The U.S. Nuclear Regulatory Commission conducts an extensive evaluation of reactor technology before approving and ultimately licensing nuclear power plants. Korea Hydro and Nuclear Power Co. Ltd. began the process of certifying its APR1400 design nearly five years ago and its efforts have finally paid off.
The U.S. Nuclear Regulatory Commission (NRC) issued a final safety evaluation report and standard design approval (SDA) to the Korea Hydro and Nuclear Power Co. Ltd. (KHNP) and Korea Electric Power Corp. (KEPCO) for their Advanced Power Reactor, a 1,400-MW electrical power reactor (APR1400). KHNP’s APR1400 Standard Plant Design application is the first non-U.S. reactor design to receive an SDA under Section 103 of the Atomic Energy Act and Part 52 of Title 10 of the Code of Federal Regulations (10 CFR), “Licenses, Certifications, and Approvals for Nuclear Power Plants.”
The APR1400 is a two-loop pressurized water reactor, developed in the Republic of Korea, based on innovative design improvements and technology enhancements built on the design, construction, operation, and maintenance of the Optimized Power Reactor 1000. The APR1400 has a design life of 60 years.
KHNP’s dedicated APR1400 project team assembled dozens of companies and expertise from around the globe to bring innovation in design and licensing approaches. KHNP not only relied on the engineering and technology manufacturing capabilities of Korea, but it also depended on numerous U.S. engineering, licensing, consulting, and supply chain partners, including AECOM, Jensen and Hughes, MPR Associates, Structural Integrity, and Westinghouse, to name a few. The collective efforts truly demonstrated a collaborative international success—further promoting the tenants of the U.S.-Korean Energy Cooperation—and working together to meet the energy needs and economic opportunity as global demand for nuclear energy accelerates.
A Time-Consuming Process
The NRC’s safety assessment was achieved during 42 months of careful review and consideration to certify the reactor. The NRC staff review also drew upon process efficiencies gained and lessons learned from its own Part 52 experiences, which allowed the NRC to meet the 42-month agency benchmark set for conducting the technical reviews, as well as the Advisory Committee on Reactor Safeguards (ACRS) approval, which concluded, “The APR1400 design is mature and robust” and it can be “constructed and operated without undue risk to the health and safety of the public.”
KHNP overcame many challenges and used some of them to its advantage to assure meeting a 42-month review schedule. For example, KHNP was able to reduce the response time in interacting with NRC staff by utilizing the 14-hour time difference between the countries to its advantage. KHNP’s willingness to hold meetings on Eastern U.S. time (despite it being late evening in Asia) allowed NRC reviewers the necessary interactions with subject matter experts in Korea, and in many cases, follow-up information was provided early the next business day.
“I am pleased to say that through extensive staff and applicant [KHNP/KEPCO] efforts, including the development of novel approaches to the remaining challenging issues, the staff completed its first design certification review within 42 months and issued the standard design approval for the APR1400,” said Rob Taylor, director of the Licensing, Siting, and Environmental Analysis division for the NRC’s Office of New Reactors.
As part of its commitment to the application’s success, KHNP established a dedicated team of more than a dozen technical and licensing experts in a Washington, D.C., Center (WDCC), which enabled the quick response and vital interface necessary with the NRC staff. KHNP’s WDCC makeup included AECOM and representative managers of sister companies from Korea. The WDCC was instrumental in driving issue identification, effective responses, and closure of NRC audits and Design Control Document (DCD) chapter reviews; whereas, other applicants that maintained either remote and/or larger staffs to coordinate technical exchanges and interactions met lesser success.
KHNP submitted its application to the NRC for certification of the APR1400 design on December 23, 2014. The application was submitted in accordance with 10 CFR Part 52, Subpart B, “Standard Design Certifications.” KHNP also requested a design approval in accordance with 10 CFR Part 52, Subpart E, “Standard Design Approvals.” The APR1400 application consisted of the DCD, including an extensive probabilistic risk assessment (PRA), along with a number of key issue topical reports and an environmental report.
The DCD information was divided into two parts (Tier 1 and Tier 2). Tier 1 contains the portion of the generic design-related information that is proposed for approval and certification in the rule, including the inspections, tests, analyses, and acceptance criteria (ITAAC). Tier 2 information includes a description of the design of the facility for a final safety analysis report, as required by 10 CFR 52.47.
During the NRC staff’s review, KHNP made three updates to the DCD. As part of the NRC safety review, KHNP satisfactorily responded to 2,315 questions raised by the NRC technical staff and addressed the Commission-approved Fukushima actions described in SECY-12-0025, and NRC Orders EA-12-049 and EA-12-051, along with the Nuclear Energy Institute’s (NEI’s) guidance NEI 12-06. APR1400 also took advantage of industry efforts to standardize ITAAC for Part 52 applications.
While there are more than 1,000 ITAAC for the APR1400 design, KHNP made use of NEI’s standardization guidance. It also incorporated lessons learned from recent industry construction experience. More importantly, what is unique to the APR1400 design approval is that it had no Tier 2* information—adding clarity and regulatory certainty for future utility applications, including critical ITAAC associated with structural design of safety-related structures and other systems.
The SDA authorization, which indicates the NRC found the APR1400 design safe and technically acceptable, was issued for 15 years. The SDA allows a utility to reference the APR1400 design when applying for a license to build and operate a nuclear power plant, and it may be used for a Part 50 license application as well. KHNP is currently anticipating certification of the APR1400 design through rulemaking under Part 52 later this year.
Keys to Success
KHNP led the efforts to advance the APR1400 design to new heights. A few of the innovative and advanced APR1400 design features that add to safety, and to improved plant performance and efficiency, include:
- ■ The most-comprehensive aircraft impact analysis performed in accordance with NEI 07-13 and approved under 10 CFR 50.150(a) and RG 1.217, demonstrating the APR1400’s structural and system integrity is maintained for all strikes.
- ■ Fully digitalized instrumentation and control systems with a Diverse Protection System and Diverse Indication System, along with an advanced control room design (Figure 1).
1. An advanced control room and human-factors-engineered design helped the APR1400 achieve timely Standard Design Approval. Courtesy: Korea Hydro and Nuclear Power Co. Ltd. (KHNP)
- ■ The first human-factors-engineered design compliant with NUREG-0711 Revision 3.
- ■ An in-containment water storage system, including the in-containment refueling water storage tank (IRWST), providing storage, delivery, and heat sink functions inside containment during normal and accident conditions, reducing risk and reliance on outside systems and operator action.
- ■ A first-of-a-kind operational safety injection tank fluidic device that optimizes injection flow rates during the initial blowdown and subsequent, long-term, core reflood phases—the only such device in the world that underwent a full-scale demonstration (Figure 2) to prove its functional and safety capabilities.
2. A full-scale safety injection tank (SIT) and fluidic device test facility was constructed to prove the design’s capabilities. Courtesy: KHNP
- ■ The APR1400 was the first Part 52 design applicant to fully address GSI-191, including use of non-fibrous insulation in the zone of influence and a successful demonstration of IRWST sump strainer performance tests in accordance with NEI 04-07 and RG 1.82.
- ■ Advanced steam generator tubing material (alloy 690), high-strength materials (alloy 718), and advanced welding to improve reliability.
- ■ A cutting-edge fuel design, called PLUS7, that uses advanced cladding materials (called ZIRLO) and a spacer/mixing grid design that improves thermal-hydraulic performance.
- ■ A proven building structure based on APR1400’s reference plant design, with a demonstrated construction sequence and post-construction analyses for the nuclear island.
- ■ Four independent trains of safety injection, incorporating direct vessel injection, as well as four emergency diesel generators for emergency power and a gas turbine generator for station blackout recovery.
- ■ The APR1400 PRA was recognized by the NRC and ACRS as the most-thorough PRA by a Part 52 design applicant. The PRA was performed based on ASME/ANS RA-Sa-2009, with its scope including Level 1 and Level 2 analysis for internal and external events at full-power, and at low power and shutdown (LPSD) conditions. For at-power internal events, the core-damage frequency (CDF) is 1.1 x 10-6 per reactor year (ryr), and the large-release frequency (LRF) is 1.0 x 10-7 per ryr. For LPSD internal events, the CDF is 1.8 x 10-6 per ryr, and the LRF is 1.2 x 10-7 per ryr. The APR1400 design and risk profile are significant improvements over current operating plants.
- ■ APR1400 deploys passive autocatalytic recombiners and hydrogen igniters for hydrogen mitigation, and other design enhancements to better execute severe accident management strategies, such as an emergency containment spray backup.
- ■ APR1400 incorporated post-Fukushima safety enhancements developed through NEI and NRC cooperation. The APR1400 is a FLEX-ready design including backup power supplies using mobile generators (onsite and offsite); reactor coolant system makeup and core cooling using FLEX pumps; and spent fuel pool level instrumentation and makeup/spray using FLEX pumps.
Though the APR1400 includes many advanced design features, KHNP was committed to an innovative approach to licensing the reactor design. In meeting the 42-month review schedule, the APR1400 project team developed new ideas and sought efficiencies in the regulatory process—helping to remove unnecessary roadblocks and right-sizing the review process—without compromising the thoroughness of the NRC safety review. While KHNP is headquartered nearly halfway around the world from the NRC, the company clearly recognized that its project team had to address licensing and regulatory interactions from a different perspective in order to be successful.
A Pioneering Approach
A few of the innovative licensing process improvements, accomplishments, and highlights that underscore the SDA success, as well as regulatory stability, predictability, and enhancements for future applications, included:
- ■ Establishing a dedicated, integrated project management and licensing team to oversee all regulatory interactions and supporting contract work in the U.S. to support licensing commitments and schedules. WDCC worked diligently with the NRC to mutually emphasize project management of the reviews, including collection, analysis, and sharing of metrics and milestones.
- ■ Adopting a collective understanding and willingness between KHNP and the NRC to apply lessons learned from prior reviews and employ continuous improvement and improved interactions, including enhanced pre-application review meetings, frequent clarification calls and audits, and appropriate review phase discipline, including dedication in keeping with the goal of a 30-day turnaround time for requests for additional information (RAI).
- ■ WDCC worked closely with the NRC to help drive improvements to the electronic-RAI system. It also used the system to provide critical data and metrics for project management purposes for both KHNP and NRC management.
- ■ KHNP was the first Part 52 design applicant to exclusively submit its licensing documents to the NRC via the Electronic Information Exchange (EIE) system—resulting in a more timely and cost-effective means for transmittal and management of APR1400 information.
- ■ Applying effective use of audits to help leverage and expedite information exchanges and NRC understanding prior to detail-review and RAI processes, reducing unnecessary regulatory burdens both for the NRC and KHNP.
- ■ The APR1400 team established an effective balance and use between the design specific ITAAC and the NEI-led industry-generic ITAAC guidance.
- ■ APR1400 was the first to receive an exhaustive ITAAC cross-reference evaluation and most-thorough NRC legal review—increasing efficiency, clarity, and reliability for future applicant implementation and closure of ITAAC.
- ■ KHNP eliminated the need for Tier 2*, as well as ITAAC redundancy and inconsistency between competing or varying requirements, working together with NEI and other industry counterparts.
- ■ KHNP led efforts to work with the NRC staff to ensure the level of detail for Tier 1 was kept to what was necessary and sufficient. For example, KHNP and the NRC staff considered alternate methods for providing structural information. This allowed for an appropriate level of flexibility in the construction phase, such as the use of a design-load-per-design-capacity ratio, rather than specific dimensions—avoiding future issues during construction and many millions of dollars in delays and unnecessary regulatory reviews.
- ■ KHNP worked diligently with the NRC to find areas where improvements to regulatory approaches could be made, meanwhile assuring that adequate safety reviews were conducted and allowing more-effective use of resources in other areas. For example, APR1400 adopted a graded-licensing approach in the piping design area instead of using design acceptance criteria through active technical interactions with NRC staff.
- ■ KHNP was effective in reducing unnecessary staff burdens, helping the APR1400 achieve the lowest cost in NRC review fees of any prior Part 52 design applicants—on the order of more than 30% less in NRC fees over other applicants.
- ■ KHNP and the NRC staff agreed to pursue a direct final rulemaking approach for the design certification rulemaking, making APR1400 the first design certification to use this process. The approach is anticipated to shave months off the rulemaking schedule used on other applications.
In a recent briefing, the NRC staff recognized the processes being developed today are forging new ground and establishing the necessary framework for future applications. In that regard the NRC has pointed to recent design certification review lessons learned, including the positive experiences from the APR1400 review. The NRC noted that successfully addressing prior challenges and implementing innovative improvements to the process, including preparations of the licensing framework, will be critical for future applications and the next generation of advanced reactors.
Leading the Way
KHNP established many firsts in achieving a timely SDA by applying innovation in the unit’s design and licensing. The APR1400 design is the result of years of innovation and collaboration between KHNP and its Korean and U.S. partners. It is an outstanding example of a design based on the best of the best, incorporating an extensive number of design and safety improvements. The APR1400 has transformed the industry in addressing regulatory and safety goal objectives. What’s more, the design has extensively assessed nuclear safety risks, and it has one of the lowest CDF/LRF of any design ready for deployment today.
The APR1400 has demonstrated through the SDA that it made significant improvements that saved upfront costs in reviews and application of its design features. Additionally, the APR1400 is a proven design, illustrated by concurrent construction projects overseas with on-time and on-budget construction, and several units coming into commercial operation (Figure 3).
3. The first APR1400 reactor to enter commercial operation was Shin Kori 3 in December 2016. Shin Kori Unit 4—another APR1400—achieved first criticality on April 8, 2019, and was grid connected later that month. Courtesy: KHNP
Through the efforts made during the design approval process, KHNP and its partners have laid the foundation for future domestic Part 52 or Part 50 applicants who wish to deploy a large reactor design with demonstrated success in licensing and construction, thus providing predictability and surety in advancing nuclear power as a clean energy solution in the U.S. and around the world. ■
—Yunho Kim is president of KHNP’s Central Research Institute, Jeongkwan Suh is general manager of KHNP’s APR1400 Licensing Team, Chewung Ha is a research engineer with KHNP’s APR1400 Licensing Team, Jiyong Oh is senior manager of project coordination with KHNP’s WDCC, and Robert Sweeney is an international industry consultant.