Procedures

Management of Unsealed Radioactive Waste - Procedures

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1. Purpose and Objectives

The disposal of unsealed radioactive wastes in Queensland is controlled by the provisions of Part 5 of the Radiation Safety Act 1999 and Part 4 of the Radiation Safety Regulation 2010. This procedure provides advice on the processes required to ensure compliance with the Act and Regulation while carrying out research and teaching activities, to ensure user safety and public safety and to prevent environmental contamination. 

2. Definitions, Terms, Acronyms

Act - Radiation Safety Act 1999

Benchkote® - Benchkote® is an absorbent material designed to protect laboratory surfaces against knocks and spillage. The material is comprised of high quality, smooth absorbent paper which quickly absorbs spilt liquids, and a layer of strong polyethylene which prevents liquids penetrating to the surface of the worktop. Used Benchkote® sheets must be disposed of in the clinical waste streams and not placed in normal paper disposal waste streams.

Becquerels (Bq) - the special name for the SI unit of activity and is the number of disintegrations per second

dpm - disintegrations per minute

Regulation - Radiation Safety Regulation 2010

RSO - Radiation Safety Officer

RSPP - Radiation Safety and Protection Plan

UQ RPA - UQ Radiation Protection Advisor

Radiation Waste is classified as:

EW - Exempt Waste - Waste that meets the criteria for clearance, exemption or exclusion from regulatory control for radiation protection purposes.

VSLW - Very Short Lived Waste - Waste that can be stored for decay over a limited period of up to a few years and subsequently cleared according to arrangements approved by the regulatory authority, for uncontrolled disposal, use or discharge. This would include radioactive waste containing primarily radionuclides with short half-lives often used for research and medical purposes.

VLLW - Very Low Level Waste - Waste which does not meet the criteria as EW, but which does not need a high level of containment and isolation and therefore is suitable for disposal in near-surface landfill type facilities, with limited regulatory control. Such landfill type facilities may also contain other hazardous waste. Typical waste in this class would include soil and rubble with low activity concentration.

LLW - Low Level Waste - Waste that contains material with radionuclide content above clearance levels, but with limited amounts of long-lived radioactivity. It requires robust isolation and containment for periods of up to a few hundred years and is suitable for disposal in engineered near-surface facilities. It covers a very broad range of materials including short-lived radionuclides at high activity levels and long-lived radionuclides at relatively low activity levels.

ILW - Intermediate Level Waste - Waste which requires a higher level of containment and isolation than is provided by near-surface disposal. However, it needs no (or only limited) provision for heat dissipation during its storage and disposal. It may include long-lived radionuclides, in particular alpha emitting radionuclides that will not decay to an activity level acceptable for near surface disposal during the time which institutional controls can be relied upon, and therefore requires disposal at greater depths of the order of tens up to a few hundred metres.

HLW - High Level Waste - Waste with radioactivity levels high enough to generate significant quantities of heat by the radioactive decay process or with large amounts of long-lived activity which need to be considered in the design of a disposal facility for such waste. Disposal in deep (usually several hundred metres or more below the surface), stable geological formations is the generally recognized option for its long-term management.

3. Procedures Scope/Coverage

This procedure details ways of meeting requirements for the liquid and solid radioactive wastes produced by research laboratories using unsealed radioactive sources. Unsealed radioactive waste generated as a result of research activities at The University of Queensland may be classified as VSLW, VLLW and LLW.

All radioactive waste procedures for particular facilities will be specified in the relevant facility's approved Radiation Safety and Protection Plan (RSPP).

4. Procedures Statement

There are essentially two ways of managing radioactive wastes: dilution and dispersion, or concentration and containment. While the latter option is appropriate for materials associated with the nuclear fuel cycle, it is not required for the relatively low radiotoxicity substances used for research in the biological sciences or most other research fields at the University. Radioactive wastes can generally be disposed of safely by dilution to very low concentrations prior to release. This is recognised by international bodies and acceptable concentrations of most isotopes are specified in the regulations of all Australian states and territories.

The legislation provides for two ways in which radioactive material can be disposed of:

  • by compliance with particular schedules of activities and concentrations given in the Regulation [part 4 Sections 15, 16, and 17 and Schedules 1 or 3 of the Regulation, whichever may apply], or
  • by the granting of a specific approval [Section 26(1) and Section 58 of the Act].

5. Types of Wastes

The physical nature of the waste determines to a significant degree the actual disposal procedures to be adopted.

  • Liquid wastes divide into those that are water soluble and those based on organic solvents.
  • Solid wastes generally consist of laboratory trash (e.g. contaminated glassware, consumables) and other research material such as plant and animal tissues which still contain radioactive tracer material.

6. Management of Liquid Radioactive Wastes

6.1 Water soluble materials

61.1 General requirements

The Regulation allows for disposal of radioactive material to the sanitary sewer provided the activity concentrations are below scheduled limits. There are also requirements under other Acts and Regulations that restrict sewer disposal of certain chemicals.

In disposing of liquids to the sewers, 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.

6.1.2 Required dilutions

Requirements for the maximum concentrations of radioactive substances allowable in waste water that flows to a sewer main are given in Column 4 of Schedule 3 of the Regulation.

The point of disposal at which the concentration of a radionuclide is to be decided is the point where the sewerage pipe leading from premises joins the main reticulation line of the sewerage system. From this it might reasonably be inferred that individual laboratories could take advantage of the total water flow from a building (or the whole campus) to determine their own release criteria, provided the final concentration at the sewer main connection was below the relevant limit.

However, this approach pre­sents practical difficulties, including the need to take into account releases from other laboratories on the same property and the variability of water flow - which could be significant given that the Regulation does not allow time averaging. It would therefore be prudent for the University licensees to regard the pub­lished concentration limits as applying to their individual laboratories. Given the additional dilution that will certainly occur, this will provide a very good assurance that the University as a whole will comply with the Regulation.

6.2 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 as 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).

The Regulation requires that the concentration of a radionuclide in waste (other than where the waste is disposed of into the air, water or a sewer system) be less than half the concentration given in Column 2 of Schedule 1.

The radioactive content of the scintillant waste 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.

It is important not to mix scintillants containing different radionuclides as this would make activity assessment difficult - as well confusing matters with regard to decay times.

The activity concentrations in most scintillant wastes is likely to be well below the level of prescription although some may require storage for decay or additional dilution.

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

Flammable solvents must be stored in accordance with the requirements outlined in the Storage and Handling of Flammable and Combustible Liquids Policy (2.70.06).

7. Management of Solid Radioactive Wastes

The Regulation requires that the concentration of a radionuclide in waste (other than where the waste is disposed of into the air, water or a sewer system) be less than half the concentration given in Column 1 of Schedule 1.

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 the levels that are exempt under the Regulations.

Generally, a period of ten (10) half-lives will be more than sufficient to ensure compliance for typical solid wastes generated in the University laboratories - 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 and contaminated lab consumables 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 carbon 14, the amounts packaged for disposal will always need to be within the guidelines as there will be no appreciable decay of activity over practical time spans.

7.1 General advice on disposal procedures for solids

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

Areas in which wastes are stored for decay need to be appropriately signed and access and must be controlled by the local organisational area Radiation Safety Officer (RSO).

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

Solid wastes with a sufficiently low activity concentration 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.

8. Disposal Approvals under Section 26 of the Act

It is possible that in some rare cases, significant difficulties may arise in achieving compliance with the very conservative requirements of the schedules given in the Regulation.

There may also be cases in which the nature of the waste or the proposed method of disposal do not fit clearly into the categories set out in Part 4 of the Regulation.

Section 26 (1) (b) of the Act provides for a specific disposal approval to be granted. The criteria for assessment of an application are set out in Section 58.

The assistance of the UQ Radiation Protection Adviser (RPA) should be obtained where the need for such an application arises.

9. Requirements for Record Keeping

Record keeping is required for all radioactive waste categories.

Holders of use licences are required to record details of the disposal of unsealed radioactive substances in a register provided by the possession licensee for the practice.

For each disposal operation a record should be kept which includes:

  • the date,
  • the manner of disposal,
  • the isotope,
  • the amount disposed of, and
  • the user licensee responsible.

Where small amounts of radioactive material are continually disposed of in the course of particular experimental procedures, the user should make a note in the use/disposal record for the particular item purchased, e.g. for the records pertinent to one particular stock solution vial.

While it is the user licensee who is formally obliged to keep these records, the Radiation Safety Officer (RSO) for a practice has a specific function to monitor and review such records to determine whether the Radiation Safety and Protection Plan (RSPP) for the specific practice and other radiation safety standards are being complied with.

Custodians
Director, Occupational Health and Safety
Mr Jim Carmichael
Custodians
Director, Occupational Health and Safety
Mr Jim Carmichael