Mark E. Tonacci

Senior Consultant (AdSTM)
Core Competencies: 

Extensive knowledge of technical, regulatory and policy issues for new nuclear reactor licensing including the next generation of small modular and advanced nuclear reactors. Broad industry, technical and regulatory experience gained over 25 years working at nuclear power stations, the Nuclear Regulatory Commission (NRC), the Institute of Nuclear Power Operators and World Association of Nuclear Power Operators.

Key experience includes leading and managing people to achieve results, as well as facilitation, coordination and cooperation across divergent business and organizational interests to advance resolution of issues. Areas of expertise include:

  • Small Modular Reactor regulatory, technical and policy challenges
  • Broad real world industry operational experience at nuclear stations
  • 10 CFR Part 52 safety reviews of many reactor design certification and combined license applications
  • Coordination with regulator and industry for pre-submittal and acceptance reviews of applications
  • Project Management at the NRC for large reactor design application safety reviews
  • Project Management in Industry on numerous projects
  • Supervision of engineering and administrative staff to achieve results 
Career Highlights: 
U.S Nuclear Regulatory Commission
2005 - 2016

Served in a supervisory leadership role responsible for project management of numerous 10 CFR Part 52 combined license and design certification reviews in the Office of New Reactors. Oversaw work to ready the licensing and technical staff in the Office of New Reactors for acceptance review and subsequent design review of the first Small Modular Reactor design certification application. Worked with vendors and utilities including: NuScale, LLC; BWX Technologies, Inc.; Holtec International; Tennessee Valley Authority; and the Nuclear Energy Institute to identify key topics of interest to industry. Supervised and brought to completion over 70 design review standards spanning many technical areas to support the NuScale review (ML16257A558). Focused efforts also included issuance of numerous letters describing staff technical and regulatory perspectives on 20 exceptionally challenging topics unique to the NuScale, LLC small modular reactor (SMR) technology. These topics included control room staffing, containment design, multi-module considerations, auxiliary feedwater, instrumentation, and reactor safety systems. Participated in initial meetings for Small Modular Reactor International Regulator’s Forum; establishing working groups addressing common challenges.

Prior to working on SMR licensing, provided supervisory leadership for review of multiple new reactor applications while consistently engaging industry counterparts. This work included reviewing and approving numerous safety reviews, addressing technical, regulatory and human resource issues challenging schedules, and proactively identifying and addressing project risks. Accomplishments include issuance of the first new US nuclear plant licenses in 30 years in 2012 for the AP1000 reactors at Vogtle 3 and 4 and Summer 2 and 3 respectively. Simultaneously, actively interacted with industry counterparts to coordinate and advance work on license applications for the Levy, Lee and Turkey Point AP1000 applications. Provided project management and supervision for additional combined license applications including: South Texas Project 3, Fermi, and Grand Gulf 3, the Victoria early site permit, and the Economic Simplified Boiling Water Reactor (ESBWR) reactor design certification. Supervised work resulting in the air craft impact design certification amendment and resulting rulemaking for the Advanced Boiling Water Reactor (ABWR).

Proactively developed and implemented infrastructure procedures and training to issue the first license amendments, exemptions, and preliminary amendment requests for the Office of New Reactors to support AP1000 new reactor construction. Selected by NRC management for a temporary assignment to develop briefings for a Commission Office as part of preparation for the Vogtle Commission hearing and the V. C. Summer Commission hearing, for issuance of the combined licenses.

Extensive experience in the Office of Nuclear Reactor Regulation, working with regulatory staff and the Nuclear Energy Institute to resolve Reactor Oversight Program issues; implemented the Unplanned Scrams with Complications Performance Indicator for industry self-reporting of events.

Baltimore Gas & Electric/Constellation Energy (Calvert Cliffs Nuclear Power Plant)
1988 – 2005

As General Supervisor of Chemistry at the Calvert Cliffs Nuclear Power Plant my responsibilities included a multimillion dollar budget and three branches of 35 professional staff and technicians at a two unit Combustion Engineering, 865 MW pressurized water nuclear reactor site. Performed monitoring and control of primary and secondary water chemistry, radioactive liquid and gaseous discharges, air and water environmental compliance, controlled and hazardous chemical programs, and radioactive waste shipping.
While supervisor of the Plant Design Support Unit at Calvert Cliffs, led a 10-person team of multi-disciplined engineers to resolve urgent station technical design challenges that enabled keeping the two generating units running while meeting challenging schedule, technical, and regulatory compliance needs.

Selected by senior management to serve as a loaned engineer to the Institute of Nuclear Power Operations (INPO) Engineering Department as an Engineering Evaluation. In this capacity, performed engineering evaluations and performance recommendations for all aspects of engineering at more than 10 US nuclear stations and two international stations associated with the World Association of Nuclear Power Operators.

Prior to these assignments, supported Calvert Cliffs plant operations as a Primary Systems engineer. Developed and reviewed engineering modifications for the nuclear station while working in the Design Engineering, Instrumentation and Controls Unit.

Hercules, Inc.
1979 - 1988

Senior Production Engineer for cellulose derivative chemical plants.

Professional Development and Achievements: 

Virginia Commonwealth University, Nuclear Engineering Curriculum Board

Numerous Performance Awards from Constellation Energy and U. S. Nuclear Regulatory Commission Constellation Energy – Management Training on Combustion Engineering PWR Plant Operations

Letters of Recognition from Institute of Nuclear Power Operators and World Nuclear Power Operators for assistance to nuclear power stations including: Three Mile Island in Pennsylvania, Angra nuclear station in Brazil, Kuosheng nuclear power station in Taiwan.

“The Right Chemistry” published by the Institute of Nuclear Power Operators magazine, Nuclear Professional, first quarter 2005.

Formerly held Professional Engineering Licenses for the States of Georgia and Maryland


B.S., Chemical Engineering, with Distinction, University of Virginia, 1979
Master of Business Administration, Virginia Commonwealth University, 1985