4.10.1 INTRODUCTION
Sources of ionising radiation are employed for several purposes within the ADGAS Industrial Area. These are:
· Sealed sources of radioactive material used in Nucleonic instruments, installed on Plant for Process Control, e.g. level measurement.
· Temporary use of sealed sources by the C&ID or by Contractors for checking the quality of welds by radiographic methods (NDT).
· X-ray generator for radiography.
· Use of sealed sources in the Nucleonic Analyser, for alloy identification.
The potential for personal injury resulting from excessive doses of ionising radiation is well known, but as radiation is not detected by any of the human senses, controls are necessarily rigidly enforced by strict safety procedures and practices.
Further Information
ADNOC-COPV3-09 (GUIDELINES): Ionising Radiation
4.10.2 DEFINITIONS 4.10.2.1 EMPLOYER
The PMshall be regarded as the agent of the Employer on the site and all formal
communications with external bodies, i.e. Government Departments or other companies, must be channelled via the PROM. For administration of radiological matters, the
PROM's nominees are the HC&I/DHC&I for all NDT operations and the SIE/LIE’s for all Nucleonic Instrument equipment and procedures.
4.10.2.2 RADIATION PROTECTION SUPERVISORS (RPS)
Radiation Protection Supervisors are nominated by the HC&I for their departmental operations. The SIE and LIE are nominated as RPS’s for PROM&ED. The personnel
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nominated as RPS’s are appointed in writing by the Plant Manager. See Appendix 4-10-6.
The RPS should be directly involved with the work with ionising radiations and employ such supervision that will ensure that the work is done in accordance with the written procedures and practices.
No person should be appointed as an RPS unless they:
Know and understand the requirements of the regulations, written procedures and practices.
Understands the necessary precautions to be taken in the work which is being done and the extent to which these precautions will restrict exposures.
4.10.2.3 RADIATION PROTECTION ADVISOR (RPA)
In the event of an incident involving radioactive isotopes, the use of a normal Radiation Protection Advisor should be used to provide advice on a call off basis. A contact for this type of service is:-
Synetix Services, Tracerco,
P.O.Box 1
R2 Building, Belasis Avenue, Billingham
Cleveland, England.
Telephone: 0044 1642 522350 Fax: 0044 1642 522991
4.10.2.4 CLASSIFIED WORKERS
Any person who is (or is liable to be) employed for any part of their time in an area designated as a radiation controlled area and authorised under a written system of work, will be a "Classified Worker"
4.10.2.5 MONITORED PERSONNEL
All authorised personnel who come into contact, with Nucleonic devices and operate under a written system of work which includes monitoring their exposure by an acceptable method, will be "Monitored Personnel" only.
Note
Contractors shall ensure ADGAS that all designated "Classified Workers" meet the requirements of the mandatory regulations. ADGAS personnel who perform the functions of a "Classified Worker" will be so certified.
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Further Information
Chapter 4.10.2 DEFINITIONS for additional definitions
4.10.3 PERSONAL MONITORING
4.10.3.1 THERMOLUMINESCENT DOSEMETER (TLD)
It is mandatory that all classified personnel and authorised monitored personnel are issued with monitoring badges (TLDs) and that they are worn at all times when working with radiation.
Any lost, damaged or accidentally exposed badge must be reported immediately and a replacement obtained before work in continued.
4.10.3.2 DOSIMETRY
Monitoring badges (TLDs) are normally issued to be worn over a four week period and then assessed by an Approved Dosimetry Service e.g. The National Radiological Protection Board (NRPB) in the UK, where the radiation dose records are kept. Copies of the TLD assessments will be retained by the Contractor.
4.10.3.3 TRANSFER RECORDS
It is the responsibility of the contractor to comply with all regulations pertaining to transfer records of Classified Workers.
4.10.3.4 HIGH EXPOSURE
If at any time it appears that a person has received a radiation dose greater than 15 mSv (three tenths of permitted dose), the HC&I/DHC&I or the SIE/LIEs will;
· Contact the MHSE who will then notify the PMand Head of Medical Services Das (HMSD).
· Initiate an investigation into the circumstances leading to the exposure and report their findings to the MHSE, who will ensure that the principle of individual
responsibility has been complied with by all involved personnel. The final report will be submitted to the PROM.
4.10.3.5 MEDICAL SURVEILLANCE
All medical arrangements required for Contractor Classified Workers, and the keeping of their Health Records, is the responsibility of the Contractor.
4.10.4 INDIVIDUAL RESPONSIBILITY
It is the individual's responsibility to ensure, so far as is reasonably practicable, that exposure to ionising radiation shall not be greater than is necessary for the purpose of his work. Dose rates shall be maintained below the value given Section 4.10.16.
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4.10.5 EMERGENCY EXPOSURE
Personnel involved in an emergency exposure to radiation will undergo a medical examination and monitoring.
4.10.6 WORK PERMIT REQUIREMENTS
All use of portable radioactive sources for radiography will require the coverage of a Hot Work Permit and be conducted by approved Classified Workers. All work will be
conducted by a minimum of a two man team, never by a single person.
The prepared Safety Checklist for Radiography, Figure 4-3, is attached to the White copy of the permit. This gives details of the isotope and the safety requirements prior to
commencing work. The ADGAS NDT Specialist, carrying out the work, will then tick the boxes according to the needs of the job. The HSED will then sign the checklist after checking that all the requirements have been met.
4.10.7 RADIOGRAPHY
Radiography can isolate substantial work areas and for this reason is usually restricted to the hours with the minimum of personnel activity.
No other work permits may be issued or remain current for the area designated.
The approved radiation symbol is to appear on all packages and storage containers and on barrier signs around the radiation work areas.
4.10.7.1 SAFETY PROCEDURES
With the work place and affected area identified, the checklist must be rigorously applied.
Along with the items in the checklist the following actions are required.
· Good liaison and communications should be established in case field personnel need to access past the barriers.
· All radioactive sources are to be stored within locked shields when not in use.
· If there is a plant emergency, the radiation source is returned immediately to its safe storage.
· All sources of ionising radiation shall, where reasonably practicable, be adequately shielded.(Collimated)
· Radioactive sources must only be manipulated by remote handling equipment.
4.10.8 CONTROL OF RADIOACTIVE SOURCES 4.10.8.1 MAXIMUM HOLDINGS
The maximum quantity of sealed sources of Iridium 192 for radiography purposes on Das Island at any one time shall not exceed 3.7 TBq (Terabecquerels) (100 Curies)
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The size of any single Iridium 192 source shall not exceed 1.1 TBq (30 curies).
Total holdings of Caesium 137 and Cobalt 60 sources shall not exceed 111GBq (Gigabecquerels) (3 Curies).
4.10.8.2 NOTIFICATION OF IMPORT TO DAS ISLAND
The HC&I and the SIE/LIE shall ensure that the following information is submitted to the ADMA-OPCO Safety and Environmental Protection Department (SEPD – Das) and copied to the MHSE at the time of mobilisation and that the radioactive sources are within the agreed limitation set by ADMA-OPCO.
· Completed Radioactive Isotope Movement Form.
· Decay Table (Iridium Sources)
· Radioactive Source Test Report.
· Radioactive Material Package Certificate.
· Civil Defence Valid Registration Certificate.
Prior notification of disposal shall also be given to the ADMA-OPCO SEPD and copied to the MHSE. (See appendix 4-10-5).
4.10.8.3 MASTER REGISTERS
It is the responsibility of the HC&I to maintain an up-to-date Register of sealed sources, for general NDT, and the same applied to the SIE/LIE for Nucleonic Sources.
Each specific source shall be identified by its serial number.
Copies of all certificates and decay charts (where applicable) shall be copied to the MHSE, this also applies to Contractors carrying out radiography work.
4.10.8.4 STORAGE OF RADIOACTIVE SOURCES
There are two main stores for radioactive isotopes within the ADGAS Industrial Area.
502 Laydown Area
The storage area consists of two stores, one for Nucleonic sources under the control of the SIE/LIEs and one for general NDT sources controlled by the HC&I.
Train 3 Area
This store area is used for general operational NDT sources for ADGAS and for all ADGAS subcontractors sources and is under the control of the HC&I.
When not installed on the plant, in use, or in transit, all radioactive sources shall be housed in adequately shielded containers within the radioactive source stores.
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Every container shall be marked with a warning notice and shall specify the identification number of the source, the isotope and strength.
The stores shall be reserved exclusively for the storage of sealed radioactive sources and, in particular, no flammable material will be located in the store area.
The stores shall be kept locked and the keys shall be under the control of the HC&I and SIE/LIE’s for their respective store areas, allowing access to authorised personnel only.
The function may be carried out by the departmental RPS.
The maximum reading at the outside of the radiation stores must not exceed 2.5 mSv/hr (0.25 mrem/hr) at any place around the perimeter. Suitable signs must be displayed on the outside of the stores advising of the nature of the hazard presented by the contents and also information must be displayed regarding RPS and emergency contact numbers.
A radiation Dose Rate Meter or monitor should always be used when approaching or entering the isotope stores to remove or replace an isotope or when checking the contents.
Note
All notices shall be in Arabic and English
4.10.8.5 ISOTOPE MOVEMENT REGISTER
When an isotope is removed from, or returned to any radiation store, the details must be entered into the source Movement Register together with the signature of the authorised person in charge of the movement.
This also applies to any Nucleonic source that may be placed in the pit for long term storage or on a temporary base, having been removed from the Plant.
4.10.8.6 LOCATION OF RADIOACTIVE SOURCES
General NDT isotopes will always be placed in the radioactive source stores when not in use.
The location of all nucleonic sources is listed in Figure 4-4.
It shall be the responsibility of the SIE/LIE to advise the MHSE of any changes to the location list so that amendments may be notified to all Manual holders.
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4.10.9 NUCLEONIC SOURCES 4.10.9.1 DESIGN REQUIREMENTS
Each installation shall be such that the dose rates on any external surface of the instrument or plant on which it is installed shall not exceed 7.5 mSv/hr ( 0.75 mR/hr).
To ensure that this is achieved, each radioactive source shall be securely housed in a shielded container of sufficient size to ensure that radiation dose rates on all accessible surfaces are below 7.5 mSv/hr. If this is not possible, extra guards must be positioned and fixed securely in place to ensure that the dose rate at the guard is less than 7.5 mSv/hr.
Additionally, radiation dose rates on all surfaces of the vessel or item to which the installation is fixed should be less than 7.5 mSv/hr, even when empty. If not, then
additional guards must be positioned and fixed securely in place and the dose rate at the guard must not exceed 7.5 mSv/hr.
The immediate source container shall be painted yellow and bear the international radiation symbol (black trefoil on a yellow background).
The shielded source container shall provide protection of the source against damage and collimate the useful beam to the minimum dimensions necessary for efficient operation of the installed instrument.
The shielded source container shall be fitted with a shutter that shall be capable of being locked in the closed position, to attenuate the useful beam such that any residual dose rate accessible to personnel does not exceed 7.5 mSv/hr. Clear notices should be fixed to the container to indicate whether the shutter is in the open or closed position.
The source holder shall be locked into the shielded source container and the keys controlled by the OSS.
4.10.9.2 WARNING NOTICES
Fixed to the shielded source container or immediately adjacent to it there must be a notice that bears the radiation symbol. The notice must also indicate the presence of a radioactive source and give the following information:
"Make no adjustment to the installation without clearance from SIE/LIE. In the event of any unusual occurrence involving the source the OSS must be contacted immediately"
In cases where a source is installed on or inside a process vessel having manhole access, then additional notices of a similar type must be fitted to each manhole. These should bear the additional instruction:
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"Contact the SIE/LIE before entering vessel"
Note
Warning notices shall be in Arabic and English.
4.10.9.3 INSTALLATION
A suitable area around the Plant on which an instrument is to be installed shall be isolated by temporary barriers at which the dose rate will not exceed 7.5 mSv/hr.
Installation shall be carried out by Authorised Persons from the Instrument Section.
A calibrated Radiation Dose Rate Meter must be used during the installation process.
4.10.9.4 SUPERVISION
The RPS shall be responsible for ensuring that the shutter is locked in the closed position. The keys will be under the control of the OSS.
4.10.9.5 MAINTENANCE
Access to installed equipment will require a Hot Work Permit issued by the OSS and countersigned by the RPS.
The RPS shall issue specific instructions on precautions to be taken before dismantling or removing a shielded container from it's normally installed position.
4.10.9.6 ACCESS
No person shall be permitted to enter a vessel or have access to any vessel, pipe, or other part of the Plant on which a sealed source is installed without clearance from the RPS.
Further Information
Operations Department Permit to Work Manuals. Sections 6.13 and 10.47
4.10.9.7 LEAKAGE TESTING
A test for leakage of radioactive substances shall be organised by an RPS, who shall arrange for swabs to be taken and assayed by a qualified person at least once in every period of twenty-six months of:
· Every immediate container or bonding which forms part of a sealed source, OR
· Every container in which a sealed source is permanently installed but which does not form part of a sealed source according to the relevant British Standard
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Further Information
BS 5288 : 1976: Specification. Sealed radioactive sources. Section D21 Each leakage test shall be indicated by the request of the RPS from the Department responsible for the use and control of the source.
The result of each test shall be entered into a Master Register. A satisfactory result will be recorded if the activity measured on the swab is less than 185 Becquerels (5
nanocuries)
If any leakage is observed above this level, the RPS will arrange for its safe disposal and replacement.
4.10.10 SITE RADIOGRAPHY
The requirements relating to site radiography are as follows:
4.10.10.1 PRIOR TO EXPOSURE
The Controlled Area, within which the radiography takes place, shall be segregated by means of a barrier at such a position to prevent access by other than classified persons associated with the radiography work.
The instantaneous dose rate shall not exceed 7.5 mSv/hr at the barrier.
No classified personnel should be within the Controlled Area during radiographic exposure.
When this cannot be avoided for the purpose of commencing or terminating an exposure, a person entering should not be exposed to an instantaneous dose rate more than 2 µSv/hr(200 mR/hr).
Local shielding of sources, including collimators, should be used where possible to reduce dose rate and size of controlled area.
Warning signs should be clear, unambiguous and carefully situated so that any person within or approaching an area is made aware of the presence of radiation.
Further Information
Chapter 3 Section 8 Safety Signs and Barriers.
4.10.10.2 DURING EXPOSURE
Once the exposure has commenced no alterations shall be made to the radiographic set-up until the exposure has terminated.
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4.10.10.3 AFTER EXPOSURE
After every exposure using sealed sources, a check using a monitoring instrument should be made to ensure that the source has properly retracted into its shield or container.
Sources must never be handled with the bare hands; handling tools must always be used. Lead shot and sheet for shielding purposes shall be readily available for use in an emergency.
X-ray equipment shall be provided with effective means of isolation to prevent unauthorised use. Source containers shall have a lock to prevent unintended or unauthorised exposure. The lock should be such that if defective it does not prevent retraction of the source and the act of unlocking does not give rise to an immediate exposure of the source.
Every exposure container used with radiography shall comply with BS 5650:1978, ISO 3999-1977: Specification for apparatus for gamma radiography (for remote exposure units only) and the position of the shutter, whether open or shut, shall be clearly indicated.
4.10.11 OTHER APPLICATIONS
Any work with sources of ionising radiation not covered by these instructions shall be carried out only with the approval of the MHSE
4.10.12 MONITORING 4.10.12.1 GENERAL
The RPS shall ensure that adequate and appropriate monitoring equipment is available to assess the radiological safety of all applications of sources of ionising radiation in progress at any time on the Site.
4.10.12.2 MAINTENANCE AND CHECKING
The RPS of the Department concerned shall ensure that each Radiation Dose Rate Meter is maintained in good working order and is calibrated by a qualified person according to the following:-
· Once in every period of 14 months, and
· After any repair.
The calibration report shall be retained by the RPS with a copy to the MHSE.
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4.10.13 RADIOACTIVE EMERGENCY
4.10.13.1 OCCURRENCE CONSTITUTING AN EMERGENCY
Any suspected loss of, breakage of, or damage to any sealed source of radioactive material or to the shielding of any source or any circumstance which may result in these occurrences (e.g. fire on the plant) shall be regarded as an emergency.
Further Information
Emergency Plans and Procedures Manual Section "Loss of Radioactive Source".
4.10.14 TRANSPORT 4.10.14.1 INTRODUCTION
All regulations governing the transport of radioactive materials, nationally or
internationally, are based on the International Atomic Energy Agency's "Regulations for the Safe Transport of Radioactive Materials".
internationally, are based on the International Atomic Energy Agency's "Regulations for the Safe Transport of Radioactive Materials".