Job specific evaluation and analysis

In addition to the periodic assessment of the global exposure situation, the planning of all jobs that might lead to an occupational exposure should include, as early as possible before the job starts, a broad evaluation of the levels of collective and individual doses directly associated with the job. This evaluation should be performed by the responsible work group, that is the group that will actually be carrying out the job, in close co-operation with and with assistance from the radiation protection group. It needs to be based on a technical description of the job and be associated with an evaluation of the radiological conditions in which the work will be performed.

The objectives of a prior evaluation of the exposure levels of jobs can include:

— Obtaining the elements needed to identify and elaborate on job related dosimetric goals;

— Identification of the exposure conditions (i.e. where, when and how the workers are exposed);

— Bringing together the appropriate individuals in both the responsible work group and the radiation protection group;

— Identification of the jobs to be further analysed to improve radiological protection.

The level of evaluation, planning and review should be commensurate with the estimated doses associated with the jobs concerned. It may be useful to determine a reference value in terms of the individual or collective doses such that if the exposure estimate of a job were to exceed this predetermined value a further formal analysis would be conducted to identify the dose reduction options, followed by a senior management review of the evaluation and planning efforts. The categories of job and related ALARA reviews proposed by the National Council on Radiation Protection and Measurements for nuclear power plants is given in the example in Table III [11].

The reference value is likely to be different for each type of facility.

The selection of jobs needing further detailed analyses can also be made through a comparison with results previously obtained for the same type of job (either in the facility concerned or other comparable facilities), which may reveal that a better performance can be obtained. In this case not only the collective dose trends but also the evolution of the main parameters that contribute to exposures (i.e. the dose rates, duration of the job and number of workers) are significant. The analysis of the collective dose trends associated with repetitive jobs (e.g. routine annual maintenance jobs) or similar jobs performed in different places should be complemented by an analysis of the ambient dose rate as well as the exposure workload (the total time spent by an entire team in a work area, measured in person-hours) to detect the possible changes in radiological or technical conditions from one job to another (see the example in Section 3.2.1.1). This type of analysis may show that an increase in the collective dose is not due to the poor performance of a job but

TABLE III. EXAMPLE 5: COLLECTIVE DOSE CRITERIA TO DETERMINE THE LEVEL OF A JOB ANALYSIS

Category Dose estimate Review

1 <10 man·mSv By a radiation protection technician as part of a radiation work permit preparation

2 10–50 man·mSv By a radiation protection technician and radiation protection supervisor

3 50–500 man·mSv By a radiation protection supervisor and engineer responsible for ALARA planning

Dose estimate and planned dose reduction techniques to be documented in a pre-job report to management 4 >500 man·mSv In addition to the above, review by the plant’s

management or an ALARA committee

to an increase of the ambient dose rate (and similarly a decrease in the collective dose due only to a decrease in the ambient dose rate can be offset by an increase of the number of workers exposed or the duration of the exposure).

3.2.1.1. Example 6: Analysis of similar jobs performed successively in different workplaces

This example presents the type of analysis that can be done when looking at the dose trends for a job performed several times by the same team (i.e. the same number of workers) but in different workplaces.

The first step of evaluation usually consists of an analysis of the trend in the collective dose. In this example (see Table IV) it appears that the collective dose for the job is progressively decreasing, which seems to indicate a better performance of the job and an improvement in work efficiency.

However, because the job has been performed in different workplaces, in order to make a true interpretation of the dose trend (Table V) it is necessary to look at the ambient dose rates as well as the exposure workload. Table V shows that, although

TABLE IV. TREND OF THE COLLECTIVE DOSE Job sequence

1 2 3 4 5

Collective dose 36 30 24 17 15

(man·mSv)

TABLE V. INTERPRETATION OF THE DOSE TREND Job sequence

1 2 3 4 5

Collective dose 36 30 24 17 15

(man·mSv)

Ambient dose rate 0.4 0.3 0.3 0.2 0.1

(mSv/h)

Exposure workload 90 100 80 85 150

(person-hours)

the collective dose for the job is decreasing, the time taken to carry out the job is increasing. The decrease in the collective dose is due to a decrease in the ambient dose rate only. In terms of the optimization of protection, such a result should call for a more detailed analysis of the way the job was performed in order to check for possible mishaps or technical problems that increased the exposure workload.

3.2.2. Analysis of exposure situations for specific jobs in the context of carrying out a detailed study for the optimization of radiation protection

A detailed analysis is a necessary step for performing studies for the optimization of radiation protection (see Fig. 2). It is normally done not only for the jobs identified by global evaluations of exposure but also for all major new work.

Moreover, a periodic analysis should be performed for all the radiation related jobs at the facility concerned in order to determine what could be done to reduce the levels of doses (even if the levels of occupational doses associated with these jobs seem satisfactory).

The purpose of these analyses is to identify the possible factors that contribute to the level of doses that could be improved or changed. It should be based on a precise description of all the tasks performed in the job, in radiological, technical and environmental (which equates to a description of the area) terms. This means that detailed information concerning the time of exposure, the number of workers involved, ambient dose rates in the work areas, the use of protective clothing, procedures and tools, and the configuration of the work areas (including ergonomic criteria, the possible position of shielding, scaffolding, materials and tools) need to be obtained. The various groups of workers that interact in the preparation or performance of these jobs and that are directly involved in the identification of the means to reduce exposures need to participate in the collection of data and in the analyses of the jobs.

3.3. HOW TO OBTAIN THE DATA