Information Notice 1995-38, Degradation of Boraflex Neutron Absorber in Spent Fuel Storage Racks
-
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555-0001
September 8, 1995
DEGRADATION OF BORAFLEX NEUTRON ABSORBER IN
SPENT FUEL STORAGE RACKS
Addressees
All holders of operating licenses or construction permits for nuclear power
reactors.
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees to a potentially significant problem pertaining to
degradation of the Boraflex neutron absorber material in spent fuel storage
racks. 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
Degradation of Boraflex has been previously addressed by the NRC in
Information Notice (IN) 87-43, "Gaps in Neutron-Absorbing Material in High- Density Spent Fuel Storage Racks," September 8, 1987, and IN 93-70,
"Degradation of Boraflex Neutron Absorber Coupons," September 10, 1993. The
Electric Power Research Institute (EPRI) has been studying the phenomenon of
Boraflex degradation for several years and recently issued EPRI report
TR-103300, "Guidelines for Boraflex Use in Spent-Fuel Storage Racks,"
December 1993, identifying two issues with respect to using Boraflex in spent
fuel storage racks. The first related to gamma radiation-induced shrinkage of
Boraflex and the potential to develop tears or gaps in the material. The
second concerned gradual long-term Boraflex degradation over the intended
service life of the racks as a result of gamma irradiation and exposure to the
spent fuel pool environment. This second issue has previously been observed
in degradation of Boraflex surveillance coupons at the Palisades plant
(IN 93-70), but further testing of the actual Palisades storage racks
indicated no similar degradation. Because of the relatively watertight
Boraflex panel enclosures in most spent fuel storage rack designs, this type
of degradation was typically not previously considered.
The potential exists for a gradual release of silica and boron carbide from
Boraflex following gamma irradiation and long-term exposure to the spent fuel
pool environment. When Boraflex is subjected to gamma radiation in the
aqueous environment of the pool, the silicon polymer matrix becomes degraded
and silica filler and boron carbide are released.
Because Boraflex is
9509050009 2.d I o q
I¶I
PcMk~.0t 9S-t3r
Q4Qp
- °?
iv> IN 95-38 September 8, 1995 composed of approximately 25 percent silica, 25 percent polydimethyl siloxane
polymer, and 50 percent boron carbide, the presence of silica in the pool
provides an indication of depletion of boron carbide from Boraflex. The loss
of boron carbide (washout) from Boraflex is characterized by slow dissolution
of the silica from the surface of the Boraflex and a gradual thinning of the
material. In a typical spent fuel pool, the irradiated Boraflex represents a
significant source of silica (several thousand kilograms) and is the most
likely source of pool silica contamination.
The boron carbide loss will
result in an increase in the reactivity of the matrix of fuel and Boraflex in
the spent fuel pool.
EPRI report TR-103300 has identified several factors that influence the rate
of silica release from Boraflex. The presence of water around the Boraflex
panels is perhaps the most significant factor influencing the rate of silica
dissolution from Boraflex.
Because of the different rack designs, this rate
will vary from plant to plant. The rate of dissolution also increases with
higher pool temperature and gamma exposure, suggesting that Boraflex
degradation can be reduced by keeping pool temperatures low and by not placing
freshly discharged fuel assemblies in the same storage cells at each refueling
outage.
Description of Circumstances
The South Texas Project, Unit 1, has fuel storage racks installed in the spent
fuel pool that use Boraflex as a neutron absorber. The pool contains two rack
types. The Region 1 racks are designed to receive high reactivity fuel
assemblies, including fresh fuel, and use Boraflex panels in a removable
stainless steel box.
The Region 2 racks are designed for low reactivity spent
fuel assembly storage and contain fixed Boraflex panels between the cell
walls. The Boraflex panels were designed to ensure that adequate negative
reactivity would be maintained if the pool were accidentally flooded with
unborated water.
Blackness (neutron absorption) testing was performed during August 1994 on
selected South Texas Project Unit I spent fuel pool storage racks to determine
the condition of the Boraflex and to determine the size and location of any
gaps that may have developed. However, in addition to gap development, which
is a known phenomenon, the results also indicated that the Boraflex had
significantly degraded due to a decrease of the boron content in several of
the storage cells tested. Of the eight cells that had been designated to
receive an accelerated gamma dose in Region 1, five cells exhibited large
areas of degradation (0.9 to 1.4 meters [3 to 4.5 feet] in length) postulated
to result from accelerated dissolution of the Boraflex caused by pool water
flow through the panel enclosures as well as the high accumulated gamma dose.
Similar Boraflex degradation was discovered at the Fort Calhoun Station. As
part of their rerack project, the old spent fuel storage racks containing
Boraflex were removed and disassembled in December 1994 to determine the
condition of the Boraflex.
Two cells from the removed Boraflex racks which
had experienced the highest gamma flux since 1983 were inspected. Only
40 percent of the Boraflex remained in one of the panels from these cells
while another panel in the same cell exhibited no loss of Boraflex. An
s> < IN 95-38 September 8, 1995 adjacent cell had a panel which had some Boraflex loss but subsequent
attenuation and density tests confirmed that the average boron-10 areal
density still exceeded the material minimum certifications.
The new Fort
Calhoun Station storage racks do not contain Boraflex.
Discussion
Because Boraflex is used in the South Texas Project spent fuel storage racks
for absorption of neutrons, a reduction in the amount of Boraflex could result
in an increase in the reactivity of the spent fuel pool configuration, which
may approach, or even exceed, the current NRC acceptance criterion of k~ff no
greater than 0.95.
In response to the identified Boraflex problem, Houston Lighting & Power
Company, the licensee for the South Texas Project, developed restrictions to
not use the substantially degraded storage cells in Region 1 for discharged
spent fuel.
In addition, the licensee is developing a long-term neutron
absorption panel management plan, as well as a dose-to-degradation
correlation, which will aid in establishing restrictions for use of the spent
fuel racks in both Units 1 and 2. The licensee also cited criticality
analyses that showed that the fuel will remain subcritical by at least
5 percent, even with no Boraflex, as long as the soluble boron concentration
is at least 2,500 ppm.
Although pressurized-water reactor spent fuel pool water is normally borated
to approximately 2,000 ppm of boron, current regulatory requirements do not
allow credit for the soluble boron except under accident conditions. Many
boiling-water reactor (BWR) storage racks also contain Boraflex.
Because BWR
spent fuel pool water does not contain boron, any significant Boraflex
degradation in a BWR pool may challenge the 5 percent subcritical margin.
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.
n'Mis
.Crut
tor
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Laurence I. Kopp, NRR
(301) 415-2879
K. I. Parczewski, NRR
(301) 415-2705 Attachment:
List of Recently Issued NRC Information Notices
A~I.' fref
A,.Achment
September 8, 1995 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information
Date of
Notice No.
Subject
Issuance
Issued to
95-37
95-36
95-35
95-34
93-83, Supp. 1
95-33
95-10,
Supp. 2
95-32
95-31
Inadequate Offsite Power
System Voltages during
Design-Basis Events
Potential Problems with
Post-Fire Emergency
Lighting
Degraded Ability of
Remove Decay Heat by
Natural Circulation
Air Actuator and Supply
Air Regulator Problems in
Copes-Vulcan Pressurizer
Power-Operated Relief Valves
Potential Loss of Spent
Fuel Pool Cooling After a
Loss-of-Coolant Accident
Switchgear Fire and
Partial Loss of Offsite
Power at Waterford
Generating Station, Unit 3
Potential for Loss of
Automatic Engineered
Safety Features Actuation
Thermo-Lag 330-1 Flame
Spread Test Results
Motor-Operated Valve
Failure Caused by Stem
Protector Pipe Inter- ference
09/07/95
08/29/95
08/28/95
08/25/95
08/24/95
08/23/95
08/11/95
08/10/95
08/09/95
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 (PWRs).
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 nuclear power reactors.
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
'V September 8, 1995 adjacent cell had a panel which had some Boraflex loss but subsequent
attenuation and density tests confirmed that the average boron-10'areal
density still exceeded the material minimum certifications. The new Fort
Calhoun Station storage racks do not contain Boraflex.
Discussion
Because Boraflex is used in the South Texas Project spent fuel storage racks
for absorption of neutrons, a reduction in the amount of Boraflex could result
in an increase in the reactivity of the spent fuel pool configuration, which
may approach, or even exceed, the current NRC acceptance criterion of kff no
greater than 0.95.
In response to the identified Boraflex problem, Houston Lighting & Power
Company, the licensee for the South Texas Project, developed restrictions to
not use the substantially degraded storage cells in Region 1 for discharged
spent fuel.
In addition, the licensee is developing a long-term neutron
absorption panel management plan, as well as a dose-to-degradation
correlation, which will aid in establishing restrictions for use of the spent
fuel racks in both Units 1 and 2. The licensee also cited criticality
analyses that showed that the fuel will remain subcritical by at least
5 percent, even with no Boraflex, as long as the soluble boron concentration
is at least 2,500 ppm.
Although pressurized-water reactor spent fuel pool water is normally borated
to approximately 2,000 ppm of boron, current regulatory requirements do not
allow credit for the soluble boron except under accident conditions. Many
boiling-water reactor (BWR) storage racks also contain Boraflex.
Because BWR
spent fuel pool water does not contain boron, any significant Boraflex
degradation in a BWR pool may challenge the 5 percent subcritical margin.
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.
orig /s/'d by DMCrutchfield
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Laurence I. Kopp, NRR
(301) 415-2879
K. I. Parczewski, NRR
(301) 415-2705 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME:
95-38.IN
- See previous concurrence
To receive a copy of this docurnent, Indicate In
the box: wCw a Copy without attachmentlenclosure
'E' = Copy with attachment/enclosure 'N' = No copy
-
-
OFFICE
RXB:DSSA
E EMCB:DE
E OECB:DOPS
E ADM:PUB
N SC/EMCB:DE m
NAME
LIKopp*
J
KIParczewski*
PCWen*
Tech Editor*
RAHermann*
DATE
06/27/95
06/28/95
06/27/95
06/27/95
06/29/95 OFFICE
C/EMCB:DE
E CDSSA
E SC/PECB:DRPM
N
NAME
JRStrosnider*
EWWEiss*
RCJones*
GMHolahan*
EFGoodwin*
DATE
107/03/955/95
07/07/95
08/02/95
08/03/9 OFFICE
PECB:DRPM
lE C/PECB:DRPM
N D/DRP
i
111 NAME
RJKiessel*
AEChaffee*
DCrut efibld
_
DATE
08/21/95
08/25/95
09/ Ir/95
OFFICIAL RECORD COPY
- ~ IN 95-XX
August xx, 1995 attenuation and density tests confirmed that the average boron-10 areal
density still exceeded the material minimum certifications.
The new Fort
Calhoun Station storage racks do not contain Boraflex.
Discussion
Because Boraflex is used in the South Texas Project spent fuel storage racks
for absorption of neutrons, a reduction in the amount of Boraflex could result
In an increase in the reactivity of the spent fuel pool configuration, which
may approach, or even exceed, the current NRC acceptance criterion of keff no
greater than 0.95.
In response to the identified Boraflex problem, Houston Lighting & Power
Company, the licensee for the South Texas Project, developed restrictions to
not use the substantially degraded storage cells in Region 1 for discharged
spent fuel. In addition, the licensee is developing a long-term neutron
absorption panel management plan, as well as a dose-to-degradation
correlation, which will aid in establishing restrictions for use of the spent
fuel racks in both Units 1 and 2. The licensee also cited criticality
analyses that showed that the fuel will remain subcritical by at least 5 percent, even with no Boraflex, as long as the soluble boron concentration is
at least 2,500 ppm.
Although pressurized-water reactor spent fuel pool water is normally borated
to approximately 2,000 ppm of boron, current regulatory requirements do not
allow credit for the soluble boron except under accident conditions. Many
boiling-water reactor (BWR) storage racks also contain Boraflex.
Because BWR
spent fuel pool water does not contain boron, any significant Boraflex
degradation in a BWR pool may challenge the 5-percent subcritical margin.
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.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: Laurence I. Kopp, NRR
(301) 415-2879
K. I. Parczewski, NRR
(301) 415-2705 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\\PETER\\BORAFLEX.IN
- See previous concurrence
To receive a copy of this document, indicate In the box: wCw -
Copy without attachment/enclosure
E = Copy with attachment/enclosure
"NF - No copy
OFFICE
SRXB:DSSA
E EMCB:DE
E OECB:DOPS
E ADM:PUB
N SC/EMCB:DE LE
NAME
LIKopp*
KI Parczewski*
PCWen*
Tech Editor*
RAHermann*
DATE
06/27/95
106/28/95
06/27/95
06/27/95
06/29/95 OFFICDE
IC,
E
E/SRXB:DSSA
I /DSSA l IE
SC/PECB:DRPM
N
NAME
IJRStrosnider*
EWWEiss*
RCJones*
GMHolahan*
EFGoodwin*
E07/05/95
07/07/95
08/02/95
08/03/95 OFFICE
PECB:DRPM
E C/PECB:DRPM
N D/DRPM
L
NAME
RJKessel*
AEChaffee*i
DCrutchfield
DATE
08/21/95
08/25/95
/
/95
OFFICIAL RECORD COPY
+\\ a\\5b
IN 95-XX
August xx, 1995 the material minimum certifications. No other storage cells exhibited as
significant a loss of Boraflex. The new Fort Calhoun Station storage racks do
not contain Boraflex.
Discussion
Because Boraflex is used in the South Texas Project spent fuel storage racks
for nonproductive absorption of neutrons, a reduction in the amount of
Boraflex could result in an increase in the reactivity of the spent fuel pool
configuration, which may approach, or even exceed, the current NRC acceptance
criterion of ke
no greater than 0.95. The NRC has established this
5-percent subcrgticality margin to comply with General Design Criterion 62,
"Prevention of Criticality in Fuel Storage and Handling."
In response to the identified Boraflex problem, Houston Lighting & Power
Company, the licensee for the South Texas Project, developed restrictions to
not use the substantially degraded storage cells in Region 1 for discharged
spent fuel. In addition, the licensee is developing a long-term neutron
absorption panel management plan, as well as a dose-to-degradation
correlation, which will aid in establishing restrictions for use of the spent
fuel racks in both Units 1 and 2. The licensee also cited criticality
analyses that showed that the fuel will remain subcritical by at least 5 percent, even with no Boraflex, as long as the soluble boron concentration is
at least 2,500 ppm.
Although pressurized-water reactor spent fuel pool water is normally borated
to approximately 2,000 ppm of boron, current regulatory requirements do not
allow credit for the soluble boron except under accident conditions. Many
boiling-water reactor (BWR) storage racks also contain Boraflex. Because BWR
spent fuel pool water does not contain boron, any significant Boraflex
degradation in a BWR pool may provide a more significant challenge to the
5-percent subcritical margin.
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.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts: Laurence I. Kopp, NRR
(301) 415-2879
K. I. Parczewski, NRR
(301) 415-2705 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\\PETER\\BORAFLEX.IN
- See previous concurrence
To receive a copy of this document, Indicate In
the box: AC.
- Copy without attachnent/enclosure
'Ed
- Copy with attachmentlenciosure 'N' - No copy
OFFICE
SRXB:DSSA
E
K
M
j]E
jj
OECB:DOPS
E ADM:PUB
I N SC/EMCB:DE-l E
NAME
LIKopp*
KIParczewski*
PCWen*
Tech Editor*
jRAHermann*
DATE
06/27/95
06/28/95
06/27/95
06/27/95
106/29/95 OFFICE
C/EMCB:D
E
IE C/SRXB:DSSA
[E
D/DSSA
I
[ SC/PECB:DRPM
N
NAME
JRStrosnider*
EWWEiss*
RCJones*
GEFGoodwi*
DATE
107/03/95
07/05/95
07_07_95
_
08/02/95____
_
__
__
OFFICE
PECB:DRPM
E C/PEW.
I
D/DRPM
NAME
RJKiessel*
AECt
-,e
DCrutchfield
l
_l
DATE
08/21/95 I/
/95
/
/95
_
IN 95-XX
August xx, 1995 In response to the identified Boraflex problem, Houston Lighting & Power
Company, the licensee for the South Texas Project, developed restrictions not
to use the substantially degraded storage cells in Region 1 for discharged
spent fuel.
In addition, the licensee is developing a long-term neutron
absorption panel management plan, as well as a dose-to-degradation
correlation, which will aid in establishing restrictions for use of the spent
fuel racks in both Units 1 and 2. The licensee also cited criticality
analyses that showed that the racks will remain subcritical by at least 5 percent, even with no Boraflex, as long as the soluble boron concentration is
at least 2,500 ppm.
Although pressurized-water reactor spent fuel pool water is normally borated
to approximately 2,000 ppm of boron, current regulatory requirements do not
allow credit for the soluble boron except under accident conditions.
Many
boiling-water reactor (BWR)
storage racks also contain Boraflex.
Because BWR
spent fuel pool water does not contain boron, any significant Boraflex
degradation in a BWR pool may more realistically challenge the 5-percent
subcritical margin.
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.
Dennis M. Crutchfield, Director
Division of Reactor Program Management
Office of Nuclear Reactor Regulation
Technical contacts:
Laurence I. Kopp, NRR
(301) 415-2879
K. I. Parczewski, NRR
(301) 415-2705 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME:
G:\\PETER\\BORAFLEX.IN
To receive a copy of this document, Indicate In the box: 'C' -
Copy without attachment/enclosure
'E
Copy with attachment/enclosure
'N' - No copy
OFFICE
SRXB:DSSA
I E EMCB:DE
E OECB:DOPS
EADM:PUB
SC/EMCB:DE
E
NAME
LIKopp*
KIParczewskl*
PCWen*
Tech Editor*
RAHermann*
DATE
6/27/95
6/28/95
6/27/95
6/27/95
6/29/95 OFFICE
C/EMCB:DE
I E JSC/SRXB:DSSA
C/SRXB:DSSA
E D/DSSA
SC/PECB:DRPM
NAME
JRStrosnider*
IEWWEiss*
RCJones*
GMHolahan*
EEGoodwin
DATE
7/3 /95
1 7/5,q
7/7/95
8/2/95 t:di/95 OFFICE
PECB:DRPM
"
i
JWCB:DRPM
I
D/DRPM
I
NAME
lRJKiesselAEChaffee ATg3
DMCrutchfield
DATE
/S/9F
1 K
I
/95
/95
/I
OFFICIAL RECORD COPY
- See previous concurrence
V
-> IN 95-XX
July xx, 1995 In response to the identified Boraflex problem, Houston Lighting & Power
Company, the licensee for the South Texas Project, developed restrictions not
to use the substantially degraded storage cells in Region 1 for discharged
spent fuel. In addition, the licensee is developing a long-term neutron
absorption panel management plan, as well as a dose-to-degradation
correlation, which will aid in establishing restrictions for use of the spent
fuel racks in both Units 1 and 2. The licensee also cited criticality
analyses that showed that the racks will remain subcritical by at least 5 percent, even with no Boraflex, as long as the soluble boron concentration is
at least 2,500 ppm.
Although pressurized-water reactor spent fuel pool water is normally borated
to approximately 2,000 ppm of boron, current regulatory requirements do not
allow credit for the soluble boron except under accident conditions. Many
boiling-water reactor (BWR) storage racks also contain Boraflex.
Because BWR
spent fuel pool water does not contain boron, any significant Boraflex
degradation in a BWR pool may more realistically challenge the 5-percent
subcritical margin.
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.
Brian K. Grimes, Director
Division of Project Support
Office of Nuclear Reactor Regulation
Technical contacts:
Laurence I. Kopp, NRR
(301) 415-2879
K. I. Parczewski, NRR
(301) 415-2705 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\\PETER\\BORAFLEX.IN
To receive a copy of this document, indicate in the box:
NC" = Copy without attachment/encLosure
"E' = Copy with
attachment/enclosure
'M"
= No copy
_
__
.
_
.
OFFICE
SRXB:DSSA
E l CB:DE
j
E CB:DJP
jj A PSC/EMCB:DE I E
NAME
LIKopp*
KIParczewski*
PCWen*
Tech Editor*
RAHermann*
DATE
6/27/95
6/28/95
6/27/95
6/27/.95
1#
6/29/95 OFFICE
C/EMCB:DE
E SC/SRXB:DSSA
CSRXB:DSSA
m
ECB:DOPS
NAME
JRStrosnider*
EWWEiss*
RCJones* X
1 ah'iVEFGoodwin
DATE
7/3 /95
7/5/95
7/7/95
/
/95
95 OFFICE
OECB:DOPS
C/OECB:DOPS
D/DOPS
NAME
RJKiessel
AEChaffee
BKGrimes
II
DATE
I
/95 I
/95 I /95
OFFICIAL RECORD COPY
- See previous concurrence
DOCUMENT NAME:
G:\\PETER\\BORAFLEX.IN
To receive a copy of this
document, Indicate In the box:
C, - Copy without attachmentlenclosure
'E
- Copy with attachment/onclosure
N -
No copy
OFFICE
SRXB:DSSA
E EMCB:DE
E OECB:DOPS
E ADM:PUB([
SC/EMCB:DE
E
NAME
LIKopp*
KIParczewski*
PCWen*
Tech Editor*
RAHermann*
DATE
6/27/95
6/28/95
6/27/95
6/27/95
6/29/95 OFFICE
C/EMCB:DE
E
/SRXB:DSSA
C/SRXB;:
A E D/DSSA
SC/OECB:DOPS
NAME
JRStrosnider*
EWWEiss*
RCJonef>RPve
EFGoodwin
DATE
7/3 /95
7/5/95
7/ 7 /I
/95
/ /95 OFFICE
OECB:DOPS
C/OECB:DOPS l_ D/DOPS_
NAME
RJKiessel
AEChaffee
BKGrimes
I
DATE
/ /95
/ /95 I /95
OFFICIAL RECORD COPY
- See previous concurrence
--2 IN 95-XX
July xx, 1995 In response to the identified Boraflex problem, Houston Lighting & Power
Company, the licensee for the South Texas Project, developed restrictions not
to use the substantially degraded storage cells in Region 1 for discharged
spent fuel.
In addition, the licensee is developing a long-term neutron
absorption panel management plan, as well as a dose-to-degradation
correlation, which will aid in establishing restrictions for use of the spent
fuel racks in both Units I and 2. The licensee also cited criticality
analyses that showed that the racks will remain subcritical by at least 5 percent, even with no Boraflex, as long as the soluble boron concentration is
at least 2,500 ppm.
Although pressurized-water reactor spent fuel pool water is normally borated
to approximately 2,000 ppm of boron, current regulatory requirements do not
allow credit for the soluble boron except under accident conditions. Many
boiling-water reactor (BWR) storage racks also contain Boraflex. Because BWR
spent fuel pool water does not contain, boron, any significant Boraflex
degradation in a BWR pool may more realistically challenge the 5-percent
subcritical margin.
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.
Brian K. Grimes, Director
Division of Project Support
Office of Nuclear Reactor Regulation
Technical contacts:
Laurence I. Kopp, NRR
(301) 415-2879
K. I. Parczewski, NRR
(301) 415-2705 Attachment:
List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\\PETER\\BORAFLEX.IN
To receive a copy of this document, indicate in the box:
IC" I Copy without attachment/enclosure
"E" = Copy with
attachment/enclosure
I" I No copy
lOFFICE
SRXB:DSSA
EMECB:DOPS
E
l
SC/EMCB:DE
I]
INAME
LIKopp
KIParczewsk
PCWen
Tech Eitofr
RAHermanI_
lDATE
/97
/95 n
/8/95
6/, /j-/95
8/:)7/j95 1 OFFICE
C/EMCB:DWM IC£ SC/SRXBWA
C/SRXB:DSSA
D/DSSA
SC/OECB:DOPS
]
NAME
JRStrosni
EWWEist3 RCJones
GMHolahan
EFGoodwin
DATE
/3/9,5
7/
/
/95
/
/95
/ _/95 OFFICE
OECB:DOPS
C/OECB:DOPS
D/DOPS
1
111 NAME
RJKiessel
AEChaffee
BKGrimes
DATE
/
/95
/
/95
/
/95 OFFICIAL RECORD COPY