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

2 WASTE CHARACTERIZATION METHODS 1. Measurement methods 2. Predictive calculation models

3 Table of contents Introduction LLWAA Code (Low Level Waste Activity Assessment) LLWAA-DECOM Code 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 of radionuclides taken into account by LLWAA Activation Products 14 C 36 Cl 58 Co 60 Co 55 Fe 59 Ni 63 Ni 94 Nb 3H3H Fission Products 90 Sr 99 Tc 129 I 134 Cs 135 Cs 137 Cs 234 U 235 U 237 Np 238 U 238 Pu 239 Pu 240 Pu 241 Pu 242 Pu 241 Am 243 Am 244 Cm

7 Activities in Reactor Coolant System and in Nuclear Auxiliary Systems Core activities inventories Measured I-131, I-133, I-134, Cs-134 and Cs-137 activities in the RCS 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 Cs-137 cladding defects and recoil FP, TRU-recoil FP, TRU cladding defects Activation of corrosion products Activities build-up and inventories in On site conditioned wasteNon-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  60 Co activity in the primary coolant (activation products)  137 Cs activity in the primary coolant (fission products)  131 I, 133 I and 134 I 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 activities of mixed spent IERs at Tihange NPP in 2001 [MBq/m³] 3H3H 6.23E Co 5.74E Cs 2.64E Pu 9.52E C 2.04E Ni 2.05E Cs 6.14E Pu 1.34E Cl 2.56E Nb 5.72E U 3.83E Pu 3.31E Mn 2.53E Sr 8.38E U 1.04E Am 2.72E Fe 4.70E Tc 2.41E Np 8.01E Pu 4.76E Co 2.46E I 3.61E U 8.56E Am 2.97E Ni 1.76E Cs 6.73E Pu 7.63E Cm 7.25E+00

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 Inventories conditioned waste packages Inventories non conditioned waste packages Combustible waste Non-combustible waste DECL LLWAA Calculated specific activities scaling factors Category 1, 2 and 3 parameters Measurements gamma spectrometry contact dose rates Deposited activities scaling factors LLWAA-DECOM Input number of cycles, cycle length particle properties piping properties thermal hydraulic conditions Measurements gamma spectrometry Co-60, Cs-137 contact dose rates Deposited activities inventories LLWAA-ASHES Scaling factors ashes Co-60, Cs-137 spectrometric measurements Inventories ashes 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/m 2 ) 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-DECOM codes increase confidence in source terms for near-surface or geological repositories