Gauges and well logging Potential exposure and radiation ...

IAEA International Atomic Energy Agency

Gauges and well logging

Potential exposure and radiation

protection programme

Day 6 –Lecture 5

IAEA

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 logging

Routine 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 gauges

Typical 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 gauges

Typical 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 gauges

Typical 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 gauges

Typical 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 logging

Typical 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

• Management

Obtain necessary authorizations

Provide necessary facilities, personnel,

equipment and training

establish 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 Workers

Become familiar with equipment, safety and

warning systems

Become familiar with any local rules and adhere

to them

Notify the RPO of any unusual occurrences

Use 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 stores

around fixed gauges during some

maintenance operations

inside 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 use

inside the source store

around the logging tool during source

loading operations

around 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

l Work in a controlled area must be carried

out in accordance with written local rules,

l Local rules should include:

n name of person(s) responsible for

supervising the work

n description of controlled and

supervised areas

n general radiation safety measures

n dose investigation levels

n 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 source

necessary precautions

actions to limit consequences

liaison 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?

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