Influence of Radon and Decay Products on Field Equipment Service Personnel
Authors: Takhautdinov Sh.F. , Sizov B.A. , Diyashev R.N. , Zaitsev V.I. , Antonov G.P. 
Published: December 2007

Processes of oil production, gathering, transportation and treatment are accompanied by scaling of radioactive materials (NORM) on technological equipment.

Previously, as a rule, radiative influence at the expense of only external irradiation was estimated during servicing and repair of this equipment. Risk of internal irradiation at the expense of radon and other alpha-emitting isotopes was considered only for technological processes of gathering and treatment of natural and associated gas.

The presentation is dedicated to risk evaluation of personnel internal irradiation in servicing and repair of the equipment contaminated by NORM.

Investigation results are obtained based on physical-chemical properties of scales, study isotope composition of radioactive materials determination and laboratory tests of scales emanating power. Results have been compared with emanation of pure salts.

Field and laboratory experiments showed that radon discharge up to 30-50 *10-3 Ci into atmosphere is possible during repair of contaminated equipment. Minimum fivefold air exchange is required to remove residual radon activity from technological vessels.

Evaluation of internal irradiation dose in the process of servicing and repair of NORM contaminated equipment has been carried out.

Results of studies should be taken into consideration when organizing works for servicing and repair of technological equipment, as well as for development of its design.

Introduction

The problem of radioactive contamination of technological equipment, environment during production, gathering, transportation, treatment and processing of oil and gas has a global character. According to Dr. Gray's data about 30% of the producing oil wells in the USA are contaminated with radioactive salts. Radioactive scales are also revealed on technological equipment of oil and gas fields in North sea as well as in other regions of the world.

In oil fields of Tatarstan radioactive scaling on the equipment of wells was for the first time recorded in the middle of 60s. At the end of 80s there was found out an intensive creation of radioactive scales on technological equipment of the most oil treatment units (OTU) and tank farms (TF). Radioactive scales in production and treatment of oil are also recorded in practically all main producing regions of the former USSR.

Presence of considerable amount of radioactive materials on technological equipment during production and treatment of oil, and gas may lead to personnel irradiation exceeding allowable levels and creates potential hazard to environmental pollution.

As a rule, in previous investigations of scales, being created during production and treatment of oil only uranium, thorium and radium isotopes content was studied, while in evaluation of radiative situation only possibility of external irradiation was considered. The role of radon and its decay products in pollution of environment and internal personnel irradiation was not practically studied.

Liberation of radon with decay products from scales and their entry into atmosphere may lead to radioactive pollution of environment, which increases the risk of internal personnel irradiation. In this connection this paper has studied the intensity of radon accumulation and liberation at different stages of oil treatment technological processes.

The results of the work are obtained on basis of laboratory experiments, analysis of scientific-technical information and calculations.

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