Information Notice 1993-45, Degradation of Shutdown Cooling System Performance

Degradation of Shutdown Cooling System Performance

ML031070480
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	06/16/1993
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
IN-93-045, NUDOCS 9306090036
Download: ML031070480 (9)

UNITED STATES NUCLEAR REGULATORY

COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 June 16, 1993 NRC INFORMATION

NOTICE 93-45: DEGRADATION

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 to alert addressees

to degradation

of shutdown cooling system performance

at the Oyster Creek Nuclear Generating

Station resulting

from inadequate

operating

procedures.

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

On January 23, 1993, the Oyster Creek Nuclear Generating

Station was in day 57 of the 14R refueling

outage. The plant was in a normal cold-shutdown

condition

with the primary containment

open and the reactor coolant system at about 43' C [110* F]. One reactor recirculation

loop was in service, one recirculation

loop was open, and the remaining

three recirculation

loops were either idled or isolated.

Two shutdown cooling loops were operating

with a combined flow rate of 11,735 liters per minute 13,100 gpm].In order to support the planned activities, the licensee elected to secure operation

of all recirculation

pumps and lower reactor water level. This configuration

would allow completion, in parallel, of recirculation

pump maintenance

activities

and main steam isolation

valve local leak rate testing.When the operators

lowered the reactor water level to approximately

419 cm (165 inches] above the top of active fuel and secured the running.recirculation

pump, the shutdown cooling water took the least resistance

path through the open recirculation

loop, and the majority of flow bypassed the core (see Attachment

1). During the time that the planned activities

were in progress, plant personnel

did not realize that shutdown cooling system performance

was degraded, allowing unmonitored

heatup of the reactor core.On January 25, 1993, after completing

the main steam isolation

valve local leak rate testing, an operations

engineer discovered

that the reactor vessel metal temperature

was about 109C 1228F] at the mid-vessel

point. Several 9306090036 PDI I.E No*[ct 3-. oj58 P ..'v1\

IN 93-45 June 16, 1993 Technical

Specifications

prerequisites

for exceeding

100. C [212 F] were not met, including

the requirement

to establish

primary containment

integrity.

After discovery, operators

took immediate

measures to reduce reactor coolant system water temperature

by first maximizing

flow in the two operating shutdown cooling loops and then placing a third shutdown cooling loop in service. Additionally, the reactor water level was raised to approximately

508 cm [200 inches] above the top of active fuel and a recirculation

pump was started.The immediate

cause of the event was determined

to be plant conditions

established

by a temporary

procedure

change to the shutdown cooling operating procedure

that failed to provide sufficient

forced flow through the reactor core to prevent thermal stratification.

The temporary

procedure

change had been implemented

to allow shutdown operations

with all recirculation

pumps secured and the nominal reactor water level less than the level at which spillover

from the core region to the annulus is assured (approximately

470 cm[185 inches] above the top of active fuel). The change had been developed from a draft engineering

evaluation, but did not include a requirement (stated in the body of the evaluation)

to maintain a specified

shutdown cooling flow of 22,712 liters per minute [6,000 gpm]. Instead, the usual shutdown cooling flow of about 11,735 liters per minute [3,100 gpm] was maintained

which, due to the specified

configuration, allowed the inadvertent

reactor heatup.Further details can be found in Licensee Event Report 50-219/93-002 and NRC Augmented

Inspection

Team Inspection

Report No. 50-219/93-80.

Discussion

This event at Oyster Creek indicated

that the temporary

procedure

change represented

a significant

procedure

revision and that the review process did not identify deficiencies

in the procedure

before it was implemented.

The temporary

procedure

change had been developed

from a draft engineering

evaluation

which concluded

that two shutdown cooling loops in operation

would adequately

cool the core. An additional

assumption

in the body of the evaluation

was that each loop of shutdown cooling would be operating

at its design flow rate of 11,356 liters per minute [3,000 gpm], for a total flow rate of 22,712 liters per minute [6,000 gpm]. This flow rate would be adequate to induce spillover

from the core region to the annulus at the reduced nominal water level. The temporary

procedure

change that implemented

the engineering

evaluation

did not require a minimum flow rate of 22,712 liters per minute [6,000 gpm]. As a result, the operators

following

the deficient

temporary

procedure

change placed two shutdown cooling loops in operation, but did not provide sufficient

shutdown cooling water to the reactor core to maintain reactor vessel temperatures.

In addition, the temporary

procedure

change contained

no provision

or guidance for monitoring

available

instruments

to ensure that decay heat was being adequately

removed from the reactor core.As part of the licensee corrective

actions, the licensee reviewed the effectiveness

of its safety review process concerning

temporary

changes and provided training on the subject of this event to all site personnel

who perform technical

and safety reviews.

IN 93-45 June 16, 1993 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

Offic of Nuclear Reactor Regulation (NRR) project manager.Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

contacts:

James S. Stewart, RI (215) 337-5240 Peter C. Wen, NRR (301) 504-2832 Attachments:

1. Figure 1, *Oyster Creek Shutdown Cooling System Flow With Open Recirculation

Loop" 2. List of Recently Issued NRC Information

Notices

K. /I'l I Steam Flow *-4-TO Recirculation

1. ~Loop Shutdown Cooling System (3 Cooling Loops)Figure 1 Attachment

1 1iK 93-45 June 16, 1993 Open Recirculation

Loop Oyster Creek Shutdown Cooling System Flow With Open Recirculation

Loop

I Attachment

2 IN 93-45 June 16, 1993 LIST OF RECENTLY ISSUED NRC INFORMATION

NOTICES Information

Date of Notice No. Subject Issuance Issued to 93-44 93-43 93-42 Operational

Challenges

During A Dual-Unit Transient Use of Inappropriate

Lubrication

Oils in Safety-Related

Applications

Failure of Anti-Rotation

Keys in Motor-Operated

Valves Manufactured

by Velan 06/15/93 06/10/93 06/09/93 All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.93-41 One Hour Fire Endurance Test Results for Thermal Ceramics Kaowool, 3M Company FS-195 and 3M Company Interam E-50 Barrier Systems 05/28/93 All holders for nuclear of OLs or CPs power reactors.93-40 ,93-39 93-38 Fire Endurance

Test Results for Thermal Ceramics FP-60 Fire Barrier Material Radiation

Beams from Power Reactor Biolog-ical Shields Inadequate

Testing of Engineered

Safety Features Actuation System 05/26/93 05/25/93 05/24/93 All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.All holders for nuclear of OLs or CPs power reactors.93-37 Eyebolts with Indeter-minate Properties

In-stalled in Limitorque

Valve Operator Housing Covers 05/19/93 All holders of OLs or CPs for nuclear power reactors.0L -Operating

License CP -Construction

Permit

IN 93-45 June 16, 1993 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.Original !1gnd by Brian K. Gdmeg Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

contacts: James S. Stewart, RI (215) 337-5240 Peter C. Wen, NRR (301) 504-283], Attachments:

6 1. Figure 1, "Oyster Creek Shutdown Cooling System Flow With Open Recirculation

Loop'2. List of Recently Issued NRC Information

Notices*rFF pRmVrnus CONCURRFNCF

OFFICE *OGCB:DORS

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NAME PCWen/vsb

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RSanders I GHMarcus ACThadani 04/29/93 05/10 05/24/93.=DOCUMENT NAME: 93-45.IN**SEE MEMO FROM M.. HODGES TO B.K. GRIMES DATED 3/19/93 PM (A. Dromerick), EAB (J. Carter) and AIT Team Leader (J. Beall) were consulted

during the development

of this IN.

IN 93-XX May xx, 1993 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.Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

contacts: James S. Stewart, Region I (215) 337-5240 Peter C. Wen, NRR (301) 504-2832 Attachments:

1. Oyster Creek Shutdown Cooling System Flow With Open Recirculation

Loop 2. List of Recently Issued NRC Information

Notices*SEE PREVIOUS CONCURRENCE

OFFICE *OGCB:DORS

• DRS:RI **SC:DRS:RI

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NAME PCWen/vsb

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PKEapen JPDurr MWHodges DATE l04/29/93 l05/03/93 I 03/19/93 l 03/19/93 l03/19/93*Tech Ed.*C:OGCB:DORS

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during the development

of this IN.530 ACiwAt #f A);mli v-AV'I/tllos

IN 93-XX May xx, 1993 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.Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

contacts: James S. Stewart, Region I (215) 337-5240 Peter C. Wen, NRR (301) 504-2832 Attachments:

1.2.Oyster Creek Shutdown Cooling System Flow With Open Recirculation

Loop List of Recently Issued NRC Information

Notices*SEE PREVIOUS CONCURRENCE

.OFFICE *OGCB:DORS

DRS:RI SC:DRS:RI

BC:DRS:RI

D:DRS:RI NAME PCWen/vsb

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PKEapen JPDurr MWHodges DATE 04/29/93 05/3,0 Cal P/1/93 0/ l/9 3 I__ 1_/93_J*Tech Ed.C:OGCB:DORS

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IN 93-XX May xx, 1993 Page 2 of 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.Brian K. Grimes, Director Division of Operating

Reactor Support Office of Nuclear Reactor Regulation

Technical

contacts: James S. Stewart, Region I (215) 337-5240 Peter (301)C. Wen, NRR 504-2832 Attachments:

1.2.Oyster Creek Shutdown Cooling System Flow With Open Recirculation

Loop List of Recently Issued NRC Information

Notices OFFICE OBORS DRS:RI SC:DRS:RI

BC:DRS:RI

D:DRS:RI NAME PCWen/vsb

JSStewart

PKEapen JPDurr MWHodges DATE _/aq/93_ 05/ /93 05/ /93 05/ /93 105/ /93 Tech Ed.C:OGCB:DORS

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