Clean Energy Insight - Moving Energy Forward

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Myth: As Nuclear Power Plants Age, They Become More “Risky”

A generality that the 104 commercial U.S. Nuclear Power Plants (NPPs) commonly fall victim to is that as things age, they are at a greater risk for potential failure.  The more miles on your car, the more time you usually spend at the repair shop.  The longer you live in your house, the more trips you have to make to the nearby home improvement store.  Although this is common with most things that we encounter in our everyday lives, this is not the case for NPPs.

The Nuclear Regulatory Commission (NRC) initiated the Industry Trends Program (ITP) to monitor trends of industry performance indicators to ensure safety at NPPs is maintained.  If any adverse trends are detected in the performance indicators, the NRC will evaluate the issue and take appropriate regulatory action to address it.  Each year these performance indicators are reviewed by the NRC as part of the Agency Action Review Meeting (AARM).  Any statistically significant adverse trends are included in the NRC’s Performance and Accountability report to Congress.

“No statistically significant adverse trends have been identified through the end of fiscal year (FY) 2008, based on the ITP indicators and the Accident Sequence Precursor (ASP) program.” – NRC website, Industry Trends page

Full details of the trends monitored by the NRC as part of the ITP can be found in the current ITP report, SECY-09-0048.  Definitions and descriptions for performance indicators can be found in the NRC Inspection Manual Chapter (IMC) 0313, Appendix A.  Below you can find several of the Fiscal Year 2008 Long-Term Industry Trends Results from the most recent ITP report along with a brief description of the indicator.

Significant Events

Definition: Significant Events are defined as —

1. A Yellow or Red Reactor Oversight Process (ROP) finding or performance indicator
2. An event with a Conditional Core Damage Probability (CCDP) or increase in core damage probability (ΔCDP) of 1×10-5 or higher
3. An Abnormal Occurrence as defined by Management Directive 8.1, “Abnormal Occurrence Reporting Procedure”
4. An event rated two or higher on the International Nuclear Event Scale

Forced Outage Rate (FOR)

Definition: The forced outage rate is the number of forced outage hours divided by the sum of unit service hours and forced outage hours.

Safety System Actuations (SSA)

Definition: Safety system actuations are manual or automatic actuations of the logic or equipment of either certain Emergency Core Cooling Systems (ECCS) or, in response to an actual low voltage on a vital bus, the Emergency AC Power System.

Automatic Scrams While Critical

Definition: The number of unplanned automatic scrams that occurred while the affected reactor was critical.  A Scram is an emergency shutdown of a nuclear reactor.

Opponents to the industry trending rationale may state that NPPs are subject to negative aging effects, such as equipment failures.  My response to this claim is that you are exactly correct.  Every plant does experience some form of equipment aging or failure, but being realistic, nothing is made to last forever.  Equipment aging begins as soon as a piece of equipment is operated for the first time.  The important issue is how the utilities manage the aging effects and also how they identify and mitigate the risks associated with the operation of their plants.  NPPs are designed to sustain equipment aging and failures through redundancy and dedicated systems that are capable of and dedicated to maintaining public safety.

Along with the ITP, there are also measures to evaluate the ability of NPPs to maintain safety on an individual basis.  INPO routinely sends teams to evaluate plant operations, processes and personnel.  INPO then assigns a score to the plant based on observations during the assessment.  Negative ratings from the assessment generally warrant more demanding requirements to maintain safety by the NRC and can even lead to a NPP being shut down.

The information presented in the annual ITP report confirms that the safety of operating nuclear power plants is being maintained.  The decreasing trends can be attributed to the dedication of the individuals in the commercial nuclear power industry to deliver safe and reliable power to the public, as well as:

• Regulatory guidance (NRC)
• Industry organization involvement (INPO, EPRI, etc.)
• Improved processes and procedures
• Evaluation and incorporation of operating experience and lessons learned
• Advances in technology / Plant modifications
• Predictive and preventive maintenance capabilities
• Economic benefit to maintain a plant

Another intriguing subject that comes up when discussing the safety of NPPs is the potential for a plant to become a terrorist target.  Mike Bullard will be addressing this issue in two weeks.  Next Wednesday, Jonny Abendano will take on the myth that nuclear energy emits greenhouse gases.

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See, sometimes people don’t think bigger is better.

Neither does the Tennessee Valley Authority (TVA).  TVA has agreed to assist Babcock & Wilcox of Lynchburg, Va. in gaining certification of a “mini” nuclear power plant. TVA has signed a non-binding agreement to evaluate a possible site for building a small modular reactor near Oak Ridge National Laboratory in Tennessee.

The nuclear reactors would be approximately one tenth (≥125 MW) the size of a normal size nuclear power plant (1000 - 1600 MW). The nuclear reactions would be contained in an enclosure that is stored underground.

It is roughly estimated that a 125 MW reactor would cost somewhere in the neighborhood of $750 Million, whereas recent estimates for the new generation nuclear plants that are being reviewed by the NRC show a cost of construction around $10 Billion.

The article mentions that one issue the companies may face in obtaining a design certification is that the NRC is currently busy with licensing requests from utilities for new designs of standard size nuclear plants. A license application for a “mini” reactor has not yet been submitted to the NRC, but could be in as little as two years, states Chris Mowry (President and Chief Executive of B&W Modular Nuclear Energy LLC). Once an application is submitted to the NRC, a review could potentially take several years.

Here is a link to the original article.

Here is a link to another recent article that discusses the possibility of this “mini” reactor: