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WASTE CHARACTERIZATION METHODSS. Vanderperre

Belgatom

Vanderperre, Belgatom, chapter 7

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WASTE CHARACTERIZATIONMETHODS

1. Measurement methods

2. Predictive calculation models

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Table of contents

• Introduction• LLWAA Code

(Low Level Waste Activity Assessment)

• LLWAA-DECOM Code

• Conclusions

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Introduction

• Typical approaches used in most EU countries to determine critical nuclide inventories of waste packagessimplified 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

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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

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List of radionuclides taken into account by LLWAA

Activation Products 14C 36Cl 58Co 60Co 55Fe 59Ni 63Ni 94Nb 3H

Fission Products

90Sr 99Tc 129I 134Cs 135Cs 137Cs 234U 235U 237Np

238U 238Pu 239Pu 240Pu 241Pu 242Pu 241Am 243Am 244Cm

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Activities in Reactor Coolant System and in Nuclear Auxiliary SystemsActivities 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 chemicaladditive activation

products H-3, C-14, Cl-36

Cs-137 cladding defects and recoil

FP, TRU-recoil FP, TRU claddingdefects

Activation of corrosionproducts

ActivitiesActivities build-upbuild-up andand inventoriesinventories ininOn site conditioned waste Non-conditioned waste

Scaling factors

LLWAA general structure

Water and chemicaladditive activation

productsH-3, C-14 and Cl-36

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LLWAA category 1 parameters

• Parameters adapted each year to produce specific annual outputs of the code60Co activity in the primary coolant (activation products)

137Cs activity in the primary coolant (fission products)

131I, 133I and 134I activities in the primary coolantChlorides concentration in the primary coolantNumber of refueling operation (0 or 1)

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LLWAA input screen for category 1 parameters

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LLWAA category 2 parameters

• Parameters that can vary according to NPP operating conditionsprimary-to-secondary leak rateprimary coolant purification ratesteam generator blowdown rateboron concentration at BOLboron concentration in non recycled waste evaporator

evaporator concentrates production

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LLWAA modification screen with category 2 parameters

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LLWAA category 3 parameters

• Design parameters of the code that are fixed and not accessible to the usercore activity inventoriescladding defects and diffusion coefficientsfraction of activity in soluble and in insoluble forms

decontamination factors of ion exchange resins and filters

equipment corrosion rates

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LLWAA calculated activitiesof mixed spent IERs at Tihange NPP

in 2001 [MBq/m³]

3H 6.23E+01 60Co 5.74E+05 135Cs 2.64E-01 239Pu 9.52E-01

14C 2.04E+03 63Ni 2.05E+05 137Cs 6.14E+04 240Pu 1.34E+00

36Cl 2.56E+00 94Nb 5.72E+02 234U 3.83E-03 241Pu 3.31E+02

54Mn 2.53E+05 90Sr 8.38E+02 235U 1.04E-04 241Am 2.72E+00

55Fe 4.70E+05 99Tc 2.41E+01 237Np 8.01E-04 242Pu 4.76E-03

58Co 2.46E+06 129I 3.61E-01 238U 8.56E-04 243Am 2.97E-01

59Ni 1.76E+03 134Cs 6.73E+04 238Pu 7.63E+00 244Cm 7.25E+00

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LLWAA validation

• Comparison of LLWAA predicted values with values derived from measurements performed by the Belgian Nuclear Research Centre (SCK CEN) on samples ofspent ion exchange resinsspent filters cartridgesevaporator concentrates

• On behalf of ONDRAF/NIRAS, in-depth critical review by AVN (Belgian Licensing Authority)

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Inventoriesconditioned

waste packages

Inventories non conditioned waste packages

Combustiblewaste

Non-combustible waste

DECLDECL

LLWAALLWAA Calculated• specific activities

• scaling factors

Category1, 2 and 3

parameters

Measurements• gamma spectrometry

• contact dose rates

Deposited activities

scaling factors

LLWAA-DECOMLLWAA-DECOMInput• number of cycles, cycle length• particle properties• piping properties• thermal hydraulic conditions

Measurements• gamma spectrometry

Co-60, Cs-137• contact dose rates

Depositedactivities

inventories

LLWAA-ASHESLLWAA-ASHES

Scaling factors ashes Co-60, Cs-137spectrometricmeasurements

Inventoriesashes

LLWAA Code LLWAA Code ExtensionsExtensions

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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

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LLWAA-DECOM input parameters

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LLWAA-DECOM output

• Particle deposition and release rates• Deposited activities (Bq/m2) and scaling factors at any

given time (shutdown, decontamination or decommissioning)

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LLWAA-DECOM output

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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

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Conclusions

LLWAA and LLWAA-DECOM codes

are predictive calculation codes used for Belgian NPPs

allow significant savings in time, money and operator exposure

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Conclusions

LLWAA and LLWAA-DECOM codes increase confidence in source terms for near-surface or geological repositories