POSIVA 2012-41

February 2014

POSIVA OY

Olki luoto

FI-27160 EURAJOKI, F INLAND

Phone (02) 8372 31 (nat. ) , (+358-2-) 8372 31 ( int. )

Fax (02) 8372 3809 (nat. ) , (+358-2-) 8372 3809 ( int. )

Martti Hakanen

Heini Ervanne

Esa Puukko

University of Helsinki

Department of Chemistry

Laboratory of Radiochemistry

Safety Case for the Disposal of Spent Nuclear Fuel at Olkiluoto

Radionuclide Migration Parameters for the Geosphere

ISBN 978-951-652-221-3ISSN 1239-3096

Tekij(t) Author(s) Martti Hakanen, Heini Ervanne, Esa Puukko University of Helsinki Department of Chemistry Laboratory of Radiochemistry

Toimeksiantaja(t) Commissioned by

Posiva Oy

Nimeke Title SAFETY CASE FOR THE DISPOSAL OF SPENT NUCLEAR FUEL AT OLKILUOTO - RADIONUCLIDE MIGRATION PARAMETERS FOR THE GEOSPHERE Tiivistelm Abstract

This report presents an updated radionuclide sorption database for the far-field of the Olkiluoto nuclear waste disposal site.

The geochemical environments are based on site investigations of the present conditions and on modelled evolution of the geosphere. Sorption was estimated to four rock types and on clays, kaolinite and illite, that are common on fracture surfaces in the Olkiluoto site. The possible intrusion of shallow oxidising waters to bedrock was taken into account by estimation of sorption of the redox-sensitive radionuclides in addition to the present anaerobic conditions in oxic modifications of the glacial, fresh and saline waters. The best estimate and the lower limit values were derived to radionuclides that are considered in the safety case of the disposal of spent UO2 fuel.

The speciations and solubilities of the radionuclides in the water were calculated using the ThermoChimie 7b geochemical database by ANDRA and the PHREEQC code. The ThermoChimie database was complemented with data for new complexes of radionuclides for the comparison of speciation with experimental sorption values, or because the results of experimental speciations in natural waters or a better fit of modelled sorption to experimental data were achieved including these complexes. The speciation and solubility calculations of beryllium were made using the MINTEQ database.

The experimental in-house sorption data from the University of Helsinki for Olkiluoto rocks from the site investigation period, as well as the new data produced for this report, were preferred as the source data. In-house data for rocks and water from the other sites studied during the site investigation period by Posiva were also used. Literature on sorption data to well-defined materials, especially clays, and experiments were used to complement the other data and when no in-house data was available. Sorption of chemical analogues was used for the derivation of sorption values to the radionuclides for which there were no relevant experimental data.

The experimental sorption data to rocks consisted of distribution coefficients to crushed rocks. Conversion of these sorption values to distribution coefficients for intact rock was based on the results of the mineral-specific sorption of radionuclides in diffusion experiments and in sorption to rock surfaces. All these indicate that the mica minerals and other high CEC or high surface area minerals dominate in sorption to intact rock. In this report, sorption to intact rock was taken to take place only to the micaeous minerals and hornblende. Sorption to crushed rock was conservatively assumed not to be mineral-specific. The conversion factors for crushed rock to intact rock were the ratios of the specific surface areas of the micaeous minerals and hornblende to the surface areas of the crushed rocks. Sorption of radionuclides by cation exchange was estimated by model calculation regarding biotite only or based on the estimation of the proportion of sorption to biotite in the crushed rock.

For the clays, the best estimate for the accessibility of the sorption capacity in the intact clays was taken to be the same as that for the dispersed clays used in the experiments. Avainsanat - Keywords Sorption, Radionuclides, Far-Field, Olkiluoto ISBN ISBN 978-951-652-221-3

ISSN ISSN 1239-3096

Sivumr Number of pages 378

Kieli Language English

Posiva-raportti Posiva Report Posiva Oy Olkiluoto FI-27160 EURAJOKI, FINLAND Puh. 02-8372 (31) Int. Tel. +358 2 8372 (31)

Raportin tunnus Report code

POSIVA 2012-41 Julkaisuaika Date

February 2014

Tekij(t) Author(s) Martti Hakanen, Heini Ervanne, Esa Puukko University of Helsinki Department of Chemistry Laboratory of Radiochemistry

Toimeksiantaja(t) Commissioned by

Posiva Oy

Nimeke Title TURVALLISUUSPERUSTELU KYTETYN POLTTOAINEEN LOPPUSIJOITUKSESTA OLKILUOTOON: RADIONUKLIDIEN KALLIOPERKULKEUTUMISEN PARAMETRIT Tiivistelm Abstract

Tm raportti sislt uudistetun tietokannan radionuklidien sorptioparametreist kaukoalueella Olki-luodon kallioperss.

Tarkasteltavat geokemialliset olosuhteet perustuvat Olkiluodon paikkatutkimuksissa todettuihin nykyisiin olosuhteisiin sek malleilla laskettuihin tuleviin olosuhteisiin. Radionuklidien sorptio arvioitiin neljlle kivilajille sek rakopinnoilla Olkiluodossa yleisille saville. Mahdollinen hapellisten vesien tunkeutuminen kalliopern otettiin huomioon tarkastelemalla redox-herkkien aineiden sorptiota mys potentiaalisesti aerobisissa vesiss. Sorptioparametreille arvioitiin sek ilmeisin arvo ett alaraja-arvo.

Radionuklidin kemialliset muodot vesiss sek liukoisuus laskettiin kytten ANDRA:n kehittm Thermo_Chimie 7b -tietokantaa ja geokemiallista PHREEQC-malliohjelmaa. Thermo_Chimie-tietokantaa tydennettiin kirjallisuudesta saaduilla uusimmilla parametriarvoilla, jotka on todettu trkeiksi luonnon vesi analysoimalla ja joiden avulla kokeellinen sorptio ja laskennallinen sorptio ovat aiempaa paremmin saatu yhteensopiviksi.

Sorption arvioinnin lhttietoina kytettiin ensisijaisesti Helsingin yliopiston Radiokemian laboratoriossa Olkiluodon kiville ja vesille saatuja tuloksia sek Posiva Oy:n paikkatutkimusvaiheessa saatuja muita sorptiotuloksia. Nit tydennettiin tmn raportin teon aikana Radiokemian laboratoriossa tehtyjen kokeiden tuloksilla sek kirjallisuudessa hyvin kuvattujen kokeiden tuloksilla, erityisesti saville mritetyill arvoilla. Muun tiedon puuttuessa radionuklidin sorptio arvioitiin sen kanssa kemiallisesti samankaltaisen aineen sorptiosta. Kivimateriaaleille on tehty kokeita pasiassa kytten murskattuja kivi. Murskeille saatujen sorptio-arvojen muuttaminen ehjille kiville perustui sek jo aikaisemmin diffuusiokokeissa ett kivipinnoille saatuihin tuloksiin, joiden mukaan radionuklidit sorboituvat valtaosin kiven kiillemineraaleihin sek muihin suuren kationin-vaihtokapasiteetin omaaviin ja huokoisiin suuren pinta-alan mineraaleihin. Tss raportissa sorptioarvojen muuttaminen murskeelle saadusta arvosta ehjlle kivelle tehtiin olettamalla, ett murskeessa kaikki mineraalipinnat sorboivat samalla tehokkuudella, mutta ehjss kivess sorptio tapahtuu vain kiillemineraalehin ja sarvivlkkeeseen. Muut mineraalit oletettiin sorboimattomiksi. Sorptioarvon muuntokertoimena kytettiin kiillemineraalien ja sarvivlkkeen kokonaispinta-alan ja kivimurskeen ominaispinta-alan suhdetta. Vain kationivaihdolla sorboituvien alkali- ja maa-alkalikationien sorptio joko laskettiin sorptiomallilla tai perustui arvioon biotiitin osuudesta murskatulle kivelle mitatusta sorptiosta.

Saville ilmeisimmn sorptioarvon arvioinnissa oletettiin kirjallisuudessa esitettyihin tuloksiin perustuen, ett sorptio ehjlle savelle on sama kuin kokeissa kytetylle hienojakoiselle savelle.

Avainsanat - Keywords

Sorptio, radionuklidit, kaukoalue, Olkiluoto ISBN ISBN 978-951-652-221-3

ISSN ISSN 1239-3096

Sivumr Number of pages 378

Kieli Language Englanti

Posiva-raportti Posiva Report Posiva Oy Olkiluoto FI-27160 EURAJOKI, FINLAND Puh. 02-8372 (31) Int. Tel. +358 2 8372 (31)

Raportin tunnus Report code

POSIVA 2012-41 Julkaisuaika Date

Helmikuu 2014

ABBREVIATIONS API American Petroleum Institute BET (BET/N2) surface area determined by nitrogen gas adsorption CAT cationic charge concentration CEC cation exchange capacity DDL double diffuse layer DOC dissolved organic carbon EPA Environmental Protection Agency, United States Office Of

Air and Radiation FSS fraction of sorbed species GW groundwater HTO tritiated water HU University of Helsinki, Laboratory of Radiochemistry ICP-MS inductively coupled mass spectrometry IS ionic strength JNC SDB sorption database from Japan Nuclear Cycle Development

Institute (now Japan Atomic Energy Agency, JAEA) KBS-3H disposal method with long horizontal deposition drifts Kd mass distribution ratio of element (nuclide) for, e.g., intact

rock and clay Ki Kivetty LFER Linear Free Energy Relationship LLD lower limit of determination Ln(III) lanthanide LSC liquid scintillation counter MINTEQ v.4 thermodynamic database in PHREEQC NEA TDB thermodynamic database from Nuclear Energy Agency OL Olkiluoto PHREEQC a geochemical modelling programme PZC point of zero charge Ra experimental value of surface sorption distribution ratio of

element (nuclide) Rd experimental value of mass distribution ratio of element

(nuclide) REF pH of reference water Rmax Rd value based on counting error addition Rmin Rd value based on counting error subtraction RN radionuclide Ro Romuvaara S(%) sorption percentage SA surface area SD source data rock SDB sorption database SOH2+ positively char