Chemical modifications induced by ionizing radiations on polymers the specificity of Swift Heavy Ions (SHI)

HAL Id: hal-02445720

https://hal-cea.archives-ouvertes.fr/hal-02445720 Submitted on 20 Jan 2020

HAL is a multi-disciplinary open access

archive for the deposit and dissemination of sci-entific research documents, whether they are pub-lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Chemical modifications induced by ionizing radiations on polymers the specificity of Swift Heavy Ions (SHI)

M. Ferry, S. Esnouf, Y. Ngono, E. Balanzat

To cite this version:

M. Ferry, S. Esnouf, Y. Ngono, E. Balanzat. Chemical modifications induced by ionizing radiations on polymers the specificity of Swift Heavy Ions (SHI). 19ème Colloque GANIL - 19th Colloque GANIL 2015, Oct 2015, Anglet, France. �hal-02445720�

Chemical modifications

induced by ionizing radiations

on polymers: the specificity of

Swift Heavy Ions (SHI)

M. Ferry1_{, S. Esnouf}1

,Y. Ngono-Ravache2, E. Balanzat2

1_{CEA, DEN, DPC, SECR, LRMO, F-91191 Gif-sur-Yvette, France.}

Ionizing radiations effects on

polymers

| PAGE 3 -C-C -H- + e -H - H-H --C-CH-

*

-H - H-H --C-C°H- + -H - H-H --C-C°- H-H- H -P° : alkyl radical -H° -H₂ +H° PH -H° -C-C + - H-H- H --H° -C=C* -H- H - -C=C-H- H -trans-vinylene -C=C-C°-H -H- H -allyl radical -H°

S*

S

--H₂

?

-C°-C+ -H- H -carbenium ion -C-C- H-H - H-H -+ PH - P° H-H --C-CH-+ -H H carbonium ion -H°

Radiation - organic matter interaction: primary

processes (PE example)

| PAGE 4

Rivation, Cambon & Gardette, Nucl. Instrum. Methods Phys. Res., Sect. B 227 (2005), 357

Radiation chemical yield G (10-7 _{mol/J) :}

Amount of defects n created by unit of energy E deposited into the material Rate of defects creation dn/dt created by unit of dose D deposited

𝐺𝐺 = _{𝐸𝐸 =}𝑛𝑛 _{𝐷𝐷 �}1 𝑑𝑑𝑛𝑛_{𝑑𝑑𝑑𝑑}

Radiation - organic matter interaction: secondary

processes in presence of oxygen

Induced modifications in polymers

| Page 5

Molecular changes observed in a polymer due to ionizing rays Emission of volatile compounds (H₂, CO, CO₂, CH₄...),

Creation of unsaturations and other molecular bonds and of low molecular weight molecules (alcohols, carboxylic acids…),

Crosslinking and chain scissions.

All these molecular changes are dependent of the structure of the polymer and of the irradiation conditions

Polymer structure parameters

-Repetition unit (side-chain groups) -Crystallinity

-…

Irradiation conditions

-Dose and dose rate

-Surrounding atmosphere (inert or oxidative) -Irradiation temperature

-Linear Energy Transfer (γ-rays, electrons vs SHI) -…

What about the SHI in the nuclear

industry context ?

Polymers widely used in nuclear industry

| PAGE 7

Intermediate Level Long Lived Waste packages (IL-LLW) : various organic materials, including polymers, in presence of radionuclides

Dose received ≈ 10 MGy or even higher when in contact with PuO₂pellet Objective: find a solution for the packages disposal

France: projected of a deep underground geological repository 1.3% 40.5% 16.3% 0.3% 10.1% 2.4% 18.1% 11% _Polyurethane Chlorinated polymers Polyolefins Polyamides Cellulose Fluorinated polymers Ion-exchange resin Other polymers

500-meter deep and around 300 years of use to fill the cells before the supposed closing of the repository

Different phases risks

During the opened filling period

-Risks issued from gas emission (inflammation, corrosion, carbonation…)

After closure

-Irradiated polymers leaching and radionuclides (RN) complexation risk

| PAGE 8

Deep underground geological repository

Organic material and radionuclides (RN) in the ILLW packages : α and β/γ emitters

Understanding of the becoming of organic materials in the nuclear waste containers over several

hundreds of years (≈ tens / hundreds of MGy) Emitters simulation

β/γ emitters : γ irradiations using 60_{Co and} 137_Cs

sources (0.3 to 0.7 kGy.h-1₎

α emitters :

-Irradiations of simulation, using C and Ar ions (≈ 500 kGy.h-1_{, at GANIL, Caen, France)}

Estimation of the H₂ (and other gases) evolution as a function of the Irradiation type Dose | PAGE 9

α

β

γ

| PAGE 10

Gervais & Bouffard, Nucl. Instrum. Methods Phys. Res., Sect. B 88 (1994), 355

101 102 103 104 10-2 10-1 100 101 102 L E T ( k e V /µ m ) Energy (MeV/A) medium energy high energy He C Ar Ne GANIL 40 µm 7830 µm 870 µm 160 µm α particle Homogeneous irradiation under several

microns (case of PE)

Ion beams to simulate α irradiations ?

Why SHI instead of α ?

LET equivalent to radionuclides-emitted α Higher penetration range

Ionizing radiations effects on

polymers

The Swift Heavy Ions (SHI)

specificity

What about the SHI specificity ?

Hydrogen emission

H₂ emission as a function of the LET of the particles and of the polymer structure

Almost independent of the LET in aliphatic polymers

LET threshold observed in case of polystyrene

-More radiation resistant, under low-ionizing rays, than polyethylene

-Radiation-resistance lost above the LET threshold, due to ring opening

At the highest LET, H₂ emission from PE and PS equivalent

Radiation-resistance conferred by the aromatic ring lost

| PAGE 12

Chang & LaVerne, J. Polym. Sci.: Part A: Polym. Chem. 38 (2000),1656

1 10 100 1000 0.01 0.1 1 10 C He H PS PMMA PP G (H 2 ) [ m o lecu les/ 100eV ] LET [eV/nm] PE CH₂ CH₂ n CH₂ CH n CH₃ CH₂ C n C CH₃ O O CH₃ CH₂ CH n

What about the SHI specificity ?

Unsaturated bonds formation

Unsaturated bonds creation

Almost no effect on trans-vinylene, vinylidene and trans-trans-diene formation from polyethylene

Specificity of the vinyl bonds

-Signature of the main chain scission => necessity of high

ionizations/excitations density

-Vinyl concentration increases from low-ionizing radiation to SHI and with LET

| Page 13

Ngono-Ravache et al., Polym. Deg. Stab. 111 (2015), 89

0 2 4 6 8 10 12 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 Dose [MGy] LET = 4.3 MeV.mg-1.cm2 LET = 8.0 MeV.mg-1.cm2 LET = 11.5 MeV.mg-1.cm2 V iny l c o nc e nt ra ti on [mol .k g -1 ] CH₂ CH₂ CH₂ CH CH₂ CH n m p CH₃ CH2 CH CH CH₃

What about the SHI specificity ?

New bonds specific to SHI formation

New bonds specific to SHI => LET threshold Triple bonds: alkynes, cyanates…

Cumulated double bonds: allenes, isocyanates…

LET threshold value depends on the polymer and on the new bond Threshold in case of alkyne creation

-LET > 6.6 MeV�mg-1�cm2for PE, PP, PB -LET ≈ 2/3 MeV�mg-1�cm2for PS

If LET < LET_threshold

New bond created above a dose threshold

| Page 14

Ferry et al, J. Phys. Chem. B 112 (2008), 10879

0 10 20 30 40 50 60 70 80 0.0 2.0x10-8 4.0x10-8 6.0x10-8 8.0x10-8 1.0x10-7 0 2 4 6 8 10 12 0.0 5.0x10-9 1.0x10-8 1.5x10-8 2.0x10-8 Alkynes: 3300 cm-1 G (al kyn es) [ 10 -7 mo l. J -1 ] LET [MeV.cm2.mg-1] G (a lk y n e s ) [1 0 -7 m o l. J -1] LET [MeV.cm2 .mg-1 ]

Double bonds formation in cyclohexane/benzene organic glasses and in

ethylene/styrene copolymers irradiated using ion beam at 11 K under vacuum Radiation chemical yields equivalent in both systems

-Intrachain and/or interchain (intermolecular) transfers efficient at low temperature -Transfers nature equally effective

Cyclohexane/benzene mixtures never studied at RT using ions irradiation under inert atmosphere

H₂, cyclohexene formation quantification but also benzene destruction

-Comparison with results obtained at 11 K | PAGE 15

Energy transfers towards defects evidences

Small molecules as models

Ferry et al., J. Phys. Chem. B 117 (2013), 14497

0 5 10 15 20 25 0.0 0.2 0.4 0.6 0.8 1.0 Cyclohexene formation in cyclohexane/benzene glasses Trans-vinylene formation in ethylene/styrene copolymers G (C = C ) / G (r ef er en ce)

Irradiation under oxidative atmosphere H₂ instantaneous emission rate ↘ when dose ↗

Previously observed by Seguchi

-Under vacuum and γ-rays up to 2 MGy -Assigned to energy transfers towards

radiation-induced C=C double bonds

In this work, first evidence of radiation protection

-Under oxidative atmosphere and ion beam up to doses as high as 10 MGy -Assigned to energy transfers towards

oxidized defects

| PAGE 16

Energy transfers towards defects evidences

Hydrogen emission as a function of dose

0 2 4 6 8 10 12 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 G (H 2 ) [1 0 -7 mo l. J -1 ] Dose [MGy]

Energy transfers towards defects evidences

Hydrogen emission as a function of PE

| Page 17

Irradiation under oxidative atmosphere

Study of several polyethylenes (PE) with different defects

Evolution of G(H₂) as a function of the material irradiated

G(H₂) ↘ with the ketones bonds content

-Ketones act as energy and/or radicals scavenger

-Already observed by Slivinskas & Guillet under γ-rays

No effect of –OH/-OOH bonds

-Simple bonds less effective than double bonds

4000 3500 3000 2500 2000 1500 1000 500 0.00 0.05 0.10 0.15 0.20 0.25 G(H₂)=4.8 G(H₂)=5.0 G(H₂)=4.6 G(H₂)=3.8 G(H₂)=5.3 G(H₂)=0.4 A b so rb an ce Wavenumber [cm-1] UHMWPE Xc = 45% PEHD Sigma 181900 PE Sigma 427780 (C=O) PE Sigma 427772 (C=O) PE MB145 (-OH, -OOH) PE Luponen (C=O)

Conclusion

In the deep underground repository context

Protocol developed to quantify gases even at high doses

-Use of SHI to simulate irradiations due to α emitters

Allows the modeling of the gases evolved from real ILLW packages, even after thousands of years

From a fundamental point of view Dose effect study

Energy and/or radicals transfers evaluation Effect of oxidation under irradiation

-On the gaseous radiation chemical yields -On the in-film defects

Better understanding of the irradiation effects, using SHI, on

polymeric materials

Thank you for your

attention