P-9-119
Potential Exposures in Mobile Industrial Radiography
L.Tauhata1, J.C.Leocádio1and V.R.Crispim2
1.Instituto de Radioproteção e Dosimetria - Comissão Nacional de Energia Nuclear, Av.Salvador Allende, s/n Recreio - CEP 22.780-160 - Rio de Janeiro – Brazil – email: [email protected]
2.Coordenação dos Programas de Pós-Graduação em Engenharia - Universidade Federal do Rio de JaneiroAv.Brigadeiro Tompowsky,s/n - Ilha do Fundão- C.P.68510 – CEP 21945-970 -Rio de Janeiro - Brazil.
INTRODUCTION
The non-destructive testing became essential in the modern industry development to garantee the
quality control of many types of devices, pieces and machines operation, according to norms and regulatory
guides.
In Brazil, there are about 127 radiographic services, involving 1 200 workers and 293 gammagraphy
devices. About 88% of installations of industrial radiography operate in Southeast region of the country, and
89% of workers and 100% radiographic companies.
Significant fraction of industrial radiography testing is made using mobile devices in open facilities,
using radioactive sources, like as 192Ir , with activities ranging from 0.78 TBq to 1.48 TBq. Statistically, the
day’s work is compound of 45% daylight job, and 55% nocturne activity (1, 2).
In the period from 1989 to 1991, among the faults were found 22.6% of lack of maintenance of
radiography devices, 20.5 misoperation of area monitoring, 13.7 inadequate device transportation, and 6.8 of
radiation protection failures. In same period, 28 abnormal occurrences and emergency situations emergency
situations were observed. Due to this scenario the evaluation of the potential risk is very important to prevent
and to stablish references levels for radiation protection procedures.
Then, is very important to analyse the radiation protection conditions of the mobile or open industrial
radiography facilities and to estimate the value of the potential exposure risk, the mean annual dose and the dose
distribution function of the workers.
METHODOLOGY
To estimate the potential exposure the concepts described in ICRP 64 (3) and Safety Series 104 (4)
were used. The annual mean value of abnormal events occurred in the operations of to remove and to retract the
radioactive source of exposure device recorded in data bank of National Commission of Nuclear Energy (CNEN),
in a period from 1992 to 1996, were used to obtain the risk value.
To evaluate the worker exposures, data obtained by accompaniment the radiographic testing in 5
installations, representative of all radiographic facilities in Brazil and the data bank of CNEN were used. To
obtain the statistical dose distribution data from individual monitoring of the workers of these installations were
used, data from additional individual monitoring and data bank of CNEN.
RESULTS
The absorbed mean dose value in the period from 1992 to 1996 maintained about 0.2 mSv/year like as
in the period from 1990 to 1994, with a maximum value of 0.55 mSv/year in 1988 (1). The statistical distribution
in a period from January to December 1996, behaviour likes as lognormal type (2).
The estimated risk value for potential exposure was 4 x 10-6 per year, in the period from 1992 to 96.
Using the data bank of CNEN, in a period from 1976 to 1992, the estimate value was 6.6. 10-6 per year, using the
same methodology.
CONCLUSION
The comparison of the failed operation probability value of operator/device/local system, in a period
from 1976 to 1992 and in 1996, shows an increasing of 0.5 x 10-11 to 1.1 x 10-11 per year, due mainly to the
radiographic device and accessories become oldest, in spite of maintenance care. However, due to the radiation
procedure improvements, the potential risk value reduced about 40%, that are from 6.6 x 106 to 4 x 10-6 per year.
REFERENCES
(1).
(2).
(3).
Martins,M.M. – O Serviço de radiografia industrial no Brasil sob o aspecto da Proteção Radiológica –
Master Science Thesis – UERJ, Rio de Janeiro – Brazil – 1994.
Leocádio,J.C. – Análise da radioproteção em instalações abertas de radiografia industrial – Master
Science thesis – UFRJ – Rio de Janeiro – Brazil – 1998.
ICRP-64 – Protection from Potential Exposures: a Conceptual Framework – ICRP, Vienna – Pergamon
Press, 1992.
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(4).
Safety Series 104 – Extension of the Principles of Radiation Protection to Sources of Potential Exposure
– IAEA, Vienna, 1990.
2