Nuclear Fuel Waste Management

• The Problem • The Proposed Canadian Solution • The Expected Results

DonWiles Almonte Lecture, 24 February, 2017

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● How does nuclear power work?

● What is the problem? ● What proposals are there? ● What results are expected? ● What is the next step?

2

NeutronProton

Neutron + Uranium-235 Fission products + Neutrons

Nuclear Fission

3

NeutronProton

Fission Fission

Lost

Lost

Lost

Nuclear Chain Reaction

4

Fuel Bundle and Uranium Pellet

Fuel Pellet

UO2 ~ 19 kg Uranium5

Fuel Bundle

1

~

Coal, Oil, Gas,

Nuclear

Basically Similar in all Plants

Generic Power Plant

6

Heat Source

Heat Exchanger Turbine Generator

● How does nuclear power work?

● What is the problem?

● What proposals are there? ● What results are expected? ● What is the next step?

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Nuclear Fuel Composition

8

Component Initial Used

98.50.20

99.30.71

238235

Radioactive fission products

Uranium

0.16

Possible Health Effects

External Sources: β, γ

General, Topical, Radiation Sickness

Internal Sources: α. β

Organ-specific: Thyroid, Bone Marrow, Liver, Others

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Dose - Response Curves

How many Cancers (per million) for how much radiation (per mSv)

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Can

cers

(per

mill

ion)

Dose (mSv)

Data

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Dose (mSv)

Data

Linear with Threshold

Can

cers

(per

mill

ion)

12

Dose mSv)

Data

Hormesis

Can

cers

(per

mill

ion)

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Natural Background Radiation

Source Dose Rate (mSv/a) Cosmic Radiation 0.3 - 0.5 Concrete House 0.5 - 1.5 4-hour Jet flight 0.01 Radon (outdoors) 0.2 Medical x-rays 0.3 - 0.4 Human Body (14C, 40K) 0.2

Total (Average) 2 - 3 mSv/a

Lethal Dose ~ 4,000 - 5,000 mSv

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Canadian Inventory of Used Fuel

Currently: > 2.6 Million bundles Adding about 90,000 per year

Where is the Used Fuel Now?

In Storage at the Reactor Sites.

15

Current Wet Storage ~ 10 years

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Dry Storage

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Current Dry Storage

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19

90Sr 129I 137Cs 90Sr 29I 137Cs

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Nuclide Half Life Radiation, Energy(years) (MeV)

Zr,Nb -93 1.5 x 106 â– 0.06 x Tc-99 2.1 x 105 â– 0.29Pd-107 7 x 106 â– 0.04Cd-113m 7.7 x 1015 â– 0.58Sn,Sb -126 1.0 x 105 â– 0.06, 1.9I-129 1.7 x 107 â– 0.15Cs-135 2.3 x 106 â– 0.21Pu-139 24000 á 5.16Pu-240 6580 á 5.17

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Where are the Radionuclides in the Fuel Pellet? Some fit the structure of the UO2 Actinides, most fission products Remain in the UO2 crystal

Some form at crystal boundaries and other gaps Mo, Pd, Rh, Ru, Tc, Te.....

Some may migrate to the surface Cs, Sr, I, Sn, Se

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Used Fuel Cross Section

Lubricant Grain boundary UO2 matrix

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The Instant Release Nuclides • A few of the more volatile elements are found

on the outside surface of the fuel

• Less than 8% of each of:

36Cl, 99Tc, 129I, 135Cs and a few others

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At Depth Oxygen concentration is Low

UO2 UO4--

The Fuel pellets don’t dissolvc

Technetium is TcO2 not TcO4-

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Earlier CNSC Regulations

• For up to 10,000 years

• Current standards of exposure limits

• Risk of cancer less than 1 in a million

(Using a Dose-Conversion ratio 0.02 per Sv)

(∴ Dose Rate less than 0.05 mSv/a)

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0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

Expo

sure

(mSv

/a)

Source

Normal Radiation Exposure

Cos

mic

Ray

s

Con

cret

e H

ouse

Jet F

light

Rad

on

Med

ical

Hum

an B

ody

NW

MO

?

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● How does nuclear power work? ● What is the problem?

● What proposals are there?

● What results are expected? ● What is the next step?

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Some Unacceptable Solutions

• Storage Forever

• Burial at Sea or in Space • Burial in the Polar Ice Caps • Transmutation • Shoot it into the Sun • Bury it in old Mines

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The Multi-barrier Concept

• Any barrier will eventually fail

• A failed barrier is backed up by another

• Each barrier provides delay

• Delay leads to decay

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The Engineered Barriers

• The Clay Buffer Box

• The Fuel Container

• The Cladding of the Fuel Bundle

• The Fuel pellet itself

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The Natural Barriers

• The Buffer

• The Intact Rock

• The Geosphere

• The Biosphere

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Current Proposal

• To be buried deep (500 - 1000 m) in intact rock

• The Fuel Bundles held in a Steel - Copper Container

• The container to be packed in a bentonite clay ‘box’

• To be backfilled with bentonite, rock and cement

• Surrounded by at least 50 m of intact rock.

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Vault Layout

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NWMO News 14-1-201635

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Nothing Happens Until

Water Corrodes the container and the sheathing

and dissolves the Instant Release Nuclides

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The Processes

• Resaturation • Container Failure, Cladding Failure • Radionuclide Release • Radionuclide Migration out through

• The Buffer • The Buffer and The Intact Rock

• The Geosphere

• The Biosphere - Isotope dilution

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Engineered Barriers

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Bentonite Clay

Container: 3 mm Cu

Fuel Cladding – Zr

Fuel UO2 Ceramic

Biosphere

Geosphere

Intact Rock

Buffer

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● How does nuclear power work? ● What is the problem? ● What proposals are there?

● What results are expected?

● What is the next step?

41

The Intact rock

is an important barrier

Water diffuses << 1 mm per year

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Therefore to go through Intact Rock

= More than 50,000 years

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My Earlier Estimates

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ResaturationContainer FailureSheath FailureInstant Release

Migration: BufferIntact RockGeosphere

100 years30,0001,000

0100

15,00010,000

Total 56,000 years

Where to Put it?

Ontario??

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Seismicity in Canada

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The Canadian Shield

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What are Other Countries Doing?

Finland Sweden

USA UK

France ....

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● How does nuclear power work? ● What is the problem? ● What proposals are there? ● What results are expected?

● What is the next step?

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Where are we now?

OPG and the Industry has set up

Nuclear Waste Management Organisation

Annual Reports

Frequent News Reports

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The Choices:

• Storage where it is now • Storage at a central site • Final Burial

The Selection:

Adaptive Phased Management

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Adaptive Phased Management:

• Storage at a central site

• Test and Improve the science

• Finally bury

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9 Areas being considered

Blind River Central Huron

Elliot Lake Hornepayne

Huron-Kinloss Ignace

Manitouwadge South Bruce White River

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Site Selection Criteria − Social

• Acceptable to the local people

• Acceptable to nearby communities

• Acceptable to the wider public

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Site Selection Criteria − Technical

• Absence of Seismic Activity

• Absence of mineral values

• Intact rock with adequate thickness and low porosity

• Rock that is strong enough

• Ground water that is and will remain reducing

• Recharge zone with very old water

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Thank You

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