NUCLEAR WASTE MANAGEMENT

April 26, 2004

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PWR Fuel Assembly

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Deep divisions of opinion about the feasibility of

nuclear waste disposal . . . .

• The critics:

– Risks are very high

– Absence of demonstrated disposal technology after 40+ years proves that nuclear power is fundamentally flawed

– Irresponsible to generate more waste while the problem remains unsolved

• The advocates

– ‘High-level waste is a non-risk ’

– ‘It is embarrassingly easy to solve the technical problems, yet impossible to solve the political problems ’

– Harold Lewis, Technological Risk, 1990

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Source: DOE Office of Civilian Radioactive Waste Management, Yucca Mountain Project Home Page, http://www.ymp. gov/timeline/index.htm

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DOE Yucca Mountain Project

website

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Key policy issues posed by nuclear w aste

 the balance of authority between federal, state, and local jurisdictions

 intertemporal equity and our obligations -- economic and environmental -- to future generations

 the assessment of technical risk and the ‘verification’ of system performance when no true verification is possible

 Public management of large-scale programs

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History of nuclear waste management includes false

starts and failures

• 1972: U.S. Atomic Energy Commission abandons repository project at a salt mine in Lyons, KA. Promotes Retrievable Surface Storage Facility (RSSF) as 100-year interim solution.

• 1975: RSSF abandoned. Geologic disposal adopted as preferred alternative.

• 1977: Spent fuel reprocessing indefinitely deferred.

• Complex national geologic repository site selection process initiated, then abandoned. Yucca Mountain picked instead.

• DOE contracts with utilities to take possession of utility spent fuel beginning in 1998, but fails to do so.

• Leaks of high-level radioactive waste from tanks at DOE sites in Washington and South Carolina.

• Disclosures of contamination and excessive radiation doses to workers throughout DOE nuclear complex over a period of decades.

• Continuing conflict between federal, state, and local jurisdictions over siting, regulatory issues

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DOE/Defense high level waste mostly stored in tanks at Hanford and Savannah River

Current inventories of high-level waste

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How much spent fuel?

U.S. power reactor fleet:

10 (m 3 /reactor-year) x 40 (years) x 100 reactors ~ 40,000 m 3

8m

50m

100m

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Hotv hazardous is spent fuel?

Siuface r«diation dose 1 meter from 5- year-old PWR spent ñiel asseuibly ili air: ?5,000-50,000 reuis/hr

LD50 dose: 400-500 reixs

Wast e Deca y Behavior

Spent fuel radioactivity =   i N i (t) (Becquerels/MTHM)

where

 i (t) = d ecay constant for isotope i (sec ) = (ln 2)  t 1/2

-1

N i (t) = # of atoms of isotope i per MTHM

= N i (0) e

-  t

Courtesy of Brett Mattingly. Used with permission.

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Radioactivity units:

1 Becquerel (Bq) = 1 disintegration per second 1 Curie = 3.7 x 10 10 Bq

Decay behavior (contd.)

Courtesy of Brett Mattingly. Used with permission.

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Disposition alternatives for high level waste

• Surface or near-surface engineered storage

• Geologic repositories

• Deep borehole disposal

• Sub-seabed disposal

• Ice-sheet disposal

• Extra-terrestrial disposal

• Waste partitioning

– Reprocessing and recycling of economically useful species

– Partitioning and transmutation of long-lived species

• (D o nothing)

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Location of Yucca Mountain, Nevada

Slid e 17

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Source: U.S. Dept of Energy, http://ocrwm.doe.gov/newsroom/photos/photos_graphics.shtml

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Yucca Mountain Site

• 100 miles NW of Las Vegas

• Volcanic tuff

– Layers of consolidated, compacted ashfalls from volcanic eruptions occurring more than 10 million years ago

– Underlying the tuff is sedimentary carbonate rock

• Repository horizon in ‘unsaturated zone’, about 300 meters below the surface, and 300-500 meters above the water table

• Two major aquifers in the saturated zone below Yucca Mountain, one in tuff, one in carbonate rock.

Source: U.S. Dept of Energy, http://ocrwm.doe.gov/newsroom/photos/photos_graphics.shtml

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Yucca Mountain, Nevada

Source: U.S. Dept of Energy, http://ocrwm.doe.gov/newsroom/photos/photos_graphics.shtml.

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Aerial view of the crest of Yucca Mountain, NV

Source: U.S. Dept of Energy, http://ocrwm.doe.gov/newsroom/photos/photos_graphics.shtml.

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Another aerial view of Yucca Mountain (from the South)

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Source: U.S. Dept of Energy, http://ocrwm.doe.gov/newsroom/photos/photos_graphics.shtml

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Figure 8.5 Artist’s r endition of t he Yucca Mountain repository

Source: U.S. Dept of Energy, http://ocrwm.doe.gov/newsroom/photos/photos_graphics.shtml.

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The repository will be series of emplacement ‘drifts’ where waste packages will be emplaced and monitored.

Source: U.S. Dept of Energy, http://ocrwm.doe.gov/newsroom/photos/photos_graphics.shtml.

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Waste Package Placement

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Source: U.S. Dept of Energy, http://ocrwm.doe.gov/newsroom/photos/photos_graphics.shtml

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Cutaway of drift with three types of waste packages

Source: U.S. Dept of Energy, http://ocrwm.doe.gov/newsroom/photos/photos_graphics.shtml.

.

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Policy Analysis

For how long should the waste be confined?

• ‘Radiotoxicity’ -- a crude measure of waste hazard:

– the total volume of water that would be required to dilute each of the radionuclides in 1 MT of spent fuel down to the safe drinking water concentration

• The radiation protection authorities have specified ‘ maximum permissible concentrations’ of individual radionuclides in water (and air) so that an individual obtaining total intake of water (or air) would not receive more than maximum allowable radiation dose (50 millirem/yr)

• We can then define a time-dependent ingestio n hazar d index :

Ingestion hazard index at time t 

all radionuclides    N ( t ) 



i

i i



 M PC water 



i

Example for Sr  90 :

ICRP  72 ingestion dose coefficient  2.8  10  8 Sv / Bq

Thus , total allowable annual int ake for committed effective dose of 5  10  4 Sv ( i . e .50 mrem )

  1.786  10 Bq / yr

5  10  4

4

2.8  10  8

M aximum allowable concentration of Sr  90



1.78 6  1 0 4 ( B q / yr ) 0.002 ( m 3 / day )  365 ( d / yr )

 2.45  10 Bq / m

4

3

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Radiotoxicit y decay

profil e fo r spen t PWR fue l (m 3 /MTHM)

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Potential failure modes for geologic repositories

• Natural degradation over time of the natural and

engineered barriers in the repository

– Dissolution and transport of radionuclides in groundwater

– Natural exhumation processes

• Tectonic processes (e.g., folding, faulting, magmatic intrusions, volcanism)

• Erosion (wind, water, glaciation)

• Breaching of barriers by human activity

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Performanc e Assessment s o f Repositor y System

• Rate of inflow of groundwater into the repository

– Hydrology-- current and long-term, fracturing, faulting, thermal stresses in host rock

• Rate of corrosion of canister, other barriers, and primary waste form

– temperature, oxidation/reduction conditions, materials properties of waste package

• Radionuclide transport in groundwater

– hydrology, sorption on rock surfaces, actinide chemistry

• Biosphere transport

– potable water supplies, irrigation water, demography -- current and long-term

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Groundwater hydrology of Yucca Mountain region

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Source: U.S. Dept of Energy, http://ocrwm.doe.gov/newsroom/photos/photos_graphics.shtml

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High-level waste disposal plans of leading nuclear countries

United States

DOE

Volcanic tuff 2010

Site selected (Yucca Mountain, NV);

application for construction license underway

Finland

Power companies Crystalline 2020

(Posiva Oy) bedrock

Site selected (Olkiluoto, SW Fi nland) –

decision ratified by Parliament in May 2001

Sweden Power companies Crystalline rock 2020

(SKB)

Switzerland Power company Crystalline rock 2020 or later

Searching for a suitable si te

Searching for a suitable si te

cooperative or clay

(Nagra)

France

Independent pu blic Granite or clay authority (ANDRA)

Crown corporation Granite (AECL)

National agency Not selected

(NUMO)

2020 or later

Developing repository concept

Canada

2025 or later

Reviewing repository concept

Japan

2030

Searching for suitable site

United Kingdom Under review Not selected After 2040 Delaying decision until 2040

Germany

Federal contractor Salt

company (DBE)

No date specified Moratorium on repository development fo r

3-10 years

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International Programs in High-Level Waste

Management

• All the leading nuclear countries have adopted the geologic repository approach for HLW disposal

• No country has yet established an operating repository

• There are important differences in technical strategies

– Spent fuel vs. reprocessed HLW

• Spent fuel (U.S., Canada, Finland)

• Reprocessed, vitrified HLW (UK, France). (Japan and Russia have announced prohibitions on direct disposal of spent fuel

• Store spent fuel temporarily and decide later

– Candidate geologic media

– Geochemical environment

– Reliance on engineered vs. natural barriers to radionuclide transport

– Thermal design of facility (including age of waste at emplacement)

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Comparison of U.S. and Finnish Repository

Programs

•

•

U.S.

Direct disposal of spent fuel

Stainless steel canister + Alloy 22 shell

‘Drip shield’; no backfill Unsaturated zone Oxidizing environment

Package surface temperature > 100C

Reliance on engineered barriers increasing

•

•

•

•

•

•

•

•

•

•

•

Finland

Direct disposal of spent fuel

Cast iron canister + copper mantle

Bentonite backfill Saturated zone Reducing environment

Low temperature operating condition

• Primary reliance on engineered barriers

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Finnis h high-leve l waste

repository

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Three key issues

• The repository site selection process

• The interim spent fuel management system

• Regulation of high level waste repositories

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History of U.S. repository siting efforts

1957: National Academy of Sciences recommends geologic disposal; identifies salt rock as the preferred medium

1972: U.S. Atomic Energy Commission abandons repository project at a salt mine in Lyons, KA. Research on alternative methods, including other geologic media, deep seabed, etc. begins. AEC promotes RSSF as 100-year interim solution.

1975: RSSF abandoned. Geologic disposal adopted as preferred alternative.

1978: President Carter affirms principle of not handing responsibility for disposal to future generations, as well as feasibility of geologic disposal. Advocates ‘consultation and concurrence’ policy towards states.

1982: Nuclear W aste Policy Act -- lays out comprehensive screening process leading to 2 sites in West and East; establishes Nuclear Waste Fund, financed by 0.1 cent/kwh nuclear electricity levy; directs DOE to begin accepting spent fuel from utilities in 1998.

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Some Possible Scenarios at Yucca Mountain

• The site will be selected; the Federal government will be

found to have the necessary legal authority, and will proceed to design, license, and build a repository.

• The site will be selected, the Federal government will be found to have the necessary legal authority, but the project will be stopped by political and other roadblocks.

• The site will be selected, but the Federal government’s effort to pre-empt state authority will ultimately be found unconstitutional and the project will be stopped.

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An Interim Storage Facility for Spent Fuel?

• Advocates:

– Provide breathing room for reactors running out of on-site storage space

– Will provide more time to understand repository science and engineering, find an acceptable repository site, explore disposal alternatives (including transmutation), etc.

• Opponents:

– Will become a de facto alternative to disposal

– Will be no easier to site than a repository

– Will reduce momentum to develop a repository

• 1987 legislation -- ties MRS construction to approval of final site; prohibits siting MRS in Nevada; subsequent Congressional efforts to overturn this and build MRS in Nevada vetoed by Clinton.

• Senate legislation introduced this year would prevent ‘irreversible action relating to disposal of spent nuclear fuel’ and provide more funding for partitioning and transmutation.

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Regulating Geologic Repositories

• Standards -- who will decide?

• Standards -- how safe is safe enough?

• Verification -- how sure must we be?

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Performance Standards for HLW

Repositories: Who’s in charge?

• Authority to set criteria and standards and to license high level waste repositories vested in the Federal government

• Jurisdiction is divided; boundaries often ill-defined

– EPA responsible for promulgating ‘generally applicable standards’ for protection of the general environment

– NRC responsible for:

• establishing criteria and standards for the facility itself

• Responsible for licensing the facility

– DOE responsible for implementation, including demonstrating compliance with EPA and NRC standards and regulations

• Constant tension between agencies; occasionally open warfare . . .

• Legal challenges

• Congress increasingly involved in technical standard-setting . . .

• Alignment of EPA, NRC and DOE standards largely achieved by 2001

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Congress becoming increasingly active

• NWPA of 1982:

– EPA shall promulgate generally applicable standards for protection of the general environment from offsite releases . .

– NRC shall promulgate technical requirements and criteria . . .not inconsistent with any comparable standards of EPA

• Energy Policy Act of 1992

– Requires EPA to promulgate a standard specifically for Yucca Mountain, to be consistent with findings and recommendations of a study to be performed by the National Academy of Sciences

• NAS -- 1996 study

– Risk at 10 -5 to 10 -6 at calculated peak risk, whenever it occurs (200,000-300,000 years) -- 2-20 mrem/yr

• S.104,1997

– EPA standard shall limit lifetime risk, to the average member of the critical group, of premature death from cancer . . .to approximately, but not greater than 1 in 1000. (~30 mrem/yr)

– Shall not have release limits or contaminant levels for individual nuclides

• HR 1270, 1997 (proposed)

– NRC rule should be less than 100 mrem/yr to average member of gen. pop

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S ome key issu es th at an y tech nical

standard must address:

• Allowable risk from repository relative to natural background risks (how safe is safe enough?)

• Assumptions about future human activities and lifestyles

• How far into the future is it reasonable to project disposal system performance?

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Generic EPA Standard for Disposal of HLW ,

Spent Fuel and TRU Waste (10 CFR 191)

• Population risk standard: Health impacts for the first 10,000 years for a repository containing 100,000 metric tons of heavy metal should not exceed 1000 fatal cancers

– Cancer risk based on assumed incidence of 5.75 x 10 -4 fatal cancers per rem of population dose.(linear, non-threshold dose-response model)

– Risks to future generations from a geologic respository for high-level wastes during the first 10,000 years should be no greater than the risks from an equivalent amount of unmined uranium ore.

• Individual protection requirement

– Annual effective dose equivalent, for all pathways of exposure, should be no greater than 15 mrem/year, for 10,000 years.*

• Additional ground water protection limits

– Concentration of radioactivity in any underground source of drinking water should not exceed Maximum Contaminant Levels of Safe Drinking Water Act.

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* Natural background: 300 mrem/yr

EPA Site-Specific Disposal Standards for Yucca

Mountain (10 CFR 197; issued in 1999)

• Individual protection standard

• Groundwater protection standard

• Human intrusion standard

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EPA Disposal Standards for Yucca Mountain

(10 CFR 197; finalized June 2001)

• Individua l protectio n standard

– No greater than 1 5 mrem per year for the maximally-exposed individual during first 10,000 years

– Equivalent to an annual fatal cancer risk of 8.5x10 -6 per year to the maximally-exposed individual

– EPA: “Determining the appropriate dose level is ultimately a question of both science and public policy”

– National Academy of Sciences:“The level of protection established by a standard is a statement of the level of the risk that is acceptable to society. Whether posed as ‘How safe is safe enough?’ or as ‘What is an acceptable level?’ , the question is not solvable by science’

– Total dose limit recommended by ICRP from all sources of radiation, except from background and medical procedures: 100 mrem/year

• (Other sources in the area -- Nevada Nuclear Testing Site, LLW and TRU waste)

– EPA: “To avoid unsupportable speculation regarding human activities and conditions, we believe it is appropriate to assume that . . parameters describing human activities and interactions with the repository (e.g., the level of human knowledge and technical capability, human physiology and nutritional needs, general lifestyles and food consumption patterns of the population, and potential pathways through the biosphere leading to radiation exposure or humans) wil l remai n a s the y ar e today (emphasis added)

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• Controlled Area:

– Maximum of 300 km 2 of surface area above repository

– No more than 5 km from edge of repository footprint (except in predominant direction of groundwater flow)

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Why 10,000 years?

• National Academy of Sciences:

– “ There is no scientific basis for limiting the time period of the individual risk standard to 10,000 years or any other value.”

– The probabilities and consequences of the relevant features, events and processes “ . . . are sufficiently boundable so that these factors can be included in performance assessments that extend over periods on the order of about one million years.”

• EPA:

– “ We believe that such an approach is not practical for regulatory decisionmaking, which involves more than scientific performance projections using computer models.”

– “We have included a 10,000-year compliance period in regulations for non-radioactive hazardous waste.”

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How to verify compliance with the EPA’s standards?

• This is the task of the NRC

• NRC will requires DOE to demonstrate compliance with this standard using performanc e assessment (systematic analysis of events, processes, and features affecting isolation performance)

• Future human activities and biosphere conditions?

– EPA: “To avoid unsupportable speculation regarding human activities and conditions, we believe it is appropriate to assume that . . parameters describing human activities and interactions with the repository (e.g., the level of human knowledge and technical capability, human physiology and nutritional needs, general lifestyles and food consumption patterns of the population, and potential pathways through the biosphere leading to radiation exposure or humans) wil l remai n a s the y ar e today (emphasis added)

• Treatment of unlikely events

– “Events that are very unlikely (less than 1 in 10,000 over 10,000 years) can be excluded [from the performance assessment]”

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How to determine compliance with standards?

§ 191.15 Individua l protectio n requirements .

(a) Disposal systems for waste and any associated radioactive material shall be designed to provide a reasonable expectation that, for 10,000 years after

disposal, undisturbed performance of the disposal system shall not cause the annual committed effective dose, received through all potential pathways

from the disposal system, to any member of the public in the accessible environment, to exceed 15 millirems (150 microsieverts).

.

.

.

(c) Compliance assessments nee d no t provid e complet e assurance that the requirements of paragraph (a) of this section will be met. Because of the long

time period involved and the nature of the processes and events of interest, there will inevitably be substantial uncertainties in projecting disposal system

performance. Proof of the future performance of a disposal system is not to be had in the ordinary sense of the word in situations that deal with much

shorter time frames. Instead, wha t i s require d i s a reasonabl e expectation , o n th e basi s o f the recor d befor e th e implementin g agency , that compliance

with paragraph (a) of this section will be achieved. (Emphasis added)

.

[58 FR 66414, Dec. 20, 1993]

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NRC Requirements

• Consistency with EPA standards

– Individual protection

– Groundwater contamination in the accessible environment

– Human intrusion

• Multibarrier approach

• Future human activities and biosphere conditions

– “Characteristics of the reference biosphere and the reasonably maximally exposed individual are to be based on current human behavior and biospheric conditions in the region”

• Treatment of unlikely events

– “Events that are very unlikely (less than 1 in 10,000 over 10,000 years) can be excluded [from the performance assessment]”

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N RC regulations prescribe a multibarrier approach

• Rationale for multibarrier approach

– Geologic barriers: “ Although there is an extensive geologic record ranging from thousands to millions of years, this record is subject to interpretation and includes many uncertainties.”

– Engineered barriers: “Although the composition and configuration of engineered structures can be defined with a degree of precision not possible for natural barriers, it is recognized that except for a few archaeological and natural analogs, there is a limited experience base for the performance of complex, engineered structures over periods longer than a few hundred years . . .”

– “These uncertainties are addressed by requiring the use of a multiple barrier approach; specifically an engineered barrier system is required in addition to the natural barriers provided by the geologic setting.”

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Selected NRC Technical Criteria for High

Level Waste Disposal (10 CFR 60) -- 1984

• NRC took a ‘defense-in-depth’ approach to setting repository performance standards. Minimum performance standards were prescribed for each of the major elements of the repository (i.e., the waste package, the underground facility, and the geologic setting)

• Performance requirements:

– substantiall y complet e containment of HLW within the waste packages for from 300 to 1000 years

– subsequently, the total release rate of radionuclides from the engineered barrier system (i.e., waste packages + underground structure) shall not exceed 10 -5 /yr of the waste inventory present after 1000 years

– pre-waste emplacement groundwater travel time from the repository to the accessible environment shall be at least 1000 yrs

+ many additional qualitative siting and design criteria

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N RC Regulatory Requirements for Y ucca

M ountain specifically (10 CFR 63 -- N ov. 2001)

• Fundamentally different from 10 CFR 60

– 10 CFR 60 relied on several quantitative subsystem performance objectives

– NRC no longer believes that this is the best approach for ensuring compliance with overall environmental standards

• 10 CFR 63 is based instead on only one quantitative standard: demonstratin g complianc e wit h th e individua l dos e limit of 15 mrem/yr for 10,000 years.

• Requires DOE to demonstrate compliance with this standard using performanc e assessment (systematic analysis of events, processes, and features affecting isolation performance)

– 10 CFR 63 specifies performance assessment methodology

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Lessons from history of nuclear w aste

regulation

• Some key technical issues have no ‘right answer’ (‘ transcientific questions’)

• Setting standards and regulations is not solvable by science. It is ultimately a question of public policy.

• Implementation of regulations will require the exercise of technical judgements by technical experts. Proof of compliance with standards in the normal sense is not achievable.

• Regulation does not occur in a political vacuum; it is a public process. The credibility in the public domain of the technical experts who will be called upon to make these judgments will be crucial.

• Public credibility, once lost, is extremely difficult to restore.

• Because the regulatory process (both standard-setting and implementation) is a public process, it will also be affected by public perceptions of risk

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