Sealed sources are sources of ionising radiation (IR).They contain radioactive substances and are manufactured so that in normal use radioactive material cannot be dispersed, thereby avoiding any contamination hazard. Examples are radiochemical powders encapsulated in materials such as metal, plastic or epoxy resin, radionuclides electro-deposited onto carrier metals, and radioactive metal foils.
The most commonly used sealed sources in the University are those which are incorporated into analytical laboratory instruments but there are other applications for non-incorporated sealed sources such as instrument calibration, thickness, density and level gauges, radiography sources for non-destructive testing, irradiators for sterilisation, smoke detectors and static eliminators.
High Activity Sealed Sources (HASS) are classified separately because they contain very high levels of radioactivity, presenting higher risks to human health and the environment.
There are strict regulations governing use and security of sealed sources in the workplace. Anyone wanting to acquire and use sealed sources must follow the instructions below. Additional conditions for HASS must be met including a higher level of security and financial requirements for ultimate disposal.
The instructions represent best practice in restricting exposure to ionising radiations (as low as reasonably practicable, ALARP) and are in accordance with ‘best available technique’ (BAT) to prevent contamination of the environment with radioactivity.
The instructions apply to all the University campuses and to all Departments of the University.
Ionising radiation from sealed sources must only be used if there is no safer alternative way of carrying out the work and use of ionising radiation is unavoidable i.e. use of sealed sources must be justified.
2. Environmental Permit
Environmental Permits issued by the Environment Agency are the means by which the keeping, use and ultimate disposal of radioactive substances are regulated.
The main University campus site has an Environmental Permit for sealed sources.
Before radioactive sealed sources are acquired and or brought onto University premises a check must be made that the Environmental Permit is valid (a) for the intended work activity (b) for the particular radionuclide and amount (activity level) contained in the sealed source.
If the activity exceeds a certain level the sealed source must be classed as HASS (High-Activity Sealed Source). A special Permit is required with additional conditions attached (see Instruction 18).
If a new sealed source is not covered by an existing Permit a variation to the Environmental Permit must be applied for. The acquisition must not proceed until a Permit variation is granted.
The University Radiation Protection Officer is responsible for submission of applications for permit variation. There are charges for Permit variations and it takes approximately 3 months from application for a Permit variation to be granted.
A copy of the Environmental Permit must be displayed with the name(s) of the person(s) supervising the keeping and use of the sealed source.
3. Risk assessment
A risk assessment must be carried out to identify the measures necessary to restrict the exposure of employees and others from ionising radiation. The work must not begin until the risk assessment has been undertaken.
The risk assessment must identify exposure protection measures, such as safety features, maintenance requirements, designation of areas, radiation monitoring regimes, staff training needs, and plans for controlling exposure in the event of reasonably foreseeable accidents.
4. Area designation
The risk assessment (Instruction 3) must identify whether a sealed source should be used in a Supervised or Controlled Area, based on dose rates from the source.
A Supervised Area must be designated if;
• the annual radiation dose to an employee (aged 18 or over) working in the area might exceed 1mSv,
• it is necessary to keep conditions in the area under review in case re-designation as a Controlled Area is required.
A Controlled Area must be designated if;
• the annual radiation dose to an employee (aged 18 or over) working in the area might exceed 6mSv, i.e. 7.5µSv.hr-1.
• the risk assessment indicates that “special procedures “ must be followed to restrict exposure during normal operations or limit the probability of an accident,
• where access to anyone not connected with the work must be prevented.
Warning signs must be displayed at the entrances to designated areas.
5. Local Rules.
Written instructions in the form of Local Rules must be produced for any Controlled Area or Supervised Area.
Local Rules must give instruction on carrying out work with sealed sources in ways that protect against the risk of radiation exposure, and give instructions on what to do in the event of an accident (a contingency plan). They must also include the name of the Radiation Protection Supervisor for the Area, a description of the Controlled or Supervised area, reference to relevant risk assessments and instruction on what monitoring must be carried out.
Local Rules must be on display in the area in which the sealed source is located.
6. Radiation Protection Supervisor
A Radiation Protection Supervisor must be appointed for the area in which the sealed source is located.
7. Accounting for sealed sources.
Sealed sources must have on them in clearly visible form, a unique identification number, the word ‘radioactive’ and an ionising radiation (trefoil) warning symbol.
An up-to-date inventory of sealed sources must be kept. The University uses IsoStock for this purpose, a computer-based source accounting system. Details of radioactive sealed sources must be logged on IsoStock for auditing purposes. Information which must be provided is:
• Date of first receipt on the premises.
• The manufacturer’s unique identification number marked on the sealed source.
• The number of MegaBecquerels contained in the source at the time of receipt.
• The normal location on the premises.
Any additional written information supplied with a sealed source by the manufacturer and or supplier must also be kept locally where the sealed source is usually stored or used. For example how the sealed source is marked, details of its radioactive content, description of the encapsulation method.
8. Classified persons
Anyone carrying out work with sealed sources where there is a risk of annual whole body dose of more than 6mSv per annum or a finger dose more than 150mSv, must be registered as a Classified Person.
The need to register Classified Persons will be identified by the risk assessment (Instruction 3).
Classified Persons must have a medical carried out by a Health and SE appointed doctor. Medicals must be arranged through the Health, Safety and Occupational Health Services.
Personal radiation exposure monitoring (dosimetry) must be provided if the risk assessment (Instruction 3) indicates that it is necessary. There are two types of dosimetry badge; film badges for measuring whole body radiation, changed at 2 monthly intervals and thermoluminescent devices (TLD) finger badges for measuring doses to the hand, changed monthly.
If risk assessment indicates that personal dosimetry is necessary the local Radiation Protection Supervisor must be contacted, who will advise on the local administrative arrangements for obtaining and returning dosimetry badges.
Anyone issued with badges must use them as instructed and must return the badges for dose analysis at stipulated times.
10. Radiation workers
Only authorised staff and students are allowed to work with sealed sources.
Staff and students must receive training before starting work with sealed sources. They must understand the hazards from ionising radiation and must be knowledgeable about and competent to use control measures to minimise risk. They must also be trained to understand the importance of security and source accountancy arrangements.
Staff and students must be authorised by the RPS for the area, based on them having received training.
A risk assessment must identify what level of training and competence is needed for staff working with sealed sources.
Monitoring tests must be carried out to confirm that:
• Exposure control measures are effective i.e. dose rates do not exceed permissible limits. Records must be kept of the results, and if corrective action is necessary, details of any work carried out and subsequent confirmatory test results must be recorded. The frequency of these tests must be decided by risk assessment.
• Containment of radioactive material is effective (‘Leak Test’). This must be carried out at least every 2 years, more frequently if there is any concern about the integrity of the means of containment e.g. visible or suspected damage or corrosion. Records must be kept of the results, and if corrective action is necessary, details of any work carried out and subsequent confirmatory test results must be recorded. Testing will be arranged by the University Radiation Protection Officer.
Monitoring results must be retained for a minimum of 2 years from when the measurement was made.
12. Monitor testing.
Monitoring instruments used to check exposure control measures e.g. dose-rate meters and area contamination monitors, must be tested regularly and calibrated annually.
The University Radiation Protection Officer must be provided with information about monitoring instruments. This must be done so that an up-to-date inventory can be kept by the Health and Safety Department for auditing purposes.
For radioactive sealed sources intending to be moved (transported) between different sites on public roads a check must be made to see whether special conditions apply, for example type of package and warning labels. Any transported sealed sources must comply with the Carriage of Dangerous Goods Regulations 2009 (“CDG2009”).
The University Radiation Protection Officer must be consulted for advice.
Approved couriers must be used wherever possible.
Transport must not be carried out using private vehicles other than in exceptional circumstances for which special arrangements have been made including vehicle insurance cover.
14. Disposal / Transfer
The University Radiation Protection Officer must be notified before any disposal or permanent transfer of a sealed source to another person or institution takes place. A check must be made that the intended recipient holds an appropriate permit and that the source is going by an appropriate route.
The following information must be supplied to the Radiation Protection Officer to keep the sealed source inventory up-to-date.
• The date when the source is exchanged or disposed of.
• The address to which it is removed and the name of the occupier of those premises.
• The number of MegaBecquerels at the time of transfer / disposal.
Arrangements must be made to prevent unauthorised access to, damage or loss or theft of any sealed source or its damage by fire or other means.
In practice this means that sealed sources must be kept in stores in containers both of which are constructed of non-combustible materials and which do not contain or are located close to corrosive or flammable materials. Both stores and containers must be clearly marked with the word ‘radioactive’ and with the radiation symbol. Source stores should be soley reserved for that purpose.
Regular sealed source accounting checks must be made and records kept. These must be at least monthly but more frequently if the risk of loss or theft is higher due to the nature of work activities.
16. Contingency measures.
If it becomes known or it is suspected that any radioactive material from a sealed source has escaped because of a defect or damage, measures must be taken to prevent any further escape and limit spread of any contamination. The University Radiation Protection Officer and the Radiation Protection Adviser must be informed immediately, the Environment Agency must be notified as soon as possible. Depending on the source activity and level of contamination it may also be necessary to report the loss to the HSE. The University RPO and RPA will advise on this.
If it becomes known or it is suspected that a sealed source has been lost or stolen all reasonable steps must immediately be taken to recover it. The University Radiation Protection Officer must be informed immediately, the police and Environment Agency and possibly the HSE must be notified as soon as possible.
17. High Activity Sealed Source
High activity sealed sources (HASS) are subject to additional special conditions.
The University does not currently hold any HASS nor does it hold an Environment Permit that permits a HASS source to be brought onto University premises.
A HASS must not be brought onto University premises until an Environment Permit has been granted.
Financial provision must be arranged to cover eventual costs associated with ‘disuse’ of the HASS i.e. transfer / disposal when it is no longer wanted by the University. These arrangements must be stated on the Permit application form and a permit will only be granted if the EA is satisfied they are adequate.
A document must be written describing special security measures for protecting the HASS, including measures to prevent, detect and extinguish fire. This must be submitted along with the Permit application. A Permit will only be granted if the EA is satisfied the security measures meet the requirements set out in ‘Security Requirements for Radioactive Sources (NaCTSO & NSAC 2005)’ and that the necessary security measures are in place.
Written emergency procedures must be produced describing actions to take in the event of loss, theft, unauthorised use or damage. These must include measures for checking the integrity of a HASS that may have been damaged in an incident.
Photographs must be taken and kept as a record, of HASS sources, the source container, transport packaging and any associated equipment. This requirement is in addition to the HASS being marked with clearly visible unique identification number, the word ‘Radioactive’ and the ionising radiation symbol. The photographs must be supplied to the EA in the event of any loss, theft.
HASS must be leak tested every two years.
An annual HASS Record Form must be sent to the EA.
Any unplanned exposure of a worker or member of the public from a HASS source must be notified to the University Radiation Protection Officer, the Radiation Protection Adviser and the Health and Safety Executive without delay.