Information Notice 1989-51, Potential Loss of Required Shutdown Margin During Refueling Operations

Potential Loss of Required Shutdown Margin During Refueling Operations

ML031180659
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, 05000000, Zimmer, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	05/31/1989
From:	Rossi C Office of Nuclear Reactor Regulation
To:
References
IN-89-051, NUDOCS 8905240229
Download: ML031180659 (5)

- UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION.

WASHINGTON, D.C. 20555 May 31, 1989 NRC INFORMATION NOTICE NO. 89-51: POTENTIAL LOSS OF REQUIRED SHUTDOWN

MARGIN DURING REFUELING OPERATIONS

Addressees

All holders of operating licenses or construction permits for nuclear power

reactors.

Purpose

This information notice Is being'provided to alert addressees to the potential

loss of required shutdown margin during the movement and placement of highly

reactive fuel during refueling operations. It is expected that recipients will

review the information for applicability to their facilities and consider

actions, as approprlate,-to avoid similar problems. However, suggestions

contained in this information notice do not constitute NRC requirements;

therefore, no specific action or written response is required.

Description of Circumstances

Baltimore Gas-and-Electric Company (BG&E) submitted a10 CFR Part 21 report

to the NRC on. March 15, 1989, regarding the potential loss of shutdown margin

during refueling operations at its Calvert Cliffs Nuclear Power Plant, Units 1 and 2. BG&E reported that it had increased the fuel enrichment during the last

several fuel cycles. Inthe current cycle, 4.3 weight percent U-235 fuel was

loaded into the core. During a review of NRC Information Notice No. 88-21,

"Inadvertent Criticality Events at Oskarshamn and U.S. Nuclear Power Plants,"

BG&E discovered that the Calvert Cliffs refueling procedures allowed the

placement of fuel assemblies in-intermediate positions during core alterations.

Inaddition, BG&E determined that the potential existed for placing several

fresh 4.3 weight percent reload assemblies together and losing some of the

required 5 percent shutdown margin. Calculations also showed that under

extreme conditions an inadvertent criticality could occur ifa number of highly

reactive assemblies were grouped together and no credit was taken for control

rods or burnable poisons.

BG&E has revised the Calvert Cliffs refueling procedures to ensure that fuel

assemblies will not be placed in intermediate positions during core alterations

without first verifying their potential reactivity. The revised procedures

allow fuel to be positioned only in intermediate core locations that will

contain fuel of equal or greater reactivity in the final core configuration.

8905240229

. . -

IN 89-51 May 31, 1989 Discussion:

As a result of longer fuel operating cycles, utilities have been increasing

the enrichment of reload fuel. Some of these fresh reload assemblies may be

highly reactive under refueling conditions. Although analyses are performed

to confirm that the refueling boron concentration is sufficient to maintain

the required shutdown margin (subcriticality) for the final core configuration, these analyses may not be sufficient to assure that the shutdown margin will be

maintained for all intermediate fuel assembly positions. In addition, explicit

procedural controls may not exist to control the location and movement of highly

reactive fuel assemblies during refueling. Because a significant amount of

reactivity can be added to subcritical configurations by the addition of a

single highly reactive assembly, it is possible that an inadvertent criticality

could occur if a number of such assemblies are grouped together. With this

highly reactive fuel, subcritical multiplication-(inverse count rate) may not

provide adequate warning of an approach to criticality.

Combustion Engineering, Inc. (CE), the nuclear fuel design consultant for

Calvert Cliffs, recognized this potential problem and recently issued an

information bulletin regarding shutdown margin during refueling to all utili- ties with CE-designed plants. These utilities have been advised to review

their fuel shuffle procedures that control the location of highly reactive

fuel and to be aware that the refueling boron concentration' necessary to

maintain the required shutdown margin, which is based on the final core

conf -gu a--I maT nut bersufftwa-to-ass re'that-the-r-requtred shutduwui -

margin will be maintained for all intermediate-fuel assembly positions. In

circumstances in which explicit analyses areinot available for each inter- mediate fuel assembly position, CE recommends positioning fuel only in

intermediate core locations that will contain fuel of equal or greater

reactivity in the final core configuration.

No specific action or written response is required by this information notice.

If you have any questions regarding this matter, please contact the technical

contact listed below or the Regional Administrator of the appropriate regional

office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Laurence I. Kopp, NRR

(301) 492-0879 Attachment: List of Recently Issued NRC Information Notices

I . - ,

'Attachment

IN 89-51 May 31, 1989 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

88-88, Degradation of Westinghouse 5/31/89 All holders of OLs

Supp. 1 ARD Relays or CPs for nuclear

power reactors.

89-50 Inadequate Emergency 5/30/89 All holders of OLs

Diesel Generator Fuel or CPs for nuclear

Supply power reactors.

89-49 Failure to Close Service 5/22/89 All holders of OLs

Water Cross-Connect or CPs for nuclear

Isolation Valves power reactors.

89-48 Design Deficiency in the 5/22/89 All holders of OLs

Turbine-Driven Auxiliary or CPs for nuclear

Feedwater Pump Cooling power reactors.

Water System

_ 89-47 tntll_ .roblc-mEl ~+-5l8/aS -lA.1,,bol depr if s,,,

Worn or Dlstorted Hose; or CPs for nuclear

Clamps'on. Self-Contained power reactors and

Breathing Apparatus fuel facilities.

89-46 Confidentiality of 5/11/89 All holders of licenses

Exercise Scenarios for fuel cycle facilities

and byproduct material

licensees having an

approved emergency

response plan.

89-45 Metalclad, Low-Voltage. 5/8/89 All holders of OLs

Power Circuit Breakers or CPs for nuclear

Refurbished with Sub- power reactors.

standard Parts

89-44 Hydrogen Storage on the 4/27/89 All holders of OLs

Roof of the Control Room or CPs for nuclear

power reactors.

88-82, Torus Shells with Corrosion 5/2/89 All holders of OLs

Supp. 1 and Degraded Coatings in or CPs for BWRs.

BWR Containments

OL = Operating License

CP = Construction Permit

IN 89-51 May 31, 1989 Discussion:

As a result of longer fuel operating cycles, utilities have been increasing

the enrichment of reload fuel. Some of these fresh reload assemblies may be

highly reactive under refueling conditions. Although analyses are performed

to confirm that the refueling boron concentration is sufficient to maintain

the required shutdown margin (subcriticality) for the final core configuration, these analyses may not be sufficient to assure that the shutdown margin will be

maintained for all Intermediate fuel assembly positions. In addition, explicit

procedural controls may not exist to control the location and movement of highly

reactive fuel assemblies during refueling. Because a significant amount of

reactivity can be added to subcritical configurations by the addition of a

single highly reactive assembly, it is possible that an inadvertent criticality

could occur if a number of such assemblies are grouped together. With this

highly reactive fuel, subcritical multiplication (inverse count rate) may not

provide adequate warning of an approach to criticality.

Combustion Engineering, Inc. (CE), the nuclear fuel design consultant for

Calvert Cliffs, recognized this potential problem and recently issued an

information bulletin regarding shutdown margin during refueling to all utili- ties with CE-designed plants. These utilities have been advised to review

their fuel shuffle procedures that control the location of highly reactive

fuel and to be aware that the refueling boron concentration necessary to

maintain the required shutdown margin, which is based on the final core

configuration, may not be sufficient to assure that their required shutdown

margin will be maintained for all intermediate fuel assembly positions. In

circumstances in which explicit analyses are not available for each inter- mediate fuel assembly position, CE recommends positioning fuel only in

intermediate core locations that will contain fuel of equal or greater

reactivity in the final core configuration.

No specific action or written response is required by this information notice.

If you have any questions regarding this matter, please contact the technical

contact listed below or the Regional Administrator of the appropriate regional

office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Laurence I.Kopp, NRR

(301) 492-0879 C 4 2 Attachment: List of Recently Issued NRC Informat on 5

• SEE PREVIOUS PAGE FOR CONCURRENCE

D/ A *C/OGCB:DOEA:NRR*RPB:ARM

C CHBerlinger TechEd

05/ i9H 05/23/89 05/17/89

• OGCB:DOEA:NRR *SRXB:DEST:NRR *C/S XB:DEST:NRR *SAD/DEST:NRR *D/DEST:NRR

JGuillen LKopp WHodges AThadani LCShao

05/17/89 05/18/89 05/19/89 05/17/89 05/22/89

I . ~ ~

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IN 89-XX

May xx, 1989 Discussion:

As a result of longer fuel operating cycles, utilities have been increasing the

enrichment of reload fuel. Some of these fresh reload assemblies may be highly

reactive under refueling conditions. Although analyses are performed to

confirm that the refueling boron concentration is sufficient to maintain the

required shutdown margin (subcriticality) for the final core configuration, these analyses may not be sufficient to assure that the shutdown margin will be

maintained for all intermediate fuel assembly positions. In addition, explicit

procedural controls may not exist to control the location and movement of

highly reactive fuel assemblies during refueling. Because a significant amount

of reactivity can be added to subcritical configurations by the addition of a

single highly reactive assembly, it is possible that an inadvertent criticality

could occur if a number of such assemblies are grouped together. With this

highly reactive fuel, subcritical multiplication (inverse count rate) may not

provide adequate warning of an approach to criticality.

Combustion Engineering, Inc. (CE), the nuclear fuel design consultant for

Calvert Cliffs, recognized this potential problem and recently issued an

information bulletin regarding shutdown margin during refueling to all utili- ties with CE-designed plants. These utilities have been advised to review

their fuel shuffle procedures that control the location of highly reactive fuel

and to be aware that the refueling boron concentration necessary to maintain

the required shutdown margin, which is based on the final core configuration, may not be sufficient to assure that their required shutdown margin will be

maintained for all intermediate fuel assembly positions. In circumstances in

which explicit analyses are not available for each intermediate fuel assembly

position, CE recommends positioning fuel only in intermediate core locations

that will contain fuel of equal or greater reactivity in the final core

configuration.

No specific action or written response is required by this information notice.

If you have any questions regarding this matter, please contact the technical

contact listed below or the Regional Administrator of the appropriate regional

office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Laurence I. Kopp, NRR

(301) 492-0879 Attachment: List of Recently Issued NRC Informationoti

D/DOEA:NRR C/OG X 'EA:NRR RPB:ARM

CERossi CHBerlinger TechEd

05/ /89 05/ /89 05/ FV8 OG SRXB:D J NRR C/SRXB:D T R SAD DEST D/DEST: NRR,0 .

JGu en LKopp WHodges AThajani LCShao

05 89 05/fa/89 05/( /8 05/ 89 05J / 8;9t