Radioactive materials should be stored in a safe and secured place. Only the licensee and the radiation workers under his charge may have access to the radioactive materials. Outside the defined area where the radioactive materials are stored, the radiation levels must not exceed 0.5 µSv/hr. Precautions for the safe storage and keeping of radioactive materials are also specified, including specifications for storage containers, fire and chemical safety etc.
Accounting of radioactive materials
Licensees should keep proper records of radioactive materials used by them and under their charge e.g. the date of receipt, the nature and form, the activity of the radioactive material at the date specified by the manufacturer, the whereabouts of the radioactive material at any time etc.
If the radioactive material is missing and is not accounted for within 24 hours, the licensee must notify RPNSD.
Checking of leakage of sealed source
Once in every 12 months, a wipe test must be performed on each sealed radioactive source to ensure that it is not leaking.
If it is found to be leaking, RPNSD must be immediately informed and the source must be removed and stored in a proper manner. It must not be brought back into use until all necessary repairs have been effected. The areas affected by the leakage must be decontaminated under the supervision of RPNSD.
Use of sealed sources and irradiating apparatus in industrial radiography
For a radiation source in a walled enclosure or a cabinet, the radiation level anywhere outside the walled enclosure or cabinet, accessible to anyone, should not be more than 10 µSv/hr.
For radiation work in a field site, a boundary must be set up and clearly defined by ropes, fences, walls of buildings etc., and the radiation hazard logo and warning notices incorporating the words “DANGER – RADIATION”, such that the radiation level outside the boundary should not exceed 25 µSv/hr. There should be continuous and competent supervision of the site whenever a sealed source is exposed or an irradiating apparatus is energised within the site. A survey meter should be available and used at the field site to check the radiation level boundary requirement and that the radiation source has returned to the OFF condition immediately on completion of each exposure.
Any radiation area monitor, survey meter or direct reading personal dosimeter used for any purpose in connection with the Regulations, must be calibrated once every 12 months.
Use of irradiating apparatus for medical, dental and veterinary diagnostic purposes
The X-ray room should have sufficient space to provide safe accommodation for everyone who is in the room. The walls and the door of the X-ray room should have adequate thickness or adequately lead-lined such that when the machine is operated at its maximum rated current for the maximum rated voltage and at its normal operating positions, the radiation level outside the room, at any position accessible to anyone, should not exceed 10 µSv/hr.
There should be a red light placed at a conspicuous place outside the X-ray room, which must be switched on whenever the X-ray machine is being used to deter the entry of anyone not connected with the X-ray examination.
Lead gloves, lead aprons and lead screens must be available for the protection of staff and patients. The field size should be limited to the area of interest and, unless inappropriate for the technique employed, fast films and intensifying screens must be used so that the irradiation of the patient is not more than is necessary to produce a satisfactory diagnostic result.
If a weak patient or child has to be supported during the X-ray examination, or a dental film has to be held for a patient, mechanical devices may be used as far as is practicable, otherwise the person rendering such assistance must be provided with protective clothing and be positioned so as to avoid the primary beam. This person cannot be a radiation worker, a pregnant woman or a person below the age of 18 years.
Similarly, an animal must not be held by anyone unless other means of immobilisation are impracticable. If manual restraint is necessary, the animal must be held down by a minimum number of people who are not staff of the veterinary establishment, not pregnant and not below the age of 18 years. If it is necessary for the animal to be held by members of the veterinary establishment, only those who have been registered as radiation workers and have been trained for such purposes may be so employed and they will be provided with protective clothing and be positioned so as to avoid the primary beam.
Protective clothing like lead aprons must be examined visually frequently and examined radiographically at least annually to ensure that the protection afforded has not been impaired as a result of cracks in the material.
Use of irradiation for medical therapeutic purposes
The radiation treatment room must have sufficient space to provide safe accommodation for everyone in the room. The walls and door of the radiation treatment room should have adequate thickness to provide protection against the primary beam and the secondary radiation so that the radiation level at any location outside this radiation treatment room, accessible to anyone, does not exceed 10 µSv/hr when the radiation source inside is on.
The control panel should be outside and there must be a warning red light placed in a conspicuous position, both inside and outside the radiation treatment room. These red lights must be on whenever the radiation source is on. Means must be provided for observing the patient during treatment and for communication between the patient in the treatment room and the operator at the control panel outside.
The door of the treatment room must be fitted with an interlocking device and the radiation source must be provided with a device which will automatically terminate the treatment after a preset time or radiation dose.
Use of radioactive sources for medical purposes
Any hospital or medical institution using sealed or unsealed sources for medical purposes must be equipped with suitable radiation monitors or survey meters.
Hospitalised patients undergoing treatment with any sealed or unsealed source must be accommodated in dedicated rooms with a warning notice on the door. If the radiation level at one metre from the patient exceeds 20 µSv/hr, the radiation hazard logo and a notice containing any necessary nursing precautions must be attached to the bed.
Admittance to the room should be strictly controlled and the patient cannot leave the room without the approval of the radiologist in charge of the treatment.
Any temporary implant of a sealed source, including a nuclear battery used to power a cardiac pacemaker, must be removed from a corpse before the corpse is disposed of.
No post mortem examination, cremation or embalming process should be carried out on a corpse known to contain a sealed or unsealed source without approval from RPNSD or the Medical Director of the hospital responsible for the implanting of the sealed source.
Use of unsealed sources in medical, industrial and research installations and in educational institutions
All installations and institutions where unsealed radioactive substances are used or handled must have adequate facilities where appropriate for radioisotope storage, preparation, administration, monitoring and counting.
All work surfaces must be made of non-porous and non-reactive material such as stainless steel. A fume cupboard may be provided to perform operations likely to produce radioactive contamination of the air through the production of aerosols, smoke or vapours.
All radioisotope laboratories or workrooms must be adequately ventilated and be provided with washing facilities suitable for decontamination purposes.
The dos and don’ts of working in a radioisotope laboratory are stated in the Regulations. Contaminated items for disposal must be put in special plastic bags and this radioactive waste must be put in a radioactive storage room.
Radiation accidents in medical and non-medical applications of ionising radiation or radioactive materials are defined in the Regulations.
In a non-medical application, a radiation accident is considered to have occurred if an unplanned, uncontrolled high level of radiation occurs, such a lost radioactive source, or damage of the radiation shielding of a sealed radioactive source or irradiating apparatus; or a person enters a high radiation field by accident; or if there is a spillage or leakage of unsealed radioactive material causing contamination; or if radioactive material is accidentally released into the environment in excess of the permitted discharge level.
In medical application, a radiation accident is considered to have occurred if any therapeutic treatment is delivered to the wrong patient or to the wrong tissue of any patient; or if the patient is treated with a dose or dose fractionation which differs by more than 10 per cent from the value prescribed by the radiologist in charge of the treatment; or if the wrong radiopharmaceutical is used. A radiation accident is also considered to have occurred if any diagnostic exposure given is 50 per cent greater than the intended dose or if the patient receives a dose significantly different from that which was intended.
If an accident should occur, the actions to be taken by the licensees or safety officers are spelt out. The licensee has to notify the appropriate authorities and in all cases, the licensee must notify RPNSD and give a preliminary oral report of the accident within 24 hours, which is to be confirmed in writing within 48 hours and a full written report of the accident within 10 days.
The First Schedule gives a table of the licensing exemption limits for each radionuclide in terms of maximum activities and activity concentrations. The Second Schedule gives the dose limits for radiation workers and for members of the public. The Third Schedule tabulates the annual limits on intake (ALI) for radiation workers, the Fourth Schedule shows the radiation hazard logo and the Fifth Schedule gives the limits for contamination of surfaces.
Unlicensed radioactive sources
In the event that any individual encounters a suspected unlicensed radioactive source, please contact NEA via the online feedback form (https://www.nea.gov.sg/corporate-functions/feedback) or myENV app. Members of the public are advised to minimize physical contact with the suspected radioactive source. Radioactive sources should not be disposed of without authorization from NEA.