REQUIRED ACCURACY AND DOSE THRESHOLDS IN INDIVIDUAL MONITORING

The paper follows the approach given in recent revisions of CEC and IA EA recommendations on requirements in individual monitoring for extern al radiations. The ICRP requirements on overall accuracy for individua l monitoring, as given in ICRP Publication 35 (1982), form the basis f or the specification of detailed accuracy requirements which are neede d in practical routine monitoring. The ICRP overall accuracy requireme nt is defined as an allowable maximum uncertainty factor at the 95% co nfidence level for a single measurement of the relevant dose quantity, i.e. H(p)(10) and H(p)(0.07). From this uncertainty factor, a value o f 21% can be evaluated for the allowable maximum overall standard devi ation for dose measurements at dose levels near the annual dose limits increasing to 45% for dose levels at the lower end of the dose range required to be monitored. A method is described for evaluating the ove rall standard deviation of the dosimetry system by combining random an d systematic uncertainties in quadrature, and procedures are also give n for determining each individual uncertainty connected to the dose me asurement. In particular, attention is paid to the evaluation of the c ombined uncertainty due to energy and angular dependencies of the dose meter. In type testing of personal dosimetry systems, the estimated ov erall standard deviation of the dosimetry system is the main parameter to be tested. An important characteristic of a personal dosimetry sys tem is its capability of measuring low doses. The paper discusses diff erent definitions of the lower detectability of dosimetry systems for individual monitoring.