The expert group “Dosimetry of External Radiation“ (AKD) in the Swiss‑German Fachverband für Strahlenschutz [1] appreciates the theoretical fundamentals of the Operational Quantities for External Radiation Exposure as described in the joint report of ICRU and ICRP especially from an academic point of view.
However AKD would like to raise strong concerns over the implementation of the changes proposed. The major concerns are:
AKD claims a feasibility study for a dosimeter that complies with the new concept in terms of IEC 62387 in its current edition.
So far AKD has identified the following advantages and concerns of the new concept:
Advantages
The new operational quantities correct actual deficiencies. The new conversion factors will better describe doses for high energies and large angles. Beyond that additional conversion factors for higher energies and additional particles such as muons will be made available. The theoretical approach is easier to convey and to teach.
Concerns
Unless a feasibility study has proven anything different, the new concept requires a radical redesign of dosimeters for photon energies below 70 keV. Most likely such dosimeters will not fit official dosimetry services, neither practically nor economically. AKD assumes that the German dosimetry services [2] would have to invest approximately 20 M€ to implement the new concept. This amount solely reflects the purchase of new dosimeters. The new concept will force smaller dosimetry services to quit business.
The new operational quantities will replace quantities, i.e. HP(10), that are well conservative in the energy range below 70 keV. Although the new quantities theoretically will be “better”, the new concept will downgrade the practical radiation protection: Currently the overestimation by about a factor of 5 (for perpendicular incidence) is advantageous as soon as the radiation worker is considered as a moving object in a radiation field. Actual dosimeters that are worn on the chest do and future dosimeters are expected to underestimate the dose compared to perpendicular incidence. The new concept will void the overestimation and therefore the conservatism of today.
The new concept will allow to reduce the shield thickness of X‑ray equipment. The radiation exposure in the vicinity of such equipment will physically increase even though the new quantities may result in lower dose results.
The implementation of the new dose quantities will substantially burden the budget in the nuclear (power) sector without providing relevant improvements for photon fields between 70 keV and 10 MeV.
It is expected that the new concept will cause lower dose values especially in the medical sector which represents some 50% of the radiation workers. Consequences of which range between innocent misunderstandings and severe suspects of data manipulation. Clarification will be costly!
AKD suspects that the introduction of the new operational quantities will bring forward problems that have been observed for the quantity H*(10) already. Decades after H*(10) was made the exclusive dose quantity, practical and affordable H*(10) dosimeters for X-ray applications have not yet won recognition. In the vast majority of cases HX is still utilized.
[1] http://www.fs-ev.org
[2] The four official German dosimetry services monitor approximately 360.000 radiation workers.