Fast Links:

• Guidelines for working with radioactivity
• Radiation Badges
  • Photon radiation (X and gamma rays)
  • Beta radiation
  • Using dosemeters
  • Wearing periods
• Radioactive waste
  • Types of wastes
  • Management of liquid radioactive wastes
    • Water soluble materials
    • Organic solvent wastes
  • Management of solid radioactive wastes
  • General advice on disposal procedures for solids
• SASVRC Radiation SAfety and Protection Plan (pdf document)

1.1 Guidelines for working with radioactivity

• All laboratories in which radioactive substances are stored or used must be appropriately signed with the radiation warning symbol and the legend: "Caution - Radiation Hazard" - or other suitable wording as appropriate to the circumstances.
• No unauthorised persons are to be permitted to enter a radioisotope laboratory or use radioactive materials. All visitors shall be accompanied by the radiation safety officer (RSO).
• Records of all stocks of radioactive substances must be kept in each laboratory. The following information shall be recorded:
  (a) type and activity of each substance
  (b) date of receipt
  (c) place of storage or use
  (d) date and manner of disposal.
  Records shall also be kept of the progressive use of each stock solution container, details recorded shall include: the amount used, the date and the name of the user.
• The RSO is to be contacted before purchasing any radioactive substance not previously used in the laboratory or included on the practice licence. There may be a need for the licence to be amended before the substance can be obtained, and there will in any case be a need to obtain information regarding the safety measures appropriate to the particular substance. Additional protective equipment or changes to monitoring instruments and techniques may be required to enable the substance to be used safely.
• Radioactive substances must only be disposed of in accordance with the Radioactive Substances Regulation 1961 and the NH&MRC Code of practice for the disposal of radioactive substances by the user (1985). Detailed procedures are given in a separate procedure sheet.
• The following protective clothing is to be worn when working with radioactive isotopes:
  (a) laboratory coat
  (b) gloves appropriate to the chemical solvents being used
  (c) safety glasses (if aerosols may be generated outside a Biosafety cabinet)
  (d) closed footwear.
• Active and inactive work areas are to be segregated.
• Eating, drinking, smoking or application of cosmetics are not permitted in the laboratory.
• Food and drink for human consumption shall not be brought into the laboratory and must never be stored with radioactive substances.
• All containers in which radioactive materials are stored must be clearly marked with a self adhesive label bearing the radiation symbol, details of the chemical compound, radionuclide, activity, the date and the name of the person responsible.
• Where there is a risk of contamination to the surface of the laboratory bench, the surface must be covered with an appropriate absorbent material.
• All work with liquid unsealed sources is to be carried out over a spill tray.
• Operations which could produce a radioactive vapour, spray, or dust must be carried out in an appropriate fume cupboard.
• Operations using high energy beta emitters (for example 32P) shall be performed behind perspex shields of appropriate thickness - 10 mm will be sufficient for all radionuclides used in SASVRC. Implement the inverse square law at all times for the safety of all workers.
• Where high specific activity radioactive solutions are to be manipulated, appropriate handling equipment such as forceps and perspex holding blocks, must be used. All work involving radioactive iodine shall be performed in compliance with the Safety Guideline specific to this work.
• Prior to leaving the laboratory, working areas should be monitored for radioactive contamination. Any contamination detected should be removed so that levels are comparable with background. Results of monitoring and of any decontamination performed shall be recorded in a log book of laboratory use.
• The RSO must be contacted when any spill or other accident involving radioactive materials occurs.
• All laboratory users should wash and monitor their hands prior to leaving the laboratory.

1.2 Radiation Badges

There are legislative provisions for the monitoring of persons who are exposed to radiation in the course of their work (Part VI, Radioactive Substances Regulation 1961). In determining who needs to be monitored there are two important factors:

The preferred monitoring techniques for a number of types of ionizing radiation are outlined below.

1.2.1 Photon radiation (X and gamma rays):

Thermoluminescent (TLD) dosemeters are the most appropriate means of monitoring the radiation exposure of users of gamma emitters - including unsealed sources of ¹²⁵I and 51Cr and sealed sources such as ¹³⁷Cs and ⁶⁰Co.

TLD personal dosemeters are available from the Queensland Radiation Monitoring Service via the SASVRC Administrative Officer.

1.2.2 Beta radiation:

Tritium, ¹⁴C , ³⁵S and ³³P have relatively low average beta energies and external monitoring will be of little value (none in the case of tritium) when the relatively small amounts typically handled in the laboratories are considered. In any case, the principal hazard of these substances is from inhalation or ingestion rather than from external exposure and control measures are directed at entirely preventing the exposure rather than at monitoring.

The Harshaw® dosemeters supplied by the Queensland Radiation Monitoring Service are also sensitive to beta radiation, although the lower energy limit for useful results has not been characterised. However, from theoretical considerations it is likely that these dosemeters, like the TLD units, will be useful only for ³²P (and other high energy beta emitters listed above) and not for monitoring users of ¹⁴C and ³⁵S or ³³P.

1.2.3 Using dosemeters

• Dosemeters should only be worn in the workplace and should be returned to a designated location at the end of the work period.
• All dosemeters should be stored in the same location when not in use together with any control dosemeter issued. The area chosen for dosemeter storage must be located away from sources of radiation.

• Dosemeters are issued to a particular person (unless supplied as spares). They should not be worn by any other person or used for any purpose other than the monitoring of that person's exposure to radiation. The use of dosemeters as area monitors or for other radiation dosimetry activities can only be undertaken by arrangement with the issuing service and with the approval of the statutory authority, the Radiation Health section of the Queensland Health Department

1.2.4 Wearing periods

PRACTICE CATEGORY - Unsealed sources research laboratories
DOSEMETER WEARING PERIOD - 1 month

1.3 Radioactive waste

The disposal of unsealed radioactive wastes in Queensland is governed by the 1961 Regulation made under the Radioactive Substances Act. This guideline provides advice on the procedures required both to ensure compliance with the Regulation and also with the more recent recommendations of the National Health and Medical Research Council (NH&MRC). Please read the "Management of unsealed radioactive wastes" document prepared by The University of Queensland Occupational Health & Safety Unit.

As a general principle, the waste management methods adopted by SASVRC must have the goal of ensuring that radiation doses to the public resulting from disposal practices are
insignificant. There are essentially two ways of achieving this: the dilution and dispersion of radioactive wastes or their concentration and containment. While the latter option is appropriate for materials associated with the nuclear fuel cycle, it is not required for the low radiotoxicity substances used in biological sciences research work. These can be disposed of safely by dilution to very low concentrations prior to release. This is recognised by the NH&MRC and is reflected in the regulations of all Australian states and territories.

1.3.1 Types of wastes

Procedures for dealing with all of these waste types are given below:

1.3.2 Management of liquid radioactive wastes

a) Water soluble materials

General requirements
In disposing of liquids containing radioactivity, precautions are required to prevent splashing or aerosol formation which could spread contamination or create a respirable fraction. Most existing laboratories will only have standard (or deep) laboratory sinks rather than the "flushing rim" type which allows flushing with known volumes of water while minimising splashing. Liquids can be diluted and flushed quite safely in conventional sinks provided suitable arrangements are made to prevent splashing and to allow for the gradual flow of waste liquid into a stream of water as it runs to waste. The sink used for disposal should have a direct connection to the sewer and should be clearly signed as the designated disposal point.

Required dilutions
Requirements for the maximum concentrations of radioactive substances allowable in waste water are given in Section 82(2) of the Radioactive Substances Regulation 1961. The Regulation is made under the Radioactive Substances Act 1958 - 1978 and consequently has the force of law. The National Health and Medical Research Council (NH&MRC) has published requirements for the sewer disposal of soluble radioactive materials in their Code of Practice for the Disposal of Radioactive Wastes by the User (1985). In this code the NH&MRC recommends sewer disposal limits of no more than twenty times the Annual Limit on Intake by ingestion (ALI ing ) for each user (i.e. licenced practice or laboratory) per seven day period. The annual limits on intake are published by the International Commission on Radiological Protection (ICRP) and the most recent revision was made in 1990.

The maximum concentrations given in the Regulation should be used to determine dilutions and the NH&MRC Code requirements used as the upper bound on the amount of material disposed of. The required dilution factors for a number of common radionuclides are given in Table 1.

Table 1

¹²⁵I and ³³P do not appear in the Regulation, the values given for ¹²⁵I are based on Western Australia's requirements. For ³³P the same values as ³⁵S are used because the radiotoxicities are virtually identical.

b. Organic solvent wastes

While the use of organic scintillants is now generally discouraged, there may be occasional use made of them for some particular applications. Solvent waste cannot be disposed of to general waste streams because of the hazardous properties of the solvent itself, even where the radioactive content is insignificant. Consequently, solvent wastes must be collected in drums according to solvent type and then disposed of as chemical waste (generally this will mean processing for solvent recovery).

Although the potential for exposure of humans is absolutely minimal, only materials which are not prescribed radioactive substances can be released for reprocessing, therefore only solvents with a radioactive content of less than 74 kBq activity per kg of solvent can be treated in this way. The radioactive content of the waste scintillant can be assessed by counting a sample in a liquid scintillation counter with automatic quench correction. Concentrations in dpm per litre can be converted to becquerels per litre by dividing by 60.

NB: It is important not to mix scintillants containing different radionuclides as this would make activity assessment difficult - as well as confusing matters with regard to decay times. In general, activity concentrations in scintillant waste will be well below the level of prescription.

Where solvents have to be stored for decay, they must be appropriately labelled with details of the contents, (i.e. chemical nature of the solvent, the radioisotope and the activity) the person responsible and the date after which the solvent can be disposed of.

NB: Flammable solvents must be stored in accordance with the requirements outlined in the Flammable and Combustible Liquids Safety Guideline.

1.3.3 Management of solid radioactive wastes

The NH&MRC Code of Practice for the Disposal of Radioactive Wastes by the User (1985) gives details of procedures for disposal of solid wastes with significant radioactive content into landfill sites. Such arrangements are dependent on the approval and co-operation of the local government authorities and have not been established in this State. This section of the Code is therefore effectively inoperable in Queensland and more stringent controls must be observed.

The 1961 Regulation excludes sources from control where the activity is less than the Prescribed Minimum Amount for the isotope concerned (or where the substance is present in a concentration of less than 74 kBq per kg). However, these requirements do not reflect current international recommendations based on more up-to-date knowledge of the toxicity of radioactive substances.

NB: There are some substances which remain hazardous even at sub-licenseable levels. As well as satisfying the legal requirements we need to adopt practices which ensure that radiation doses to members of the public arising from disposal processes are restricted to insignificant levels. To achieve this, short lived solid wastes (i.e. those with half lives of the order of less than a few months) should be retained until the activity has fallen to about 1% of the minimum Annual Limit on Intake (ALl min ) as given in ICRP Publication 61.

Table 2 gives the suggested maximum amounts of various radionuclides which may be disposed of without further controls (and for comparison, the Prescribed Minimum Amounts given in the Regulation).

Generally, a period of ten (10) half-lives will be more than sufficient to ensure compliance for typical solid wastes generated in the laboratory - although, even in cases where the activities are believed to be very low, it would be prudent to store the material for a period consistent with the highest activity likely to be present.

In practical terms this means that the person who creates the waste will need to make some assessment of the activity present in materials such as discarded wipes, pipette tips or contaminated benchkote that form the bulk of solid wastes from laboratories. While a survey meter can be used to detect the presence of activity, attenuation by packaging material and irregular source geometry can lead to substantial underestimation of the amount of active material present. It is best to err on the side of caution and store a package for a longer period if there is any uncertainty.

With tritium and ¹⁴C the amounts packaged for disposal will always need to be within the guidelines as there will be no appreciable decay of activity over meaningful time spans.

Table 2

1.3.4 General advice on disposal procedures for solids

As with liquid wastes, solid wastes being stored for decay need to be labeled with details of the radioactive content, the person responsible and the date after which the material can be disposed of.

Areas in which wastes are stored for decay need to be appropriately signed and access must be controlled by the Radiation Safety Officer.

Wastes which can be disposed of as non-radioactive may still have other hazardous properties, that is they may contain substances with infectious, flammable, toxic or carcinogenic properties. Disposal of such wastes must comply with the requirements relevant to these properties.

Solid wastes with a sufficiently low level of activity to allow uncontrolled disposal, and which have no other hazardous properties, must not bear any radioactive or other warning labels. Empty packaging which once contained radioactive materials must also have all hazard warning labels removed.