MSE CONTROLLED DOCUMENT. NORM Guidelines Master Document

Transcription

1 MSE CONTROLLED DOCUMENT NORM Guidelines Master Document Document No: Supersedes Revision no: 1 Date:1/10/2004 Custodian: MSE Revision no: 1 Date: 1/10/2006 Filename: NORMMGT. DOC Administered by: Verified: Date: Verified: Date: Approved: Date: Approved: Date: MSE RPA OND/OSD UWD/GD Date: 1/10/2004 Date: Date: Date: Reason for revision: This document contains proprietary information and is intended for use by PDO and Contractor staff only. The contents of this controlled document shall not be changed without formal approval of the document custodian.

2 Contents 1. Purpose of this document Introduction Policy Policy Statement Policy implementation Organisation Structure Radiation Advisory Committee (RAC) Radiation Protection Adviser (RPA) Radiation Protection Supervisor (RPS) Radiation Protection Technician (RPT) Tasks/ responsibilities Radiation Advisory Committee Corporate Radiation Focal Point (CRFP) Radiation Protection Supervisor (RPS) Radiation Protection Technicians (RPT) Training Recommended Radiation Dose Limits Dose limits Derived limits Dose rate limits Inhalation an/or Ingestion limits Monitoring of personnel Measurements Field measurements Laboratory measurements Protective measures NORM locations Registration Register of radiological workers Personal radiation dose records Registration of ionising radiation sources NORM Storage, transport and disposal Emergency procedures NORM procedures References APPENDICES Appendix 1 Glossary of Abbreviations Appendix 2 List of NORM Guidelines Page 1

3 1. Purpose of this document The purpose of this document is to lay down how the hazards of Ionising Radiation are managed within Petroleum Development Oman (PDO). 2. Introduction Exposure to ionising radiation may cause detrimental effects on the human body and in the long term may lead to adverse health effects such as cancer or leukaemia. For these effects the severity increases with the amount of radiation received and PDO has adopted a policy of reducing exposures to as low as reasonably achievable (ALARA). Examples of radioactive sources used by PDO and its contractors include: x-ray devices, well logging tools, density gauges and multiphase flow meters. There are also natural occurring ionising sources such as cosmic rays from the sun and naturally occurring radioactive elements such as Uranium 235, Thorium 232 and Potassium 40. Everyone is exposed to naturally occurring radioactive sources on a daily basis and even these vary from country to country and from region to region. This is also true for Oman and the average background radiation due to terrestrial radiation is 0.3 msv per annum compared to the world average of 0.4 msv per annum. Unstable isotopes of Uranium, Thorium, radium and radon, for example, exist naturally and they are referred to as Naturally Occurring Radioactive Materials (NORM). For these radioactive atoms (also referred to as radionuclides or radioisotopes) to become more stable, the nuclei eject or emit subatomic particles (alpha and/or beta) and high-energy photons (gamma rays). This process is called radioactive decay. NORM namely, Uranium-235 and Thorium-232, exist in the formation rock and were formed with the creation of the earth millions of years ago. The parent elements uranium and thorium decay to their daughter isotopes which are also radioactive. Uranium decays through a series to radium- 226 and thorium decays through its series to radium-228. The radium isotopes are water soluble dissolve in the reservoir water in contact with the formation rock. When our production activities extract reservoir water/oil, NORM (seen as Ra-226 and Ra-228) precipitates on the interior of production equipment as scale (Barium/Radium Sulphate scale) and solids such sand/clay and silts deposit with the oil in vessels and separators. Wax from pigging activities on the inside of pipes may also contain some NORM and should be treated as contaminated until proven otherwise by monitoring. Page 2

4 3. Policy 3.1 Policy Statement PDO will: Protect its personnel, contractors, 3rd parties and the environment against the hazards of exposure to ionising radiation due to PDO activities. Avoid uncontrolled releases of radioactive contaminated substances and to minimise the effects of past deposits Apply the principles of ICRP 60 for radiation protection (justification of a practice, optimisation of protection and dose & risk limitation) No new practices shall be adopted without justification that they are of benefit Keep exposure As Low As is Reasonably Achievable (ALARA) where exposure to ionising radiation is not avoidable Prevent any exposure to ionising radiation levels that result in an effective dose of more han 1mSv/y above background to non-classified personnel and to the public Avoid the need for classified radiological workers wherever reasonably practicable 3.2 Policy implementation The following will apply: Adherence to Policy All activities with, or related to, ionising radiation sources are to be documented in procedures. Adherence to these procedures will be audited. Justification Justifications for changes to established procedures, which involve exposure risks, are to be agreed by the Radiation Advisory Committee (RAC). Optimisation Where exposure to Ionising Radiation is possible, measures need to be taken to keep the exposure As Low As is Reasonably Achievable (ALARA). The RAC will provide further guidance on reasonable achievability. Procedure to be followed to deviate from policy MSE is owner of Ionising Radiation Policy and, acting on recommendation of the RAC, has final responsibility for authorising any modifications or deviations. Any deviations from the policy will be documented in procedures. Page 3

5 Specific objectives for NORM are: To identify all sites where radioactive substances are present to: implement suitable PPE when required implement clean up efforts using a cost/benefit approach prevent spreading of radioactive substances in the environment treat, store and dispose of contaminated equipment and radioactive waste in a controlled manner 4. Organisation 4.1 Structure Five organisational entities advise on Ionising Radiation: the Radiation Advisory Committee (RAC), the Corporate Radiation Focal Point (CRFP) the Radiation Protection Adviser (RPA), the Radiation Protection Supervisor (RPS) and the Radiation Protection Technician (RPT) Radiation Advisory Committee (RAC) The RAC sets PDO s policy with respect to Ionising Radiation. The RAC reports to the PDO MSE Steering Committee and comprises: OSD (Chairman), MSE 32 (Secretary), ONO1 OSO1 MSE23 On invitation representatives from drilling (UWD1) The RAC reports to the PDO HSE Steering/Implementation Committee Radiation Protection Adviser (RPA) The RPA is PDO s external expert on Ionising Radiation. He advices on policy proposals and undertakes audits of PDO s radiation management system to ensure PDO is current with best Page 4

6 practice on an international level. The RPA will be a source of expert advice for all matters concerning Ionising Radiation. PDO will use an external consultant as part-time RPA and utilise the experience within the organisation to develop policy and procedures for managing ionising radiation Radiation Protection Supervisor (RPS) Measurements and radiological assistance in supervision of work involving Ionising Radiation will be done by Radiation Protection Supervisors (RPSs), Radiation Protection Technicians who will report to the line. PDO does not currently have an experienced Senior Radiation Protection Supervisor. The CRFP will act as representative on behalf of the RPA and will be based at Muscat Radiation Protection Technician (RPT) To support the RPS s a number of employees (e.g. maintenance operators, MSE Advisors, Production Supervisors, Campaign Supervisors) will be trained as Radiation Protection Technicians. RPT Level is the minimum level of training required to conduct NORM Radiological Survey as part of the PTW when a specific part of the installation is opened. The NORM Radiological Report is then attached to the PTW for the Production Supervisor or Worksite Supervisor to interpret and sign-off. The RPT adhere to the instructions of the Production Supervisor, Worksite Supervisor or other permitted to authorise a PTW involving maintenance on plant that has conveyed reservoir water/oil/gas. 4.2 Tasks/ responsibilities Radiation Advisory Committee The role of the RAC is listed. The roles of the RAC, the CRFP and the RPA are complementary. The CRFP in consultation with the line puts forward proposals and the RAC decides on the course of action with the advice from the RPA where necessary. 1. Leadership and commitment 1.1 Set priorities 1.2 Make resources available 2. Policy and strategic objectives 2.1 Compare standards, Oman and international legislation, and advice on standards to be adopted. 2.2 Review policy statements 3. Organisation 3.1 Identify need for additional resources 4. Hazards and effects management 4.1 Evaluate radiological data 4.2 Identify risk-reducing measures 4.3 Set realistic objectives and performance criteria 4.4 Identify credible emergency events and identify response requirements and plans Page 5

7 5. Planning and procedures 5.1 Review procedures with respect to Ionising Radiation every two years 6. Implementation, Monitoring, Corrective Action 6.1 Monitor compliance with the company s NORM policy and advise on corrective actions 7. Audits 7.1 Ensure NORM is covered in MSE audits 7.2 Advise MSE with respect to audits on NORM (on request). 8. Management review 8.1 Ensure that NORM Management System is subject to management review Corporate Radiation Focal Point (CRFP) In addition to the tasks and responsibilities mentioned above, the CRFP or the RPS (see below) shall: be current on all potential and actual NORM-related activities within the company at all times ensure records/registers are kept on radiological workers, Ionising Radiation sources, NORM measurements (count and dose rates, specific activity), radioactive waste, radioactive contaminated equipment act as secretary for the RAC meetings identify the number of RPSs and RPTs required audit implementation of the NORM management system Radiation Protection Supervisor (RPS) The RPS s will act as focal points for the CRFP and will maintain an overview of all radiological activities in the interior. The RPS s will resolve queries on behalf of the CRFP. The RPS s shall: inspect and give radiological assistance in supervision of work involving ionising radiation sources of a non-routine nature ensure quality assurance of radiation protection organise the required monitoring and sampling qualify waste with respect to radioactivity ensure that radioactive waste and NORM-contaminated equipment is stored, packaged, transported and disposed off in compliance with regulations and procedures communicate with and report to the CRFP Radiation Protection Technicians (RPT) The RPT s shall: undertake NORM measurements whenever no data are available on installation parts to be opened register and report the results in compliance with the relevant NORM Procedure notify the RPS/CRFP if count rates exceed the agreed standards give radiological assistance in supervision of routine NORM jobs as agreed by the RAC Page 6

8 4.3 Training PDO have a suite of courses dedicated to NORM. The line shall develop and maintain a training database specifying requirements per job. This includes training requirements for Contractors. 5. Recommended Radiation Dose Limits 5.1 Dose limits The ICRP recommends that the exposure of individuals to radiation should be subject to dose limits. The occupational dose limits are aimed at ensuring that no individual is exposed to unacceptable risks as well as preventing any deterministic effects and minimising the chance of stochastic effects. The natural background radiation, including radon, is excluded for the dose limitations. Radiation doses arising from medical procedures are also excluded from the dose limitations. Certain activities or job types within PDO have potential to expose workers to higher radiation doses than others. PDO has adopted two dose limits for workers based on job types. These limits are defined as Target and Maximum limits for workers likely to be exposed to NORM during the course of their normal work activities. The Target Limit is a dose that PDO believes all workers should not exceed on an annual basis. Doses received by workers above the Target Limit indicate that controls may not be effective, however workers can continue to work in their given job type provided the controls are reviewed and the maximum dose limit is not reached. The Target Limit for members of the public due to PDO activities shall not exceed 0.3 msv/y above background. The Target Limit for workers likely to be exposed to NORM is: 1 msv/year. The Target Limit for vessel/tank cleaning workers is: 2 msv/year The Maximum Limit for workers who may be exposed to Ionising Radiation during their work activities is 10 msv/year as defined in the MD249/97. Occupationally Exposed Workers (Radiation Workers) Exceptions are made for Contractors who are classified as Radiation Workers and are submitted to medical examination as defined by a Medical officer. Employees who have the potential to receive combined doses (internal/external) as a result of their work above 6 msv/year shall be classified as Radiological Workers. For these workers, the dose must not exceed 10 msv/year. Radiation Workers shall be defined and record in the Health Risk Assessment for the Job Type. The Target level for Radiation Workers for NORM is less than 2 msv/year. Individuals below the age of 18 years and pregnant women shall not be involved in work with ionising radiation sources. Page 7

9 In specific situations the RAC will decide if other exceptions are allowed. Affected Group Target Limit (msv) Annual Effective Dose Limit (msv) Five Year Cumulative Dose Limit (msv) Incidentally exposed workers Tank/Vessel Cleaners Sludge Farm Operator Radiation Workers NORM Members of Public Derived limits Exposure to Ionising Radiation is possible by external radiation and by internal radiation due to inhalation and/or ingestion of radioactive substances. For practical purposes it is useful to define job related exposure limits Dose rate limits For worker protection when exposed to external radiation, where the radiation contour exceeds 2.5μSv/h then the area shall be designated as a radiologically Supervised Area. For example, this might be the area immediately surrounding a vessel which is demarcated with tape and radiation warning signs. In a Supervised Area exposure conditions are monitored to allow for reliable prediction of the dose to individual workers. The dose-rate in a Supervised Area shall not exceed 7.5μSv/h. Where the radiation contour exceeds 7.5 μsv/h, the area shall be designated as a Controlled Area where specific protective measures and safety provisions are required. The dose rate at the border of storage facilities inside the PDO premises, e.g. the designated area for radioactive waste in Bahja shall not exceed 0.5 μsv/h. Fences around PDO assets to which the public has access shall be set such that the maximum dose rate at the outside of the fence shall not exceed 0.5 μsv/h above background Inhalation an/or Ingestion limits To ensure that doses for inhalation/ingestion are ALARA, PDO has adopted a total protection philosophy. Suitable PPE (e.g. filter masks) shall be used to prevent inhalation/ingestion of radioactive substances arising from dust generating activities. Note: An inhalation risk only exists where NORM contaminated scale, sludge, pigging wax or production water becomes airborne. Where measurements with the Mini 900 with 44A probe indicate five (5) counts per second above background, workers shall be required to wear the specified PPE. Page 8

10 5.2.3 Monitoring of personnel In order to monitor radiation exposure to individuals to ensure that the target limits are not exceeded the dose of individuals shall be recorded and registered in a database. The action level has been set at 1.0 µsv/h. Where the daily dose can exceed 8.0 μsv/day, this shall be recorded on the NORM Radiological Survey with details of the individuals exposed. It is expected that the data will indicate that actual exposure levels are well below set limits. 6. Measurements Qualitative and quantitative field measurements of Ionising Radiation can be carried out at the worksite, to determine the presence of ionising radiation sources and to check compliance with dose limits. Quantitative measurements of radioactive substances have to be carried out in a properly equipped laboratory. These measurements are used to determine the composition and destiny of radioactive waste or radioactive contaminated materials. Procedures MSE.04 and MSE.06 explain the use of radiation instruments, interpretation of the results and the actions to be taken. 6.1 Field measurements Properly trained personnel using radiation monitors suitable for the type and energy of the Ionising Radiation to be measured shall measure Ionising Radiation. The RPA advises on equipment to be used. The selection of a monitor depends strongly on a number of factors such as measurement principles, sensitivity, energy-dependence and robustness. The following radiological protection instruments are currently in use at PDO. Graetz5X survey meters for the measurement of external gamma dose-rate in (μsv/h). The 900 Series Mini Monitor with Probe type 44A for the qualitative detection of gamma radiation (in counts per second). The 900 Series Mini Monitor with Probe type EP 15 for the detection of alpha/beta contamination, (in counts per second). All results shall be recorded on the NORM Radiological Report and entered into the database. NORM contaminated equipment to be replaced or scrapped shall be monitored and each component recorded using the NORM Report Form located in SP 1170 (Appendix I) 6.2 Laboratory measurements Measurement of samples (activity concentration) needs sophisticated equipment, which is not present in the field. If necessary, samples will be sent to a specialised institute, such as the Sultan Qaboos University (SQU). MSE.07 Sampling for NORM provides guidance on the sampling procedure. It includes the analysis request from, labelling and transport requirements to SQU. Page 9

11 The results shall be ed to the CRFP s, Production Chemistry and the requestor. All results will be stored in the NORM Database. 7. Protective measures Working with Ionising Radiation may lead to increased health risks. Therefore protective measures have to be taken. Standard operating procedures will specify the required protective measures (see NORM procedures MSE.03). Attention has to be given to: instruction and information, e.g. in the toolbox meetings, sanitary regulations, monitoring by radiation experts, supervision through controlled areas and restricted access, appropriate use of PPE and auxiliaries. 8. NORM locations NORM has been demonstrated at many places in or adjacent to PDO controlled areas. A detailed overview is available from the NORM Database and each Asset shall have access to this information. PDO shall have an annual program to identify NORM locations through surveys. There is an ongoing programme for decontamination of affected areas. Criteria for remediation are being specified. 9. Registration In order to manage NORM in a controlled manner constant quantification of NORM contamination is required through proper registration. Below, the required registers are summarised, while detailed requirements for registration are specified in SP Register of radiological workers It is PDO s policy to keep exposure to PDO employees below 1 msv/year above background wherever reasonably practicable. As a consequence there should be no one classified as radiological worker and if so no dose registration is obligatory for PDO employees. Also no medical surveillance and record keeping is necessary. Contractors undertaking cleaning of NORM contaminated tanks/separators shall undergo personal dosimetry through the use of TLD badges as they may exceed 2 msv/year. Contractors shall be responsible for developing and maintaining their own registers which must be readily accessible to the worker and PDO auditors. 9.2 Personal radiation dose records For re-assurance purposes dosimeters will be used on a selective basis for PDO employees and results will be entered into the controlled database by the CRFP or an assistant. This database will contain dose estimates calculated from work records where the daily dose exceeds 10 usv/day. These will be made available on request. For exposure control NORM dose estimates shall be made using dose rate and exposure time data. Page 10

12 9.3 Registration of ionising radiation sources Records must be kept of all ionising radiation sources on Company premises. Their exact location should be known at any time (logbook). SP 1237 will specify the data to be kept. Contractors shall keep their own registers and ensure that as a minimum the PDO requirements will be kept. 9.4 NORM A registration system shall be used, that contains the relevant information to calculate risks and/or dose estimates, plan protective measures and discuss options for waste disposal and decontamination of equipment. The CRFP is responsible for this system and will specify registration forms to be used by the RPS/RPT. 10. Storage, transport and disposal Storage, packaging, transport and disposal are specified in MSE Emergency procedures An emergency situation is defined as an unplanned, potentially hazardous exposure to Ionising Radiation. An additional requirement is that corrective actions shall be taken within a reasonable timeframe (one hour). Due to the source strengths of isotopes within PDO the most likely emergency scenarios are: an unplanned exposure to ionising radiation sources trespassing the demarcated area loss or any other unaccounted absence of ionising radiation sources transport accident Line management shall ensure emergency procedures are in place. Where the radiation work is done by a contractor, the Contract Holder shall ensure the contractor has adequate emergency procedures in place. These shall include the prescription of protective equipment (e.g. shielding materials, remote handling equipment) and all corrective actions. In addition to the urgent corrective actions, PDO management and the CRFP shall be informed immediately to estimate exposure consequences and to plan additional actions. 12 NORM procedures Whilst some references are contained within this document the total NORM management system consists of: NORM Specification SP 1170 NORM Management Guidelines An overview of the NORM guidelines are enclosed in Appendix References [1] Ionising Radiation Safety Guide, Shell Safety & Health Committee, 11/93 [2] PDO NORM Guidelines [3] SP 1170 HSE Specifications NORM Page 11

13 Glossary of Abbreviations Appendix 1 ALARA ICRP NORM PPE RAC RPA RPS RPT CRFP As Low As Reasonably Achievable International Commission on Radiological Protection Naturally Occurring Radioactive Material Personal Protective Equipment Radiation Advisory Committee Radiation Protection Adviser Radiation Protection Supervisor Radiation Protection Technician Corporate Radiation Focal Point Page 12

14 List of NORM Guidelines MSE No. TITLE Remarks 00 NORM Guidelines Master Document Version Basis for derived limits and decision making 02 Routine and non routine jobs on NORM installations 03 Protection of personnel against NORM risks 04 Carrying out, recording and interpreting NORM surveys 05 Supervised and Controlled Areas 06 Registration of NORM contaminated materials, equipment & waste 07 Sampling for NORM 08 Packing, temporary storage, transport and final storage 09 Decontamination of personnel 10 NORM measuring programme 11 Radiological safety precautions for wireline jobs 12 Radiological safety precautions for dismantling equipment 13 Radiological safety precautions for NORM contaminated filters 14 Radiological safety precautions for NORM contaminated vessels and tanks 15 Radiological safety precautions for pigging operations 16 Radiological safety precautions for the workshop 17 Clean up of NORM contaminated areas 18 Control, issue and care of Radiation Protection Instrumentation 19 Dose rate assessment 20 Disposal of equipment To be issued 21 Decontamination of equipment 22 Control of contaminated equipment To be issued 23 NORM training 24 Radiological safety precautions for well re-entry 25 Radiological HSE Precautions for clean out of wells using Coil Tubing Units Ionising Radiation Safety Guide Shell 1993 Appendix 2 Page 13