IAEAInternational Atomic Energy Agency

Gauges and well logging

Potential exposure and radiation protection programme

Day 6 –Lecture 5

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Objective

• To discuss about potential for radiation exposure associated with nuclear gauges and well logging.

• To discuss aim, structure and requirement of the Radiation Protection Programme (RPP) as applied to working with gauges and well logging

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Contents

• Pathways of Exposure Routine Exposure Gamma Gauges Beta Gauges Neutron Gauges

• Radiation Protection Programme (RPP) Structure of RPP Classification of Areas Emergency Plans

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Pathways of exposure

External Exposure

Internal Exposure

Ingestion

Absorption

Inhalation

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Nuclear gauges and well loggingRoutine exposure

• External doses• possible, although

unlikely to be significant

• Internal doses• unlikely, due to sealed source construction • gamma and neutron sources special form

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• 111 GBq Cs-137

Contact dose rate

up to 75 Sv/h

Dose rate at 1m

1 Sv/h

Gamma gaugesTypical external dose rate

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Gamma gauges - routine exposure

• Assume, for example, that employee spends 6 hours per year with hands in contact with gauge = 0.45 mSv annual extremity dose

• Assume, for example, that employee spends 50 hours per year working 1 metre away from gauge = 0.05 mSv annual effective dose

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Gamma gauges - routine exposure

• In reality, doses may be even lower than those indicated on the previous slide

• Consider that most process control gauges (level gauges, density gauges etc) are sited in areas that are not usually occupied

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• 3.7 GBq Pm-147 • Shutter open (beta)• Dose rates will be higher for larger sources

Between guide plates

up to 10 Sv/h

Dose rate at 0.5m

<1 Sv/h

Beta gaugesTypical external dose rate

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• 46 GBq Kr-85 • Shutter closed (Bremsstrahlung)

Contact dose rate

up to 2 mSv/h

Dose rate at 1m

up to 10 Sv/h

Beta gaugesTypical external dose rate (worst case)

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Beta gauges - routine exposure

• Assume, for example, that employee spends 6 hours per year cleaning gauge head (shutter closed), with hands in contact with gauge = 12 mSv annual extremity dose

• Assume, for example, that employee spends 50 hours per year working 1 metre away from gauge (shutter closed) = 0.5 mSv annual effective dose

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• 1.85 GBq Am-241/Be • neutron and gamma dose rate

Contact dose rate

up to 30 Sv/h

(source retracted)

Operator position

during use up to

15 Sv/h

Neutron gaugesTypical external dose rate

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Neutron gauges - routine exposure

• Assume, for example, that employee spends 50 hours per year with hands in contact with gauge (source retracted) = 1.5 mSv annual extremity dose

• Assume, for example, that employee spends 250 hours per year using the gauge = 3.75 mSv annual effective dose

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• 37 GBq Am-241/Be • neutron and gamma dose rate

10 cm from tool

up to 2.1 mSv/h

Surface of source

transport container

up to 150 Sv/h

Well loggingTypical external dose rate

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Well logging - routine exposure

• Time with source exposed likely to be only a few seconds per operation. Assume, for example, that employee spends 8 hours per year with hands at 10 cm from exposed source = 16.8 mSv annual extremity dose

• Assume, for example, that employee spends 50 hours per year close to transport container = 7.5 mSv annual effective dose

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Radiation Protection Programme

• What is an RPP?• Structure of the RPP• Assignment of responsibilities• Role of the Qualified Expert• Classification of areas• Local rules and supervision (RPO)• Radiation monitoring• Record Keeping• Emergency plans• Audit and review

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What is an RPP?

• A programme that reflects the application of management responsibility for radiation protection and safety

• Key factor for the development of a safety culture• Effectiveness depends on management

commitment• Essential to undertake a prior radiological

evaluation and safety assessment before developing the RPP

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Structure of the RPP

• assignment of responsibilities• classification of areas• local rules• supervision arrangements, including RPO

appointment• arrangements for area monitoring• arrangements for individual monitoring

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Structure of the RPP

• record keeping• education, information and training• emergency plans• health Surveillance• quality Assurance• reviewing/ auditing the RRP

Qualified Experts to provide advice on contents of RPP

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Radiation Protection Responsibilities

• ManagementObtain necessary authorizationsProvide necessary facilities, personnel,

equipment and trainingestablish and maintain a “safety first” culture

Radiation Protection Officer (RPO) Implement the RPP Implement the local rules Provide information and training

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Radiation Protection Responsibilities

• Operators and WorkersBecome familiar with equipment, safety and

warning systemsBecome familiar with any local rules and adhere

to themNotify the RPO of any unusual occurrencesUse all safety equipment provided

Clients Provide a safe working environment and

adequate time for the job

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Role of the Qualified Expert

• Provides advice on observance of the BSS• Registrants/licensees to identify suitable

Qualified Expert(s)• Registrants/licensees to inform the

Regulatory Authority of their arrangement with Qualified Expert

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Classification of Areas

• A controlled area is an area where procedural controls are required in order to restrict radiation exposures

• A supervised area is one that does not require classification as a controlled area, but where exposure conditions should be kept under review.

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Controlled areas

• Examples of controlled areas associated with nuclear gauges are:around portable gauges (eg soil moisture

probes and nuclear density gauges) during use and transport

inside portable source storesaround fixed gauges during some

maintenance operationsinside vessels on which level gauges are fitted

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Controlled areas

• Examples of controlled areas associated with well logging are:around the borehole head during useinside the source storearound the logging tool during source

loading operationsaround the source containers during

transport of equipment

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Controlled Area Requirements

• Demarcation• Restriction of access• Signs• Monitoring• Local rules

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Local Rules

Work in a controlled area must be carried

out in accordance with written local rules, Local rules should include:

name of person(s) responsible for supervising the work

description of controlled and supervised areas

general radiation safety measures dose investigation levels emergency plans

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Supervised areas

• Examples of supervised areas associated with nuclear gauges are:around fixed gauges (gamma and beta)

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Supervised Area Requirements

• Delineation• Signs• Monitoring

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Supervision

• Radiation Protection Officer (RPO) supervises the work

• Ensures any local rules are followed• Should be enough RPOs to ensure

adequate supervision at all times

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Area Monitoring

• Monitoring of radiation dose rate required for all controlled and supervised areas

• Records of monitoring should be kept• Purpose of monitoring is to ensure that

radiation levels remain within expected limits

• Good idea to set action levels above which steps are taken to reduce the radiation dose rate

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Individual monitoring

• Required for all those who access controlled areas

• May require assessment of gamma and neutron dose

• Records of individual monitoring must be kept• Purpose of monitoring is to demonstrate that

exposures are adequately controlled• Investigation level must be set

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Individual dose meters

TLD - gamma, X, neutron and beta

Film - gamma, X and beta

OSL - gamma, X, neutron and beta

PADC - neutron

Consult Qualified Expert regarding type of dosemeter and wear period

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Record keeping

• Source accountancy• updated frequently for portable gauges

• Dose rate monitoring results• Checks on safety systems and warning

devices• Equipment maintenance • Source leak test certificates• Radiation monitoring instrument test

certificate

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Education, information and training

• Training of RPO• Radiation awareness training for other

staff• nature of the hazard• extent of any controlled or supervised

areas• requirements of local rules• emergency plans

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Emergency plans

• Consider reasonably foreseeable accidents

• Provide instruction to limit the consequences

• Rehearse periodically

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Protection of the public

• Emergency plans to consider possible accidents involving the public, eg loss or theft of a sourcenecessary precautionsactions to limit consequencesliaison with Emergency Services

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Audits and Reviews

• Aim : To enhance the effectiveness and efficiency of the RPP

• Objectives :To identify and correct problems that may prevent the achievement of the programme's objectives

• Conducted by competent persons

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Summary

• Potential for radiation exposure associated with nuclear gauges and well logging• routine use• accidents

• Aim, structure and Requirement of the RPP as applied to working with gauges and well logging

• Any questions or comments?