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Radiation Protection Services
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9/22/2015 Radiation Protection Services
http://cms.nea.gov.sg/antipollutionradiationprotection/radiationprotection/radiationprotectionservices 1/4
Radiation Protection ServicesConsultancy Wipe Test for Sealed SourcesCalibration of Survey MetersPersonal Dose MonitoringGamma SpectroscopyRadiofrequency Radiation and Electromagnetic Field MeasurementTraining and Education
Consultancy
RPNSD provides consultancy services to industries, hospitals and some government agencies. Theseconsultancy services include the monitoring of radiation levels in industries, medical institutions and residentialpremises.
Wipe Test for Sealed Sources
Wipe Test For Sealed Radioactive SourcesUnder the Radiation Protection (Ionising Radiation) Regulations 2000, it is required that a wipetest be done once every 12 months for sealed radioactive sources to determine whether anyleakage has occurred. The procedure for getting a wipe test done is described here.
The wipe can be done by the licensee of the company in possession of or having under itscontrol any sealed radioactive source or by an officer from RPNSD.
Items to do a WipeWipe medium e.g. filter paper, cotton wool or any other material of high wet strength and absorbent capacity(recommended size 2 cm x 2 cm).Water or methylated spirit or any other liquid which will not attack the material of the housing.Surgical / disposable glovesForceps or tongs2 x small zip lock bagsIdentification labels / marking pen
ProcedureThe wipe medium is moistened with water or other appropriate liquid and used to wipe the bonding or surface ofthe sealed source if it is not installed in a container or the immediate container if it is installed therein.
After the wipe, each wipe medium used must be doubly packed in 2 small zip lock bags with an identificationlabel (type of radionuclide and serial number of the source). Alternatively, one could write a description andidentification on the bag.
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PrecautionsSurgical / disposable gloves should be worn to protect the hands from possible radioactive contamination.
Forceps or tongs should be used to minimise radiation exposure of the hand.Sources which are installed in devices like gauges, should have the shutter closed before the wipe is done.The sealed plastic bag containing the wipe medium should not be opened prior to measurement of theradioactivity of the sample.
Measurement of Radioactive ContaminationThe wipe medium is brought back to the laboratory and checked for any radioactive contamination. Thecontamination monitoring equipment used depends on the type and energy of the ionising radiation emitted fromthe radioactive sealed source tested. In general, for beta emitters, a proportional endwindow counter is used andfor gamma emitters, a welltype Sodium Iodide (NaI) detector is used. An analysis report is generated and sent tothe company concerned.
If the source is found to be leaking, it should be dismantled and put into a leakproof container. It shall not bebrought into use until all necessary repairs have been effected. The areas affected by the leakage should bedecontaminated under the supervision of RPNSD.
Calibration of Survey Meters
Under the Radiation Protection (Ionising Radiation) Regulations 2000, any radiation monitor used in connectionwith any radiation work such as survey meters, direct reading personal dosimeters etc. must be calibrated onceevery 12 months by a person approved by the DirectorGeneral as a qualified person for this purpose. RPNSDcalibrates survey meters, dosimeters and quartz fibre electrometers (QFEs) used by companies and hospitals inSingapore.
For the purpose of this calibration, RPNSD operates a Secondary Standards DosimetryLaboratory (SSDL) for Protection and Environmental Dosimetry.This SSDL was established with the support of the International Atomic Energy Agency (IAEA)and the World Health Organisation as part of the international network of secondary referencelaboratories.
The reference instruments maintained by the SSDL have calibration certificates traceableto BIPM the International Bureau of weights and measures in France. These reference dosimeters andcalibrated radiation sources are used to calibrate radiation monitoring equipment in Singapore.
Personal Dose Monitoring
Under Regulation 13(8) of the Radiation Protection (Ionising Radiation) Regulations 2000, every individual who isworking with ionising radiation shall wear a personal monitoring device. Under these Regulations, it is theresponsibility of the license holder to provide radiation workers with approved personal monitoring devices and toensure that these devices are analysed at regular intervals.
RPNSD provides the service of issuing TLD cards on a periodic basis. Upon receiving new TLD cards, allpreviously issued TLD cards should be returned to RPNSD within two weeks. These returned TLD cards will beanalysed within one week. After the TLD cards are analysed, a dose report will be generated and sent to theorganisation involved.
ThermoluminescenceWhen certain materials are exposed to ionising radiation, some of the energy absorbed is stored. This storedenergy is released in the form of light when the material is heated. Lithium fluoride has this property which iscalled thermoluminescence. The amount of light emitted on heating the lithium fluoride is proportional to theamount of radiation that had been incident on it.
Thermoluminescent Dosimeter (TLD)The thermoluminescent dosimeter consists essentially of two parts a TLD card and a TLD card holder.
9/22/2015 Radiation Protection Services
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The thermoluminescent dosimeter consists essentially of two parts a TLD card and a TLD card holder.
The TLD card consists of two or more Lithium Fluoride (LiF) chips mounted on analuminium card. Each card is identified by a unique barcode. The issued TLD card issealed in a plastic wrapper and labelled with the period of issue, wearer's name, wearer'sID number, Company Code and TLD number. The plastic wrapper should not beremoved at any time. The card has a cutaway corner to ensure that it fits exactly intothe TLD card holder. One LiF chip will be behind the open window for estimating skindose while the other chip is behind a filter to estimate body dose.
The TLD card, encased within the holder, is called the thermoluminescent dosimeter (TLD) or more frequentlyreferred to as the TLD badge. The correct way to wear it is to attach it to the trunk of the body at chest level or atwaist level. If a protective apron is worn, the badge should be worn under the apron.
The TLD badge, as described above, shall be worn at all times while the individual is doing radiation work.
Instructions regarding use of TLD cards
1Place the TLD card in the holder such that the cutaway corner fits the groove in the holder. The wearer'sname should be visible through the transparent window of the holder. The wearer's name should be facethe wearer when the badge is worn.
2 Do not store the cards in a place where they could be exposed to radiation as this could lead toinaccurate determination of dose received by the wearer.
3
If the badge was accidentally irradiated e.g. dropped in a place where radiation work was being done,please report and return the badge to the Radiation Protection & Nuclear Science Department (RPNSD)immediately and state that the badge was accidentally irradiated. If you do not inform us and the TLDcard is analysed, it will be recorded that you have received excessive dose and you may be suspendedfrom radiation work, depending on the dose recorded.
4 If you suspect that you have received an excessive dose due to an accident, please report andreturn your TLD badge to RPNSD immediately for evaluation of dose received.
5 Extreme heat, direct sunlight, pressure (e.g. by finger nails, bending stapling etc.) should be avoided asthese can damage the TLD card.
6 Company shall be liable for the cost of any unreturned, lost or damaged TLDs at $47.25 each (GSTinclusive). Please note that late payment interest (LPI) may be imposed.
7 The TLD card holder is sold separately at NEA Customer Service Centre at $25.20 (GST inclusive).
8TLD cards are issued periodically (e.g. monthly, bimonthly and quarterly, etc.). The TLD card is aproperty of RPNSD and must be returned immediately once the wearer has resigned or posted to adifferent department/institution/organisation.
9 All previously issued TLD cards must be returned to RPNSD within two week upon receiving new TLDcards.
Dose Report and Dose LimitsAfter the TLD cards are analysed, a dose report is generated and sent to the organisationinvolved. This dose report should be properly kept by the licensee, safety officer or employer andmade available to any radiation worker in the organisation who wants to know the dose he/shereceived in the course of his/her work.
The radiation dose received by an individual exposed to radiation is expressed in the unit called milliSievert, or'mSv'. Under the Radiation Protection (Ionising Radiation) Regulations 2000, the effective dose limit to the wholebody for occupationally exposed individuals is 20 mSv a year, averaged over defined periods of 5 years and withthe further provision that the effective dose shall not exceed 50 mSv in any single year.
Each report will show the dose received during the period being monitored, the annual accumulated dose from 1January of that year, the 5year accumulated dose and the lifetime accumulated dose.
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Gamma Spectroscopy
Assessment of any release of radioactivity to the environment is important for the protection ofpublic health, especially if the released radioactivity can enter the food chain, or result in theunnecessary radiation exposure to population. Analysis is performed on food samples.Companies or individuals who would like such tests to be conducted on their food samplesmay send their samples to RPNSD. RPNSD provides the service for detecting radioactivity infood using Sodium Iodide (NaI) detector. Gammaray spectrometry is an important techniqueused by RPNSD as it provides a rapid, reliable and accurate method for analysis of variousradionuclides.
Radiofrequency Radiation and Electromagetic Field Measurement
RPNSD provides radiofrequency radiation and electromagnetic field measurement services to industries,government agencies and the public. These services are done using broadband measurement meters.
Training and Education
To promote the safe use of ionising and nonionising radiation, the Singapore Environment Institute (SEI)conducts courses in its Radiation Safety Series for radiation workers on various aspects of radiation safety.
The courses in the Radiation Safety Series are:
Basic Ionising Radiation Safety (General) / Short Notes (/docs/defaultsource/antipollutionradiationprotection/radiationprotection/shortnotesl.doc?sfvrsn=0)Basic Ionising Radiation Safety (NDT) Basic Laser Radiation Safety / Notes about laser radiation (/docs/defaultsource/antipollutionradiationprotection/radiationprotection/notesaboutlaserradiation.doc?sfvrsn=0), Course Syllabus (/docs/defaultsource/antipollutionradiationprotection/radiationprotection/laserradiationsafetycoursel.docx?sfvrsn=0)Please refer to SEI's website (http://sei.nea.gov.sg) for information on the Radiation Safety Series courses.
