The role of superplasticizers and their degradation products on radionuclide mobility

The most widely accepted option for the long-term management of radioactive waste materials considers their disposal in deep underground facilities (examples are Finland, Belgium, France, Sweden, etc.). Such installations should ensure the safety of the waste disposal and minimize possible future ex...

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Author: García Cobos, David Manuel
Format: doctoral thesis
Status:Published version
Publication Date:2018
Country:España
Institution:CBUC, CESCA
Repository:TDR. Tesis Doctorales en Red
OAI Identifier:oai:www.tdx.cat:10803/663163
Online Access:http://hdl.handle.net/10803/663163
https://dx.doi.org/10.5821/dissertation-2117-122700
Access Level:Open access
Keyword:Àrees temàtiques de la UPC::Enginyeria química
66
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network_name_str España
repository_id_str
dc.title.none.fl_str_mv The role of superplasticizers and their degradation products on radionuclide mobility
title The role of superplasticizers and their degradation products on radionuclide mobility
spellingShingle The role of superplasticizers and their degradation products on radionuclide mobility
García Cobos, David Manuel
Àrees temàtiques de la UPC::Enginyeria química
66
title_short The role of superplasticizers and their degradation products on radionuclide mobility
title_full The role of superplasticizers and their degradation products on radionuclide mobility
title_fullStr The role of superplasticizers and their degradation products on radionuclide mobility
title_full_unstemmed The role of superplasticizers and their degradation products on radionuclide mobility
title_sort The role of superplasticizers and their degradation products on radionuclide mobility
dc.creator.none.fl_str_mv García Cobos, David Manuel
author García Cobos, David Manuel
author_facet García Cobos, David Manuel
author_role author
dc.contributor.none.fl_str_mv Grivé i Solé, Mireia
Duro Pérez, Lara
Universitat Politècnica de Catalunya. Departament d'Enginyeria Química
dc.subject.none.fl_str_mv Àrees temàtiques de la UPC::Enginyeria química
66
topic Àrees temàtiques de la UPC::Enginyeria química
66
description The most widely accepted option for the long-term management of radioactive waste materials considers their disposal in deep underground facilities (examples are Finland, Belgium, France, Sweden, etc.). Such installations should ensure the safety of the waste disposal and minimize possible future external waste perturbation. Concrete and concrete-based materials are widespread in those facilities. Superplasticizers (SPs) are organic polymers used to improve several concrete properties such as workability. The hyperalkaline conditions developed in cementitious environments, can cause chemical transformations of these polymeric materials (degradation, aging, etc.) with the subsequent production of new organic compounds with different chemical properties. Several organic compounds have a high capacity to form stable complexes with some radionuclides of interest from the point of view of radiological and toxicological doses. Therefore, the understanding on the nature and strength of the interactions between radionuclides and organic admixtures present in the concrete formulations (and their degradation products) is of the outmost importance to conduct adequate assessments of the future performance of the disposal facility. Overall the work presented in this thesis tries to discern the effect that polycarboxylic ether-based (PCE) SPs present in the concrete admixtures used in the deep disposal repository may have on radionuclide mobility. To this aim, the stability of PCE towards temperature, radiolysis and hydrolysis degradation processes has been also studied. This provides a test of the integrity of SPs under the expected repository conditions. This work presents a state-of-the-art of the degradation process of SPs and a thermodynamic study on the effect that model compounds, considered as proxy SPs degradation products, have on the chemistry of several radionuclides (Ni, Eu, U). Short-chain organic compounds such as acetate, phthalate, oxalate, phenol, urea, etc., have been confirmed as possible SPs degradation products. Our results indicate that the complexation capacity of the proxy SPs degradation products considered (i.e. acetate, phthalate, phenol and urea) towards Ni Eu and U is almost negligible under alkaline conditions, while relatively important in the near-neutral pH range. In parallel, the experimental degradation of two PCE SPs, one commercial and one synthetic, has been investigated in this work. Our results indicate that the studied SPs remain unaltered when exposed to hydrolysis processes. On another hand, high temperatures or radiation doses cause important changes in the SPs structure, although the main chemical groups remain unaltered. The effect of a PCE SPs, Glenium®27, on nickel hydroxide solubility has been experimentally evaluated. The results indicate that when Glenium®27 is added to water and then mixed with cement, this polymeric material is stabilized (e.g. adsorbed into the cement phases) and not released back to the aqueous solution, with negligible effects on the mobility of nickel. On the contrary, when added directly into synthetic cement porewater samples at high dosages the solubility of nickel hydroxide increases in more than two orders of magnitude. Thermodynamic calculations indicate that the effect of such component on Ni is comparable to the effect exerted by other organic compounds (i.e. isosaccharinate, gluconate, oxalate), thus pointing towards these organics as good surrogates for understanding SPs complexation capacity.
publishDate 2018
dc.date.none.fl_str_mv 2018
2018
2018
dc.type.none.fl_str_mv info:eu-repo/semantics/doctoralThesis
info:eu-repo/semantics/publishedVersion
format doctoralThesis
status_str publishedVersion
dc.identifier.none.fl_str_mv http://hdl.handle.net/10803/663163
https://dx.doi.org/10.5821/dissertation-2117-122700
url http://hdl.handle.net/10803/663163
https://dx.doi.org/10.5821/dissertation-2117-122700
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.format.none.fl_str_mv 196 p.
application/pdf
application/pdf
dc.publisher.none.fl_str_mv Universitat Politècnica de Catalunya
publisher.none.fl_str_mv Universitat Politècnica de Catalunya
dc.source.none.fl_str_mv TDX (Tesis Doctorals en Xarxa)
reponame:TDR. Tesis Doctorales en Red
instname:CBUC, CESCA
instname_str CBUC, CESCA
reponame_str TDR. Tesis Doctorales en Red
collection TDR. Tesis Doctorales en Red
repository.name.fl_str_mv
repository.mail.fl_str_mv
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spelling The role of superplasticizers and their degradation products on radionuclide mobilityGarcía Cobos, David ManuelÀrees temàtiques de la UPC::Enginyeria química66The most widely accepted option for the long-term management of radioactive waste materials considers their disposal in deep underground facilities (examples are Finland, Belgium, France, Sweden, etc.). Such installations should ensure the safety of the waste disposal and minimize possible future external waste perturbation. Concrete and concrete-based materials are widespread in those facilities. Superplasticizers (SPs) are organic polymers used to improve several concrete properties such as workability. The hyperalkaline conditions developed in cementitious environments, can cause chemical transformations of these polymeric materials (degradation, aging, etc.) with the subsequent production of new organic compounds with different chemical properties. Several organic compounds have a high capacity to form stable complexes with some radionuclides of interest from the point of view of radiological and toxicological doses. Therefore, the understanding on the nature and strength of the interactions between radionuclides and organic admixtures present in the concrete formulations (and their degradation products) is of the outmost importance to conduct adequate assessments of the future performance of the disposal facility. Overall the work presented in this thesis tries to discern the effect that polycarboxylic ether-based (PCE) SPs present in the concrete admixtures used in the deep disposal repository may have on radionuclide mobility. To this aim, the stability of PCE towards temperature, radiolysis and hydrolysis degradation processes has been also studied. This provides a test of the integrity of SPs under the expected repository conditions. This work presents a state-of-the-art of the degradation process of SPs and a thermodynamic study on the effect that model compounds, considered as proxy SPs degradation products, have on the chemistry of several radionuclides (Ni, Eu, U). Short-chain organic compounds such as acetate, phthalate, oxalate, phenol, urea, etc., have been confirmed as possible SPs degradation products. Our results indicate that the complexation capacity of the proxy SPs degradation products considered (i.e. acetate, phthalate, phenol and urea) towards Ni Eu and U is almost negligible under alkaline conditions, while relatively important in the near-neutral pH range. In parallel, the experimental degradation of two PCE SPs, one commercial and one synthetic, has been investigated in this work. Our results indicate that the studied SPs remain unaltered when exposed to hydrolysis processes. On another hand, high temperatures or radiation doses cause important changes in the SPs structure, although the main chemical groups remain unaltered. The effect of a PCE SPs, Glenium®27, on nickel hydroxide solubility has been experimentally evaluated. The results indicate that when Glenium®27 is added to water and then mixed with cement, this polymeric material is stabilized (e.g. adsorbed into the cement phases) and not released back to the aqueous solution, with negligible effects on the mobility of nickel. On the contrary, when added directly into synthetic cement porewater samples at high dosages the solubility of nickel hydroxide increases in more than two orders of magnitude. Thermodynamic calculations indicate that the effect of such component on Ni is comparable to the effect exerted by other organic compounds (i.e. isosaccharinate, gluconate, oxalate), thus pointing towards these organics as good surrogates for understanding SPs complexation capacity.L'opció més àmpliament acceptada per a la gestió a llarg termini de residus radioactius considera el seu aïllament en instal·lacions subterrànies profundes (aquesta opció és fermament recolzada per països com Finlàndia, Bèlgica, França o Suècia). Aquestes instal·lacions han d'assegurar la seguretat de la disposició dels residus i minimitzar-ne possibles pertorbacions externes. El formigó és un material àmpliament utilitzat en aquests tipus d’instal·lacions. Els superplastificants (SPs) són polímers orgànics que s'utilitzen per millorar diverses propietats mecàniques del formigó, de manera que és previsible que aquests components estiguin presents en aquests magatzems en quantitats elevades. Les condicions alcalines que es generen en entorns de ciment i formigó poden induir a modificacions químiques dels SPs com ara la seva degradació o envelliment amb la conseqüent formació de noves molècules orgàniques. En general, l’afinitat de les molècules orgàniques amb els radionúclids ha estat àmpliament reconeguda en estudis anteriors. Aquesta gran afinitat pot derivar en un potencial augment del transport de radionúclids en l’entorn del magatzem de residus. Aquesta tesi té com a principal objectiu discernir si la presència de SPs (específicament els de tipus policarboxilat, PCE) en el formigó pot tenir un impacte rellevant en la mobilitat dels radionúclids, i per tant en l’estabilitat de les instal·lacions estudiades. Així mateix, aquesta tesi té com a objectiu donar resposta a l’estabilitat d’aquests polímers envers a canvis de temperatura, a l’impacte de radiació i a la seva capacitat d’hidròlisis, processos força comuns en magatzems de residus nuclears Aquest treball de tesi inclou una àmplia recerca bibliogràfica sobre els possibles processos de degradació dels SPs (temperatura, radiació, hidròlisis i activitat microbiana) i un estudi termodinàmic sobre l’efecte de molècules model (assimilables als productes de degradació dels SPs) en la mobilitat de diferents radionúclids (Ni, Eu i U). Aquest estudi ens fa concloure que els compostos orgànics de cadena curta, com l’acetat, el ftalat, l’oxalat, el fenol o la urea, podrien ser alguns dels principals productes de degradació dels SPs. Els càlculs termodinàmics indiquen que la complexació d’aquests compostos envers els radionúclids estudiats és negligible en condicions alcalines, tot i que en sistemes de pH neutre pot arribar a ser important. Paral·lelament a aquest estudi bibliogràfic, s’ha dut a terme un estudi experimental de degradació de dos SPs de tipus PCE, un comercial i un sintètic. Els resultats obtinguts indiquen que els processos d’hidròlisi no afecten aquests materials. Per altra banda quan aquests materials s’exposen a radiació o a elevades temperatures, poden patir canvis importants a la seva estructura tot i que els grups químics principals sembla que resten inalterats. També s’ha fet un estudi de l’efecte d'un SPs de tipus PCE (Glenium®27) en la solubilitat de l’hidròxid de Ni. Els resultats presentats en aquest treball indiquen que quan aquest SPs s’afegeix a l’aigua que es fa servir per preparar les provetes de formigó, aquest material polimèric s’estabilitza (adsorbint-se sobre el propi ciment) i no es torna a solubilitzar. En aquestes condicions l’efecte sobre la solubilitat del Ni és concloentment irrellevant. En canvi, quan aquest material s’afegeix en quantitats elevades directament a l’aigua sintètica de por de ciment, sense estar en contacte amb ciment, s’observa un important efecte en el comportament del Ni, augmentant la seva solubilitat gairebé dos o tres ordres de magnitud. Els càlculs termodinàmics fets en aquest treball indiquen que l’efecte del SPs sobre el Ni és similar a l’efecte que produeixen altres compostos orgànics (isosacarinat, gluconat, oxalat) sobre el mateix element. Això ens fa concloure que aquests poden ser bons substituts per comprendre la capacitat de complexació dels superplastificacdorsDOCTORAT EN ENGINYERIA DE PROCESSOS QUÍMICS (Pla 2012)Universitat Politècnica de CatalunyaGrivé i Solé, MireiaDuro Pérez, LaraUniversitat Politècnica de Catalunya. Departament d'Enginyeria Química201820182018info:eu-repo/semantics/doctoralThesisinfo:eu-repo/semantics/publishedVersion196 p.application/pdfapplication/pdfhttp://hdl.handle.net/10803/663163https://dx.doi.org/10.5821/dissertation-2117-122700TDX (Tesis Doctorals en Xarxa)reponame:TDR. Tesis Doctorales en Redinstname:CBUC, CESCAInglésADVERTIMENT. L'accés als continguts d'aquesta tesi doctoral i la seva utilització ha de respectar els drets de la persona autora. Pot ser utilitzada per a consulta o estudi personal, així com en activitats o materials d'investigació i docència en els termes establerts a l'art. 32 del Text Refós de la Llei de Propietat Intel·lectual (RDL 1/1996). Per altres utilitzacions es requereix l'autorització prèvia i expressa de la persona autora. En qualsevol cas, en la utilització dels seus continguts caldrà indicar de forma clara el nom i cognoms de la persona autora i el títol de la tesi doctoral. No s'autoritza la seva reproducció o altres formes d'explotació efectuades amb finalitats de lucre ni la seva comunicació pública des d'un lloc aliè al servei TDX. Tampoc s'autoritza la presentació del seu contingut en una finestra o marc aliè a TDX (framing). Aquesta reserva de drets afecta tant als continguts de la tesi com als seus resums i índexs.info:eu-repo/semantics/openAccessoai:www.tdx.cat:10803/6631632026-06-14T12:46:07Z
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