TECDOC 855 and RS-G1.7 • Gunnar Olsson and Lise-Lotte Spontón • TW5-TSW-002, D1 • Final meeting, TW5-TSW-001 and -002, 23-24 October 2006, UKAEA, Culham, UK
Background and task description • 1996 IAEA published TECDOC 855 ”Clearance levels for radionuclides in solid materials” in the form of an interim report for comment. First international document to contain nuclide specific acitvity limits for unconditional clearance of very low level radioactive waste. Never finalised. • 2004 IAEA published Safety Guide No. RS-G-1.7, “Application of the Concepts of Exclusion, Exemption and Clearance”, giving specific activity values for the release from regulatory control of radioactive material in bulk quantities. The specific activity levels differ sometimes considerably between RS-G-1.7 and TECDOC 855. In this task the two documents are compared, and differences are pointed out and discussed. Consequences for clearance of PPCS Model A-C is studied.
TECDOC 855 • The radiological basis is the international consensus on the principles for the exemption of radiation sources and practices from regulatory control, published in IAEA Safety Series No. 89 (1988). • A group of experts has examined published studies relating the activity concentration or total activity in materials to radiation dose. • Clearance level is determined by the scenario and exposure pathway which gives rise to the highest radiation dose. • Clearance levels for 56 nuclides. • Due to the uncertainties in the results of the studies, the nuclides are grouped into five clearance level ranges: (0,1 - 1), (1.0 - 10), (10 - 100), (100 - 1000) and (1000 - 10 000) Bq/g • Formulas for calculating the clearance for mixtures and for nuclides included.
RS-G-1.7 • Background document: IAEA Safety report no 44 “Derivation of Activity Concentration Values for Exclusion, Exemption and Clearance”, in which nuclides are discussed in detail. • Clearance levels for 258 artificial nuclides • Derivation of clearance levels • Formula for calculating the clearance for mixtures similar to formula in TECDOC 855 • No formula for not listed nuclides. • Nuclides not listed in RS-G-1.7 can be found in UKAEA European Activation File (EAF). The latest version FUS 517 constitutes a comprehensive extension of RS-G-1.7, encompassing all radionuclides to be expected in fusion waste analysis.
Comparison • List with artificial nuclides from RS-G-1.7, extended with calculated values from UKAEA FUS, compared with TECDOC 855 • It is noticed that common fusion waste nuclides are more restricted in RS‑G-1.7. TECDOC 855 RS-G-1.7 (Bq/g) (Bq/g) H-3 3000 100 C-14 300 1 Fe-55 300 1000 Co-60 0.3 0.1 Ni-59 300 100 Ni-63 3000 100 Zr-93 300 10 Nb-94 0.3 0.1 Mo-93 30 10 Tc-99 300 1
Consequences • When RS-G-1.7 is applied on waste from PPCS Models A-D over a decay period up to 100 years, the waste amount for Model A and Model C will be increased and for all models there will be a need for more interim storage time before clearance.