Information Notice 1994-57, Debris in Containment and Residual Heat Removal System

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Debris in Containment and Residual Heat Removal System
ML031060503
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  Entergy icon.png
Issue date: 08/12/1994
From: Grimes B
Office of Nuclear Reactor Regulation
To:
References
IN-94-057, NUDOCS 9408080111
Download: ML031060503 (8)
v • d • e


UNITED STATES

NUCLEAR REGULATORY COMMISSION

  • OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555 August 12, 1994 NRC INFORMATION NOTICE 94-57: DEBRIS IN CONTAINMENT AND THE RESIDUAL HEAT

REMOVAL SYSTEM

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

PurDose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this Information

notice to alert addressees to the problem associated with debris recently

discovered in the containment and the residual heat removal (RHR) system at

some BWR sites. 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

The following are instances in which debris were found in BWR suppression

pools.

LaSalle County Station. Unit I

On April 26 and May 11, 1994, while in a refueling outage, the licensee made

two dives into the Mark II design suppression pool to clean the emergency core

cooling system (ECCS) suction strainers of a small amount of debris which

caused less than I percent clogging. The diver found that the strainers had

experienced no apparent damage or deformation of the strainer faces. However, while in the pool on both occasions, the divers found and removed an

assortment of operational debris. On the first dive, the diver removed a

hardhat, a pair of anti-contamination coveralls, a 15.2 meter (m) [50 ft]

length of Tygon tubing, 3 nuts, and a 4.6 m [15 ft] length of black duct tape.

On the second dive, the diver removed four lengths of 1.9 cm [3/4 in] hose

ranging in length about 8 m [25 ft] to about 46 m [150 ft], three lengths of

Tygon tubing ranging in length from 6 m [20 ft] to 15 m [50 ft], a short

length of 5 cm by 10 cm [2 in by 4 in] wood, and a flashlight.

The diver also noted that a sediment had formed on the suppression pool floor

ranging in thickness from 0.3 cm to 5 cm [1/8 in to 2 in]. The suppression

pool floor is a level floor with raised ridges in a waffle pattern. The

5 cm [2 in] accumulations of sediment were found in the raised corners of

9408080111 4 doi P0P rf  ? q o9

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'N94-57

4 ugust 12, 1994

-f the waffle pattern. The licensee took a sample of the sediment and had it

analyzed. The analysis results showed that the filterable solid consisted of

over 99 percent iron oxide, with trace amounts of nickel, copper, and chrome.

The filtrate contained 120 parts per billion (ppb) dissolved nickel. No

organic constituents were found. Radiologically, the sample consisted of

75 percent cobalt-60 with small contributions from manganese-54, cobalt-58, and iron-59. The licensee concluded that the sample contained normal system

corrosion products with no contaminants such as hydraulic fluid or solvents.

Before startup, the licensee cleaned all ECCS strainers of debris and removed

all objects from the pool.

River Bend Nuclear Station

On June 13, 1994, while the plant was In a refueling outage, the licensee

conducted an inspection of the ECCS suction strainers and the Mark III design

suppression pool. During the inspection, 16 objects were located in the

suppression pool. One of these objects, a plastic bag, was removed from the

residual heat removal system 'A"suction strainer. The other objects that

were removed from the pool included a hammer, grinding wheel, slugging wrench, socket, hose clamp, bolt, nut, step-off-pad, two ink pens, antenna, scaffold

knuckle, short length of rope, and used tape. Most of these items were not

listed in the station suppression pool lost item log. These findings prompted

the licensee to take the following corrective actions: (1)remove all items

from the suppression pool, (2)inspect all accessible areas for additional

debris, (3)verify the strainers for all ECCS pumps to be clean, and (4)

increase surveillance of the suppression pool work area to minimize additional

objects dropped into the pool. The licensee is reviewing its policies and

practices regarding loose objects in and around the grating areas in the

containment to determine their adequacy.

The licensee also found sediment in the suppression pool. During the previous

refueling outage, that ended in September 1992, the licensee drained and

cleaned the pool. However, the licensee was unable to completely clean the

pool. After draining the pool, there was still about 0.3 m [1 ft] of water

inside the weir wall that was "mucky." During the current refueling outage, the licensee used a portable cleanup system to clean the water in the pool.

By the end of the outage, water clarity in the pool significantly improved.

However, a layer of sediment still remains on the pool floor. The licensee is

planning to install a permanent pool cleanup system two outages from now;

however, the planned system will not be able to remove the sediment inside the

weir wall.

The following is an instance in which debris was found in the RHR system.

Ouad Cities Unit 1

On July 14, 1994, during a post-maintenance test run of the 'A"loop of the

RHR system, test data indicated that the RHR torus cooling/test return valve, valve 1001-36A, was plugged. When the 36A valve was opened for inspection, the remains of a plastic bag were found shredded and caught within the

-'N 94-57 V- August 12, 1994 anti-cavitation trim which was installed during the recent outage. Some of

the material appeared to have travelled the entire way through the

anti-cavitation trim. The majority of the material was found lodged on the

suction side of the valve trim. A few small pieces of plastic were found in

the Mark I design suppression pool and removed.

Subsequent to the July 14 event, the licensee observed reduced flow from the

IC' RHR pump and initiated further investigation. On July 23, 1994, licensee

maintenance personnel removed a drain plug on the volute of the *CO RHR pump

and used a boroscope to inspect the pump internals. A 10 cm [4-inch] diameter

wire brush wheel and a piece of metal were found wrapped around a vane of the

pump. The licensee had opened the RHR system during the outage to work on the

RHR 7D valve and removed a butterfly valve on the common suction line (valve

RHR 6B). The licensee retrieved the wire wheel brush, the metal and two

washers from the pump.

Discussion

The events described above illustrate the potential for adverse effects on

emergency core cooling system performance due to debris. The debris resulted

from inadequate control of foreign material inside the containment or resulted

from inadequate inspection after maintenance activities were performed on a

safety system (the RHR system).

Previous NRC generic communications have noted that ECCS strainer clogging

represents a potential threat to the reliable functioning of the ECCS pumps

throughout a design basis accident. These previous NRC communications have

dealt with the potential to clog ECCS strainers with debris generated during

plant work activities, debris from a loss-of-coolant accident (LOCA), or a

combination of these. The types of debris described herein are further

examples of debris licensees have found in their suppression pools or in the

RHR system. Although the licensees in the LaSalle and River Bend cases stated

that the debris found in their suppression pools would have been insufficient

to clog strainers, these debris in combination with the debris generated

during a LOCA could accelerate a loss of net positive suction head for the

ECCS pumps or cause other types of damage to the strainers. For example, corrosion sediment in the pool could clog the strainers if debris such as the

anti-contamination clothing were already drawn to the strainer surface where

the clothing could filter the finer particles of sediment out of the water.

In addition, damage to strainers might occur if some of the heavier tools were

to strike the strainers during the early stages of a LOCA blowdown.

Previous NRC generic communications also have addressed plant events where

debris was found in safety systems, namely the auxiliary feedwater system and

the safety injection system, and resulted in reduced flow during testing of

the systems. The Quad Cities event discussed above involved debris in the RHR

system. The debris in this case could potentially cause a transient, result

in failure to mitigate a transient or accident, or result in damage to

equipment.

N 94-57 S ~ugust 12, 1994 Related Generic Communications

Emergency Core Cooling Function due to a Combination of Operational and

Post-LOCA Debris in Containment'

Cooling Suction Strainers'

Cooling Systems caused by Foreign Material Blockage'

Strainers at a Foreign BWRO

Piping Systems'

Recirculation Capability Due to Insulation Debris Blockage"

This information notice requires no specific action or written response. If

you have any questions regarding the information in this notice, please

contact one of the technical contacts listed below or the appropriate Office

of Nuclear Reactor Regulation (NRR) project anager.

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Robert B. Elliott, NRR

(301) 504-1397 Amy E. Cubbage, NRR

(301) 504-2875 Attachment:

List of Recently Issued NRC Information Notices

FIc4oswuL- frl- V.aciJ

t,~ kc

Att, )ment

IN SS-57 August 12, 1994 Page I of I

LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

94-56 Inaccuracy of Safety Valve 08/11/94 All holders of OLs or CPs

Set Pressure Determinations for nuclear power reactors.

Using Assist Devices

94-55 Problems with Copes- 08/04/94 All holders of OLs or CPs

Vulcan Pressurizer for nuclear power reactors.

Power-Operated Relief

Valves

91-79, Deficiencies Found in 08/04/94 All holders of OLs or CPs

Supp. 1 Thermo-Lag Fire Barrier for nuclear power reactors.

Installation

94-54 Failures of General 08/01/94 All holders of OLs or CPs

Electric Magne-Blast for nuclear power reactors.

Circuit Breakers to

Latch Closed

91-45, Possible Malfunction of 07/29/94 All holders of OLs or CPs

Supp. 1 Westinghouse ARD, BFD, for nuclear power reactors.

and NBFD Relays, and

A200 DC and DPC 250

Magnetic Contactors

94-42, Cracking in the Lower 07/19/94 All holders of OLs or CPs

Supp. 1 Region of the Core Shroud for boiling water reactors

in Boiling-Water Reactors (BWRs).

94-53 Hydrogen Gas Burn Inside 07/18/94 All holders of OLs or CPs

Pressurizer During Welding for nuclear power reactors.

94-52 Inadvertent Containment 07/15/94 All holders of OLs or CPs

Spray and Reactor Vessel for nuclear power reactors.

Draindown at Millstone

Unit 1

94-51 Inappropriate Greasing 07/15/94 All holders of OLs or CPs

of Double Shielded Motor for nuclear power reactors.

Bearings

OL - Operating License

CP - Construction Permit

IN 94-57 VJAugust 12, 1994 Related Generic Communications

Emergency Core Cooling Function due to a Combination of Operational and

Post-LOCA Debris in Containment"

Cooling Suction Strainers"

Cooling Systems caused by Foreign Material Blockage'

Strainers at a Foreign BWR'

Piping Systems"

Recirculation Capability Due to Insulation Debris Blockage'

This information notice requires no specific action or written response. If

you have any questions regarding 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 signed by

Brian K.Grimes

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Reactor Regulation

Technical contacts: Robert B. Elliott, NRR

(301) 504-1397 Amy E. Cubbage, NRR

(301) 504-2875 Attachment:

List of Recently Issued NRC Information Notices

  • SEE PREVIOUS CONCURRENCE

SCSB:DSSA OGCB:DORS TECHED SC/SCSB:DSSA

RBE11iott* PCWen* JDMai n* RMLobel*

07/14/94 07/14/94 07/15/94 07/15/94 C/SCSB:DSSA SRXB:DSSA AC:SRXB:DSSA AD/DSSA

RJBarrett* AECubbage* TECollins* MJVirgilio*

7/15/94 07/29/94 08/01/94 C/OEAB:DORS AC/OGCB:DORS

AEChaffee* ELDool ittle*

08/02/94 08/03/94 OFFICIAL RECORD COPY DOCUMENT NAME: 94-57. IN

IN 94-XX

July xx, 1994 Related Generic Communications

Emergency Core Cooling Function due to a Combination of Operational and

Post-LOCA Debris in Containment'

Cooling Suction Strainersm

Cooling Systems caused by Foreign Material Blockage'

Strainers at a Foreign BWRI

Piping Systems"

Recirculation Capability Due to Insulation Debris Blockage"

This information notice requires no specific action or written response. If

you have any questions regarding 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: Robert B. Elliott, NRR

(301) 504-1397 Amy E. Cubbage, NRR

(301) 504-2875 Attachment:

List of Recently Issued NRC Information Notices

  • SEE PREVIOUS CONICURRENCE

SCSB:DSSA OGCB:DORS TECHED SC/SCSB:DSSA

RBElliott* PCWen* JDMain* RMLobel*

07/14/94 07/28/94 07/14/94 07/28/94 07/15/941 07/15/94 Ji/28/94 C/SCSB:DSSA SRXB:D KRI AC:SRXB: AD/DSSA IO

RJBarrett* AECu MPR TECollins MJVirgilio

7/15/94 07/28/94 07l2/9 A~r 07/2(/94 lO/ /94) DM

C/OEAB:DORS(3 A D/DORS

91 AEChaffee E BKGrimes

07/ /94 MlCA /94 COP

OFFICIAL RECORD COPY DOCUMENT NAME: G:\PETER\DEBRIS.IN

IN 94-XX

July xx, 1994

. Related Generic Communications

Emergency Core Cooling Function due to a Combination of Operational and

Post-LOCA Debris in Containment"

Cooling Suction Strainers"

Strainers at a Foreign BWR"

Recirculation Capability Due to Insulation Debris Blockage"

This information notice requires no specific action or written response. If

you have any questions regarding 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: Robert B. Elliott, NRR

(301) 504-1397 Amy E. Cubbage, NRR

(301) 504-2875 Attachment:

List of Recently Issued NRC Information Notices

  • SEE PREVIOUS CONCURRENCE

SCSB:DSSA O

0GCB:D9RS) TECHED SC/SCSB:DSSA

RBElliott*PL- X PCWen*

07/14/94 4IW4qy 07/14/4 JDMain*

07/15/94 RMLobel* Qu

07/15/94 tj 1+49 C/ i gjSA SRXB:DSSA SC/SRXB:DSSA AC:SRXB:DSSA AD/DSSA

RJ AECubbage MPRubin TECollins MJVirgil io

7 /07/ /94 07/ /94 07/ /94 07/ /94 C/OEAB:DORS AC/OGCB:DORS D/DORS

AEChaffee ELDoolittle BKGrimes

07/ /94 07/ /94 07/ /94 OFFICIAL RECORD COPY DOCUMENT NAME: G:\PETER\DEBRIS.IN


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