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{{#Wiki_filter:IUNITED STATESNUCLEAR REGULATORY COMMISSIONOFFICE OF NUCLEAR REACTOR REGULATIONWASHINGTON D.C. 20555September 10, 1993NRC INFORMATION NOTICE 93-70: DEGRADATION OF BORAFLEX NEUTRON ABSORBERCOUPONS
{{#Wiki_filter: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==
==Addressees==
All holders of operating licenses or construction permits for nuclear powerreactors.PurDoseThe U.S. Nuclear Regulatory Commission (NRC) is issuing this informationnotice to alert recipients to a potentially significant problem pertaining todegradation of Boraflex neutron absorber coupons. It is expected thatrecipients will review the information for applicability to their facilitiesand 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.BackgroundPalisades has high-density fuel storage racks installed in the spent fuelpoolthat use Boraflex, a proprietary neutron absorbing material that wasmanufactured by Brand Industrial Services, Incorporated (BISCO). The storageracks are supplied by Westinghouse. The Boraflex is attached to the walls ofeach canister and is held in place by a stainless steel wrapper, which is spotwelded to the walls.The licensee has a surveillance program using Boraflex coupons to indicate thestatus of the Boraflex contained in the high density storage racks in thespent fuel pool. Recently observed degradation of several of these coupons,which may be due to exposure to high level gamma radiation in conjunction withinteraction with pool water, raised questions about the integrity of theBoraflex contained in the storage racks. Significant loss of Boraflex in thehigh-density fuel racks could result in loss of the subcriticality margin inthe spent fuel pool. 'Through a commitment to the NRC, Palisades was required to test and inspectthe Boraflex coupons after 5 years of use. The tests include opening thecoupons for visual observation, neutron attenuation determination, and aBoraflex hardness test.DescriDtion of CircumstancesDuring a period from August 17 through 19, 1993, 5 of the existing 10 Boraflexcoupons were removed from the spent fuel pool, 4 being full-length coupons9309070206Phi tE funt 3- O7G O1~  
All holders of operating
IN 93-70September 10, 1993 and 1 a short-set coupon (see Figure 1). During removal of the full-lengthcoupons a powdery substance and a grey debris cloud were observed emanatingfrom the coupons. Further investigation of the full-length coupons revealedthat one coupon had lost an estimated 90 percent of its Boraflex, two others50 percent, and one 38 percent. Investigation of the short-set coupon showedthat it had retained 100 percent of its Boraflex. The licensee has determinedthat the Boraflex in the 4 full-length coupons and the short-set coupon camefrom different lots of material.A principal difference between the short-set and the full-length coupons istheir geometrical design. The short-set coupon consists of eight compartmentsencapsulating the Boraflex with pool water accessing only the edges of thecoupons. However, in the full-length coupon Boraflex is sandwiched axiallyover the entire length of coupon and bolted between two 0.51-mm [0.020-inch]stainless steel metal strips. The licensee postulated that a much larger areaof the full-length coupon was exposed to the pool water environment and flow.In addition, the full-length coupon has a 12.7-mm [0.5-inch] hole through themetal strip on the top portion of the coupon, which contributes to the poolwater flow around the Boraflex. The licensee has no immediate plans forremoval or testing of the remaining five coupons in the spent fuel pool, butdoes intend to conduct neutron "blackness" testing in the spring of 1994.The licensee also had initiated measurements of the silica content of thespent fuel pool water. No increase in silica above normal 1-4 ppm levels havebeen observed except in instances when the pool boron concentration wasincreased. Because silica filler material is a constituent of Boraflex, thepresence of silica in the water may be an indication of degradation of theBoraflex in the fuel pool.DiscussionPotential degradation mechanisms for Boraflex include (1) gamma flux, whichchanges the material characteristics of the base polymer, and (2) chemicalenvironment, namely the accessibility of water to the Boraflex. The licenseehas not drawn firm conclusions as to (1) the root cause of the observeddegradation of Boraflex in the coupons, or (2) the correlation of the behaviorof Boraflex in the coupons to that in the storage racks.Degradation of the Boraflex in fuel storage racks could reduce thesubcriticality margin in the spent fuel pool. The design basis assumes a5 percent subcriticality margin on the basis of lowest pool temperature, noboron concentration in the pool water, and minimum spacing between fuelassemblies. In its preliminary analysis, the licensee assumed no boron in thepool water and a complete loss of Boraflex from the fuel storage racks. Thisreduced the subcriticality margin from greater than 5 percent to about2 percent. However, the licensee used the burnup for the currently storedfuel in the criticality calculation. This is higher than the design burnupvalue, implying less reactive fuel in the fuel pool than assumed in the designcalcul ation.The licensee took several compensatory measures, including (1) making theoperating staff aware not to dilute the spent fuel pool, (2) increasing the
 
licenses or construction
 
permits for nuclear power reactors.PurDose The U.S. Nuclear Regulatory
 
Commission (NRC) is issuing this information
 
notice to alert recipients
 
to a potentially
 
significant
 
problem pertaining
 
to degradation
 
of Boraflex neutron absorber coupons. 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.Background
 
Palisades
 
has high-density
 
fuel storage racks installed
 
in the spent fuelpool that use Boraflex, a proprietary
 
neutron absorbing
 
material that was manufactured
 
by Brand Industrial
 
Services, Incorporated (BISCO). The storage racks are supplied by Westinghouse.
 
The Boraflex is attached to the walls of each canister and is held in place by a stainless
 
steel wrapper, which is spot welded to the walls.The licensee has a surveillance
 
program using Boraflex coupons to indicate the status of the Boraflex contained
 
in the high density storage racks in the spent fuel pool. Recently observed degradation
 
of several of these coupons, which may be due to exposure to high level gamma radiation
 
in conjunction
 
with interaction
 
with pool water, raised questions
 
about the integrity
 
of the Boraflex contained
 
in the storage racks. Significant
 
loss of Boraflex in the high-density
 
fuel racks could result in loss of the subcriticality
 
margin in the spent fuel pool. 'Through a commitment
 
to the NRC, Palisades
 
was required to test and inspect the Boraflex coupons after 5 years of use. The tests include opening the coupons for visual observation, neutron attenuation
 
determination, and a Boraflex hardness test.DescriDtion
 
of Circumstances
 
During a period from August 17 through 19, 1993, 5 of the existing 10 Boraflex coupons were removed from the spent fuel pool, 4 being full-length
 
coupons 9309070206 Phi tE 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
 
coupons revealed that one coupon had lost an estimated
 
90 percent of its Boraflex, two others 50 percent, and one 38 percent. Investigation
 
of the short-set
 
coupon showed that it had retained 100 percent of its Boraflex.
 
===The licensee has determined===
that the Boraflex in the 4 full-length
 
coupons and the short-set
 
coupon came from different
 
lots of material.A principal
 
difference
 
between the short-set
 
and the full-length
 
coupons is their geometrical
 
design. The short-set
 
coupon consists of eight compartments
 
encapsulating
 
the Boraflex with pool water accessing
 
only the edges of the coupons. However, in the full-length
 
coupon Boraflex is sandwiched
 
axially over the entire length of coupon and bolted between two 0.51-mm [0.020-inch]
stainless
 
steel metal strips. The licensee postulated
 
that a much larger area of the full-length
 
coupon was exposed to the pool water environment
 
and flow.In addition, the full-length
 
coupon has a 12.7-mm [0.5-inch]  
hole through the metal strip on the top portion of the coupon, which contributes
 
to the pool water flow around the Boraflex.
 
The licensee has no immediate
 
plans for removal or testing of the remaining
 
five coupons in the spent fuel pool, but does intend to conduct neutron "blackness" testing in the spring of 1994.The licensee also had initiated
 
measurements
 
of the silica content of the spent fuel pool water. No increase in silica above normal 1-4 ppm levels have been observed except in instances
 
when the pool boron concentration
 
was increased.
 
Because silica filler material is a constituent
 
of Boraflex, the presence of silica in the water may be an indication
 
of degradation
 
of the Boraflex in the fuel pool.Discussion
 
Potential
 
degradation
 
mechanisms
 
for Boraflex include (1) gamma flux, which changes the material characteristics
 
of the base polymer, and (2) chemical environment, namely the accessibility
 
of water to the Boraflex.
 
The licensee has not drawn firm conclusions
 
as to (1) the root cause of the observed degradation
 
of Boraflex in the coupons, or (2) the correlation
 
of the behavior of Boraflex in the coupons to that in the storage racks.Degradation
 
of the Boraflex in fuel storage racks could reduce the subcriticality
 
margin in the spent fuel pool. The design basis assumes a 5 percent subcriticality
 
margin on the basis of lowest pool temperature, no boron concentration
 
in the pool water, and minimum spacing between fuel assemblies.
 
In its preliminary
 
analysis, the licensee assumed no boron in the pool water and a complete loss of Boraflex from the fuel storage racks. This reduced the subcriticality
 
margin from greater than 5 percent to about 2 percent. However, the licensee used the burnup for the currently
 
stored fuel in the criticality
 
calculation.
 
This is higher than the design burnup value, implying less reactive fuel in the fuel pool than assumed in the design calcul ation.The licensee took several compensatory
 
measures, including
 
(1) making the operating
 
staff aware not to dilute the spent fuel 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 01J0 M22 09/03/93 09/03/93 09/03/93 11 _ _ _ _ ,_C:OGCB:DORS:NRR
 
*GHMarcus
 
j I 09/03/93 09/7 /93 DOCUMENI NAME: 93-/U.IN
 
K>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 Office of Nuclear Regulatory
 
Regul 0ort at on Technical
 
Contact: Kombiz Salehi, (708) 790-5782 RIII 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 .-law. 1 OFFICE OGCB:DORS:NRR
 
DRS: RI I¢ .RP DD DR4:RIIIr SRXB:DSSA:NRR
 
: L/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 D:DSS r EMCB:DE:NRR
 
_MCB:DE:NRS
 
C: 7 U D NRR IOEAB:DORS
 
ACThada i Strosnider
 
XParczewski
 
RAHermann
 
j 0aef ffee/9 / /9 /3 /93 '1 /,3/93 § /3 /93 ___________
.. _.93 C:OGCB:DORS:NR4 D:DORS:NRR
 
GHMarcus OI M BKGrimes q/13 /93 / /93 DOCUMENT NAME: PALN0902.CVH
 
4Adr of ads? >.4 A 42XsK 4-ct-M etO 4 vJ 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
 
Technical
 
Contact: 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 rnmriIDDrrr===
*CFF DDVITNIC.3c LL. VUL J UVIRUURAJW
 
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
 
K-I Attachment
 
1 IN 93-70 September
 
10, 1993 Figure 1_Palisades
 
Boraflex a Coupon Types a Bodfes mate w boned bloom two I 3 Shoet M Paf kn*Q Ii..I I 3i i 3_..I: I --I 39r Ia le i ! 2 I I I4 i..4 I.I I E Li
 
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 93-68 92-16, Supp. 2 93-67 93-66 93-65 93-64 93-63 Radiography
 
Events at Operating
 
Power Reactors Failure of Pump Shaft Coupling Caused by Temper Embrittlement
 
during Manufacture
 
Loss of Flow from the Residual Heat Removal Pump during Refueling Cavity Draindown Bursting of High Pressure Coolant Injection
 
Steam Line Rupture Discs Injures Plant Personnel Switchover
 
to Hot-Leg Injection
 
Following A Loss-of-Coolant
 
Accident in Pres-surized Water Reactors Reactor Trips Caused by Breaker Testing with Fault Protection


IN 93-70September 10, 1993 spent fuel pool chemistry sampling frequency to daily, and (3) keeping theboron concentration in the spent fuel pool above 1800 ppm, which exceeds thetechnical specification requirement for boron concentration. With theseprecautions a subcriticality margin greater than 5 percent would bemaintained.Degradation of Boraflex has been previously addressed by NRC in InformationNotice 87-43, "Gaps in Neutron-Absorbing Material in High-Density Spent FuelStorage Racks," September 8, 1987. The Electric Power Research Institute,which has been studying this phenomenon for several years, has recentlypublished an interim report, "Boraflex Test Results and Evaluation,"TR-101986, February 1993.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.(~/'Bran Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Regulatory RegulationTechnical contacts: Kombiz Salehi, RIII(708) 790-5782K. I Parczewski, NRR(301) 504-2705Larry Kopp, NRR(301) 504-2879Vern Hodge, NRR(301) 504-1861Attachments:1. Figure 1, Palisades Boraflex Coupon Types2. List of Recently Issued NRC Information Notices
Bypassed Periodic Testing and Preventive


IN 93-70.- tSeptember 10, 1993 spent fuel pool chemistry sampling frequency to daily, and (3) keeping theboron concentration in the spent fuel pool above 1800 ppm, which exceeds thetechnical specification requirement for boron concentration. With theseprecautions a subcriticality margin greater than 5 percent would bemaintained.Degradation of Boraflex has been previously addressed by NRC in InformationNotice 87-43, "Gaps in Neutron-Absorbing Material in High-Density Spent FuelStorage Racks," September 8, 1987. The Electric Power Research Institute,which has been studying this phenomenon for several years, has recentlypublished an interim report, "Boraflex Test Results and Evaluation,"TR-101986, February 1993.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office ofNuclear Reactor Regulation (NRR) project manager.Original signed UyMaian K. Grime$Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Regulatory RegulationTechnical contacts: Kombiz Salehi, RIII(708) 790-5782K. I Parczewski, NRR(301) 504-2705Larry Kopp, NRR(301) 504-2879Vern Hodge, NRR(301) 504-1861Attachments:1. Figure 1, Palisades Boraflex Coupon Types2. List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCEOFFICE OGCB:DORS:NRR DRS:RIII DD:DRS:RIII SRXB:DSSA:NRR C:SRXB:DSSA:NRRNAME *CVHodge *KSalehi *WLForney *LIKopp *RCJonesDATE 09/02/93 09/02/93 09/02/93 09/03/93 09/03/93Tech Ed D:DSSA EMCB:DE:NRR EMCB:DE:NRR C:EMCB:DE:NRR C:OEAB:DORS*DGable *ACThadani *JStrosnider *KlParczewski *RAHermann *AEChaffee09/01/93 09/04/93 01J0 M22 09/03/93 09/03/93 09/03/9311 _ _ _ _ ,_C:OGCB:DORS:NRR*GHMarcus j I09/03/93 09/7 /93DOCUMENI NAME: 93-/U.IN
Maintenance


K>IN 93-xx ISeptember xx, 993This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactone of the technical contacts listed below or the appropriate Office of !Nuclear Reactor Regulation (NRR) project manager. IBrian K. Grimes, DirectorDivision of Operating Reactor SupiOffice of Nuclear Regulatory Regul0ortat on
of Molded Case Circuit Breakers Improper Use of Soluble Weld Purge Dam Material 09/02/93 09/01/93 08/23/93 08/16/93 08/16/93 08/13/93 All holders of OLs or CPs for nuclear power reactors and all radiography


===Technical Contact:===
licensees.
Kombiz Salehi,(708) 790-5782RIIIK. I Parczewski, NRR(301) 504-2705Larry Kopp, NRR(301) 504-2879Vern Hodge, NRR(301) 504-1861Attachments:1. Figure 1, Palisades Boraflex Coupon Types2. List of Recently Issued NRC Information Notices*SEE PREVIOUS CONCURRENCE... ..... -..' at .-law. 1OFFICEOGCB:DORS:NRRDRS: RI I¢ .RPDD DR4:RIIIrSRXB:DSSA:NRR: L/C:SRXB:DSSA:NRRLNAME CVHodge KSalehi WLForney LIKop RC ones,DATE O /l2/93 CO/72/93 £ /O2I93 7/3 /93 /3 /93*Tech Ed D:DSS r EMCB:DE:NRR _MCB:DE:NRS C: 7 U D NRR IOEAB:DORSACThada i Strosnider XParczewski RAHermann j 0aef ffee/9 / /9 /3 /93 '1 /,3/93 § /3 /93 ___________.. _.93C:OGCB:DORS:NR4D:DORS:NRRGHMarcus OI M BKGrimesq/13 /93 / /93DOCUMENT NAME: PALN0902.CVH4Adr of ads? >.4 A 42XsK 4-ct-M etO 4 vJIN 93-xxSeptember xx, 993The licensee took several compensatory measures, including (1) making theoperating staff aware to not dilute the spent fuel pool, (2) increasing thespent fuel pool chemistry sampling frequency to daily, and (3) keeping theboron concentration in the spent fuel pool above 1800 ppm, which exceeds thetechnical specification requirement for boron concentration.Degradation of Boraflex has been previously addressed by NRC in InformationNotice 87-43, "Gaps in Neutron-Absorbing Material in High-Density Spent FuelStorage Racks," September 8, 1987. The Electric Power Research Institute, whohas been studying this phenomenon for several years, has recently published aninterim report, "Boraflex Test Results and Evaluation," TR-101986, February1993.This information notice requires no specific action or written response. Ifyou have any questions about the information in this notice, please contactthe technical contact listed below or the appropriate Office of NuclearReactor Regulation (NRR) project manager.Brian K. Grimes, DirectorDivision of Operating Reactor SupportOffice of Nuclear Regulatory Regulation


===Technical Contact:===
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.All holders of OLs or CPs for pressurized
Kombiz Salehi, RIII(708)790-5782K. I Parczewski, NRR Larry Kopp, NRR Vern Hodge, NRR(301) 504-2705 (301) 504-2879 (301) 504-1861Attachments:1. Figure 1, Palisades Boraflex Coupon Types2. List of Recently Issued NRC Information NoticesrnmriIDDrrr*CFF DDVITNIC.3c LL. VUL J UVIRUURAJWOFFICE lOGCB:DORS:NRR DRS:RIII D:DRS:RIII SRXB:DSSA:NRR C:SRXB:DSSA:NRRNAME CVHodge Ug KSalehi TOMartin LIKopp RCJonesDATE Oq/ol0/93 / /93 / /93 /93 /93Tech Ed D:DSSA EMCB:DE:NRR EMCB:DE:ND C:EMCB:DE:NRR C:OEAB:DORSq j ACTHADANI JStrosnider KIParczews'ki RAHermann AEChaffee____ /93 /_/93 /_/93 9 /l/93 /L/93 / /93C:OGCB:DORS:NRRD:DORS:NRRGHMarcus [BKGrimes/ /93 J / /93DOCUMENT NAME: PALNOFIG.CVH


K-IAttachment 1IN 93-70September 10, 1993 Figure 1_Palisades Boraflex aCoupon TypesaBodfes mate wboned bloom twoI3Shoet M Paf kn*QIi..I I3i i3_..I:I --I39r Iale i ! 2III4 i..4I.IIE Li
water reactors.Al 1 for holders of OLs or CPs nuclear power reactors.08/12/93 08/11/93 All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.* OL = Operating


Axtachment 2IN 93-70September 10, 1993Page 1 of ILIST OF RECENTLY ISSUEDNRC INFORMATION NOTICESInformation Date ofNotice No. Subject Issuance Issued to93-6993-6892-16,Supp. 293-6793-6693-6593-6493-63Radiography Events atOperating Power ReactorsFailure of Pump ShaftCoupling Caused byTemper Embrittlementduring ManufactureLoss of Flow from theResidual Heat RemovalPump during RefuelingCavity DraindownBursting of HighPressure CoolantInjection Steam LineRupture Discs InjuresPlant PersonnelSwitchover to Hot-LegInjection FollowingA Loss-of-CoolantAccident in Pres-surized Water ReactorsReactor Trips Causedby Breaker Testingwith Fault ProtectionBypassedPeriodic Testing andPreventive Maintenanceof Molded Case CircuitBreakersImproper Use of SolubleWeld Purge Dam Material09/02/9309/01/9308/23/9308/16/9308/16/9308/13/93All holders of OLs or CPsfor nuclear power reactorsand all radiographylicensees.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor pressurized waterreactors.Al 1forholders of OLs or CPsnuclear power reactors.08/12/9308/11/93All holders of OLs or CPsfor nuclear power reactors.All holders of OLs or CPsfor nuclear power reactors.* OL = Operating LicenseCP = Construction Permit
License CP = Construction


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Permit}}


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Revision as of 13:56, 31 August 2018

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  Entergy icon.png
Issue date: 09/10/1993
From: Grimes B K
Office of Nuclear Reactor Regulation
To:
References
-nr IN-93-070, NUDOCS 9309070206
Download: ML031070107 (9)
v • d • e


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

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 recipients

to a potentially

significant

problem pertaining

to degradation

of Boraflex neutron absorber coupons. 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.Background

Palisades

has high-density

fuel storage racks installed

in the spent fuelpool that use Boraflex, a proprietary

neutron absorbing

material that was manufactured

by Brand Industrial

Services, Incorporated (BISCO). The storage racks are supplied by Westinghouse.

The Boraflex is attached to the walls of each canister and is held in place by a stainless

steel wrapper, which is spot welded to the walls.The licensee has a surveillance

program using Boraflex coupons to indicate the status of the Boraflex contained

in the high density storage racks in the spent fuel pool. Recently observed degradation

of several of these coupons, which may be due to exposure to high level gamma radiation

in conjunction

with interaction

with pool water, raised questions

about the integrity

of the Boraflex contained

in the storage racks. Significant

loss of Boraflex in the high-density

fuel racks could result in loss of the subcriticality

margin in the spent fuel pool. 'Through a commitment

to the NRC, Palisades

was required to test and inspect the Boraflex coupons after 5 years of use. The tests include opening the coupons for visual observation, neutron attenuation

determination, and a Boraflex hardness test.DescriDtion

of Circumstances

During a period from August 17 through 19, 1993, 5 of the existing 10 Boraflex coupons were removed from the spent fuel pool, 4 being full-length

coupons 9309070206 Phi tE 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

coupons revealed that one coupon had lost an estimated

90 percent of its Boraflex, two others 50 percent, and one 38 percent. Investigation

of the short-set

coupon showed that it had retained 100 percent of its Boraflex.

The licensee has determined

that the Boraflex in the 4 full-length

coupons and the short-set

coupon came from different

lots of material.A principal

difference

between the short-set

and the full-length

coupons is their geometrical

design. The short-set

coupon consists of eight compartments

encapsulating

the Boraflex with pool water accessing

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

coupon Boraflex is sandwiched

axially over the entire length of coupon and bolted between two 0.51-mm [0.020-inch]

stainless

steel metal strips. The licensee postulated

that a much larger area of the full-length

coupon was exposed to the pool water environment

and flow.In addition, the full-length

coupon has a 12.7-mm [0.5-inch]

hole through the metal strip on the top portion of the coupon, which contributes

to the pool water flow around the Boraflex.

The licensee has no immediate

plans for removal or testing of the remaining

five coupons in the spent fuel pool, but does intend to conduct neutron "blackness" testing in the spring of 1994.The licensee also had initiated

measurements

of the silica content of the spent fuel pool water. No increase in silica above normal 1-4 ppm levels have been observed except in instances

when the pool boron concentration

was increased.

Because silica filler material is a constituent

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

of degradation

of the Boraflex in the fuel pool.Discussion

Potential

degradation

mechanisms

for Boraflex include (1) gamma flux, which changes the material characteristics

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

of water to the Boraflex.

The licensee has not drawn firm conclusions

as to (1) the root cause of the observed degradation

of Boraflex in the coupons, or (2) the correlation

of the behavior of Boraflex in the coupons to that in the storage racks.Degradation

of the Boraflex in fuel storage racks could reduce the subcriticality

margin in the spent fuel pool. The design basis assumes a 5 percent subcriticality

margin on the basis of lowest pool temperature, no boron concentration

in the pool water, and minimum spacing between fuel assemblies.

In its preliminary

analysis, the licensee assumed no boron in the pool water and a complete loss of Boraflex from the fuel storage racks. This reduced the subcriticality

margin from greater than 5 percent to about 2 percent. However, the licensee used the burnup for the currently

stored fuel in the criticality

calculation.

This is higher than the design burnup value, implying less reactive fuel in the fuel pool than assumed in the design calcul ation.The licensee took several compensatory

measures, including

(1) making the operating

staff aware not to dilute the spent fuel 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 01J0 M22 09/03/93 09/03/93 09/03/93 11 _ _ _ _ ,_C:OGCB:DORS:NRR

  • GHMarcus

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

K>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 Office of Nuclear Regulatory

Regul 0ort at on Technical

Contact: Kombiz Salehi, (708) 790-5782 RIII 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 .-law. 1 OFFICE OGCB:DORS:NRR

DRS: RI I¢ .RP DD DR4:RIIIr SRXB:DSSA:NRR

L/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 D:DSS r EMCB:DE:NRR

_MCB:DE:NRS

C: 7 U D NRR IOEAB:DORS

ACThada i Strosnider

XParczewski

RAHermann

j 0aef ffee/9 / /9 /3 /93 '1 /,3/93 § /3 /93 ___________

.. _.93 C:OGCB:DORS:NR4 D:DORS:NRR

GHMarcus OI M BKGrimes q/13 /93 / /93 DOCUMENT NAME: PALN0902.CVH

4Adr of ads? >.4 A 42XsK 4-ct-M etO 4 vJ 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

Technical

Contact: 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 rnmriIDDrrr

  • CFF DDVITNIC.3c LL. VUL J UVIRUURAJW

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

K-I Attachment

1 IN 93-70 September

10, 1993 Figure 1_Palisades

Boraflex a Coupon Types a Bodfes mate w boned bloom two I 3 Shoet M Paf kn*Q Ii..I I 3i i 3_..I: I --I 39r Ia le i ! 2 I I I4 i..4 I.I I E Li

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 93-68 92-16, Supp. 2 93-67 93-66 93-65 93-64 93-63 Radiography

Events at Operating

Power Reactors Failure of Pump Shaft Coupling Caused by Temper Embrittlement

during Manufacture

Loss of Flow from the Residual Heat Removal Pump during Refueling Cavity Draindown Bursting of High Pressure Coolant Injection

Steam Line Rupture Discs Injures Plant Personnel Switchover

to Hot-Leg Injection

Following A Loss-of-Coolant

Accident in Pres-surized Water Reactors Reactor Trips Caused by Breaker Testing with Fault Protection

Bypassed Periodic Testing and Preventive

Maintenance

of Molded Case Circuit Breakers Improper Use of Soluble Weld Purge Dam Material 09/02/93 09/01/93 08/23/93 08/16/93 08/16/93 08/13/93 All holders of OLs or CPs for nuclear power reactors and all radiography

licensees.

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.All holders of OLs or CPs for pressurized

water reactors.Al 1 for holders of OLs or CPs nuclear power reactors.08/12/93 08/11/93 All holders of OLs or CPs for nuclear power reactors.All holders of OLs or CPs for nuclear power reactors.* OL = Operating

License CP = Construction

Permit


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