Personal dosimetry of workers without a physical dosemeter using computational methods

Abdelrahman Mahmoud

Promoter

Phillips Christophe, c.phillips@ulg.ac.be

SCK•CEN Mentor

Vanhavere Filip
filip.vanhavere@sckcen.be
+32 14 33 28 59

SCK•CEN Co-mentor

Struelens Lara
lara.struelens@sckcen.be
+32 14 33 28 85

Expert group

RP Dosimetry and Calibration

PhD started

2016-08-16

Short project description

Occupationally exposed workers of category A are obliged to wear a personal dosemeter. This dosemeter should be designed to measure the operational quantity Hp(10) as an estimate of the effective dose E. These physical measurements are routine practice, but still have a lot of disadvantages, both from practical as from a metrological point of view. The results are mostly known only after some time with passive dosemeters, and wearing a dosemeter is often seen as a burden by some workers. Also the uncertainties with the present dosemeters (within a factor of 1.5 or 2 from the real value) are not negligeable.

Recent developments are moving towards active personal dosemeters, and even active systems that can transfer the dose data on-line to all kind of applications (i-Phones, servers, real-time monitoring panels,…). This would improve the application of the ALARA principle.

On the other hand, computational techniques are also evolving very fast. In the past standard mathemathical phantoms were used, while now very detailed voxel and NURBS phantoms are available. These NURBS phantoms can be designed in all kind of shapes and positions that represent much better the real individuals. On these NURBS phantoms it is feasible to do Monte Carlo simulations so that the personal doses from any radiation field can be calculated. With increasing computational power, such calculations go faster and faster.

The idea of this work is to develop an application in which, for a certain workplace field, the doses of the workers will be calculated instead of measured. For this the spatial radiation field, including energy and angular distribution, needs to be know. This can be incurred from on-line dose measurements on several locations. Input from fixed dose monitors can be used for this. The real movement of the persons would need to be monitored, and transferred to the calculation tool. In first instance, the calculations can be analytical, and in a later stage come from Monte Carlo calculations. The final goal would be to also use real individualised phantoms from the workers, so that also organ doses can be known.

Objective

The final goal of this work is very innovative and challenging. It is foreseen that this PhD makes the first steps towards this final goal.

The starting point can be the SCK•CEN application of VISIPLAN. This is a planning tool for ALARA purposes. The geometry of the workplace is entered in the software, as well as the expected radiation sources. After that, the planned movements of the workers in the workplace are given as input, and VISIPLAN gives the expected doses to the workers. These calculations are analytical. There are routines available to adjust the radiation field based on real measurement points.

The first steps can be to include the on-line monitoring of the radiation field into VISIPLAN, so that it can be used almost in real time. The next step would be that the real movement of the workers is monitored and included in the software. Some simple examples could be tested in real fields.

It will also be a major step to go from analytical calculations to Monte Carlo simulations. With the increasing computer power this should be possible, and this would have major advantages in more complex set-ups. With these Monte Carlo simulations, also more detailed and individualised phantoms can be introduced.