Information Notice 1993-70, Degradation of Boraflex Neutron Absorber Coupons

Degradation of Boraflex Neutron Absorber Coupons

ML031070107
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:	09/10/1993
From:	Grimes B Office of Nuclear Reactor Regulation
To:
References
-nr IN-93-070, NUDOCS 9309070206
Download: ML031070107 (9)

I

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON D.C. 20555 September 10, 1993 NRC INFORMATION NOTICE 93-70: DEGRADATION OF BORAFLEX NEUTRON ABSORBER

COUPONS

Addressees

permits for nuclear power

All holders of operating licenses or construction

reactors.

PurDose

is issuing this information

The U.S. Nuclear Regulatory Commission (NRC) significant problem pertaining to

notice to alert recipients to a potentially coupons. It is expected that

degradation of Boraflex neutron absorber applicability to their facilities

recipients will review the information foravoid similar problems. However, and consider actions, as appropriate, to notice are not NRC requirements;

suggestions contained in this information response is required.

therefore, no specific action or written

Background

installed in the spent fuelpool

Palisades has high-density fuel storage racksabsorbing material that was

that use Boraflex, a proprietary neutron Incorporated (BISCO). The storage

manufactured by Brand Industrial Services,Boraflex is attached to the walls of

racks are supplied by Westinghouse. The steel wrapper, which is spot

each canister and is held in place by a stainless

welded to the walls.

Boraflex coupons to indicate the

The licensee has a surveillance program using density storage racks in the

status of the Boraflex contained in the high of several of these coupons, spent fuel pool. Recently observed degradation gamma radiation in conjunction with

which may be due to exposure to high level about the integrity of the

interaction with pool water, raised questionsSignificant loss of Boraflex in the

Boraflex contained in the storage racks. of the subcriticality margin in

high-density fuel racks could result in loss '

the spent fuel pool.

was required to test and inspect

Through a commitment to the NRC, Palisades The tests include opening the

the Boraflex coupons after 5 years of use. determination, and a

coupons for visual observation, neutron attenuation

Boraflex hardness test.

DescriDtion of Circumstances

1993, 5 of the existing 10 Boraflex

During a period from August 17 through 19, 4 being full-length coupons

coupons were removed from the spent fuel pool,

9309070206 tE

Phi funt 3- O7G O1~

IN 93-70

September 10, 1993 and 1 a short-set coupon (see Figure 1). During

removal of the full-length

coupons a powdery substance and a grey debris cloud

were observed emanating

from the coupons. Further investigation of the full-length

that one coupon had lost an estimated 90 percent coupons revealed

of its Boraflex, two others

50 percent, and one 38 percent. Investigation of

that it had retained 100 percent of its Boraflex. the short-set coupon showed

that the Boraflex in the 4 full-length coupons and The licensee has determined

from different lots of material. the short-set coupon came

A principal difference between the short-set and

the full-length coupons is

their geometrical design. The short-set coupon consists

encapsulating the Boraflex with pool water accessing of eight compartments

coupons. However, in the full-length coupon Boraflex only the edges of the

over the entire length of coupon and bolted between is sandwiched axially

stainless steel metal strips. The licensee postulated two 0.51-mm [0.020-inch]

of the full-length coupon was exposed to the pool that a much larger area

In addition, the full-length coupon has a 12.7-mm water environment and flow.

metal strip on the top portion of the coupon, which [0.5-inch] hole through the

water flow around the Boraflex. The licensee has contributes to the pool

removal or testing of the remaining five coupons no immediate plans for

does intend to conduct neutron "blackness" testing in the spent fuel pool, but

in the spring of 1994.

The licensee also had initiated measurements of

the

spent fuel pool water. No increase in silica above silica content of the

been observed except in instances when the pool boronnormal 1-4 ppm levels have

increased. Because silica filler material is a concentration was

constituent

presence of silica in the water may be an indication of Boraflex, the

Boraflex in the fuel pool. of degradation of the

Discussion

Potential degradation mechanisms for Boraflex include

changes the material characteristics of the base (1) gamma flux, which

environment, namely the accessibility of water to polymer, and (2) chemical

has not drawn firm conclusions as to (1) the root the Boraflex. The licensee

degradation of Boraflex in the coupons, or (2) cause of the observed

the

of Boraflex in the coupons to that in the storage correlation of the behavior

racks.

Degradation of the Boraflex in fuel storage racks

subcriticality margin in the spent fuel pool. The could reduce the

5 percent subcriticality margin on the basis of design basis assumes a

boron concentration in the pool water, and minimumlowest pool temperature, no

assemblies. In its preliminary analysis, the licensee spacing between fuel

pool water and a complete loss of Boraflex from assumed no boron in the

reduced the subcriticality margin from greater the fuel storage racks. This

than 5 percent to about

2 percent. However, the licensee used the burnup

fuel in the criticality calculation. This is higher for the currently stored

value, implying less reactive fuel in the fuel pool than the design burnup

calcul ation. than assumed in the design

The licensee took several compensatory measures, operating staff aware not to dilute the spent fuelincluding (1) making the

pool, (2) increasing the

IN 93-70

September 10, 1993 spent fuel pool chemistry sampling frequency to daily, and (3) keeping the

boron concentration in the spent fuel pool above 1800 ppm, which exceeds the

technical specification requirement for boron concentration. With these

precautions a subcriticality margin greater than 5 percent would be

maintained.

Degradation of Boraflex has been previously addressed by NRC in Information

Notice 87-43, "Gaps in Neutron-Absorbing Material in High-Density Spent Fuel

Storage Racks," September 8, 1987. The Electric Power Research Institute, which has been studying this phenomenon for several years, has recently

published an interim report, "Boraflex Test Results and Evaluation,"

TR-101986, February 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.

(~/'

Bran Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Regulatory Regulation

Technical contacts: Kombiz Salehi, RIII

(708) 790-5782 K. I Parczewski, NRR

(301) 504-2705 Larry Kopp, NRR

(301) 504-2879 Vern Hodge, NRR

(301) 504-1861 Attachments:

1. Figure 1, Palisades Boraflex Coupon Types

2. List of Recently Issued NRC Information Notices

IN 93-70

.- tSeptember 10, 1993 spent fuel pool chemistry sampling frequency to daily, and (3) keeping the

boron concentration in the spent fuel pool above 1800 ppm, which exceeds the

technical specification requirement for boron concentration. With these

precautions a subcriticality margin greater than 5 percent would be

maintained.

Degradation of Boraflex has been previously addressed by NRC in Information

Notice 87-43, "Gaps in Neutron-Absorbing Material in High-Density Spent Fuel

Storage Racks," September 8, 1987. The Electric Power Research Institute, which has been studying this phenomenon for several years, has recently

published an interim report, "Boraflex Test Results and Evaluation,"

TR-101986, February 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 signed Uy

Maian K.Grime$

Brian K. Grimes, Director

Division of Operating Reactor Support

Office of Nuclear Regulatory Regulation

Technical contacts: Kombiz Salehi, RIII

(708) 790-5782 K. I Parczewski, NRR

(301) 504-2705 Larry Kopp, NRR

(301) 504-2879 Vern Hodge, NRR

(301) 504-1861 Attachments:

1. Figure 1, Palisades Boraflex Coupon Types

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE

OFFICE OGCB:DORS:NRR DRS:RIII DD:DRS:RIII SRXB:DSSA:NRR C:SRXB:DSSA:NRR

NAME *CVHodge *KSalehi *WLForney *LIKopp *RCJones

DATE 09/02/93 09/02/93 09/02/93 09/03/93 09/03/93 Tech Ed D:DSSA EMCB:DE:NRR EMCB:DE:NRR C:EMCB:DE:NRR C:OEAB:DORS

• DGable *ACThadani *JStrosnider *KlParczewski *RAHermann *AEChaffee

09/01/93 09/04/93 01J0M22 09/03/93 09/03/93 09/03/93

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C:OGCB:DORS:NRR

• GHMarcus j I

09/03/93 09/7 /93 DOCUMENI NAME: 93-/U.IN

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IN 93-xx I

September 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. I

Brian K. Grimes, Director

Division of Operating Reactor Supi 0ort

Office of Nuclear Regulatory Regul at on

Kombiz Salehi, RIII

(708) 790-5782 K. I Parczewski, NRR

(301) 504-2705 Larry Kopp, NRR

(301) 504-2879 Vern Hodge, NRR

(301) 504-1861 Attachments: 1. Figure 1, Palisades Boraflex Coupon Types

2. List of Recently Issued NRC Information Notices

• SEE PREVIOUS CONCURRENCE. .. ..... - . . ' - .

at 1 law.

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OFFICE OGCB:DORS:NRR DRS: RI I¢ .RP DD DR4:RIIIr SRXB:DSSA:NRR C:SRXB:DSSA:NRRL

NAME CVHodge KSalehi WLForney LIKop RC ones, DATE O /l2/93 CO/72/93 £ /O2I93 7/3 /93 /3 /93

• Tech Ed

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ACThada i

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Strosnider

/3/93

_MCB:DE:NRS C:7 XParczewski

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RAHermann j

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q/13 /93 / /93 DOCUMENT NAME: PALN0902.CVH

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IN 93-xx

September xx, 1993 The licensee took several compensatory measures, including (1) making the

operating staff aware to not dilute the spent fuel pool, (2) increasing the

spent fuel pool chemistry sampling frequency to daily, and (3) keeping the

boron concentration in the spent fuel pool above 1800 ppm, which exceeds the

technical specification requirement for boron concentration.

Degradation of Boraflex has been previously addressed by NRC in Information

Notice 87-43, "Gaps in Neutron-Absorbing Material in High-Density Spent Fuel

Storage Racks," September 8, 1987. The Electric Power Research Institute, who

has been studying this phenomenon for several years, has recently published an

interim report, "Boraflex Test Results and Evaluation," TR-101986, February

1993.

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

you have any questions about the information in this notice, please contact

the technical contact 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 Regulatory Regulation

Kombiz Salehi, RIII

(708)790-5782 K. I Parczewski, NRR Larry Kopp, NRR Vern Hodge, NRR

(301) 504-2705 (301) 504-2879 (301) 504-1861 Attachments: 1. Figure 1, Palisades Boraflex Coupon Types

2. List of Recently Issued NRC Information Notices

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OFFICE lOGCB:DORS:NRR DRS:RIII D:DRS:RIII SRXB:DSSA:NRR C:SRXB:DSSA:NRR

NAME CVHodge Ug KSalehi TOMartin LIKopp RCJones

DATE Oq/ol0/93 / /93 / /93 /93 /93 Tech Ed D:DSSA EMCB:DE:NRR EMCB:DE:ND C:EMCB:DE:NRR C:OEAB:DORS

q j ACTHADANI JStrosnider KIParczews'ki RAHermann AEChaffee

____ /93 /_/93 /_/93 9 /l/93 /L/93 / /93 C:OGCB:DORS:NRR D:DORS:NRR

GHMarcus [BKGrimes

/ /93 J / /93 DOCUMENT NAME: PALNOFIG.CVH

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Attachment 1 IN 93-70

September 10, 1993 Figure 1_ Q

Palisades Boraflex a. .

Coupon Types Ii

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Axtachment 2 IN 93-70

September 10, 1993 Page 1 of I

LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

93-69 Radiography Events at 09/02/93 All holders of OLs or CPs

Operating Power Reactors for nuclear power reactors

and all radiography

licensees.

93-68 Failure of Pump Shaft 09/01/93 All holders of OLs or CPs

Coupling Caused by for nuclear power reactors.

Temper Embrittlement

during Manufacture

92-16, Loss of Flow from the 08/23/93 All holders of OLs or CPs

Supp. 2 Residual Heat Removal for nuclear power reactors.

Pump during Refueling

Cavity Draindown

93-67 Bursting of High 08/16/93 All holders of OLs or CPs

Pressure Coolant for nuclear power reactors.

Injection Steam Line

Rupture Discs Injures

Plant Personnel

93-66 Switchover to Hot-Leg 08/16/93 All holders of OLs or CPs

Injection Following for pressurized water

A Loss-of-Coolant reactors.

Accident in Pres- surized Water Reactors

93-65 Reactor Trips Caused 08/13/93 Al 1 holders of OLs or CPs

by Breaker Testing for nuclear power reactors.

with Fault Protection

Bypassed

93-64 Periodic Testing and 08/12/93 All holders of OLs or CPs

Preventive Maintenance for nuclear power reactors.

of Molded Case Circuit

Breakers

93-63 Improper Use of Soluble 08/11/93 All holders of OLs or CPs

Weld Purge Dam Material for nuclear power reactors.

• OL = Operating License

CP = Construction Permit