WASTE CHARACTERIZATION METHODS

1. WASTE CHARACTERIZATION METHODS S. Vanderperre Belgatom Vanderperre, Belgatom, chapter 7

2. WASTE CHARACTERIZATIONMETHODS 1. Measurement methods 2.Predictive calculation models

3. Table of contents • Introduction • LLWAA Code (Low Level Waste Activity Assessment) • LLWAA-DECOMCode • Conclusions

4. Introduction • Typical approaches used in most EU countries to determine critical nuclide inventories of waste packages • simplified calculation based on engineering judgment and extrapolation of international experience • selection of ratios between key nuclides and a critical nuclide, from experimental databases • use of predictive calculation codes taking into account the plant’s characteristics and operating conditions

5. LLWAA Code (Low Level Waste Activity Assessment) • Calculation of radionuclides inventories in process and technological NPP waste on the basis of characteristics and operating conditions of the NPP • Prediction of inventories of isotopes that are difficult to measure by routine techniques in NPP waste streams • Basis for the definition of a radiological source term for surface or near-surface repository long-term risk assessment

6. List ofradionuclides taken into account by LLWAA

7. Core activities inventories Corrosion rates of in-core and out-of-core equipment in contact with the primary coolant water and chemical additive activation products H-3, C-14, Cl-36 Measured I-131, I-133, I-134, Cs-134 and Cs-137 activities in the RCS Cs-137 cladding defects and recoil FP, TRU-recoil FP, TRU cladding defects Activation of corrosion products Activities in Reactor Coolant System and in Nuclear Auxiliary Systems Activitiesbuild-upandinventoriesin On site conditioned waste Non-conditioned waste Scaling factors LLWAA general structure Water and chemical additive activation products H-3, C-14 and Cl-36

8. LLWAA category 1 parameters • Parameters adapted each year to produce specific annual outputs of the code • 60Co activity in the primary coolant (activation products) • 137Cs activity in the primary coolant (fission products) • 131I, 133I and 134I activities in the primary coolant • Chlorides concentration in the primary coolant • Number of refueling operation (0 or 1)

9. LLWAA input screen for category 1 parameters

10. LLWAA category 2 parameters • Parameters that can vary according to NPP operating conditions • primary-to-secondary leak rate • primary coolant purification rate • steam generator blowdown rate • boron concentration at BOL • boron concentration in non recycled waste evaporator • evaporator concentrates production

11. LLWAA modification screen with category 2 parameters

12. LLWAA category 3 parameters • Design parameters of the code that are fixed and not accessible to the user • core activity inventories • cladding defects and diffusion coefficients • fraction of activity in soluble and in insoluble forms • decontamination factors of ion exchange resins and filters • equipment corrosion rates

13. LLWAA calculated activitiesof mixed spent IERs at Tihange NPP in 2001 [MBq/m³]

14. LLWAA validation • Comparison of LLWAA predicted values with values derived from measurements performed by the Belgian Nuclear Research Centre (SCKCEN) on samples of • spent ion exchange resins • spent filters cartridges • evaporator concentrates • On behalf of ONDRAF/NIRAS, in-depth critical review by AVN (Belgian Licensing Authority)

15. Input • number of cycles, cycle length • particle properties • piping properties • thermal hydraulic conditions LLWAA-DECOM Deposited activities scaling factors Measurements • gamma spectrometry Co-60, Cs-137 • contact dose rates LLWAA-ASHES Deposited activities inventories Scaling factors ashes Co-60, Cs-137 spectrometric measurements Inventories ashes Calculated •specific activities • scaling factors Category 1, 2 and 3 parameters LLWAA Measurements • gamma spectrometry • contact dose rates DECL Inventories non conditioned waste packages Inventories conditioned waste packages Combustiblewaste Non-combustible waste LLWAA Code Extensions

16. LLWAA-DECOM input parameters • Contamination in the streams of the nuclear systems (calculated by LLWAA) • Characteristics of the equipment to be dismantled (piping diameter, pipe rugosity …) • Operating conditions in piping systems (fluid velocity, pH, temperature, number of cycles, cycle life …) • Particulate diameter distribution of corrosion products • Time elapsed between the reactor final shutdown and the decontamination or dismantling

17. LLWAA-DECOM input parameters

18. LLWAA-DECOM output • Particle deposition and release rates • Deposited activities (Bq/m2) and scaling factors at any given time (shutdown, decontamination or decommissioning)

19. LLWAA-DECOM output

20. LLWAA-DECOM validation • Direct measurements of deposited activities present a number of practical difficulties and are not often available • Coupling of a dose rate model to the calculated deposited activities and comparison between calculated and measured dose rate • Good agreement between • calculated and measured dose rates during NPP shutdown and decontamination operations • predicted and measured deposited activities during steam generator replacement programmes

21. Conclusions LLWAA and LLWAA-DECOM codes • are predictive calculation codes used for Belgian NPPs • allow significant savings in time, money and operator exposure

22. Conclusions LLWAA and LLWAA-DECOMcodesincrease confidence in source terms for near-surface or geological repositories