United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 93-53, Supplement 1: Effect of Hurricane Andrew on Turkey Point Nuclear Generating Station and Lessons Learned

                                UNITED STATES 
                         NUCLEAR REGULATORY COMMISSION
                     OFFICE OF NUCLEAR REACTOR REGULATION
                            WASHINGTON, D.C.  20555

                                April 29, 1994


NRC INFORMATION NOTICE 93-53, SUPPLEMENT 1:  EFFECT OF HURRICANE ANDREW ON     
                                             TURKEY POINT NUCLEAR GENERATING   
                                             STATION AND LESSONS LEARNED 


Addressees

All holders of operating licenses or construction permits for nuclear power
reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice (IN) supplement to inform addressees of further lessons learned as a
result of the investigations undertaken to assess the effects of Hurricane
Andrew on the Turkey Point Nuclear Generating Station (Turkey Point); to
expand the scope of the lessons learned to other external events, as
appropriate; and to discuss existing regulatory guidance for various external
events.  It is expected that recipients will review the information for
applicability to their facilities and consider actions, as appropriate, to
avoid similar problems.  However, suggestions contained in this information
notice are not NRC requirements; therefore, no specific action or written
response is required.

Description of Circumstances

In IN 93-53, "Effect of Hurricane Andrew on Turkey Point Nuclear Generating
Station and Lessons Learned," the NRC provided a description of the impact of
Hurricane Andrew on Turkey Point on August 24, 1992.  The notice described
several lessons reinforced and lessons learned based on a joint NRC/industry
team review.  

Discussion

NRC NUREG-1474, "Effect of Hurricane Andrew on the Turkey Point Nuclear
Generating Station from August 20-30," indicates that two Category 5 hurricane
storms, (wind speed > 249 km/h [155 mph]), and four Category 4 hurricane
storms, (wind speed between 210 and 249 km/h [130 and 155 mph]), have hit the
eastern coast of the United States in the last 60 years.  The wind speeds used
in the design of safety-related structures of east-coast plants vary from 
177 to 210 km/h [110 to 130 mph].  As the load factor used with the design
wind loading is 1.7, when compared with the code established limit states of
the structures, these structures can withstand Category 4 and low intensity
Category 5 hurricanes (which have a range from 249 to 290 km/h [155 to 
180 mph]).  Moreover, design against tornado generated loadings (in accordance

9404280023.                                                      IN 93-53, Supplement 1
                                                      April 29, 1994
                                                      Page 2 of 4


with Regulatory Guide 1.76, "Design Basis Tornado for Nuclear Power Plants,"
and NUREG 0800, "Standard Review Plan for the Review of Safety Analysis
Reports for Nuclear Power Plants," Sections 3.3.1 and 3.5.1.4, or other
provisions accepted by the staff) provides margin against failure of safety-
related structures during hurricanes. 

Based on NRC and industry experience with plant-specific probabilistic risk
assessments (PRAs), NRC recognized that systematic examinations are beneficial
in identifying plant-specific vulnerabilities.  Thus, on November 23, 1988,
NRC issued to all licensees a request to conduct systematic examinations of
their plants for internally initiated event vulnerabilities (Generic Letter
88-20, "Individual Plant Examination for Severe Accident Vulnerabilities" and
on June 28, 1991, expanded the request to include externally initiated event
vulnerabilities (Generic Letter 88-20, Supplement 4, "Individual Plant
Examination of External Events (IPEEE) for Severe Accident Vulnerabilities"). 
NUREG-1407, "Procedural and Submittal Guidance for the Individual Plant
Examination of External Events," provides procedural guidelines for assessing
the adequacy of plant safety systems against external events, such as
earthquakes, tornadoes, external floods, transportation and nearby facility
accidents.  Following these guidelines in the implementation of the IPEEE
program will enable licensees to look for vulnerabilities to severe accidents
resulting from such events and identify cost-effective improvements.   

It is not clear whether adequate consideration has been given to the failure
(or malfunction) of nonsafety-related structures and equipment in the vicinity
of a nuclear reactor which could jeopardize the proper functioning of
safety-related structures, systems and components.  As noted in IN 93-53 and
in NRC NUREG-1474, at Turkey Point, Hurricane Andrew caused damage to a number
of nonsafety structures and equipment: 

.     all (six) steel-framed turbine canopies collapsed,

.     one of the two chimneys (associated with the two fossil units at the
      site) was severely damaged,

.     the base anchors for the vent stack on the Unit 4 containment were
      lifted 10 mm [3/8 inch],

.     ductwork from the radioactive waste building to the vent stack failed
      due to hurricane generated missiles, 

.     the nonsafety high-water tank collapsed, and fell on various
      fire-protection pumps and pipes, rendering one of the fire protection
      systems inoperable.  

In spite of the severe damage to a number of nonsafety items at Turkey Point,
the safety-related structures, systems and components of the two nuclear
reactors withstood the storm without damage and the reactors did not pose a
radiological hazard to nearby communities.  A systematic evaluation of the
available logs and data by the licensee indicated that there were no
unexpected radiation levels onsite or offsite..                                                      IN 93-53, Supplement 1
                                                      April 29, 1994
                                                      Page 3 of 4


The licensee had completed the external events analyses of Turkey Point for
wind and fire in June of 1991.  The analysis for wind indicated a need to
modify the flood wall and improve the emergency procedure for Category 5
hurricanes.  The revised procedure allowed the licensee to adequately prepare
for severe events, such as Hurricane Andrew.  In developing the response to
Generic Letter 88-20, Supplement 4, the licensee indicated that the potential
consequences (in terms of core damage frequencies) of chimney failure were
considered in the analysis and the results were found acceptable.  However,
the potential failure of the high-water tank was not explicitly considered.

NRC Regulatory Guide 1.29, "Seismic Design Classification," recommends that
nonsafety structures and equipment (including supports and anchorages) be
designed to withstand postulated seismic events if their failure could reduce
the safety function of any of the safety-related features.  Section 3.3.2 of
the NRC Standard Review Plan includes a similar provision for postulated
tornado loadings.  The practical implication of these provisions is that
either the nonsafety structures and equipment are designed to withstand the
postulated events, or an assessment is made to assure that the consequences of
their failure would not disable the safety functions of safety-related
structures, systems and components (also termed as II over I consideration). 
These documents were issued in 1975.  A number of pre-1975 plants have been
evaluated for II over I considerations under postulated external events. 
However, this may not be the case for some pre-1975 plants.  

All licensees were requested in GL 88-20, Supplement 4, to perform systematic
examinations of their plants for plant-specific vulnerabilities to severe
accidents from external events which include all plant systems and components
whose failures contribute to core damage frequency or the conditional
probability of containment failure.  Specifically, Section 5 of NUREG-1407
states that all licensees should compare the information obtained from the
review for conformance to the 1975 Standard Review Plan (NUREG 0800) criteria
and perform a confirmatory walkdown of the plant.  The walkdown should be
concentrated on onsite outdoor facilities that could be affected by high
winds, onsite storage of hazardous materials, and offsite occurrences.

As noted in GL 88-20, Supplement 4, the quality and extent of the results
derived from an IPEEE will depend on the vigor with which the licensee applies
the method of examination and on the licensee's commitment to the intent of
the IPEEE.  Matters relevant to an IPEEE analysis include the nonsafety items
(onsite and offsite) whose failures under loads generated by various credible
external events could potentially disable safe shutdown capability and the
compensatory measures that would alleviate such conditions.  
.                                                      IN 93-53, Supplement 1
                                                      April 29, 1994
                                                      Page 4 of 4


This information notice requires no specific action or written response.  If
you have any questions about the information in this notice, please contact 
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.

                                    /S/'D BY CIGRIMES/FOR


                                    Brian K. Grimes, Director
                                    Division of Operating Reactor Support
                                    Office of Nuclear Reactor Regulation

Technical contacts:  Hans Ashar, NRR
                     (301) 504-2851

                     John T. Chen, RES
                     (301) 492-3919
Page Last Reviewed/Updated Tuesday, November 12, 2013