United States Nuclear Regulatory Commission - Protecting People and the Environment

ACCESSION #:  9412050333
                       LICENSEE EVENT REPORT (LER)

FACILITY NAME:  Seabrook Station                          PAGE: 1 OF 4

DOCKET NUMBER:  05000443

TITLE:  Service Water Cooling Tower Pump Bolt Degradation

EVENT DATE:  11/02/94   LER #:  94-17-00    REPORT DATE:  12/02/94

OTHER FACILITIES INVOLVED:                          DOCKET NO:  05000

OPERATING MODE:      POWER LEVEL:

THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR
SECTION:
50.73(a)(2)(i)
50.73(a)(2)(ii)

LICENSEE CONTACT FOR THIS LER:
NAME:  Mr. James M. Peschel,
       Regulatory Compliance Mngr.          TELEPHONE:  (603) 474-9521
                                            ext. 3772

COMPONENT FAILURE DESCRIPTION:
CAUSE:      SYSTEM:       COMPONENT:       MANUFACTURER:
REPORTABLE NPRDS:  No

SUPPLEMENTAL REPORT EXPECTED:  NO

ABSTRACT:

During Seabrook Station Refueling Outage 3 an inspection of the cooling
tower basin by divers revealed two degraded column flange bolts on the
"A" cooling tower Service Water Pump [KE] (1SW-P-110A). Subsequent
metallurgical testing revealed that these bolts experienced intergranular
corrosion due to a "sensitized" condition that resulted from an improper
manufacturing process.

North Atlantic initiated actions to test and replace suspect
safety-related bolting material on all of the station's six Service Water
(SW) pumps.

All four ocean SW pumps were refurbished with no widespread bolting
material degradation observed. However, the refurbishment of the "A"
cooling tower SW pump (1SW-P-110A) revealed additional degradation to the
extent that the pump may not have been able to perform its intended
safety function following a seismic event. Since the condition of bolting
material for the redundant "B" cooling tower SW pump (1SW-P-110B) was not
known, it was conservatively declared inoperable. Subsequent
refurbishment of 1SW-P-110B revealed some bolting material degradation,
however, the number of functional bolts supported prior OPERABILITY.

The inoperability of the "A" cooling tower SW pump for an indeterminate
period of time and the unknown condition of the "B" pump was reported on
November 2, 1994, as a condition that is outside of the design basis of
the plant pursuant to 10CFR50.72(b)(1)(ii).

There were no adverse safety consequences of this event.

The cause of the event was determined to be the bolt manufacturer's
failure to perform an adequate heat treatment on the bolting material as
required by the material specification.

END OF ABSTRACT

TEXT                                                          PAGE 2 OF 4

I.  System Description

The service water system [KE] transfers heat from various sources in both
the primary and secondary portions of the plant to the ultimate heat
sink. The ultimate heat sink consists of two separate heat sinks, the
Atlantic Ocean and the service water cooling tower. Either of these heat
sinks can provide the required cooling following a design basis accident.
However, neither of these heat sinks is qualified for all design basis
accidents.

The Atlantic Ocean is considered to be the preferred heat sink and the
cooling tower is considered the backup heat sink. The service water
system is normally aligned for ocean cooling but will automatically
transfer to the cooling tower should the ocean cooling become
unavailable.

The ocean service water system includes four 100% capacity pumps arranged
in two independent trains, two pumps per train. These four pumps are
immersed in salt water. Only one of these pumps is required to provide
cooling following a design basis accident. The cooling tower service
water system includes two 100% capacity pumps arranged in two independent
trains, one pump per train. These two pumps are immersed in chlorinated
potable water that encounters ocean water intrusion. Only one of these
pumps is required to provide cooling following a design basis accident.

II.  Description of Event

During Seabrook Station Refueling Outage 3, divers performed a routine
inspection of the cooling tower basin. Two degraded column flange bolts
were discovered on cooling tower SW pump 1SW-P-110A. The bolts, which
were 1 inch diameter x 4 inch long stainless steel capscrews made from SA
193 Grade B8M material, were replaced and sent offsite for metallurgical
examination. The material evaluation report concluded that the failure
mechanism of the bolts was a "sensitized" microstructure caused by an
improper, or lack of, required solution annealing heat treatment. Since
the bolts were original equipment supplied by the pump manufacturer,
Johnston Pump Company [J105], concerns were raised regarding the
condition of other service water pump bolting and any potential impact on
pump operability.

On September 15, 1994, a Station Information Report (SIR) was initiated
to expand the scope of the bolting review to include all service water
pumps and to address the operability concerns of degraded service water
pump bolting. An Engineering Evaluation was developed to determine
service water pump operability based upon bolting material condition
criteria. All safety related pump bolting subject to the aqueous
environment, both internal and external, was considered in this
evaluation including column flange bolts and nuts, column to bowl bolts
and nuts, bowl studs and nuts, and impeller thrust ring retainer cap
screws.

The engineering evaluation established the minimum numbers of
non-degraded bolts necessary for pump operability based on the numbers of
bolts used in each joint design, the bolting material yield strength, and
the worst case design basis loads expected.

TEXT                                                          PAGE 3 OF 4

A review of service water pump maintenance history data that included
several pump overhauls and had been accumulated over some eight years of
operation, suggested that widespread pump bolting degradation did not
exist. The extent of documented bolting degradation in conjunction with
the quantities of non-degraded bolting determined by the engineering
evaluation to be necessary for pump operability, led to the conclusion
that all service water pumps remained OPERABLE.

On September 26, 1994, North Atlantic participated in a teleconference
with NRC Region 1 management to discuss the status of the aforementioned
evaluation; the basis for continued operability, and the current repair
plans. On September 30, 1994, North Atlantic submitted a letter
describing the basis for operability of the service water system and the
repair plan and the schedule to correct the subject condition.

North Atlantic initiated maintenance activities in October of 1994 to
replace all suspect safety related bolting material for all six service
water pumps.

Bolting material replacement of the four ocean service water pumps was
accomplished before bolting material replacement of the two cooling tower
pumps. All four ocean water pump bolting replacement evolutions went as
expected with no widespread bolting degradation being observed.

However, when the "A" cooling tower service water pump evolution was in
progress, an unexpected high incidence of degraded pump bolts was
discovered. The number of available non-degraded pump bolts did not meet
the minimum number criteria established by the aforementioned engineering
evaluation. Since the condition of bolting for the redundant "B" cooling
tower SW pump (1SW-P-110B) was not known, it was conservatively declared
inoperable. Subsequent refurbishment of 1SW-P-110B revealed some
degradation of pump bolting however the number of functional bolts
supported the prior determination that the pump was operable.

The inoperability of the "A" cooling tower SW pump for an indeterminate
period of time and the unknown condition of the "B" pump was reported on
November 2, 1994, pursuant to 10CFR50.72(b)(1)(ii), as a condition that
is outside of the design basis of the plant. The inoperability of the "A"
cooling tower SW pump for an indeterminate period of time is therefore
reportable pursuant to 10CFR50.73(a)(2)(ii)(B) and in addition is
reportable as a condition prohibited by Technical Specifications pursuant
to 10CFR50.73(a)(2)(i)(B). The inoperability of the "A" cooling tower SW
pump for this indeterminate period resulted in a loss of redundancy in
the cooling tower portion of the ultimate heat sink. In the unlikely
event that a design basis earthquake were to disable the ocean portion of
the ultimate heat sink and the "A" cooling tower SW pump, the "B" cooling
tower pump would be the only pump available for shutdown cooling.

III. Safety Consequences

There were no adverse safety consequences associated with this event.
Although both service water cooling tower pumps were declared inoperable,
the bolting replacement evolution for the "B" pump revealed that 1SW-P-
110B would have been capable of performing its intended safety function
during a design basis event.

TEXT                                                          PAGE 4 OF 4

IV.  Cause of the Event

The cause of this event is determined to be the failure of the bolt
manufacturer to perform a proper heat treatment to the bolts as required
by the material specification. Had the bolts received the proper heat
treatment, sensitization of the material microstructure would not have
occurred and the bolts would not have experienced extensive degradation.

A secondary cause is determined to be the failure of the pump
manufacturer to identify deficiencies in documentation and bolting
material markings using their receipt inspection program.

V.  Corrective Actions

All suspect bolting material on the six service water pumps has been
replaced. The suspect bolting material that was replaced was verified to
meet the heat treatment requirements of material specification SA-193
Grade B8M through sample testing based on the ASTM A-262 Practice A Test.

Based on a procurement document search, the concern of improperly heat
treated safety grade bolting material is limited to those bolts that were
supplied to Johnston Pump Company and used in the initial fabrication of
the station's service water pumps. Therefore, since North Atlantic
presently procures components and materials from Johnston Pump Company,
an evaluation will be made of the Quality Assurrance program that
Johnston Pump Company uses to procure and supply ASME safety class
material.

VI.  Plant Conditions

At the time of the event the plant was in MODE 1 at 100% power.

VII. Previous Occurrences

LER 92-26 describes an event related to bolting failures that were also
caused by improper heat treatment or material conditioning.

The bolts that failed in that event were Grade B6 Type 410 stainless
steel cover bolts that were supplied with Xomox [X002] Tufline plug
valves. The Xomox valves are used in various locations throughout the
plant in ASME safety class 2 and 3, as well as non-safety related
applications.

The responsible failure mechanism was attributed to Intergranular Stress
Corrosion Cracking initiated by the high hardness of the bolts in
conjunction with the environmental conditions and the tensile stress
resulting from the applied bolt torquing.

ATTACHMENT TO 9412050333                                      PAGE 1 OF 2

North                              North Atlantic Energy
Atlantic                           Service Corporation
                                   P.O. Box 300
                                   Seabrook, NH 03874
                                   (603) 474-9521, Fax (603) 474-2987

                                   The Northeast Utilities System

                                   Ted C. Feigenbaum
                                   Senior Vice President &
NYN- 94136                         Chief Nuclear Officer

December 2, 1994

United States Nuclear Regulatory Commission
Washington, D.C. 20555

Attention:     Document Control Desk

Reference:     Facility Operating License No. NPF-86, Docket No. 50-443

Subject:       Licensee Event Report (LER) No. 94-017-00: "Service Water
               Cooling Tower Pump Bolt Degradation"

Gentlemen:

     Enclosed please find Licensee Event Report (LER) No. 94-017-00 for
Seabrook Station. This submittal documents an event which was identified
on November 2, 1994. This event is being reported pursuant to
10CFR50.73(a)(2)(i) and 10CFR50.73(a)(2)(ii).

     Should you require further information regarding this matter, please
contact Mr. James M. Peschel, Regulatory Compliance Manager, at (603)
474-9521, extension 3772.

                                             Very truly yours

                                             Ted C. Feigenbaum

TCF:JRM/sm

Enclosures:    NRC Forms 366, 366A

ATTACHMENT TO 9412050333                                      PAGE 2 OF 2

United States Nuclear Regulatory Commission             December 2, 1994
Attention:     Document Control Desk                            Page two

cc:  Mr. Thomas T. Martin
     Regional Administrator
     United States Nuclear Regulatory Commission
     Region I
     475 Allendale Road
     King of Prussia, PA 19406

     Mr. Albert W. De Agazio, Sr. Project Manager
     Project Directorate 1-4
     Division of Reactor Projects
     United States Nuclear Regulatory Commission
     Washington, DC 20555

     Mr. Richard Laura
     NRC Senior Resident Inspector
     P.O. Box 1149
     Seabrook, NH 03874

     INPO
     Records Center
     1100 Circle 75 Parkway
     Atlanta, GA 30339

*** END OF DOCUMENT ***

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