma Factor (C) for ‘Whole Body’ Dose Rates (30 cm)
Cr-51 / 8 10-4 / 8 10-7
1-125 / 5.910-3 / 6.510-6
Na-22 / 7 10-2 / 7 10-5

b) Estimation of Internal Doses

Internal doses (also known as the ‘Committed Effective Doses’)can be estimated using ‘dose coefficients’ which give the dose per unit intake (Sv/Bq) for different radioisotopes and give a useful indication of the radiotoxicity of a radioisotope Dose coefficients vary depending on a number of factors including the radioisotope, the labelled substance and route of entry into the body. For the purpose of this assessment the most restrictive effective dose coefficients for the common isotopes are given in the table below.

Internal Doses Per Unit Uptake

  • Radioisotope
/ Ingestion / Inhalation
Dose coefficient Ingestion
Sv/Bq* / Intake for 1 mSv dose (MBq) / Dose coefficient Inhalation
Sv/Bq* / Intake for 1 mSv dose (MBq)
H-3 Water / 1.8 x 10-11 / 55.6 / 1.8 x 10-11 / 55.6
H-3 Organically bound tritium / 4.2 x 10-11 / 23.8 / 4.1 x 10-11 / 24.4
C-14 / 5.8 x 10-10 / 1.7 / 5.8 x 10-10 / 1.7
P-32 / 2.4 x 10-9 / 0.42 / 2.9 x 10-9 / 0.34
P-33 / 2.4 x 10-10 / 4.2 / 1.3 x 10-9 / 0.77
S-35 / 1.9 x 10-10 / 5.2 / 1.1 x 10-9 / 0.91
Ca-45 / 7.6 x 10-10 / 1.3 / 2.7 x 10-9 / 0.37
I-125 / 1.5 x 10-8 / 0.067 / 7.3 x 10-9 / 0.14

*Council Directive 92/29/Euratom, Tables C.1 and C.2

Example of Internal Dose Calculation

Consider internal dose from work activity involving P-32:

  • Assume 5% of total activity 10 MBq (i.e. 0.5 MBq) is ingested because of poor handling practices
  • Since P-32 gives an ingestion dose of 2.4 mSv / MBq, 0.5 MBq would give a dose of 1.2mSv

Absorption

  • Some organic compounds may be absorbed through surgical gloves
  • Some tritium compounds and C-14 labelled halogenated acids can be easily absorbed through skin

Inhalation

  • Consider the possibility of your work activity generating radioactive carbon dioxide; this must be contained to avoid inhalation.
  • Radiolysis of sulphur-35 labelled amino acids may lead to the production of labelled volatiles such as sulphur dioxide, hydrogen sulphide and acidic gases. Open sulphur-35 vials in a fume cupboard to avoid inhalation of radioactive volatiles.
  • Freezing or acidification of solutions containing iodide ions can lead to the formation of volatile iodine.
  • Active aerosols can be produced by opening a vial of high activity radioactive iodine- open vials of iodine-125 in a fume cupboard to avoid inhalation of volatile material and exposure to aerosols.

2. DESIGNATION OF LABORATORY FACILITIES

Laboratories used for open source radiation activities are typically designated either a ‘Supervised’ or ‘Controlled’ area. Designation of the laboratory shall be determined after consultation with the departmental Radiation Protection Supervisor with assistance from the University's Radiation Protection Advisor where necessary.

Designation of areas is helpful to define areas where radiation work with unsealed sources is being used, even if the conditions are insufficient to consider a supervised or controlled area.

Supervised Areas

An area is designated a ‘Supervised’area where:

  • annual dose to persons is likely to exceed 1 mSv (whole body) or 50 mSv (skin and extremities)
  • where conditions need to be kept under review to determine whether it should be designated as a controlled area

In practice, ‘Supervised’ areas are normally appropriate,and designated for laboratories handling modest amounts of unsealed / open radioactive materials. Working procedures for these radiation activities are likely to be similar to those required for good laboratory practice; these are not regarded as a specified system of work and the designation of a controlled area should not be necessary.

Areas are often designated as Supervised areas on the basis of surface contamination reflecting the need for periodic contamination monitoring. Access restrictions might be applied even though the area is not designated a controlled area.

Controlled Areas

An area is typically designated a ‘Controlled’area where:

  • annual dose to persons is likely to exceed 6 mSv (whole body) or 150 mSv (skin and extremities) (persons working in such an area would have to be designated as ‘Classified persons or work under a written system of work’)
  • the dose rate averaged over a working day exceeds 7.5 µSv h-1
  • if only the hands are exposed, the dose rate averaged over a working day exceeds 75 µSv h-1
  • there is a significant risk of spreading contamination outside the area
  • persons entering the area are required to follow ‘special procedures’ which are designed to restrict exposure or limit the probability and magnitude of a radiation accident.

Part Controlled