Disposal of Scintillation Liquid

Disposal of Scintillation liquid

This information sheet outlines procedures for the handling scintillation liquid after samples have been counted.This procedure is required to:

• Document how scintillation waste should be packaged for immediate disposal or for storage undergoing decay for eventual disposal
• Document how scintillation waste should be packaged for long term storage
• Ensure that documentation exists to support the fact that waste is below 100 Becquerel/gram (Bq/g) - the criteria for disposal through our hazardous waste contractors.

responsibilities

The Chief Investigator is to ensure that these procedures are implemented and followed in their research group where scintillation counting of samples is undertaken.

The individual researcher is to ensure that scintillation vials are securely capped, labelled and stored prior to their ultimate disposal as low level radioactive waste or long term storage, whichever is applicable.

Procedure

1. After vials have been counted, they should be removed from the counter, checked that they are securely capped and placed back into their original cardboard supply trays [usually 100 vials per tray]. Ideally vials should be kept in the upright position.
2. Scintillation liquid should be kept segregated by the isotope type it contains. It is essential that long half life isotopes such as C-14 and H-3 are not mixed with any isotopes of shorter half life [that is T1/2<100 days]. Note:

• All short half life isotopes will eventually decay to a level that can be disposed of through the hazardous waste service.
• The decay process is not an option for higher activities of C-14 and H-3
• Where scintillation liquid contains mixed isotopes, it will need to be assessed on the longer half life component

1. Where the total specific activity is known to be lower than 100 Bq/g and the samples are no longer required, the vials can be left in their original trays, placed into a thick plastic waste bag, labelled and a disposal request completed as per the University hazardous waste guideline. The Radiation Waste Activity Statement must be completed in the request to show that the specific activity is less than 100 Bq/g.
2. Where the gross specific activity of the vials counted is known to exceed 100 Bq/g, vials should be securely capped and placed into containers, with snap or twist type sealable lids. When full, lids should be secured, the container appropriately labelled and then placed into:

• A long term storage area if the isotopes are C-14 and H-3, Or
• Intermediate term storage for decay if the isotopes are short lived [T1/2<100 days]. Eventually these pales can be disposed of through the hazardous waste service.

Note that the containers can be either plastic pails or steel drums. The primary aim is to provide secondary containment of the liquid and a robust packaging for storage.

1. The labelling on stored material must indicate:

• The researcher’s contact details [name, room & phone number]
• The type isotope
• The specific activity of the batch
• The date placed into storage &
• The date when the <100 Bq/g level will be reached, where applicable.

Adhesive Hazardous Waste labels are available from Safety Health and Wellbeing and are ideal for this purpose.

A copy of the printout from the counter with CPM or DPM readings must be readily available to confirm that the stated specific activity of the batch.

1. Decanting a vial’s contents into a larger container, such as a Dangerous Goods Approved 15 litre cube, for long term storage is not a recommended procedure. This requires additional and unnecessary handling, which could result in spillage during transfer, and creates a potential for a larger scale spill if the 15 litre container is damaged or leaks when in storage.

For further information contact the University Radiation Safety Officer.

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