Determining the Effectiveness, Limitations, and Operator Response for Very Early Warning Fire Detection Systems in Nuclear Facilities (DELORES-VEWFIRE), Final Report (NUREG-2180)

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Publication Information

Manuscript Completed: September 2016
Date Published: December 2016

Prepared by:
G. Taylor1, S. Cooper1, A. D’Agostino1, N. Melly1, and
T. Cleary2

1U.S. Nuclear Regulatory Commission
2National Institute of Standards and Technology

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

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Aspirated smoke detection systems have been available on the commercial market for more than four decades as an alternative technology to spot-type smoke detection for detecting products of combustion. In the United States, several nuclear power plants (NPPs) have installed these systems as early as the mid-1990s as an alternative method to conventional fire detection systems with the idea to provide advanced warning of potential fire threats. Recently, there has been indication that numerous licensees of NPPs transitioning to a performancebased fire protection program have or intend to install these types of systems configured as very early warning fire detection (VEWFD). In many, but not all cases, the choice to install these systems is based on the expectation that these systems may reduce the estimated fire risk in a fire probabilistic risk assessment (PRA).

In 2008, the U.S. Nuclear Regulatory Commission (NRC) issued a staff interim position documented in a National Fire Protection Association (NFPA) Standard 805 Frequently Asked Question (FAQ) 08-0046, “Incipient Fire Detection Systems.” This staff interim position provides guidance on the use of these systems and the associated fire PRA quantification for in-cabinet applications. At that time, there was limited test data and PRA experience available for those applications and as such a confirmatory research program was needed. Research was also needed to advance the state of knowledge related to the performance of these systems. This report documents the results and findings from the confirmatory research program.

This program provides an evaluation of VEWFD and conventional spot-type smoke detection system performance, operating experience, and fire PRA quantification for applications in NPPs where these systems are expected to detect fires in their incipient (pre-flaming) stage. The results of this report show there is a wide variance in performance for both spot-type and VEWFD systems. It has been shown that variables such as ventilation, fuel type, system application/design, and operator response play a significant role in the performance of these systems to detect low-energy fires.

Ultimately, this research has shown that (1) the state of knowledge regarding the duration of an incipient stage for electrical components found in NPPs, and the associated failure modes with regard to fire development of such components is low (uncertain and highly variable), (2) in-cabinet smoke detection used to protect electrical enclosures provides the most effective and earliest notification of potential fire threats, (3) for area-wide applications the aspirated smoke detection systems when configured as VEWFD can potentially notify plant personnel of potential fire threats sooner than conventional spot-type smoke detection systems, and (4) plant personnel responsible for responding to smoke detection systems must be properly trained, follow plant procedures suitable for response to these systems, and ensure that every smoke detection system notification has adequate response time and necessary urgency. This report concludes with an updated approach to quantify the performance of these systems in Fire PRA for in-cabinet and area-wide applications in non-continuously occupied NPP areas.

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