The once seemingly insurmountable technical challenges of dismantling a commercial nuclear plant have been largely eliminated through experience. Decommissioning processes have been standardized and optimized using lessons learned, including some from the Zion plant decommissioning in Illinois. However, costs still vary significantly from plant to plant depending on the decommissioning strategy, site-specific characteristics, and project execution effectiveness.
The Nuclear Regulatory Commission (NRC), the agency that oversees and licenses commercial nuclear plants in the U.S., has an official decommissioning definition. In Title 10 of the Code of Federal Regulations Part 50.2 (10 CFR 50.2), “Definitions,” it says to decommission means to remove a facility or site safely from service and reduce residual radioactivity to a level that permits either release of the property for unrestricted use and termination of the license, or release of the property under restricted conditions and termination of the license.
The Learning Curve
Initially, decommissioning was viewed as a public demonstration to retire nuclear facilities and protect the public from residual radioactivity. Early decommissioning projects (circa 1960s–1970s) were limited to smaller demonstration plants and research reactors. Nevertheless, they created a decommissioning market, which allowed decontamination and dismantling techniques to be tested and improved.
The Atomic Energy Commission (AEC), the predecessor of the NRC, ultimately accepted four retirement alternatives in 1974. The options were:
■ Mothballing, putting the facility in protective storage and removing all fuel assemblies and radioactive fluids.
■ In-place entombment, sealing all remaining highly radioactive or contaminated components, such as the pressure vessel and reactor internals, within a structure integral with the biological shield after having all fuel assemblies, radioactive fluids and wastes, and certain selected components shipped offsite.
■ Removal of radioactive components and dismantling, removing all fuel assemblies, radioactive fluids and waste, and other radioactive materials above unrestricted activity levels from the site. The remainder of the reactor facility could be dismantled, and all vestiges removed and scrapped.
■ Conversion to a new nuclear system or a fossil fuel system, utilizing the existing turbine system with a new steam supply system. In this scenario, the original nuclear steam supply system would be separated from the electric generating system and disposed of in accordance with one of the three other retirement alternatives.
Two landmark NRC studies later examined the alternatives, assessed the technologies available at the time, and estimated costs in preparation for revising regulatory requirements. The goal was to facilitate decommissioning of the larger nuclear plants in use today. The NRC examined the decommissioning of Portland General Electric Co.’s 1,175-MW Trojan nuclear plant in June 1978, which was a pressurized water reactor (PWR), and Washington Public Power Supply System’s 1,155-MW Nuclear Project Number 2 in Hanford, Washington, in June 1980, which was a boiling water reactor (BWR).
The studies considered immediate dismantlement and passive safe storage with deferred dismantlement. Entombment was considered acceptable for the reference BWR, but deemed unsatisfactory for the PWR scenario because of radiation dose rates from long-lived radionuclides.
Subsequent updates in the 1980s and 1990s would redefine decommissioning alternative schedules and costs following the demise of the spent fuel reprocessing industry, delays by the federal waste management system to establish interim storage and permanent spent fuel disposal facilities, and accumulation of spent fuel inventories at shutdown.
Retirement-to-Decommissioning Regulation Evolution
The four original retirement alternatives were reduced to three in 1981, and then promulgated in the first comprehensive power reactor decommissioning regulations in 1988. The three alternatives—now referred to as methods or strategies—remain in use today. They are DECON, SAFSTOR, and ENTOMB. All decommissioning activities, regardless of the method, must be completed within 60 years of the plant ceasing operations. Extensions require NRC approval.
DECON (Immediate Dismantling). Radioactively contaminated equipment and structures are chemically or mechanically decontaminated and removed, permitting release of the property and NRC license termination. For example, the Electric Power Research Institute’s (EPRI’s) decontamination-for-decommissioning (DFD) process uses chemicals and ion-exchange filtering to decontaminate the primary coolant system prior to commencement of cutting and segmenting for disposal in shielded shipping containers. This facilitates decommissioning by reducing contamination within plant systems and dose rates to workers. DECON advantages include reducing state and local regulatory oversight, allowing decommissioning to be addressed sooner rather than later, and returning the land to other economic uses faster.
SAFSTOR (Deferred Dismantling). Nuclear facilities are maintained and monitored for a period of time, allowing radioactivity to decay. This delay can yield lower radiation levels to workers. Although the initial cobalt-60 radiation levels can substantially decrease, the reactor vessel internal components can still exhibit high radiation dose rates, requiring remote sectioning under shielding water due to the remaining cobalt-60 and long-lived radionuclides such as niobium-94 and nickel-59. The plant is then dismantled and property decontaminated.
ENTOMB (Entombment). Radioactive contaminants are permanently encased on-site in structurally sound material, such as concrete. The facility is maintained and monitored until the radioactivity decays to a level permitting restricted property release. NRC licensees are not expected to select this strategy.
The 1988 promulgation included formulas for calculating minimum funds for decommissioning by reactor type and power level, adjusting for escalation. The NRC revised its decommissioning regulations in 1996 to include lessons learned from earlier decommissioning activities. A series of NRC decommissioning technical reports (NUREGs) and regulatory guides (RGs) were issued between 1997 and 2001.
One example is RG 1.184, “Decommissioning of Nuclear Power Reactors,” issued in July 2000. It describes the methods NRC staff deem acceptable for implementing the 1996 requirements and major decommissioning phases. One portion of the first decommissioning phase includes ascertaining the permanent cessation of operations effective date and identifying activities required before the reactor is placed in storage or major decommissioning activities begin. The second phase encompasses activities during storage and major decommissioning activities such as decontamination and dismantlement. The third phase includes all remaining license termination activities.
A rulemaking effort to address the transition from operations to decommissioning was suspended following the September 11, 2001, terrorist attacks in the U.S., with the NRC redirecting priorities and resources to nuclear safeguards and security. Other than a few active decommissioning projects at the time, no new reactor decommissioning plans were expected in the foreseeable future.
Early Nuclear Plant Retirements
Between 2013 and 2016, five reactor licensees announced early retirements, the first to transition to decommissioning since 1998 (Table 1). Apart from early licensing action submittals by Vermont Yankee (VY) while still operating, and improving its transition efficiency by one year, these announcements were unexpected, raising concerns about decommissioning fund deficits. The NRC was further challenged to process multiple and concurrent decommissioning licensing actions—over 70 actions in a three-year period—in order to meet the licensees’ requested completion dates, and access decommissioning trust funds.
Competition, cheap natural gas, and stagnant power demands were playing significant roles in deciding a nuclear plant’s future. The trend has continued as more plants have announced either early retirement or that owners would not pursue license renewal before their operating licenses expired (Table 2).
Future closures are still possible. Dominion Energy reported it was considering shutting the Millstone nuclear plant citing economic reasons. However, ISO-New England, the grid operator, informed Dominion the next opportunity to exit the market would be in 2022, and that Dominion may instead transfer its responsibility to provide energy to a third party or pay a penalty to exit the market early. According to a report in the Hartford Courant, ISO-New England said that future capacity in the region could become a problem, and that the region needs Millstone due to the impending retirement of the Pilgrim nuclear plant and the lack of sufficient natural gas pipeline capacity.
Plan the Work, Work the Plan
Despite these early and pending retirements, Dr. Rick Reid, technical executive for EPRI’s decommissioning technology program, said that once the announcement is made, decommissioning should be completed as quickly as possible. Experience has shown that costs pile up during extended decommissioning projects lasting 20 years or more, so anything done as quickly as possible is incredibly important.
Decommissioning should be viewed as a part of the plant life cycle, not something always in the future. It’s got to be done, and will eventually happen. EPRI suggests answering 10 questions to get the planning process underway. The questions are:
■ What are the available waste disposal options?
■ What is the required waste form/packaging for disposal?
■ What are the spent fuel disposition options?
■ What is the site’s end state (restricted or unrestricted release)?
■ What are the site release criteria set by the regulator?
■ What are the site release limits (for example, residential, industrial, or other scenarios)?
■ Do clearance and/or recycle regulatory criteria exist?
■ Do I promptly decommission or wait for the remaining plants on site to permanently shut down?
■ Do I perform a full system chemical decontamination?
■ Does the regulator have a schedule for preparing decommissioning documents and/or completing decommissioning?
Reid added that the more successful utilities and plants with respect to decommissioning are the ones that are benchmarking and hiring people that have experience with actual decommissioning projects. “I think people have always recognized that, but it is certainly a key lesson and a key takeaway from my perspective,” he said.
Rich McGrath, principal technical leader for EPRI, confirmed that obtaining regulatory approvals during the transition period between operations and decommissioning offers advantages. One is that obtaining the approvals shortens the decommissioning period because actual demolition can begin sooner.
Several NUREGs and RGs control the NRC’s decommissioning process (see sidebar).
|Decommissioning Guidance Documents
The following Nuclear Regulatory Commission technical reports (NUREGs) and regulatory guides (RGs) are the main documents used to evaluate power reactors as they transition into decommissioning:
■ NUREG-1496, “Generic Environmental Impact Statement in Support of Rulemaking on Radiological Criteria for License Termination of NRC-Licensed Nuclear Facilities”
■ NUREG-1700, “Standard Review Plan for Evaluating Nuclear Power Reactor License Termination Plans”
■ NUREG-1727, “NMSS [Nuclear Material Safety and Safeguards] Decommissioning Standard Review Plan”
■ NUREG-1757, “Consolidated Decommissioning Guidance”
■ RG 1.179, “Standard Format and Content of License Termination Plans for Nuclear Power Reactors”
■ RG 1.184, “Decommissioning of Nuclear Power Reactors”
■ RG 1.185, “Standard Format and Content for Post-Shutdown Decommissioning Activities Report”
■ RG 4.21, “Minimization of Contamination and Radioactive Waste Generation: Life-Cycle Planning”
■ RG 4.22, “Decommissioning Planning During Operations”
The process also requires several regulatory submittals, which include:
■ Certification of Permanent Cessation of Operations and Permanent Removal of Fuel
■ Post Shutdown Decommissioning Activities Report (PSDAR)
■ Site-Specific Decommissioning Cost Estimate
■ Revisions to Plant Licensing Design Basis Documents
■ Defueled Safety Analysis Report (DSAR)
For example, the DSAR—equivalent to the Final Safety Analysis Report during operation—serves as the principal licensing document describing equipment, structures, systems, operational constraints, accident analyses, and decommissioning activities associated with the defueled condition.
Zion Decommissioning Update
POWER has been following the Zion Nuclear Power Station decommissioning project for years (see “Evolved Strategy Accelerates Zion Nuclear Plant Decommissioning” in the July 2014 issue). To get an update on recent developments at the site, POWER interviewed Jeff Hays, senior vice president for commercial decommissioning with EnergySolutions, a leader in the nuclear decommissioning industry and parent company of ZionSolutions, which is completing the Zion project (Figure 1).
Hays said the project currently remains on budget and two years ahead of schedule. Regarding the primary decommissioning lessons learned from the Zion station that can be applied to future decommissioning projects, Hays commented: “Most of the key lessons associated with a successful decommissioning are really very similar to what drives other large complex projects. We must maintain a strong safety culture, and establish and maintain a strong working relationship throughout the regulatory process. Detailed pre-planning and scheduling with strong project controls, monitoring, and reporting are also a top priority. There is also a need to fully test key equipment prior to first use and encourage creativity while maintaining timely staffing to control cost.”
The 2014 article included details about segmenting the reactor vessel and planning for the transfer of spent fuel to the independent spent fuel storage installation (ISFSI, Figure 2). Hays said that there is just as much emphasis being placed on planning to demolish the remaining site structures as there was during earlier work.
“The premise by which the major building demolition was performed included the removal of the large equipment from the building, for instance the turbine casing and rotor. The removal of any contaminated piping and system components occurs prior to the removal of the crane, which will be removed when it is no longer needed. A fixative would be applied to all surfaces after gross decontamination to affix any transferable contamination to preclude release of contamination during the open-air demolition of the structure. Any interior floors and nonstructural support beams would be removed, then the final engineering walk down is performed to ensure only the necessary support structures remain. The building demolition would commence using large demolition equipment from the outside of the building working their way into the building.”
Reactor coolant system (RCS) piping decontamination using the EPRI DFD process was not required due to the time between shutdown and project start. The thick-walled piping was cut into sections that fit directly into waste packages using a standard diamond wire saw. There was no added benefit from volume reduction (Figure 3).
Effective characterization allowed for the free-release of large volumes of materials and debris. In other words, the material was found to be free of detectable radioactive contamination and could be released without restrictions.
“Almost the entire turbine building was free-released. This included all of the support systems for the turbines. There were a very small number of items from contaminated systems that required surgical demolition prior to the completion of the release of the turbine building. The contents from the containment and fuel handling building were all contaminated from the operation of the plant; there were very little items deconned for free-release. The auxiliary building contained both contaminated systems and some non-contaminated systems. There were large volumes of concrete that were free-released, rubbilized, then used as backfill for beneficial reuse,” Hays reported.
Calculating and Estimating Decommissioning Costs
The NRC and licensees use formulas to prepare site-specific decommissioning cost estimates. This is required to demonstrate reasonable assurance that decommissioning funds are available leading up to and following operation cessation.
Formulas by reactor type and power level are used to calculate estimated amounts needed for decommissioning (in January 1986 dollars). For a PWR with thermal capacity greater than or equal to 3,400 MWt, the base figure is $105 million. PWRs between 1,200 MWt and 3,400 MWt are directed to use the formula:
PWR cost = $75 million + (0.0088 x P)
where P is power in MWt. For a PWR of less than 1,200 MWt, the licensee is directed to use P = 1,200 MWt.
For BWRs with thermal capacity greater than or equal to 3,400 MWt, the base cost is $135 million. The BWR formula uses the same power thresholds, but its equation is:
BWR cost = $104 million + (0.009 x P)
An adjustment factor is then added based on the following equation:
Added cost = (0.65 x L) + (0.13 x E) + (0.22 x B)
where L and E are escalation factors for labor and energy, respectively, which are taken from regional data provided by the U.S. Bureau of Labor Statistics. B is an escalation factor for waste burial and is to be taken from NUREG-1307, “Report on Waste Burial Charges.”
A nuclear decommissioning trust fund provides financial assurance in the form of:
■ Prepayment. The licensee deposits enough funds into an account.
■ External sinking fund. Funds are set aside periodically into an account.
■ Surety method, insurance, or other guarantee method. A surety bond, letter of credit, or line of credit providing financial insurance until the NRC terminates the license.
These accounts, used either individually or in combination, are segregated from licensee assets and outside administrative control of the licensee and its subsidiaries.
The site-specific decommissioning cost estimate is typically divided by a timeline into three categories: license termination, fuel storage, and site restoration. The caveat, however, is that trust fund withdrawals must be for legitimate radiological decommissioning activity expenses consistent with the decommissioning definition, excluding fuel storage and site restoration.
Spent fuel management activities, including funding provisions, are governed by 10 CFR 50.54, “Conditions of Licenses,” and 10 CFR 72.30, “Financial Assurance and Recordkeeping for Decommissioning.” The regulations impose specific requirements for both general and ISFSI licensees. Non-radiological site restoration activities are not necessary for license termination and outside the NRC’s regulatory purview.
The NRC’s regulations allow commingling of funds. For example, the supplementary information for the NRC’s final rule on the decommissioning of nuclear power reactors allows licensees to have separate subaccounts for other activities in the decommissioning trust fund, if minimum amounts specified in the rule are maintained for radiological decommissioning. Subaccounts or specific accounting practices should be established when starting the trust fund.
The NRC can approve exemptions, such as Entergy’s June 2015 request to use part of the VY trust fund for “irradiated fuel management activities, not associated with radiological decontamination,” that is, for management of used fuel assemblies stored onsite. Entergy was also allowed to forgo the directive to notify the NRC prior to such disbursements. Submitted documentation demonstrated that a combination of current funds, planned future contributions, and projected earnings of the trust provided reasonable assurance for adequate funding to complete all NRC-required decommissioning activities and conduct irradiated fuel management through license termination.
Lessons Learned and Future Regulatory Actions
Calculating the minimum amount of decommissioning funds using the NRC formula provides a useful reference. This assures the licensees demonstrate financial responsibility in accumulating funds for decommissioning. However, depending on site-specific conditions, the NRC formula results compared to site-specific decommissioning cost estimates and actual costs can vary significantly for various reasons (Table 3).
The NRC formula requirements were promulgated in the 1988-issued decommissioning rule. Revised regulations, guidance, and experience have provided improved, more-realistic estimates. Lessons from past projects have identified project management, fuel storage, and site restoration costs that are not necessarily covered by the decommissioning trust fund, but are still the responsibility of the licensee.
Lessons learned from completed and active projects are useful for developing contingencies. Costs will vary based on many factors, some of which can be anticipated by answering a series of questions. The questions include:
■ Will the project be self-managed or contracted?
■ Are labor, energy, taxes, and fee variations accounted for over the entire decommissioning schedule?
■ Have worker separation packages, national or company-mandated retraining, and retention incentives for key personnel been factored in?
■ Will delays from intervention, public participation in local community meetings, legal challenges, and national and local hearings affect the schedule?
■ Are unexpected radioactive or hazardous material contamination, inadequate groundwater and soil characterization, and as-built drawing variations likely to be discovered?
■ Have competitive negotiations been conducted and truck or rail accessibility routes assessed to determine the most cost-effective radioactive waste disposal method?
■ Are governmental policy decisions altering national commitments, such as greater-than-class C waste forms or Department of Energy acceptance of spent fuel, possible?
The NRC published a preliminary draft regulatory analysis in the Federal Register on May 9, 2017, to support a rulemaking that would amend regulations for the decommissioning of nuclear power reactors. The NRC’s goals in amending the regulations would be to provide for an efficient decommissioning process; reduce the need for exemptions from existing regulations; address other decommissioning issues deemed relevant by the NRC; and support the principles of good regulation, including openness, clarity, and reliability. Until the new rule is issued (projected in September 2019), licensees will continue to use the existing regulatory framework. ■
—James M. Hylko (JHylko1@msn.com) specializes in safety, quality, and emergency management issues and is a frequent contributor to POWER.