SSG-57 Radiation Safety in Well Logging

Provides the statutory basis for requirements for protection and safety for all exposure situations;

Specifies that the prime responsibility for protection and safety rests with the person or organization responsible for facilities and activities that give rise to radiation risks;

Specifies the scope of its applicability;

Establishes and provides for maintaining an independent regulatory body with clearly specified functions and responsibilities for the regulation of protection and safety;

Provides for coordination between authorities with responsibilities relevant to protection and safety for all exposure situations.”

Notification and authorization;

Review and assessment of facilities and activities;

Inspection of facilities and activities;

Enforcement of regulatory requirements;

The regulatory functions relevant to emergency exposure situations and existing exposure situations;

Provision of information to, and consultation with, parties affected by its decisions and, as appropriate, the public and other interested parties.”

Registers of sealed sources and radiation generators;

Records of doses from occupational exposure;

Records relating to the safety of facilities and activities;

Records that might be necessary for the shutdown and decommissioning or closure of facilities;

Records of events, including non-routine releases of radioactive material to the environment;

Inventories of radioactive waste…”

The transport of radioactive sources;

The location of radioactive sources;

Incidents involving radiation sources, such as loss of radioactive sources, damage to radioactive sources and theft of radioactive sources or radiation generators.

Review of compliance with the conditions of the authorization to possess and use radiation sources for well logging: for example, checking that the inventory includes all the authorized radiation sources and devices, and that well logging devices are used only for authorized purposes at authorized locations. If any authorized source is missing or if any source is found to be not properly authorized, the matter should be investigated and appropriate actions implemented (an immediate search should be performed for missing sources, and any unauthorized sources should be brought under regulatory control).

Confirmation that radiation sources and well logging devices meet the acceptance criteria and performance criteria established by the regulatory body.

Measurement of the radiation levels around the well logging devices and estimation of the doses to workers and members of the public.

Review of the records of workplace monitoring and individual monitoring.

Observing the use of well logging devices, including procedures for safe handling of radiation sources.

Review of control measures, such as the conduct of periodic source inventory checks, controls to ensure that sources are only used by authorized individuals, the use of appropriate engineered controls, the storage of radiation sources (including disused sources) and emergency plans and procedures.

Review of compliance with regulatory requirements for transport of radioactive material (see Section 12).

On-site inspections at client facilities where well logging devices are being used, and observing the operations involving the well logging tools, including procedures for safe use and the arrangements for the safety and security of each source.

Shall adopt objectives for protection and safety in accordance with the requirements of [GSR Part 3];

Shall apply measures for protection and safety that are commensurate with the radiation risks associated with the exposure situation and that are adequate to ensure compliance with the requirements of [GSR Part 3].”

The measures and resources that are necessary for achieving the objectives for protection and safety have been determined and are duly provided;

The programme is periodically reviewed to assess its effectiveness and its continued fitness for purpose;

Any failures or shortcomings in protection and safety are identified and corrected, and steps are taken to prevent their recurrence;

Arrangements are made to consult with interested parties;

Appropriate records are maintained.”

Applying the requirements for protection and safety coherently with other requirements, including requirements for operational performance, and coherently with guidelines for security;

Describing the planned and systematic actions necessary to provide adequate confidence that the requirements for protection and safety are fulfilled;

Ensuring that protection and safety are not compromised by other requirements;

Providing for the regular assessment of performance for protection and safety, and the application of lessons learned from experience;

Promoting safety culture.”

Promoting individual and collective commitment to protection and safety at all levels of the organization, including staff responsible for administration, security, storage facilities, operation, transport, assembly and maintenance of well logging tools, as appropriate;

Ensuring a common understanding of the key aspects of safety culture within the organization;

Supporting individuals and teams in performing well logging activities safely and successfully, with account taken of the interactions between individuals, the well logging equipment, the well logging company and the client;

Encouraging open communication and participation of operating staff, radiation protection officer(s) and other workers in the facility in the development and implementation of policies, rules and procedures dealing with protection and safety in well logging;

Ensuring accountability of the organization and of individuals at all levels for protection and safety in the procurement, storage, installation, operation, maintenance, handling and safe management of well logging sources until their safe disposal after the end of their useful life;

Encouraging a questioning and learning attitude, discouraging complacency, with regard to protection and safety, and providing means by which the organization continually seeks to develop and strengthen its safety culture.

Sound ergonomic principles are followed in the design of equipment and the development of operating procedures, so as to facilitate the safe operation and use of equipment, to minimize the possibility that operator errors could lead to accidents, and to reduce the possibility that indications of normal conditions and abnormal conditions could be misinterpreted.

Appropriate equipment, safety systems and procedural requirements are provided, and other necessary provision is made:

To reduce, as far as practicable, the possibility that human errors or inadvertent actions could give rise to accidents or to other incidents leading to the exposure of any person;

To provide means for detecting human errors and for correcting them or compensating for them;

To facilitate protective actions and corrective actions in the event of failures of safety systems or failures of measures for protection and safety.”

Shall follow any applicable rules and procedures for protection and safety as specified by the employer, registrant or licensee;

Shall use properly the monitoring equipment and personal protective equipment provided;

Shall cooperate with the employer, registrant or licensee with regard to protection and safety, and programmes for workers’ health surveillance and programmes for dose assessment;

Shall provide to the employer, registrant or licensee such information on their past and present work that is relevant for ensuring effective and comprehensive protection and safety for themselves and others;

Shall abstain from any wilful action that could put themselves or others in situations that would not be in accordance with the requirements of [GSR Part 3];

Shall accept such information, instruction and training in protection and safety as will enable them to conduct their work in accordance with the requirements of [GSR Part 3].”

The development and use of specific restrictions on exposure and other means of ensuring that the measures for protection and safety for workers who are engaged in work that involves or could involve a source that is not under the control of their employer are at least as good as those for employees of the registrant or licensee;

Specific assessments of the doses received by workers as specified in (a) above;

A clear allocation and documentation of the responsibilities of the employer and those of the registrant or licensee for protection and safety.”

Shall obtain from the employers, including self-employed persons, the previous occupational exposure history of workers … and any other necessary information;

Shall provide appropriate information to the employer, including any available information relevant for compliance with the requirements of [GSR Part 3] that the employer requests;

Shall provide both the worker and the employer with the relevant exposure records."

Individual dosimetry and dose record keeping (see Section 6);

Health surveillance arrangements (see Section 4);

Workplace monitoring arrangements (see Section 7);

Local rules (see Section 4).

The dose rates from shielded and unshielded radioactive sources and from neutron generators, as appropriate;

The exposure of well logging engineers, other workers and the public from normal well logging operations, and potential exposures from reasonably foreseeable incidents (including exposures due to loss of shielding, due to contamination from a damaged radioactive source, and from other scenarios, including very low probability events);

Limits and technical conditions for operation of the well logging source;

Ways in which structures, systems and components, as well as procedures relating to protection and safety, might fail or might otherwise lead to potential exposures, and the consequences of such failures or potential exposures;

Ways in which external factors could affect protection and safety;

Ways in which operating errors and human factors could affect protection and safety;

Evaluation of the implications of any proposed modifications for protection and safety;

Any uncertainties or assumptions, and their implications for protection and safety.

The engineered control measures that are necessary for safety.

The administrative controls that are necessary for safety, for example the development of safe working procedures (local rules) to be implemented for storage, operation, maintenance of a source inventory, servicing and maintenance, and management of disused sources.

Procedures for designating controlled areas and supervised areas (see Sections 4 and 11).

Any measures necessary for the protection of the public.

The assessment of occupational exposure (gamma and neutron radiation, as appropriate) (see Section 6).

The training programme for well logging engineers and other workers (see Section 5).

An effective emergency preparedness and response programme to manage reasonably foreseeable events (including very low probability events). This should include information on: reasonably foreseeable incidents, the measures necessary to minimize the likelihood of occurrence of such incidents and the necessary emergency arrangements (including emergency plans and procedures, and emergency equipment). (See Section 13.)

The security of radiation sources used in well logging, with the objective of deterring, delaying, detecting and responding to the theft of sources (see Section 9).

When safety might be compromised or affected as a result of modifications to facilities or activities;

When the acquisition of a new radiation source or a source with different characteristics is planned;

When operating experience or the investigation of incidents, failures or errors indicates that current safety measures are invalid or are not fully effective;

When significant changes to relevant standards, regulations or guidance have been made or are envisaged.

Chemical hazards;

Fire and explosion;

Noise and vibration;

Mechanical hazards (e.g. lifting equipment, overhead cranes);

Hazards relating to pressure vessels;

Other radiation sources (e.g. on nuclear facility sites, or sources used in industrial radiography).

The management structure and policies relevant to protection and safety;

The assignment of individual responsibilities for protection and safety;

An education and training programme on the nature of the radiation hazards associated with well logging, and on the measures required for protection and safety;

Local rules and the arrangements for supervision of work;

The designation of controlled areas and supervised areas, as appropriate;

Safety and security of radioactive sources including management of disused sources;

Emergency preparedness and response;

The arrangements for assessing occupational exposure and for monitoring the workplace, including the acquisition, testing and maintenance of workplace monitoring instruments;

The programme for health surveillance of workers;

A system for recording and reporting information relating to the control of exposures, the decisions regarding measures for occupational radiation protection and safety, and the results of individual monitoring and workplace monitoring;

Methods for periodically reviewing and auditing the performance of the radiation protection programme;

Requirements for quality assurance and procedures for process improvement.

Shall establish in writing local rules and procedures that are necessary for protection and safety for workers and other persons;

Shall include in the local rules and procedures any relevant investigation level or authorized level, and the procedures to be followed in the event that any such level is exceeded;

Shall make the local rules and procedures and the measures for protection and safety known to those workers to whom they apply and to other persons who may be affected by them;

Shall ensure that any work in which workers are or could be subject to occupational exposure is adequately supervised and shall take all reasonable steps to ensure that the rules, procedures, and measures for protection and safety are observed;

Shall designate, as appropriate, a radiation protection officer in accordance with criteria established by the regulatory body.”

Regular reviews of the radiation protection programme;

Reviews of occupational radiation doses, workplace monitoring programme results and any incident reports prepared by the radiation protection officer;

Reviews of results of audits on the performance of the radiation protection programme;

Making recommendations to senior management for improvements in the radiation protection programme;

Provision of guidance and direction on the performance of the radiation protection officer’s duties;

Monitoring the investigation of any incident with the potential for unplanned exposure to radiation;

Preparation of reports about relevant radiation safety issues for dissemination to managers and workers, as appropriate.

Controlling exposures or preventing the spread of contamination in normal operation;

Preventing or limiting the likelihood and magnitude of exposures in anticipated operational occurrences and accident conditions.”

An effective dose of 20 mSv per year averaged over five consecutive years⁶⁶ (100 mSv in 5 years) and of 50 mSv in any single year;

An equivalent dose to the lens of the eye of 20 mSv per year averaged over five consecutive years (100 mSv in 5 years) and of 50 mSv in any single year;

An equivalent dose to the extremities (hands and feet) or to the skin⁶⁷ of 500 mSv in a year.”

An effective dose of 6 mSv in a year;

An equivalent dose to the lens of the eye of 20 mSv in a year;

An equivalent dose to the extremities (hands and feet) or to the skin⁶⁷ of 150 mSv in a year.”

Dosimeters should be worn by well logging workers at all times when performing work with radiation sources.

Dosimeters should be worn in accordance with the recommendations of the dosimetry service provider.

The measuring element should be correctly positioned in the dosimeter holder.

The dosimeter should be worn only by the person to whom it is issued.

Care should be taken to avoid damaging the measuring element of the dosimeter (dosimeters can be damaged by water, high temperature, high pressure or physical impact).

Dosimeters should not be exposed to radiation when not being worn by the worker (i.e. the dosimeter should be kept away from sources of radiation when not in use).

Dosimeters should be promptly returned to the dosimetry service for processing at the end of the period of wear. Dosimeters that have been returned early owing to a suspicion of abnormal exposure should be processed urgently.

The dosimetry service should be informed if the operating organization suspects that the dosimeter has been damaged or has been exposed to radiation while the worker to whom it was assigned was not wearing it, in order that the correct dose to be assigned to the worker can be determined.

Neutron dosimeters with a suitable neutron energy response should be worn by personnel performing operations involving radioactive neutron sources or neutron generators.

Active personal dosimeters should not replace passive dosimeters unless they have been specially approved (for example by the regulatory body) for this purpose. In most cases, active personal dosimeters will supplement the passive dosimeters worn by well logging personnel.

Active personal dosimeters should not be used as a replacement for workplace monitoring instruments (e.g. dose rate meters).

Active personal dosimeters should be tested periodically in accordance with national recommendations and guidance from the manufacturer.

Active personal dosimeters should be calibrated in terms of the radiation fields likely to be encountered in the workplace.

The alarm settings of the active personal dosimeters should reflect an appropriate level of dose and/or dose rate and the alarm level should be visible during operation of the device.

Changes to active personal dosimeters should not be allowed, except by persons with appropriate roles and responsibilities.

Shall provide workers with access to records of their own occupational exposure;

Shall provide the supervisor of the programme for workers’ health surveillance, the regulatory body and the relevant employer with access to workers’ records of occupational exposure;

Shall facilitate the provision of copies of workers’ exposure records to new employers when workers change employment;

Shall make arrangements for the retention of exposure records for former workers by the employer, registrant or licensee, as appropriate;

Shall, in complying with (a)–(d) above, give due care and attention to maintaining the confidentiality of records.”

Around source storage facilities at the main base of the well logging company and, as appropriate, at the well logging site, to ensure that an adequate level of shielding is provided;

Around the barriers during well logging operations, to confirm that dose rates remain below any values specified in national regulations or guidance or by the operating organization;

At the operator’s position during loading and unloading of a logging tool or termination of operation of a neutron generator, to confirm that radiation levels are acceptable;

On the site on completion of the well logging work, to confirm that no radioactive sources have been left on the site;

Around the transport package before transporting radioactive sources to and from the site, to confirm the presence of the source, and also to demonstrate compliance with IAEA Safety Standards Series No. SSR-6 (Rev. 1), Regulations for the Safe Transport of Radioactive Material, 2018 Edition [22] (see Section 12);

Around vehicles transporting radioactive sources before departure to and from the site, including at the driver’s seat.

The location and description of each radiation generator or radioactive source for which they are responsible;

The activity and form of each radioactive source for which they are responsible.”

Sources should comply with the relevant requirements set out in ISO 2919 [31].

Sources should be certified as meeting the requirements for special form radioactive material, as established in SSR-6 (Rev. 1) [22].

Sources should be leak tested in accordance with ISO 9978 [32] or an equivalent national standard, and there should be a valid leak test certificate that is traceable to each individual source.

Sources should be marked in accordance with ISO 2919 [31] or an equivalent national standard, or, at a minimum, marked with the radiation symbol (trefoil) [20] and the word “RADIOACTIVE”.

The international ionizing radiation symbol (trefoil) [20];

The word “RADIOACTIVE” in letters not less than 10 mm in height, together with a brief warning in a language appropriate to the country or region of use;

The chemical symbol(s) and mass number of the radionuclide(s) for which the tool is suitable (e.g. 137Cs or 241Am);

The source activity in the tool, quoted for each radionuclide for which the tool is suitable, and the date of source calibration;

The make, model and serial number of the tool;

The date of manufacture of the tool.

The chemical symbol and mass number of the radionuclide;

The activity on a stated date;

The identification number of the sealed source;

The name of the source manufacturer.

Gamma and neutron radioactive sources (including calibration sources, as applicable) and neutron generators should, subject to approval by the regulatory body, be transferred to another authorized organization. If possible, the operating organization should return the source or generator to the original supplier; alternatively, the operating organization may take another action as authorized by the regulatory body. Comprehensive records should be kept by the operating organization of all authorizations for the receipt, storage, transfer or disposal of radioactive sources (including any certificates provided by recipients or by disposal facilities for radioactive waste). The relevant records should be maintained as specified by the regulatory body.

The operating organization should return disused neutron generators to the original supplier. Otherwise, the generator should be made inoperable and, subject to approval by the regulatory body, be transferred to an authorized organization for safe disposal (i.e. of the tritium source).

In cases where all radiation sources are to be removed from the facility, all radiation symbols (trefoils) and other relevant notices should be removed from the facility and a workplace monitoring survey (see Section 7) should be conducted by the radiation protection officer or a qualified expert to provide additional confirmation that the sources have been removed from the site. A final decommissioning plan should be prepared in advance, which includes the final radiation survey and details of the storage, transfer or disposal of sources of radiation. The final decommissioning plan is required to be submitted to the regulatory body for review and approval (see Requirement 11 of IAEA Safety Standards Series No. GSR Part 6, Decommissioning of Facilities [34]). Further recommendations are provided in IAEA Safety Standards Series No. SSG-49, Decommissioning of Medical, Industrial and Research Facilities [35]. Decommissioning and disposal of old well logging sources in cases where the manufacturer or original supplier is no longer in business should be arranged according to the requirements specified by the regulatory body. Further recommendations for managing orphan sources are provided in SSG-19 [14].

The operating organization should inform the relevant authorities when all sources of radiation have been removed from the site.

Radioactive waste should be managed in accordance with the recommendations provided in IAEA Safety Standards Series No. SSG-45, Predisposal Management of Waste from the Use of Radioactive Material in Medicine, Industry, Agriculture, Research and Education [36], or an equivalent national standard, and in accordance with regulatory requirements.

An option for disposal of sealed sources used in well logging devices is borehole disposal. Recommendations on borehole disposal facilities are provided in IAEA Safety Standards Series No. SSG-1, Borehole Disposal Facilities for Radioactive Waste [37]. A technical manual on borehole disposal of disused sealed sources is provided in Ref. [38].

Offshore well logging may involve two or more neutron generators. Additional precautions (including double authentication to control access) should be implemented in such cases.

Neutron generators containing tritium should be transported in accordance with SSR-6 (Rev. 1) [22].

Safe operating procedures should be observed for handling the well logging tool (see para. 11.16).

Smaller controlled areas that are easier to manage;

Lower dose rates at the barriers and at the operator’s position;

A lower radiation hazard in the event of an incident, for example, if the logging tool becomes stuck.

Workplace monitoring instrument(s) (including spare batteries) and personal dosimeters;

Source handling tools and local shielding, if required;

Temporary barriers, tapes, warning notices and warning signals, as appropriate, for demarcating the controlled area;

Emergency equipment, including remote source handling tools and a spare shielded container for emergency use.

Measuring the dose rate to confirm that the radioactive source is shielded.

Checking warning labels and plaques or tags containing source details for legibility.

Checking the source handling tools for functionality. To avoid exposure to personnel during these checks, a dummy source can be used (the diameter of the dummy source should fit the tool).

Checking that all the securing and retaining features of the well logging tool are functional.

Checking that the source transport container is in good condition and good working order and securing any shielding plugs to reduce the likelihood of loss.

From the supplier of the source to the operating organization’s facility;

From the operating organization’s facility to the site of operation;

From the operating organization’s facility to the supplier or other suitably authorized facility at the end of the useful life of the source, if it has become disused for some other reason, or following an accident involving the source.

The consignor (the person or organization that prepares a consignment for transport);

The carrier (the person or organization that undertakes transport of radioactive material);

The consignee (the person or organization that receives a consignment).

The energy resulting from a nuclear chain reaction or from the decay of the products of a chain reaction;

Radiation exposure” [45].

Mechanical damage to well logging equipment;

Loss of shielding resulting in higher dose rates than expected;

Missing (or lost) radioactive sources;

Dropped or detached sources;

Sources stuck in a well or borehole;

Leaking sources due to mechanical impact, corrosion or fire;

Natural disasters (e.g. a hurricane);

Malicious acts such as theft of sources.

Should be properly trained and qualified, and they should be competent;

Should follow the local rules and other relevant procedures;

Should use calibrated workplace monitoring instruments and wear suitable personal dosimeters before, during and after every source use;

Should undertake regular and appropriate inspections of well logging equipment before use;

Should make proper use of emergency equipment;

Should conduct a final survey of the work area before leaving the site.

Well logging equipment should meet current regulatory standards.

Workers:

A clear statement of roles and responsibilities;

A concept of operations;

Communication and coordination arrangements;

Protocols for notification of an emergency;

Instructions to site personnel;

Instructions for delineation of the affected area and access control;

Measures to protect emergency workers, as appropriate.

Appropriate workplace monitoring instruments to measure both high and low dose rates;

Active personal alarm dosimeters;

Additional personal dosimeters;

Barrier materials and warning notices for the temporary designation of a controlled area;

Local shielding, such as bags of lead shot or lead sheets;

Suitable tool kits and source recovery equipment (long handled tongs, pliers, screwdrivers, bolt cutters, adjustable spanner);

A spare shielded container;

Wipe test kit for leak testing sources and for other surface contamination checks;

Communication equipment (e.g. mobile phones, radio transmitters and receivers);

Spare batteries and torches;

Necessary personal protective equipment.

Quickly recognize an abnormal situation that might constitute an emergency and implement the appropriate emergency procedures;

Remain calm and move away from the radioactive source, and ensure that any other workers in the vicinity are evacuated and informed that there might be an emergency;

Inform the radiation protection officer of the operating organization;

Measure the neutron and/or gamma radiation dose rates and record any doses measured by active personal dosimeters;

Confirm, establish or re-establish controlled area barriers on the basis of dose rate reference levels, consistent with regulatory requirements and the emergency plan and procedures;

Prevent access to the controlled area;

Use necessary personal protective equipment;

Maintain surveillance of the controlled area;

Inform the relevant authorities (and the client, if the emergency occurs at the client’s site) and seek assistance as prescribed in the emergency plan and procedures.

Plan and implement a specific course of action on the basis of previously established emergency plans and procedures, taking care to minimize doses that might be received as a result of this course of action.

Move to a location away from the controlled area and rehearse the planned course of action before entering the controlled area to implement the emergency plan.

Implement the planned course of action to the extent that training, equipment, the actual situation and authorizations allow; under no circumstances should the source come into contact with the hands or other parts of the body.

If the course of action taken is unsuccessful, leave the controlled area and consider the next course of action while maintaining surveillance of the controlled area.

Call for technical assistance, if necessary, from a qualified expert or from the manufacturer of the source and/or well logging equipment, as appropriate. Such assistance may form part of the emergency plan and procedures, in which case it should be planned and agreed upon between the various parties in advance.

When the situation has been brought under control and the source is safe, investigate the emergency and estimate the doses received.

Return personal dosimeters to the dosimetry service for rapid assessment.

Arrange for any damaged or malfunctioning equipment to be repaired by the manufacturer or arrange for a qualified expert to undertake a detailed examination and repair before any reuse.

Prepare a report and notify the regulatory body, in accordance with regulatory requirements.

Quickly recognize an abnormal situation that might constitute an emergency and implement the appropriate emergency procedures;

Turn off the electrical power to the neutron generator;

Inform the radiation protection officer of what has happened;

Perform a radiation survey to confirm whether there is any residual radiation hazard;

Not move the well logging equipment until details such as its position, beam direction and exposure settings (tube voltage, current, and time) have been recorded;

Not use the neutron generator until it has been examined and repaired by the manufacturer or by a qualified expert;

Use necessary personal protective equipment.

Estimate the doses that could have been received;

Return personal dosimeters to the dosimetry service for rapid assessment;

Prepare a report and notify the regulatory body, in accordance with regulatory requirements.

A description of the emergency, with as much detail as possible of the equipment involved. The details should include model numbers and serial numbers, wherever possible.

Environmental conditions at the time of the emergency, with particular reference to whether or not these conditions played any significant part in causing the emergency or affecting the outcome.

The specific cause(s) of the emergency.

Details of actions taken to regain control of the situation and to restore conditions to normal, with special reference to any actions that were notably beneficial or detrimental.

The personnel involved and their duties, tasks and qualifications.

An assessment and summary of the doses received by all affected individuals.

Corrective actions recommended with the aim of preventing similar emergencies in the future.

Lessons from managing the emergency.

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Storage of the well logging sources;

Calibration and operation of the well logging tools;

Transport of the sources;

Work at the site with the well logging tools;

Maintenance of the tools;

Disposal of disused sources.

A source becoming detached from the logging tool (down the well or otherwise);

A source stuck in the tool or container;

A tool stuck down the well or borehole;

A neutron generator failing to de-energize;

High dose rates present in an area that is not designated as a controlled area; (

Suspected or actual overexposure of individuals to gamma and/or neutron radiation;

A missing, lost or stolen source;

A damaged or leaking source, for example due to mechanical damage, fire or explosion in a work area or storage area;

Events involving rupture of well logging source including rupture during attempts to recover a well logging source that has become stuck down the hole;

An accident during the transport of radioactive sources.

Radioactive sources: Gamma and, as appropriate, neutron dose rates from well logging sources during storage, use (shielded and unshielded) and transport, and in accident scenarios.

Neutron generators: Neutron and gamma dose rates from neutron generators in normal use and during accident scenarios.

Gamma radiation emitted by any neutron activation products.

Potential for contamination of the logging tool with naturally occurring radioactive material (this is out of scope of this publication);

Potential for internal exposure if a sealed radioactive source were damaged.

Workers: Well logging personnel and other workers present on the site (e.g. crane operators).

Members of the public, including visitors to the site.

Shielding of storage facilities, logging tool containers, transport packages and overpacks (for gamma emitting and neutron emitting radionuclides, as appropriate);

Design of transport packages;

The use of appropriate handling tools (i.e. to maintain distance from the source);

The design of logging tools, for example to minimize the likelihood of a detached source;

Temporary source containers to be used following an accident.

Safe working procedures, including local rules;

Transport package labelling and documentation;

Designation of controlled areas and delineation with barriers and warning signs;

Staff training and appointment of a radiation protection officer;

Advice from a qualified expert;

Workplace monitoring and individual monitoring (gamma and neutron radiation), and health surveillance;

A preventive maintenance programme and periodic checks on the condition of well logging equipment;

Periodic safety audits of operations;

Leak testing of sealed radioactive sources;

Records of source accountancy and source movements.

The ambient dose rate equivalent (neutron and gamma radiation) at 1.0 m from the neutron generator while it is being operated at nominal power;

The ambient dose rate equivalent (gamma radiation) at 0.1 m from the target of the neutron tube of a neutron generator for up to 1 hour after operation at nominal power;

The tritium activity in the target.

Steel: 1.6 cm;

Lead: 0.7 cm.

The incident was not reported when it occurred.

No recovery tool was available (none was present on the installation at which the incident occurred).

A retrieval protocol was not in place.

One employee was wearing a personal monitoring device that had not been approved for use in the State.