Information Notice 1997-06, Weaknesses in Plant-Specific Emergency Operating Procedures for Refilling the Secondary Side of Dry Once-Through Steam Generators

Weaknesses in Plant-Specific Emergency Operating Procedures for Refilling the Secondary Side of Dry Once-Through Steam Generators

ML031050378
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:	03/04/1997
From:	Martin T Office of Nuclear Reactor Regulation
To:
References
IN-97-006, NUDOCS 9703040265
Download: ML031050378 (9)

h.

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 March 4, 1997 NRC INFORMATION NOTICE 97-06: WEAKNESSES IN PLANT-SPECIFIC EMERGENCY

OPERATING PROCEDURES FOR REFILLING THE

SECONDARY SIDE OF DRY ONCE-THROUGH

STEAM GENERATORS

Addressees

All holders of operating licenses or construction permits for nuclear power reactors with once- through steam generators (OTSGs).

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert

addressees to a potential need for guidance in plant-specific emergency operating

procedures (EOPs) regarding the refilling of dried-out OTSGs. 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 May 19, 1996, the reactor at Arkansas Nuclear One, Unit I (ANO-1) tripped as a result of

circuitry problems in the main feedwater control system. The reactor trip was complicated by

a main steam safety valve (MSSV) which opened, as designed, in response to an increase in

pressure in the associated OTSG, but failed to reseat after the steam generator

depressurized. Consequently, the steam generator boiled dry and the reactor coolant system

(RCS) cooled down rapidly. The MSSV was later gagged shut.

Operators had been trained to respond to this type of event and, therefore, were familiar with

the generic guidance to refill the dried-out steam generator. However, the plant-specific

"overcooling" EOP (the EOP that addresses situations in which the RCS experiences such a

cooldown) contained no guidance for refilling the steam generator. Operators consulted with

their support staff who then drafted a modification to the "overcooling" procedure to provide

guidance on refilling the steam generator. After obtaining concurrence on the modification

from the OTSG vendor and approval of the revised procedure from the ANO-1 plant safety

committee, the licensee implemented the procedure. Operators used the revised procedure

to refill the dried-out steam generator and proceeded to stabilize the plant in the

hot-shutdown mode of operation.

9709 PD9 14EL t)oTrC.Eq7-0o 970Of!

IN 97-06 March 4, 1997 Generic guidelines for mitigating overcooling events in nuclear power reactors designed by

the Babcock & Wilcox Company (B&W) have been provided by the B&W Owners Group. I

Section III.D, Step 7, of the Generic Emergency Operating Guidelines (Volume 1) provides

guidance for refilling a dried-out steam generator during events that result in overcooling of

the RCS. In addition,Section III.G of the Bases (Volume 3) discusses steam generator tube

axial load concerns associated with cooldown scenarios. Items 3.6 and 3.8 of Section III.G

provide tensile and compressive tube-to-shell temperature difference limits and strategies for

minimizing tube compressive and tensile stresses during transients. At the time of the

May 19, 1996 event, the ANO-1 licensee was in the process of revising the plant's

"overcooling" EOP to bring it into agreement with the guidance document. In addition, lessons learned from a similar event that occurred at Oconee Unit 3 on August 10, 1994, were also being incorporated into this revision. Had these changes been completed, operators would have had the guidance necessary to refill the steam generator and would not

have had to wait for the procedure to be revised.

Discussion

During normal operation, the water and steam in a steam generator provide thermal

communication between the shell and the tubes. Wrhen a steam generator becomes dry, the

thermal communication between the shell and the tubes is lost. Therefore, temperature

changes in the RCS (including the steam generator tubes) are not transferred to the shell of

the steam generator, allowing the temperatures to diverge rapidly. The resultant tube-to-shell

temperature difference, and consequent differential thermal expansion between the tubes and

the shell, can place unacceptable stresses on the tubes. These stresses can be either

tensile or compressive during the dry-out /refill event. The loads are of a tensile nature when

the tubes are cooled faster than the shell and of a compressive nature when the shell is

cooled faster than the tubes. The differential pressure across the tube wall and the preload

at fabrication also contribute to the tube axial loads.

The results of an analysis to determine the response of a dry, pressurized OTSG to refill

under various conditions were used to develop plant operating procedures and guidance for

refilling a dry OTSG. Various combinations of initial OTSG tube temperatures and auxiliary

feedwater (AFW) flow rates were analyzed and the thermal-hydraulic results were used to

determine acceptable AFW refill flow rates for various tube-to-shell temperature differences

and initial tube temperatures. The allowable normal operating tube loads were established

using NRC-developed minimum wall thicknesses for degraded tubes and the acceptance

criteria provided in NRC Regulatory Guide 1.121, "Bases for Plugging Degraded PWR Steam

Generator Tubes" and the ASME Boiler and Pressure Vessel Code.

1 B&W Owners Group, Emergency Operating Procedures Technical Bases Document, December 16, 1996; NRC Accession Number 9612310074

IN 97-06 March 4, 1997 B&W analyses have demonstrated that the steam generator tube loads are bounded by loads

occurring during routine plant heatup and cooldown. Therefore, if up-to-date procedures and

guidelines are adhered to during the dry-out/refill event, there should be no increase in the

likelihood of a tube failure. During the ANO event, the tube-to-shell temperature difference

exceeded the allowable limits and, therefore, the loads imposed by the event were analyzed

to ensure continued operability of the steam generator.

As a result of recent operating experiences, the B&W Owners Group is currently reviewing

the present guidance on refilling dried-out OTSGs. Generic guidelines and plant-specific

EOPs are intended to reflect operating experience and the lessons learned from such

experience. Therefore, the generic guidelines may change after the B&W Owners Group

completes its review.

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.

I 1 Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Mohammed A. Shuaibi, NRR

(301) 415-2859 E-mail: mas4@nrc.gov

Jai Rajan, NRR

(301) 415-2788 E-mail: jrr@nrc.gov

Chu-Yu Liang, NRR

(301) 415-2878 E-mail: cylenrc.gov

Attachment: List of Recently Issued NRC Information Notices

K>

Attachment

IN 97-06 March 4, 1997 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

9 1-85, Potential Failures of 02/27/97 All holders of OLs

Rev. 1 Thermostatic Control or CPs for nuclear

Valves or Diesel power reactors

Generator Jacket

Cooling Water

97-05 Offsite Notification 02/27/97 All holders of OLs

Capabilities or CPs for nuclear

power reactors and

test and research

reactors

97-04 Implementation of a New 02/24/97 All materials, fuel

Constraint on Radioactive cycle, and non-power

Air Effluents reactor licensees

97-03 Defacing of Labels to 02/20/97 All material licensees

Comply with 10 CFR involved with disposal

20.1904(b) of medical waste

97-02 Cracks Found in Jet Pump 02/06/97 All holders of OLs

Riser Assembly Elbows at or CPs for boiling

Boiling Water Reactors water nuclear power

reactors models 3,

4, 5 and 6, except

those licenses that

have been amended to

possession-only

status

97-01 Improper Electrical Ground- 01/08/97 All holders of OLs

ing Results in Simultaneous or CPs for nuclear

Fires in the Control Room power reactors

and the Safe-Shutdown Equip- ment Room

OL = Operating License

CP = Construction Permit

IN 97-06 March 4, 1997 B&W analyses have demonstrated that the steam generator tube loads are bounded by loads

occurring during routine plant heatup and cooldown. Therefore, if up-to-date procedures and

guidelines are adhered to during the dry-out/refill event, there should be no increase in the

likelihood of a tube failure. During the ANO event, the tube-to-shell temperature difference

exceeded the allowable limits and, therefore, the loads imposed by the event were analyzed

to ensure continued operability of the steam generator.

As a result of recent operating experiences, the B&W Owners Group is currently reviewing

the present guidance on refilling dried-out OTSGs. Generic guidelines and plant-specific

EOPs are intended to reflect operating experience and the lessons learned from such

experience. Therefore, the generic guidelines may change after the B&W Owners Group

completes its review.

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 signed by D.B. Matthews

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Mohammed A. Shuaibi, NRR

(301) 415-2859 E-mail: mas4@nrc.gov

Jai Rajan, NRR

(301) 415-2788 E-mail: jrr@nrc.gov

Chu-Yu Liang, NRR

(301) 415-2878 E-mail: cyl@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

DOCUMENT NAME: G:MRAB1OTSGIN.EOP

To receive a copy of this document, indicate in the box C=Copy wlo attachmentlendosure E=Copy with attachment/endosure N = No copy

OFFICE Reviewers* l BC:SRXB/EMEB* I BC:PECB* liD:DRP0 I

NAME MShuaibi TCollins AChaffee TMartinY

l RBenedict:jkd RWessman

DATE 11/22/96 11/27/96 01/16/97 F0197 OFFICIAL RECORD COPY _

• \ IN 97-xx

January, 1997 B&W analyses have demonstrated that the steam generator tube loads are bounded by loads

occurring during routine plant heatup and cooldown. Therefore, if up-to-date procedures and

guidelines are adhered to during the dry-out/refill event, there should be no increase in the

likelihood of a tube failure. During the ANO event, the tube-to-shell temperature difference

exceeded the allowable limits and, therefore, the loads imposed by the event were analyzed

to ensure continued operability of the steam generator.

As a result of recent operating experiences, the B&W Owners Group is currently reviewing

the present guidance on refilling dried-out OTSGs. Generic guidelines and plant-specific

EOPs are intended to reflect operating experience and the lessons learned from such

experience. Therefore, the generic guidelines may change after the B&W Owners Group

completes its review.

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.

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Mohammed A. Shuaibi, NRR

(301) 415-2859 E-mail: mas4@nrc.gov

Jai Rajan, NRR

(301) 415-2788 E-mail: jrr@nrc.gov

Chu-Yu Liang, NRR

(301) 415-2878 E-mail: cyl@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

DOCUMENT NAME: G:%RAB1IOTSGIN.EOP

To receive a copy of this document,indicate Inthe box C=Copy wlo attachmentlendosure E=Copy with attachment/enclosure N = No copy

OFFICE I Reviewers* I BC:SRXB/EMEB* I BC:PECB I D:DRPM

NAME MShuaibi TCollins AChaffee g TMarlin (n

l RBenedict:jkd RWessman _ _ au___

_

DATE2296 11127196 I 01/V/97 _. .__ ___

___ ___ __ __ IA I rIA rk ~ £ r~~ I - - ./ -

OFFILAAL MMAJMW %oJrl

W4*0 Al1Wn

IN 97-xx

January , 1997 B&W analyses have demonstrated that the steam generator tube loads are bounded by loads

occurring during routine plant heatup and cooldown. Therefore, if up-to-date procedures and

guidelines are adhered to during the dry-out/refill event, there should be no increase in the

likelihood of a tube failure. During the ANO event, the tube-to-shell temperature difference

exceeded the allowable limits and, therefore, the loads imposed by the event were analyzed

to ensure continued operability of the steam generator.

As a result of recent operating experiences, the B&W Owners Group is currently reviewing

the present guidance on refilling dried-out OTSGs. Generic guidelines and plant-specific

EOPs are intended to reflect operating experience and the lessons learned from such

experience. Therefore, the generic guidelines may change after the B&W Owners Group

completes its review.

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.

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Mohammed A. Shuaibi Jai Rajan, NRR

(301) 415-2859 (301) 415-2788 E-mail: mas4@nrc.gov E-mail: jrr@nrc.gov

Chu-Yu Liang, NRR,

(301) 415-2878 E-mail: cyl@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

DOCUMENT NAME: G:MRAB110TSGIN.EOP

To receive a copy of this document, indicate in the box C=Copy wlo attachment/enclosure E=Copy with attachmentlenclosure N = No copy

OFFICE Reviewers* I BC:SRXB/EMEB* I BC:PECB l D:DRPM

NAME MShuaibi TCollins AChaffee TMartin

RBenedict:jkd RWessman

DATE 11/22/96 11/27/96 1 l! /96 12/ /96 OFFICIAL RECORD COPY \

le96-xx

December , 1996 event, such parameters as the average tube temperatures and primary and secondary

pressures need to be recorded and the specific event needs to be evaluated.

In the B&W Owners Group's Emergency Operating Procedures Technical Bases Document, Volume 3, Bases,Section III.G, "Cooldown Methods," Items 3.6 and 3.8 discuss these

concerns about tube axial loads. Tensile and compressive tube-to-shell temperature

difference limits are established, and strategies for minimizing tube compressive and tensile

stresses during transients are discussed. However, as a result of recent operating

experiences, the B&W Owners Group is currently reviewing the present guidance on refilling

dried-out OTSGs. Generic guidelines and plant-specific EOPs are intended to reflect

operating experience and the lessons learned from such experience. Therefore, the generic

guidelines may change after the B&W Owners Group completes its review.

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.

Thomas T. Martin, Director

Division of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Mohammed A. Shuaibi Jai Rajan, NRR

(301) 415-2859 (301) 415-2788 E-mail: mas4@nrc.gov E-mail: jrr@nrc.gov

Chu-Yu Liang, NRR, Robert A. Benedict, NRR

(301) 415-2878 (301) 415-1157 E-mail: cyl@nrc.gov E-mail: rabl@nrc.gov

Attachment: List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

DOCUMENT NAME: G:XRABlOTSGIN.EOP

To receive a copy of this document, indicate Inthe box C=Copy wlo attachment/enclosure E=Copy with attachment/enclosure N - No copy

OFFICE Reviewers* l BC:SRXB/EMEB* BC:PECB D:DRPM

NAME MShuaibi TCollins AChaffee TMartin

RBenedict:jkd RWessman

DATE 11/22/96 11127/96 12/ /96 -3 Y v 12/ /96

, OFFICIAL RECORD COPY

d4 4 o /W/,

. )

Ili-16-xx

November , 1996 B&W Owners Group guidance states that, if the tube-to-shell temperature difference exceeds

the bounds of the allowable limits, as represented in the reference curves, during the dry-out

event, such parameters as the average tube temperatures and primary and secondary

pressures need to be recorded and the specific event needs to be evaluated.

In the B&W Owners Group's Emergency Operating Procedures Technical Bas Document, Volume 3, Bases,Section III.G, "Cooldown Methods," Items 3.6 and 3.8 dis ss these

concerns about tube axial loads. Tensile and compressive tube-to-shell mperature

difference limits are established, and strategies for minimizing tube co pressive and tensile

stresses during transients are discussed. However, as a result of r ent operating

experiences, the B&W Owners Group is currently reviewing the p sent guidance on refilling

dried-out OTSGs. Generic guidelines and plant-specific EOPs intended to reflect

operating experience and the lessons learned from such exp ence. Therefore, the generic

guidelines may change after the B&W Owners Group comp tes its review.

This information notice requires no specific action or w en response. If you have any

questions about the information in this notice, please ntact one of the technical contacts

listed below or the appropriate Office of Nuclear Re otor Regulation (NRR) project manager.

T omas T. Martin, Director

ivision of Reactor Program Management

Office of Nuclear Reactor Regulation

Technical contacts: Mohammed A. Shu ibi Jai Rajan, NRR

(301) 415-2859 (301) 415-2788 E-mail: mas4 rc.gov E-mail: jrr@nrc.gov

Chu-Yu Lia', NRR, Robert A. Benedict, NRR

(301) 415 878 (301) 415-1157 E-mail: yl@nrc.gov E-mail: rabl@nrc.gov

Attachment: List of Re tly Issued NRC Information Notices

DOCUMENT NA  : G:ARAB1XOTSGlN.EOP

To receive a copy of this docur indicate In the box C=Copy wlo attachment/endosure E=Co? ,7tachment/enclosureN= =No copy

OFFICE Revieyers I BC:SRXB/EMEB I BC:PECB I D:DRPM I l

NAME ,Mfuaibi TCollins AChaffee TMartin

l Re'enedict-jkd k , iW

&Wessman- n:WQ, ?L.

l DATE 11/ /96 It V96 1A S III/ /96 OFFICIAL RECORD COPY