Reactor Dosimetry in NPP Lifetime Management and Decommissioning Tasks

BgNS International Conference September 18-21, 2013, Sunny Beach, Bulgaria

Reactor Dosimetry in NPP Lifetime Reactor Dosimetry in NPP Lifetime Management and Decommissioning Management and Decommissioning

Tasks Tasks

Sergey Belousov Krassimira Ilieva

Desislava Kirilova*Mladen Mitev

Institute for Nuclear Research and Nuclear Energy of Bulgarian Academy of Science

*Kozloduy NPP


OUTLINE

IntroductionREACTOR DOSIMETRY TasksUnits in Operation

REACTOR DOSIMETRY and PTSALifetime Extension

REACTOR DOSIMETRYin Decommissioning

General Conclusion


Introduction (1)Introduction (1)

• There are six power units at Kozloduy Nuclear Power Plant (KNPP) in Bulgaria. Two of them (VVER 1000/320 type) are in operation now when other four (VVER 440/230 type) are shut down. For the Units 5 and 6 that are in operation the lifetime extension task is one of the most important. For the Units 1 to 4 that are shut down the task of radiological characterization for decommissioning purposes is of crucial interest.



• More then thirty years, since 1989 the Institute for Nuclear Research and Nuclear Energy of Bulgarian Academy of and Sciences (INRNE) has provided for KNPP a scientific assistance in the field of rector dosimetry which is a tool for nondestructive assessment of reactor pressure vessel (RPV) metal embrittlement.



• The data for the neutron fluence accumulated on the RPVs of all units during the operated cycles was assessed by calculation and verified by ex-vessel activation detectors. Assessment of the neutron fluence on the so called surveillance samples-witness has been done according to the Surveillance program of Units 5 and 6.


Reactor Dosimetry TasksReactor Dosimetry TasksUnits in OperationUnits in Operation


Reactor Pressure Vessel (RPV)Reactor Pressure Vessel (RPV)Current state

Neutron Embrittlement

TF = AF F1/3

Rest Lifetime

Rest cycles

LT = (Fmax -F)/Favr

Fmax ← Tka ← PTSPTS

Reduction of neutron fluence

Operation management

low leakage schemedummy cassettesweld axial level

Surveilance locationsSurveilance locationsSurveilance Program

witness-samples (surveillances) treatmentwitness-samples (surveillances) treatment


NEUTRON FLUENCE ASSASSMENT (LiM)NEUTRON FLUENCE ASSASSMENT (LiM)

XS LibrariesBGL 440, 1000

Body Model(R,,Z)-meshes

Power andBurnup

Distribution

Material XSDATA

(TORT)

Loading / OperationalHistory DATA

Geometry & MaterialDATA

(R,,Z)-source(TORT)

Decay DPA’ XS Const Det’ XS

RESULTSFluence, Activity,

Damages

RC SimulationCode

DOSRC

GIP

TORT

VISDO

MCNP XS DATA

MCNP

Measured Activities,Uncertainty,Correlation

Least Squares Adjustment

“Best estimatedFluence”

Task parameters (XS,Densities, Dimensions),Uncertainty, Correlation,

Sensitivity

Decay DPA’ XS Const Det’ XS


NEUTRON FLUENCE AND DETECTORS’ NEUTRON FLUENCE AND DETECTORS’ ACTIVITY CALCULATIONACTIVITY CALCULATION

TORT deterministic discrete ordinate codes BGL multigroup library

for VVER-1000 and VVER-440 BUGLE96 multigroup library for PWR

MCNP Monte Carlo code MCNPDATA library with continuous

neutron cross section energy dependence

DOSRC, VISDO code for fixed sourcesgenerating and geometry model visualization


R1

R2

1

2

body

DOSRC, VISDO - sources generating and geometry visualization

NEUTRON FLUENCE AND DETECTORS’ NEUTRON FLUENCE AND DETECTORS’ ACTIVITY CALCULATIONACTIVITY CALCULATION


Sources of Calculation Uncertainties:

• plant independent parameters: nuclear data

• plant dependent parameters: constructional data geometry dimensions, densities and materials’ content

operational data neutron source etc.

• approximations of calculation methods


Calculation uncertaintiesCalculation uncertainties

Source of uncertaintyFluence,

%Cu detector,

%Fe detector,

%Nb

detector, %

Iron XS inelastic 8.3(4.9*) 35.(14.*) 31.(16.*) 13.(8.3*)

Iron XS elastic 8.9 8.5 12. 14.

Iron XS absorption 2.3 9.7 5.7 3.1

Chromium XS inelastic 4.9 6.4 6.5 5.5

Chromium XS elastic 1.5 0.84 1.3 1.7

Chromium XS absorption 0.12 0.43 0.27 0.15

Hydrogen XS elastic 2.5 1.4 1.9 2.4

Oxygen XS elastic 2.8 1.8 2.4 2.8

Source spectrum 4.8 12. 7.7 5.3

Source spatial distribution 3.9 3.3 3.6 3.8

Steel density 2.5 3.7 3.8 3.2

Moderator density 5.4 3.7 4.3 5.2

RPV inner radius 7.4 4.2 3.7 0.35

Total 18.(12.*) 41.(20.*) 36.(19.*) 23.(12.*)


BEST ESTIMATED FLUENCEBEST ESTIMATED FLUENCE

after 1D adjustment VVER-1000

9.7-12.6.6-15.4.4-5.24.5-5.5

STD, %δ STD, %δ , %STD, %δ , %STD, %δ , %

FluenceNb detectorFe detectorCu detector

r̂ r̂ r̂ F̂

Tasks for further improvement:

• Sensitivity matrices in maximum irradiated positions• XS uncertainty correlation matrices• XS data improvement


Methodology ValidationMethodology Validation ((NPP)

V V ER 1 00 0

R E A C TO R C OR E

R E A C T OR VE S S E L

C A VIT Y

29

07

W E L D 3

W E L D 2

22

43

15

00

13001300

S U P P OR T R A C K S

S U P P OR T S Y S TE M

N b D ET E C TO R S

Fe , C u D E TE C TO R S

DEVICE FOR IRRADIATION OF DETECTORS IN THE AIR CAVITY BEHIND THE VVER-1000 RPV

Unit 5, cycles 6

a,kBq/g 54Fe(n.p)54Mn

calc exp

8

12

16

20

140 160 180 200

a,kBq/g 63Cu(n,)60Co

calc exp

0.2

0.4

05

0.6

0.3

140 160 180 200


MethodologyMethodology Validation Validation ((NPP surveilance)NPP surveilance)

Location of surveillance assemblyin VVER-1000/320

2

4

6

8

10

12

14

16

18

20

22

24

26

2L1

Ne

utr

on

Flu

en

ce, 1

018 c

m-2

2L2 2L3

Lower, cal.

Lower, exp.

Upper, cal.

Upper, exp.

2L4 2L5


VVER-1000 Mock-up

Methodology Verification (Methodology Verification (BenchmarkBenchmark)) LR0 in Rez, Czech Republic

VVER-440 Mock-up dummy

VVER-440 Mock-up standard

Conformity Mock-up – NPP UnitAttenuation and Spectra

0 5 10 15 20 25 30

Azimuth, deg

-25

-20

-15

-10

-5

0

5

10

15

20

25

(AF

/AF

m-1

),%

VVER440 standardVVER440 dummy VVER1000


RD CollaborationRD Collaboration

The neutron fluence evaluation methodology is being developed under research projects USA NRC, IAEA and EC in close collaboration of Russia, Czech Republic, Germany, Spain, Bulgaria, Belgium, Hungary and Ukraine, and especially within the activity of the European Working Group on Reactor Dosimetry (EWGRD) and WGRD-VVER group of the countries operating VVER. The WGRD-VVER group was created in 1990. The EWGRD activity is dated from 1994.


ConclusionsConclusions

The RD methodology developed in the Institute for Nuclear Research and Nuclear Energy of Bulgarian Academy of Science is at the state of the art at the state of the art levellevel

The state of the art RD provides reliable assessment results (with uncertainty less than 10%) for neutrons with energy above .1 MeV

Further efforts are needed to achieve the same level of accuracy for thermal neutrons and gammas


Reactor DosimetryReactor Dosimetry and PTS Analysis and PTS Analysisin in Lifetime ExtensionLifetime Extension


IAEA-EBP-WWER-08 (Rev. 1)


KKII ≤ [K ≤ [KICIC]][K[KICIC] - ] - allowable stress intensity factorallowable stress intensity factor

KKII - - crack loading in terms of stress intensity factor crack loading in terms of stress intensity factorTTkk

aa - RPV maximum allowable critical brittle fracture - RPV maximum allowable critical brittle fracture

temperaturetemperature


Critical temperature of brittlenessCritical temperature of brittleness TTKK

TTKK = T = TK0K0 + + ΔΔTTFF + + ΔΔTTTT + + ΔΔTTNN

ΔTΔTFF = = AAFF . (F.10. (F.10-22-22))nn

Master Curve (MC) approach (VERLIFE)Master Curve (MC) approach (VERLIFE)

[K[KICIC] = 25.2 + 36.6 · exp ] = 25.2 + 36.6 · exp 0.019 ( 0.019 (ΔΔTT)) ΔΔT = T = RTRT00 = T = T00 + + ; Reference temperature T; Reference temperature T00

PNAE G-7-002-86 doc – accidental situationPNAE G-7-002-86 doc – accidental situation

[K[KICIC] = 26 + 36 · exp ] = 26 + 36 · exp 0.02 ( 0.02 (ΔΔTT)),, ΔΔTT = T – T = T – Tkk

base metalbase metal

[K[KICIC] = 74 + 11 · exp ] = 74 + 11 · exp 0.0385 ( 0.0385 (ΔΔTT ) ) , , ΔΔTT = T – T = T – Tkk

weld metalweld metal[K[KICIC] = 35 + 53 · exp ] = 35 + 53 · exp 0.0217 ( 0.0217 (ΔΔTT ) ) , , ΔΔTT = T – T = T – Tkk

[Kic]

0.00

100.00

200.00

300.00

400.00

500.00

600.00

700.00

-150 -100 -50 0 50 100 150

ΔT, ºC

VERLIFE

PNAE G

PNAE B

PNAE W


IAEA-EBP-WWER-08 (Rev. 1)

MATERIAL SCIENCE

REACTOR DOSIMETRY

STRUCTURAL ANALYSIS

THERMAL HYDRAULICS

Fields of studyFields of study(ALPHABETIC ARRANGEMENT)(ALPHABETIC ARRANGEMENT)


Developing the team approach …

from N. Taylor presentation at JRC WS 11-13.10.2006


Application of FFP approach requires clear description of the uncertainties of the results of all disciplines uncertainties of the results of all disciplines involvedinvolved. Uncertainty decreasing is a way for increasing of the limit values without reduction of conservatism.

Another useful approach consists in application of local Tk

a distribution over RPV. The local assessmentlocal assessment could let us to increase the fluence limit value taking into account that the positions of the highest fluence does not coincide with positions where stress intensity factor KI reaches its highest values during PTS accident.

ConclusionsConclusions


Reactor Dosimetry in Reactor Dosimetry in Decommissioning TaskDecommissioning Task


Available DocumentsAvailable Documents• [1] “Nuclear Data Requirements for Fission

Reactor Decommissioning,” IAEA INDC(NDS)-269, January 1993

• [2] “Decontamination and decommissioning of nuclear facilities,” IAEA-TECDOC-716, August 1993

• [3] “Radiological Characterization of Shut Down Reactors for Decommissioning Purposes,” IAEA Technical Reports Series No. 389, October 1998


CONTRIBUTORS TO DRAFTING AND REVIEWAnttila, M. VTT Energy, FinlandCrégut, A. Consultant, FranceCross, M.T. AEA Technology, United KingdomDlouhy, Z. Radioactive Waste Management and

Environmental Protection Consulting Services, Czech Republic

Elkert, J. ABB Atom AB, SwedenFedorowicz, R. Atomic Energy of Canada Ltd, CanadaGenova, M. Centro Informazioni Studi Esperienze, ItalyImbard, G. Commissariat à l’énergie atomique, FranceKlein, M. Centre d’étude de l’énergie

ucleaire/Studiecentrumvoor Kernenergie (CEN-SCK), Belgium

Laraia, M. International Atomic Energy AgencyLe Goaller, C. Commissariat à l’énergie atomique, FranceMadrid, F. Empresa Nacional de Residuos Radioactivos, SpainReisenweaver, D.W. Nuclear Energy Services, United States of

AmericaSancho Llerandi, C. Centro de Investigaciones Energéticas,

Medioambientales y Tecnológicas, SpainShidlovskii, V.V. Mayak Production Association, Russian

FederationSivintsev, Y. Russian Research Centre “Kurchatov Institute”,

Russian FederationSmith, R.I. Consultant, United States of AmericaValencia, L. Kernforschungszentrum Karlsruhe, Germany

Consultants MeetingsVienna, Austria: 6–10 March 1995; 18–22 November 1996

Advisory Group MeetingVienna, Austria: 12–16 February 1996


TABLE II. THE MOST IMPORTANT ACTIVATION REACTIONS CONSIDERED [3]


TABLE II. THE MOST IMPORTANT ACTIVATION REACTIONS CONSIDERED [3](continued)


TABLE VII. RADIOACTIVE INVENTORY OF A TYPICALWWER 440 (GREIFSWALD UNIT 1) FOR MAJOR COMPONENTS [3]


TABLE XII. RADIOACTIVE INVENTORY OF TRINO PWR(ITALY) [3]


RELATIVE IMPORTANCE OF RADIONUCLIDES WITH TIME [3]

The principal activation products present in reactor materials at shutdown are 55Fe, 60Co, 59Ni, 63Ni, 39Ar, 94Nb (in steels); 3H, 14C, 41Ca, 55Fe, 60Co, 152Eu, 154Eu (in reinforced concretes) and 3H, 14C, 152Eu and 154Eu (in graphites). In terms of radiation levels, 60Co is the most predominant radionuclide. For steels, 55Fe and 60Co account for the major part of the inventory in the first ten years after shutdown. In the following 50 years, most of this activity has decayed, leaving the longer lived nickel, niobium and silver isotopes to dominate. For graphites and concretes, the short term decay is dominated by 3H, leaving the longer lived 14C, 41Ca and Eu isotopes to dominate in the longer term. After decay periods of more than 100 years, sufficient gamma activity from trace rare earth elements (e.g. Eu) is present to warrant the adoption of semiremote dismantling methods for reactor bioshields.


RELATIVE IMPORTANCE OF RADIONUCLIDES WITH TIME [3]


RELATIVE IMPORTANCE OF RADIONUCLIDES WITH TIME VVER 500 Armenian NPP - calculated


PARAMETERS INFLUENCING THE RADIONUCLIDE INVENTORYPARAMETERS INFLUENCING THE RADIONUCLIDE INVENTORY

For all reactor types, the radionuclide composition of activated and contaminated materials may vary within a very wide range. The most important factors and parameters are:

•the neutron fluence, •the duration of the operation,•the time elapsed after reactor shutdown.• Reactor type, design, power level and shutdown period;• Composition of construction materials, including trace

elements;• Operational parameters, e.g. chemistry of the heat transfer

medium, and maintenance;• Unplanned events.


NEUTRON ACTIVATION ASSESSMENT (DT)NEUTRON ACTIVATION ASSESSMENT (DT)Updated INRNE MethodologyUpdated INRNE Methodology

XS LibrariesBGL 440, 1000

Body Model(R,,Z)-meshes

Power andBurnup

Distribution

Material XSDATA

(TORT)

Loading / OperationalHistory DATA

Geometry & MaterialDATA

(R,,Z)-source(TORT)

Decay ConstActivation XS

RESULTSActivity, Spectra

RC SimulationCode

DOSRC

GIP

TORT

VISDO

MCNP XS DATA

MCNP

ORIGEN

Decay ConstActivation XS

RESULTSInventiory, Activity, Doses*

EASY 2010


Tasks for further improvement:

• XS libraries generation appropriate for thermal neutrons energy range

• Methodology benchmarking (based on JPDR data [1]) for methodology verification/validation

• International collaboration improvement• FFP approach implementation

In comparison with discussed in [3] is updated by

• 3D transport codes application• EASY code implementation (appropriate ORIGEN

alternative )

NEUTRON ACTIVATION ASSESSMENT (DT)NEUTRON ACTIVATION ASSESSMENT (DT)

Microsoft PowerPoint Presentation


The RD methodology developed in the Institute for Nuclear Research and Nuclear Energy of Bulgarian Academy of Science for Surveillance Program at NPP is at the state of the art levelthe state of the art level

This methodology could be modified for the decommissioningdecommissioning purposes

Tasks for the furtherfurther methodology improvementimprovement are determined

Application of FFP approachFFP approach should be very useful for NPP problems management

General ConclusionsGeneral Conclusions


Thank you