Performance Indicators Quantifying the Contribution of Safety Functions to the Confinement of Radionuclides in a Geologi
- PDF / 211,119 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 96 Downloads / 186 Views
1265-AA09-08
Performance Indicators Quantifying the Contribution of Safety Functions to the Confinement of Radionuclides in a Geological Repository System Eef Weetjens1, Jan Marivoet1 and Suresh C. Seetharam1 1 Performance Assessments Unit, SCK•CEN, Boeretang 200, 2400 Mol, Belgium
ABSTRACT The main indicators for the evaluation of the safety of a geological repository are the dose or the risk that are estimated for a sufficiently representative set of possible evolution scenarios. In recent years complementary sets of safety and performance indicators have been developed within national geological disposal programmes and international projects. Whereas safety indicators aim at giving an indication on the level of safety provided by the repository system, performance indicators aim at illustrating how the repository system works. Most sets of performance indicators that have been introduced hitherto in safety cases of geological repositories are related to the multi-barrier concept; they quantify or illustrate the contribution of the main engineered and natural barriers to the confinement of the radionuclides within the repository system. However, the application of the defence-in-depth principle to geological disposal has led to the introduction of safety functions in safety cases. Because of the paramount role played by the multi-safety-functions concept in recent safety cases, we have derived performance indicators that quantify the contribution of the main safety functions to the confinement of radionuclides in the geological repository system. The considered safety functions are containment, limitation of release and retardation. The proposed performance indicators are based on time-integrated activity or radiotoxicity fluxes released from the main successive compartments of the repository system. The proposed indicators can be applied to individual radionuclides as well as to a weighted sum of all radionuclides.
INTRODUCTION The main objective of radioactive waste management is to protect man and the environment from exposure to ionising radiation from radionuclides, which are present in the waste, now and in the future. The strategy adopted to achieve this objective is to concentrate and confine the waste and to isolate it from the biosphere [1]. The main indicators for the evaluation of the safety of a geological repository are the dose or the risk that are estimated for a sufficiently representative set of possible evolution scenarios. However, calculation of dose or risk requires making assumptions on potential exposure pathways, including human habits and changes in the surface environment in the far future and they do not provide information on the functioning of the repository system as such. Therefore, different sets of complementary indicators have been developed in recent years, discriminating between safety and performance indicators. Whereas safety indicators aim at giving an indication on the level of safety of the integrated repository system, performance indicators aim at illustrating how the
Data Loading...
