NSEN 619 HLW Class 9

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NSEN 619 HLW - Class 9

• Mid-term Exam
• Silicate Pyramid Solution
• Term Paper
• Pu-238/(Pu-239Pu-240) ratio
• More on Glass
• Glass Composition and Corrosion

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Handouts

• CD Handout
• CD glass articles
• Analysis of Thorp Glass.pdf Japanese Research
• PNNL-SRP Glass Tutorial.pdf
• Glass composition.xls Glass composition
  worksheet
• French vitrification.pdf
• WV experience.pdf Information on West Valley
  waste treatment
• Immobilization in Glass summary.pdf DOE ESMP
  discussion of vitrification
• Advantages of Vitrification.htm
• Natural Analog Japan.pdf 2 page summary of naturB
  Plantlog work
• Glass corrosion - Hand.pdf Hand is a well known
  glass scientist
• Glass corrosion - Pain.pdf
• Glass corrosion.pdf
• B Plant_Filters.pdf Article of interest after we
  had the Sr-Cs Recovery lectures
• Thorp.ppt Copies of a Thorp article
• CentCont.ppt Nice slides on Centrifugal
  Contactors
• Calcine Vitrification.pdf
• Plus a many others
• INEEL EIS

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Class Notes and Handouts

• CD - provided
• PAPER 2004 assignment.doc
• Solution of Silicate Pyramid.doc
• Analysis of Thorp Glass.pdf
• A few thoughts about glass.doc
• Glass corrosion - Hand.pdf
• Glass corrosion - Pain.pdf

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Mid-term exam

• Cs-Sr Na(CO3)2 Metathesis to convert sulfates
  into carbonates, SrCO3 being one of the most
  insoluble
• HLW 1 - 10 Ci/gal 500 1900 Ci/gal fresh
  defense HLW
• Cs separation, NaTB, PTA, Ion exchange,
  Solvent-Solvent extraction (CSEX)
• Analogs
• MWD/MTIHM - Burn up
• Remember all of the criteria for HLW

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Pu-238/(Pu-239Pu-240) ratio

• Physics of fission processes or neutron
  interactions (reactors, bombs, neutron
  irradiation) determines the 238/239 ratio.
• It is man-made only
• Once produced, the ratio cannot be changed by
  natural or chemical processes (except by decay,
  but Pu-238 decays with ?1/2 87 y)
• Therefore isotopic ration is an origin marker
  like DNA

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Pu-238/(Pu-239Pu-240) ratio

• From IDB, and Internet
• INTEC 60 average 182 for high burnup HEU
• SRP 34
• Commercial spent fuel average 5.6
• WVDP 4
• LWR overall average 2.5
• Northern Hemisphere Fallout 0.30
• Sellafield 0.29
• NTS lagoon 0.14
• Weapons Grade (IDB - RFETS TRU) 0.026
• Hanford 0.017
• Therefore if you know the ratio, you can guess
  the point of origin

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THORP

• Thermal Oxide Reprocessing
• British reprocessing plant
• http//www.globalsecurity.org/wmd/world/uk/sellafi
  eld.htm
• Only commercial reprocessing facility except for
  France
• Only reprocessing facility for hire
• Recovers Pu and Uranium and fabricates MOX fuel,
  MOX Mixed U/Pu oxides
• Direct vitrification of HLW

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Glass

• Glass Data and Commercial Glass making (Mosers
  Paper)
• Handout papers on Glass
• Todays lecture is based on articles in Vol. 333
  of Materials Research Society Scientific Basis
  for Nuclear Waste Management XVII (1993) Page
  numbers and author references are to that book.
• The PNNL-SRP Glass Tutorial contains much the
  same material (540 pages of slides)

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Minerals

• The stability of silicates
• The silicate tetrahedron
• The structures of silicates
• Why silicates can accommodate many different ions
• Why glass accommodates even more

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Glass phase diagram
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(No Transcript)
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Glass

• Composition
• Choice of waste form
• Corrosion mechanisms

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Mosers Glass paper

• Reasonable discussion of the conflict between
  Aluminosilicate and borosilicate glass p. 21.
• Good description of glass making and some history
• Good collection of glass data from the 60s and
  70s from PNL Tables.
• OK attempt to discuss glass composition vs.
  minerals
• Good discussion of the impact of changing
  composition pages 24 - 28

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Glass Paper by Cunnane and Allison

• Choice of Glass as a waste form is to allocate
  the full requirement of 60 CFR 116 to the Waste
  Form
• The approach is to demonstrate that glass
  corrosion rate is low enough to satisfy that.
• Composition of Glass is consistent with Chemical
  Compositions of HLW
• Borosilicate glass was chosen because it has good
  product reliability, lower melting temperature
  and lower volatility at melt temperature than
  aluminosilicate

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SRP Article

• Glass Composition
• Approach to predicting containment
• Glass Weathering parameters
• Surface Area
• Temperature
• Pressure
• Composition
• Water
• pH

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Weathering of Glass

• Mechanism
• Exchange of Alkali metals with H
• Silicic acid
• Diffusion of Alkalis to the gel layer
• Expected values of corrosion.

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Release math

• Fraction of glass corroded per y F RA/W
• Where R corrosion rate in g/m2/y, W wt, A
  exposed glass surface area.
• Fraction, fi of radionuclide released per year
  F/(RF)i
• This reduces to evaluating R, estimating A, and
  knowing (RF)i

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Corrosion

• Mechanism, Fig 2, page 6 (Cunnane)
• Surface Area
• Time dependence
• Relationship to boron
• Rates - Forward and Saturation

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Results

• Table 1, page 10
• 3E-3 g/m2 d 1g/ m2 y -- In 10,000 y it would
  corrode 1cm. Is this reasonable? 1
  mm/millennium
• Figure 4, page 11

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Glass Corrosion(note Key portions of these two
papers will be provided)

• Article on Page 107
• Processes
• Surface layers
• Rate limiting steps
• Article on page 145
• Significance of thermodynamics
• Glass composition
• Mineral phases
• Significance of S/V Surface to Volume Ratio (m-1)

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Corrosion rates
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Significance of corrosion rates

• Density of glass is 2
• 1 m3 has a mass of 2 x 106g
• A corrosion rate of 1 g/m2d, if attacking a
  single face will dissolve a m3 glass block in 2 x
  106d 5500 y
• Corrosion rates less than 0.05 g/m2d will give a
  life time of the order of 100,000 y

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Waste life times

• Corrosion rates measured at 90 C,
• After first 500 years, the temperatures will drop
  to about ambient or maybe lt40 C (See the 1972 NAS
  SRP report I provided in Class 3). This will
  commensurately drop corrosion rate by 2 or 3
  orders of magnitude
• Maximum radius of glass log is 0.30 m
• Container (waste package) must last 1000 y
• It can easily be argued that, for any corrosion
  rate less than 0.02 g/m2d, measured at 90 C will
  be less than 10-5/y after 1000 year.
• These last two bullets are the 10 CFR 60 criteria
• Furthermore, the corrosion rates are generally
  determined on the basis of dissolution of the
  glass matrix. Solubility of actinide oxides is
  generally 1 to 3 orders of magnitude less than
  that of glass.

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Corrosion rates of various glasses
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Relative release rate from glass
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Corrosion mechanism

• Alkalis dissolve and go into solution in the
  surrounding water.
• Acid can attack SiO-M and dissolve the M, where
  M is any metal, the SiO-M becomes a silanol
  group SiO-H
• Base can attack SiO-Si and break the silicate
  network and produce silicic acid, for example
  H4SiO4
• Silicic acid has a number of forms A group of
  seven hydrated forms of SiO2, including the
  following silicic acids tetra, H2Si4O9, meta-di,
  H2Si2O5, meta-tri, H4Si3O8, meta, H2SiO3,
  ortho-tri, H8Si3O10, ortho-di, H6Si2O7 and ortho,
  H4SiO4. The latter formula is often written as
  Si(OH)4. Silicic acids and silicate anions
  polymerize through formation of multiple Si-O-Si
  bonds. The polysilic structure can be linear or
  cyclic and is not uniform in size.

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From Hanford Glass Science Tutorial showing
corrosion layer
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Dissolution behavior
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From Hanford Glass Science Tutorial showing
corrosion layer
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Dissolution as a function of pH
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Oxidation-Reduction

• Glass is a highly oxidized material
• However, since it is really a solution, it can
  exist with a shortage of oxygen and hence be a
  reduced glass. For example, let us be melting
  glass and then add some powdered iron into the
  molten glass.
• The state of oxidation is traditionally measured
  in terms of the ratio of Fe(II)/Fe where Fe is
  the total iron content, and Fe(II) is valence 2
  iron. In fact most of the other iron will be in
  the 3 state.

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Effects of reduction
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Effects of reduced state
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Radiation effects
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Effects of phase separation