Decommissioning of Nuclear Facilities. Decommissioning Definition: The process of safely closing a facility from service where nuclear materials are used

Decommissioning of Nuclear Facilities

Decommissioning

Definition:The process of safely closing a facility from service where nuclear materials are used at the end of the facilities’ useful life.

Reasons for decommissioning:• Too expensive to operate, maintain, or repair to maintain

operational compliance• Lack of necessity for nuclear facility• Risk to Benefit ratio is too low (congressional wisdom)

NRC: 10 CFR 50.82Termination of License

Purpose:The purpose of decommissioning is to remove the nuclear facility from service and to reduce the residual radioactivity so that the operating license may be terminated and the property may be released under restricted or unrestricted conditions.Facilities Effected:• Nuclear Power Plants (the most difficult)• Chemical Plants (that handle nuclear products)• Conversion plants• Reprocessing plants• Fabrication Plants( these facilities decommissioning equate to decontamination)

Beginning Decommissioning Process

• When it has been determined to cease operation of a nuclear power facility, a written certification, license termination plan (LTC), must be written within 30 days of the determination to the NRC consistent with guidelines of 10 CFR 50.4(b)(8)

• Once all of the fuel has been removed from the core, another written certification (LTC) must be submitted under guidelines 10 CFR 50.4(b)(9)• Written certification can be made for cease of operation with

retention of fuel in the core

• Decommissioning is addressed in 10 CFR 50. Some parts are addressed in parts 20, 30, 40, 51 ,70, 72, and the “Decommissioning Resource Manuel”

Beginning Decommissioning Process

cont.• Upon docket of permanent cessation of operation and

removal of fuel or legal order to cease operation, the post-licensee has 2 years to submit a post-shutdown decommissioning activity report (PSDAR) to the NRC and the affected state.

• No major decommissioning activity may start until 90 days after PSDAR submittal (i.e. removal of hazardous materials)

• Nuclear power facilities with multiple reactors may apply for a partial site release. The NRC will have to approve the license termination plan (LTC)

PSDAR• A description of planned decommissioning activities and

completions• Estimation of expected cost• A report that concludes that previous environmental reports

will substantiate the current environmental report parameters associated with the decommissioning site. It will discuss the appropriate activities associated with the decommissioning of the site

• Decommissioning will be completed in 60 yrs. Extensions may be granted by NRC if public health and safety are a consideration

Key points of Decommissioning Plan

• Hazardous LLW’s removal procedure• Return to unrestricted use plan (unless site has more than one

reactor, a partial site release is required )• Safety procedures and protocols (i.e. disposal of radioactive

waste procedures/methods and disposal locations)• Financial plan of decommissioning (includes removal of spent

fuel and removal of nonessential equipment necessary to license termination.

• Record keeping and time management• ALARA

Decommission Completion• Radioactive components have been removed from the site • Site Decontamination performed (if necessary)• Total Effective Dose Equivalent (TEDE) to an average member

of the critical group is less than .25 mSv/yr • Critical Group - the group of individuals expected to receive

the greatest exposure to residual radioactivity for any applicable set of circumstances (one or several groups considered)

• TEDE for restricted use must be .25 mSv with institutional controls and 1 mSv with no institutional control.

Institutional control – fences, restriction of use of site(i.e. parking, farming), access restriction

Total Effective Dose Equivalent

International Commission on Radiological Protection (ICRP)

• Leading agency that provides recommendations for radiological safety• Introduce detailed technical regulations• Develop codes of practice best suited for countries to protect their citizens• ICRP Publication 60 recommends EDE limits for exposure

ICRP Basic Radiation Safety Criteria (Groups)

• Occupational exposure• Pregnant women• Radiation workers

• General public exposure• Medical Exposure (diagnostic and therapeutic)


ICRP Basic Radiation Safety Criteria (Groups)• Occupational exposure

• Pregnant women• Radiation workers

• General public exposure• Medical Exposure (diagnostic and therapeutic)

Dose Limit System• Non-stochastic Effect – assumes a radiological dose has a threshold before

an effect takes place• Stochastic Effect – assumes that any radiological dose has the capacity : the

to have an effect; the only safe radiological dose is zero .


ALI (Annual Limit of Intake)The derived upper bound of allowed radiological dosage that

may not be exceeded per year. (workers = 2000 hours)

• Compliance is determined when the summation of the effective dose equivalent plus the committed effective dose equivalent value is less than 1.

+ x

Decommission Completion

Steps to a successful Decommissioning:1. Create an advisory committee with local people

participation2. Calculate the residual radiation level as closely as

possible3. Model and compute the exposure probabilities of

workers and the public.4. ALARA5. Protect the ground water per EPA guidelines

Decommissioning Methods• Decommissioning doesn’t include used nuclear fuel• Disposal of LLW’s and TRU leaked into coolant from fuel rods• Cost and exposure risk are major contributors to method

decisionThree methods• DECON – dismantle; all materials, equipment, machinery,

radiological sources, etc. are removed. Upon completion, the license is terminated and the site is released as unrestricted

• SAFSTOR – mothballing; radioactive material are removed. Equipment and machinery is secured and monitored. The site is licensed as restricted use until the plant is dismantle.

• ENTOMB – entombment; the site is encased in concrete and monitored until the radiological levels reduce to unrestricted levels

Decommissioning Methods

Major Considerations for deciding decommissioning method

• Whether or not other nuclear generating facilities are on site• Current and projected waste facility site availability• Current and projected cost of decommissioning and funding

availability• Regulatory outlook


• Two types of waste for disposal during process

• Leaked transuranic (TRU) in the fuel• Contaminated equipment due to neutron absorption (i.e. heat

exchangers, instrumentation cables, steam generators, reactor coolant pumps, pressurizer, and the reactor pressure vessel )• Both inside and outside of the reactor• Most Important Isotope to dispose – Co-60, Ni-59, Nb-94, and Eu-

152 due to long half life and radiological concentrations




Decontamination Methods

The process of transferring radioactive material from one surfaces to another for disposal

Benefits:• Lowers the volume of LLW and decreases cost of disposal• Lowers radiation exposure to workers4 methods of decontamination• Chemical• Physical• Electropolishing• UltrasonicJanitorial methods are done prior to these methods

Decontamination Methods

Chemical• Chemical solution used to remove radioactive materials• Solution type depends on the radioactive material and the

surfacePhysical• Pressure washing, jack hammering, pneumatic disk, etc. are

used to remove radioactive materials• Debris is package and shipped to a LLW repository

Electropolishing• Radiactive metal surfaces are put in an phosphoric acid. The

surface creates a negatively charged terminal. Electric current is applied to metal surface. A atomic layer is removed with the electrical current which carries the radionuclide.

Decontamination Method

Ultrasonic Method• Used on valves and pumps• Items are placed in a bath of liquid. Ultrasonic waves are

applied to the bath. Waves create a pressure of 10,000 psi and dislodge the material from the item

• Abrasives and chemicals may be added to the liquid to increase effectiveness of process.

Assurance of Funds for Decontamination

Prepayment (preferred)External Sinking Fund• Trust• Escrow Account• Govt. fundsCertificate of Deposit• Deposit of Govt. SecuritySurety Method, insurance, or other guarantee method• Surety bond (open ended and automatically renewable)• Must close surety in writingZ

• Letter of credit (• Line of CreditCost depends on plant size, plant design, and local labor markets





Obstacles to Decommissioning Affecting Cost

• LLW’s Facilities in the long term for storage • Transition personnel from operation professional to

shutdown/dismantlement professionals• Regulatory transition• Government uncertainty • SNF/HLW remaining on site issues (i.e. transportability,

canister licensing)• Aging Management• Operating margins no longer supporting operation due to:• Environmental hurdles• Aging facilities too costly to repair• Independent Spent Fuel Storage Installation (ISFSI)

• Safety (exposure)

Obstacles to Decommissioning Affecting Cost (cont.)

• Competitive price of natural gas (“fracking” lower cost of natural gas extrusion from 12.50 per thousand cubic ft. to 4.85 per thousand cubic ft.)

Transport of LLW’s(Containers)

• LSA material (low specific activity) – non-fisslie material that have an activity set below those prescribed by 10 CFR 71.75• May be packaged in a “essentially” Type A packaging if

determined “nonexclusive use”• Essentially – not having to meet all of the testing for Type A

packaging• Guarantee of loading procedures must be presented and adhered to• Dose rates of packaging must meet guidelines

cont.

Stability Requirements

• Must be able to maintain structural integrity under disposal conditions

• Must be noncorrosive at 1% waste volume or .5% of waste volume in stable form

• No void spaces in packaging• Clearly identified in designated• classes


Nonexclusive LSA Type A container transport criteria

• 2mSv/h at any point of packaging• If higher, an exclusive vehicle must transport the material and

satisfy additional criteria• 10 mSv if shipment is in a closed vehicle• 10 mSv if materials are secures to avoid material movement during

transport• 10 mSv if materials are not unloaded and loaded during the trip

• 2 mSv/h at any point on external surface of vehicle• 0.1 mSv/h at any point 2 meters from surface of the vehicle• 0.02 mSv/h in any normally occupied space (i.e. driver cab)

Calculating Package Classification with Several Radionuclides

The Fraction Rule

1

Apply this equation when there are more than one isotope in a package• If the isotopes are in the same column of Table 1 or Table 2, add the

summation to find if their sums equal more than or less than one. If more than one, the next higher class is designated for the class.

• The isotope of the most restrictive class designates the class of the package if two isotopes of different Tables and/or columns are in the LLW package.


• Covered in 10 CFR 71 and 49 CFR 173• Packages must pass test to satisfy shipping requirements• Three type of containers allowed for shipping• Type A package – capable of withstanding normal conditions of

transport without leaking of radioactive contents.• Class A radionuclides or a mix thereof may be packaged into Type A

packaging• Examples (fiberboard box, wooden box, steel drum


• Type B package – capable of withstanding normal and accidental transport conditions without leaking radioactive contents.• Class B radionuclides must be transported in in Type B packaging• Examples (Steel drum outer layer, shielded inner layer, thermal

insulation between layers)

Examples of Low Level WasteExamples of radioisotopes contaminated items like:• Clothing• Tools• Swipes• Trash• Liquids Low Level Waste sources include:• Nuclear plants• *Research Laboratories• *Hospitals• Radiopharmaceutical Laboratories• *Industrial Facilities

Classification of LLW’s(Near surface burial disposal site permitted for LLW packages)

Class A – This class has the least amount of radioactivity• Radionuclides not listed in Table 1 or Table 2• Radionuclides of Table 1 at 10% or less of concentration listed in Table 1• Radionuclides of Table 2 at concentrations equal to or less than the value in Col.1 of

Table 2

Class B • Radionuclides of Table 2 that have concentration values greater than Col. 1 yet less

than Col.2

Class C• Radionuclides of Table 1 with concentrations greater than 10% of the value listed in

Table 1• Radionuclides of Table B with concentration values greater than Col. 2 and less than

values listed in Col.3

Class GTCC (greater than class C)• Radionuclides of Table 1 with concentrations greater than the value listed in Table 1• Radionuclides of Table 2 with concentrations greater than the values listed in Col.3

Classification of LLW’s(Near surface burial disposal site permitted for LLW packages)

Examples of GTCC’s • Activated metals from reactors (decommissioning)• Reactor control rods• Cladding

• Sealed sources• Medical (sterilizing products)• Industrial ( xrays to detect flaws in welds)

• Radionuclides found in GTCC• Cs137Cl• Pu238• Pu240• Am241, Am243• Cm244

LLW Disposal Requirements

Minimum Requirements• Packaging in cardboard or fiberboard is prohibited• Liquid waste must be solidified (made not to leak)• In absorbent material• Liquid must not exceed 1% of waste

• Waste must not be explosive• Waste must not be pyrophoric• Waste activity must be less than 100 Ci/container and

contained at a pressure of less than 1.5 atm @ 20 degree Cel.

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Decommissioning of Nuclear Facilities. Decommissioning Definition: The process of safely closing a facility from service where nuclear materials are used