Swedish Radiation Protection Authority Radiological Survey of the Active Central Laboratory (ACL) in Studsvik, Sweden Henrik Efraimsson Swedish Radiation Protection Authority (SSI)

Contents The facility Decommissioning activities Radiation protection of workers Conditions for clean-up activities Radiological survey Documentation of the work

The Active Central Laboratory Studsvik Arnhem

ACL cross-sections Ground floor

Decommissioning activities Dismantling of equipment in the 90´s Decommissioning project started 1998 Main tasks: removal of service systems, clean-up and measurements Finished in 2004 Application for clearance and demolition in 2005

Radiation protection of workers Low-level radiation fields Protection measures during dust-generating activities No external or internal radiation doses above the limits for registration and reporting

Conditions for clean-up The licence holder shall perform reasonable clean-up activities, show compliance with EU recommendations RP 113 for the expected nuclides, make nuclide specific measurements of residual activity, search for spot activity if spots are suspected, disregard naturally occurring activity that cannot be attributed to operations in the facility, take measures against re-contamination.

Radiological survey Mapping with a grid of 1 m2 squares. Measurement of residual activity by Direct measurement with hand-held scintillation counter (100 cm2 sensitive area) Smear samples (smeared area 100 cm2) for analysis with scintillation counters Alpha, beta and gamma specific analysis of samples In-situ gamma spectroscopic (ISOCS) measurement of several m2 at once.

Radiological survey, cont. Documentation of measurement results. Eventual removal of contaminated material. Eventual complementary scintillation measurements. Confirming in-situ gamma spectroscopic measurements.

Detected nuclides Analysis of samples: Co-60, Sr-90, Cs-134, Cs-137, Eu-152, Eu-154, Eu-155, U-234, U-235, U-238, Pu-238. Pu-239, Pu-240, Am-241, Cm-244 In-situ gamma measurements: Co-60, Cs-137 and Am-241 (a-emitting Pu / Am-241  3)

Survey methods

Extent of survey – wall example 3) Gamma- spectroscopic measurement Scintillation measurements 1) Smear samples 1 m2 2) Hand-held instruments

Required documentation Description of activities during operation Description of clean-up activities Description of survey methods Transparent measurement results Estimation of residual activity Description of measures to prevent re-contamination