SAFETY ASSESMENT APPROACH FOR

DEEP GEOLOGICAL REPOSITORY

IN CZECH REPUBLIC

Václava Havlová, Dagmar Trpkošová,

Eva Hofmanová (ÚJV), Antonín Vokál (SURAO) ÚJV Řež, a. s.

24.11.2016

International Conference on the Safety of

Radioactive Waste Management, IAEA, Vienna

Content

Czech SNF and HLW disposal concept

Safety assessment (SA)

SA model components

Container

Corrosion research

Bentonite

Radionuclide migration in bentonite

Geosphere

Laboratory studies on RN migration in host rock

In-situ studis on RN migration in host rock

Biosphere

Conclusions

Czech SNF disposal concept

2

Based on Svedish KBS-3 concept

Reference project (2011)

horizontal disposal

spent nuclear fuel

carbon steel container

local Ca-Mg bentonite

granitic host rock

-

HLW disposal concept

Waste from NPP decommissioning

Activated NPP metalic parts

Concrete

Vitrified waste from research reactor

Institutional waste

Radiation sources

3

n)m)

Potential sites for DGR siting in Czech republic

7 candidate sites

Čertovka

Granitoidy tiského plutonu

Kraví hora

Strážecké moldanubikum

Svratecké krystalinikum

Horka

Strážecké moldanubikum

Granitoidy třebíčského plutonu

Hrádek

Moldanubický plutonický komplex

Čihadlo

Monotónní skupina moldanubika

Granitoidy klenovského plutonu

Magdaléna

Monotónní skupina moldanubika

Pestrá skupina moldanubika

Středočeský plutonický komplex

Březový potok

Pestrá skupina moldanubika

Středočeský plutonický komplex

Safety assessment (SA)

Safety assesssment (SA) is the key tool to prove that repository components fulfill

their safety function

DGR long term safety has to be proved to Regulator (SONS) in order to obtain a

licence for siting

one of the main requirements (Decree No. 307/2002 Coll.):

to provide a protection to man and environment in such a way that effective dose of

0,25 mSv per year for a member from critical group of inhabitant with all considered risk in

operational and post-operational phase

1.E-05

1.E-04

1.E-03

1.E-02

1.E-01

1.E+00

1000 10000 100000 1000000

čas [y]

dáv

ka [

mS

v.y-

1] A G1

A G2

A G3

A G4

limit

Effective dose, obtained by the individual from the critical group od

inhabbitants. Normal scenario development (container with

mininimum 50 000 year life time, median 110 000 y, Weibull

distribution). Reference project 2011.

SNF activity decrease. Time interval

determination for safety assessment 100 000 years

Safety assesment calculations:

Goldsim environment

Safety assesssment is the key tool to prove that repository

components fulfill their safety function

CZ: Goldsim programme based model has been

developed since 2004

SA MODEL: CONTAINER

Disposal of 6 000 carbon steel SNF container

Activity release after degradation of SNF

container.

SNF container degradation: described by

distribution curve obtained by applying the

Weibull distribution.

Minimum container life-time: 10,000 years

median:110,000 years.

The model assumes average inventory.

Corrosion rate and corrosion progress determination

8

Carbon steel sample in contact with Ca-Mg

bentonite

Installed ÚJV/SURAO MACOTE

corrosion modules, Grimsel test site

(CH)

Research and development of disposal

canister for SNF deep geological disposal.

SÚRAO project (2013 - 2017).

http://www.grimsel.com/gts-phase-vi/macote-

the-material-corrosion-test/macote-

introduction

SA MODEL: BENTONITE

Bentonite layer is modeled by fifteen concentric layers.

The outer layer represents the interface with the repository surrounding (rock compartment).

The rock diffusion layer is modeled at the interface bentonite/ rock compartment in order to eliminate the influence of advection in bentonite layer.

Bentonite_Cell1_440 Bentonite_Cell2_440 Bentonite_Cell3_440 Bentonite_Cell4_440 Bentonite_Cell5_440

Bentonite_Cell6_440 Bentonite_Cell7_440 Bentonite_Cell8_440 Bentonite_Cell9_440 Bentonite_Cell10_440

Bentonite_Cell11_440 Bentonite_Cell12_440 Bentonite_Cell13_440 Bentonite_Cell14_440 Bentonite_Cell15_440

10

Radionuclide migration in bentonite barrier

Diffusion cell for bentonite samples

(ÚJV Řež, a.s.)

Sorption and diffusion experiments

Application for local conditions and

uncertainty analyses

Local bentonite Rokle

(Ca-Mg bentonite)

Mathematic diffusion modelling

Diffusion module development description using

GoldSim, model testing (HTO, 36Cl, 125, 131I, 99Tc, 137Cs, Volclay, Rokle)

A B

0.00

0.02

0.04

0.06

0.08

0 7 14 21

c/c 0

dny

B75-1300

B75-1600

BaM-1300-1

BaM-1300-2

BaM-1600-1

BaM-1600-2

0.0

0.1

0.2

0.3

0.4

0 3 6 9 12 15

c/c 0

mm

B75-1300

B75-1600

BaM-1300-1

BaM-1300-2

BaM-1600-1

BaM-1600-2

Iodine concentration in in-let (A) and

outlet reservoire (B) for BaM bentonite

and B75 bentonite

(R&D support of DGR safety assessment

Project, 2014 – 2018, SURAO)

SA MODEL: BENTONITE/ROCK

The radionuclides are transported by diffusion through the bentonite layer towards a rock compartment (model view only). The rock diffusion layer is modeled at the interface bentonite/ rock compartment in order to eliminate the influence of advection in bentonite layer.

Rock massive is modeled as a compartment of 3km 1km 10 m size. At each time step, the concentration balance is set in this area, it means that the same conditions are valid in the whole area.

RN are transported by the groundwater flow (advection is considered as a transport process) to a preferential path in the geosphere.

Posiva Oy, 2012)

SA MODEL: GEOSPHERE

components "Pipes" (more than one), considering the model

transport processes as an advection, diffusion into the rock matrix

and sorption.

groundwater flows from the last "Pipe" into the compartment,

which model the processes in biosphere.

geosphere_deep_pathway

geosphere_shallow_pathway

geosphere_midle_pathway

depository_closed_area

M2+

M2+

M 2+

M2+

M 2+

M2+

CO32- M2+

CO32-

M2+

coll

Aqueous

complexationM2+

M2+

coll

coll

Sorption

Colloid

formation

Precipitation

of pure phases

CO32-

CO32-

M2+

M2+

M2+

M2+

M2+

M2+

M2+

M2+

M2+

M2+ M2+

M2+

M2+

Co-precipitation

Solid solutions

M2+ Radionuclides

M2+ Other cations

CO32- Anions

coll Colloids

•D. Arcos,_Amphos

Host rock: site specific samples

13

potential sites (Čertovka, Horka, Hrádek,

Březový potok, URL Bukov (Kraví hora), Čihadlo

Grimsel test site (CH)

Sweden (Oskarshamn, Forsmark)

Rock samples from Hradek, Horka and Čertovka were obtained under MPO FR TI1/367 project

Horka Hrádek Čertovka Bukov

Čihadlo

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6 14

Radionuclide migration in granite:

sorption and diffusion (Kd, De)

Diffusion cells for granite

HTO,, 36Cl, 131I, 99Tc, 75Se, 134Cs. 22Na, 85Sr

0.00

0.03

0.06

0.09

0.12

0 1 2 3 4

c/c 0

days

3-H

36-Cl

Se(VI)

99-Tc

125-I

Anion diffusion anions through Aare

granite

(LTD Phase III., project, E. Hofmanová)

Anaerobic sorption of Se(IV) on Aspo

diorite; Videnská, 2013;

CROCK EU FP7 project

Steps toward real host rock conditions

URL Josef

• testing of in-situ

methodologies

Grimsel Test site

• Long term diffusion

(LTD) experiment

Ruprechtov natural

analogue site (W Bohemia)

• observation of

U migration in clay

In-situ transport parameter determination

16

Circulation

borehole

Observation

borehole

Observation

intervalDiffusion

interval

H-3 (HTO) diffusion

plume after 2 years

Circulation interval (Kontar, 2011):l = 72 cmr = 2.8 cm

Total vol. solution: ca. 3 L

Fracture model in PAMIRE project -

preliminary results Josef URL

PAMIRE - http://www.ujv.cz/cz/pamire.

TA04020986

LTD Phase III. experiment concept. Figure

NAGRA

Long term diffusion Phase VI. project -

http://www.grimsel.com/gts-phase-vi/ltd/ltd-

introduction

PAMIRE project:

HTO injection presumed in the

rock fractures system

URL Josef

Long term diffusion III. Phase VI.

project

3H, 22Na, 133Ba, 134Cs and

non-active Se(VI);

Grimsel test site (CH)

SA MODEL: BIOSPHERE

4 compartments - a universal model according to the current lifestyle of the Czech Republic

land

cultivable

forest

pond

river

The output of the biosphere model is the effective dose rate to humans living in the area affected by DGR.

People living in this area consume only products of farming and do not import any food and beverages

Conclusions

model improvement: the source term, the refinement of

the geosphere transport model, the construction of

individual biosphere models for each DGR candidate site,

uncertainty evaluations etc.

the model is planned to be completed in 2018 which will

address in greater detail one of the potential sites for the

construction of the Czech DGR

R&D is inevitable for SA calculations;

data input cannot be solitaire

feedback from SA is needed

18

Acknowledgement

The Goldsim model development was funded by

Ministry of Trade and Industry (MPO TIP FR TI1/362) and

SURAO

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24.

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Thank you for your attention

www.ujv.cz