Neutron Reference Measurements to

Petroleum Industry

Karla C. de Souza Patrão, Evaldo S. da Fonseca, Walsan W. Pereira, Mauricio C. de Almeida and Luciane de R. Souza

karla@ird.gov.br

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LABORATÓRIO NACIONAL DE METROLOGIA DAS RADIAÇÕES IONIZANTES

IRD- Instituto de Radioproteção e Dosimetria

Neutron Reference Measurements to Petroleum Industry

• In the evaluation of the reservatories of the field, porosity is one of the key measurements for quantify oil and gas reserves.

• The measurement of porosity by neutrons, employs a neutron source to measure the rate of hydrogen in a reservoir, which is directly related to its porosity. .

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Neutron survey meter • Instrument used to measure the quantity ambient dose

equivalent in areas with individuals occupationally exposed to neutron fields.

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It used a neutron source 241Am-Be ( , n) standardized by a primary standard system Manganese Sulphate Bath at LN (according ISO 8529).

Calibration

Lab. low Scatering (LN)

0

20

40

60

80

100

120

140

160

180

2006 2007 2008 2009 2010

Calibrations performed at LN

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Neutron survey meters registered in LN

Oil & Gas

others66%

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What is the best frequency for the neutron area monitors calibration?

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Currently in Brasil

• CNEN NN 3.01 Diretrizes Básicas de Radioproteção (2005)

– Calibration periodicaly

• CNEN NN 6.04 Funcionamento de Serviços de Radiografia Industrial (1989)

– annual calibration for gamma area monitors

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Currently in Brasil

• NBR ISO/IEC 17025 General requirements for the competence of testing and calibration laboratories (2005)

―the laboratory customers should define the frequency of calibration.

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Goal

Check the calibration interval adopted for the

neutron area monitors used in oil and gas

industry.

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Methodology

• Data on the calibration of area monitors from the oil and gas industries in the period 2006 to 2010.

• Data analysis using the method Schumacher

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Number of Area Monitors Used in Oil and Gas Industry in Brazil (2006-2010)

Registered 255

4 calibrations 108

3 calibrations 32

2 calibrations 34

1 calibration 81

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0

5

10

15

20

2006 2007 2008 2009 2010

Percentage of bad monitor sent to calibration

37%

7%

12%

14% 20%

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Schumacher Method

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• Based on the last three calibrations compared to the current calibration to determine if the calibration range used can be maintained or should be reduced or increased.

CALIBRATED THREE TIMES

MAXIMUM REDUCTION 58%

REDUCTION 10,5%

REMAINS 26,3 %

INCREASES 5,3 %

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Results

• The results indicate reduction of the period performed by users of the neutron area monitors.

• The study should be thorough, considering other factors such as the origin of the instruments.

• The laboratory must improve its relationship with its customers.

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Conclusion

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Goal • Designing and Building a portable

measurement system for verification of the operating conditions of area monitors for

neutrons.

Development of a portable system to test for

neutron area monitors

• This device must be used by the users of area monitors.

• Allows a study of the stability of the monitors which helps in defining the range of instruments calibration.

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Features

first step

• Definition of geometry and materials of the system;

• Simulation with the MCNP5;

• Experimental measurements to validate the

simulation.

second step

• Construction and Approval System.

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Methodology

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• Material: high density polyethylene.

• The dimensions were defined considering its portability and its use with the display area for neutrons Ludlum 12-4, to be the most used in the brazilian market.

• The neutron source used in the system is 241Am-Be ( , n), with 14.6 GBq.

Initial Conditions

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• Rates of ambient dose equivalent:

– Were determined for each system over the rates of 50 μSv/h and 500 μSv/h. These points correspond to 50% of full scale, considering the two scales of interest in radiation protection (0-100 μSv/h and 0-1000 μSv/h).

Initial conditions

Simulation Geometry

First stage

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• Construction and approval of portable

– The portable system was built by mechanical engineering sector of the IRD.

– They performed several measurements with different models of area monitors for neutrons, seeking the approval of the system.

Second step

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LABORATÓRIO NACIONAL DE METROLOGIA DAS RADIAÇÕES IONIZANTES

Second stage

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Results Ludlum 12-4

Serial Number 12 cm

H*(10) ( Sv/h) 2 cm

H*(10) ( Sv/h)

265508 55.2 ± 4.2 524.0 ± 12.7

248440 49.3 ± 2.4 504.5 ± 31.3

216430 55.0 ± 2.0 540.0 ± 12.9

169409 45.5 ± 3.1 450.0 ± 11.8

236318 53.0 ± 4.1 510.0 ± 12.9

249364 52.0 ± 2.6 592.5 ± 16.9

223444 53.6 ± 3.3 555.0 ± 15.8

93323 52.8 ± 4.5 548.0 ± 27.0

169417 50.3 ± 4.2 510.0 ± 12.9

248431 53.8 ± 2.1 515.0 ± 12.9

Média: 52.1 ± 2.9 524.9 ± 37.7

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Results

Survey Meter Distance 12.0 cm

from source H*(10) (mSv/h)

Distance 2.0 cm from source

H*(10) (mSv/h)

Prescila – Ludlum 2363 148.5 ± 13.0 3104.4 ± 304.6

Prescila – Ludlum 2363 127.7 ± 11.6 3117.8 ± 979.1

Thermo Eberline FHT 752 87.6 ± 4.0 829.1 ± 261.9

Thermo Eberline FHT 762 53.4 ± 1.6 511.0 ± 9.2

Eberline APS1 56.8 ± 6.7 677.0 ± 24.1

Eberline E-600 58.3 ± 2.5 567.9 ± 11.3

• The system proved to be a suitable tool for checking the operating conditions of the area monitors, providing performance monitoring tools between these calibrations. This device should also be used to assist in determining the range of calibration of instruments, taking into account the intensity of use and the desired accuracy. The developed system is easy and inexpensive construction and can be purchased by users of area monitors for neutrons.

Conclusion

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