Information Notice 1987-43, Gaps in Neutron-Absorbing Material in High-Density Spent Fuel Storage Racks: Difference between revisions

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{{#Wiki_filter:Q->I SSINS No.: 6835 IN 87-43 UNITED STATES NUCLEAR REGULATORY
{{#Wiki_filter:- >
                                                            I


COMMISSION
Q


===OFFICE OF NUCLEAR REACTOR REGULATION===
SSINS No.:  6835 IN 87-43 UNITED STATES
WASHINGTON


D.C. 20555 September
NUCLEAR REGULATORY COMMISSION


8, 1987 NRC INFORMATION
OFFICE OF NUCLEAR REACTOR REGULATION


NOTICENO.
WASHINGTON D.C. 20555 September 8, 1987 NRC INFORMATION NOTICENO. 87-43:    GAPS IN NEUTRON-ABSORBING MATERIAL


87-43: GAPS IN NEUTRON-ABSORBING
,INHIGH-DENSITY SPENT FUEL STORAGE


MATERIAL ,IN HIGH-DENSITY
RACKS
 
SPENT FUEL STORAGE RACKS


==Addressees==
==Addressees==
:
:
All nuclear power reactor facilities
      All nuclear power reactor facilities holding an operating license or a con- struction permit.
 
holding an operating
 
license or a con-struction
 
permit.


==Purpose==
==Purpose==
: This notice is to alert recipients
:
      This notice is to alert recipients to a potentially significant problem per- taining to gaps identified in the neutron absorber component of the high- density spent fuel storage racks at Quad Cities Unit 1. The safety concern is


to a potentially
that certain gaps might excessively reduce the margin of nuclear subcriticality


significant
in the fuel pool. The NRC expects that recipients will review this notice for


problem per-taining to gaps identified
applicability to their facilities and consider actions, if appropriate, to


in the neutron absorber component
preclude a similar problem occurring at their facilities. However, suggestions


of the high-density spent fuel storage racks at Quad Cities Unit 1. The safety concern is that certain gaps might excessively
in-this notice do not constitute NRC requirements; therefore, no specific


reduce the margin of nuclear subcriticality
action or written response is required..


in the fuel pool. The NRC expects that recipients
==Description of Circumstances==
 
:
will review this notice for applicability
      On May 1, 1987, Commonwealth Edison Company (CECO), the licensee at Quad Cities
 
to their facilities
 
and consider actions, if appropriate, to preclude a similar problem occurring
 
at their facilities.
 
===However, suggestions===
in-this notice do not constitute
 
NRC requirements;
therefore, no specific action or written response is required..
 
Description
 
of Circumstances:
On May 1, 1987, Commonwealth
 
Edison Company (CECO), the licensee at Quad Cities 1 and 2, presented
 
data to the NRC regarding
 
gaps measured in Boraflex,.a
 
neutron-absorbing
 
material used in the high-density
 
fuel storage racks manufac-tured by the Joseph Oat Corporation (OAT). Boraflex is a trade name for a boron carbide dispersion
 
in an elastomeric
 
silicone matrix manufactured
 
by Bisco Products, Inc. (BISCO). Data pertaining
 
to the gap size and distribution
 
had been obtained by National Nuclear Corporation.(NNC)
under.contract
 
to CECO.The licensee had retained Northeast
 
Technology
 
Corporation (NETCO) to interpret the data. NETCO prefaced their assessment
 
as preliminary, noting that avail-able data was limited, but concluded
 
that the gap formation
 
mechanism
 
may be related to large local stresses in the Boraflex from fabrication-induced
 
re-straint within the rack and to tearing and shrinkage
 
of the material..
 
The average gap size is 1-1/2 inches, with the largest 4 inches.. The gaps occur in the.upper
 
two-thirds
 
of the cell length. -709010085 IN 87-43 September
 
8, 1987 These gaps are inferred from anomalies
 
in "blackness" testing results by NNC.The existence
 
of a gap in the Quad Cities neutron absorber panel has been confirmed
 
by underwater
 
neutron radiography
 
conducted
 
by Nusurtec, Inc.CECO also discussed
 
the effects these gaps might have on the approved safety analysis for the spent fuel storage racks. CECO used conservative
 
assumptions
 
for gap size, gap location, and fuel burnup. Considerable
 
margin in k-eff appears to be available
 
before the licensing
 
limit of 0.95 would be approached.
 
In July 1986, Wisconsin
 
Electric Company, the licensee at Point Beach 1 and 2, reported to the NRC that test coupons of Boraflex material had shown consider-able degradation


under high radiation.
1 and 2, presented data to the NRC regarding gaps measured in Boraflex,.a


However, the licensee asserted that this result did not represent
neutron-absorbing material used in the high-density fuel storage racks manufac- tured by the Joseph Oat Corporation (OAT). Boraflex is a trade name for a


the actual condition
boron carbide dispersion in an elastomeric silicone matrix manufactured by


of Boraflex used in its spent fuel storage racks because of differences
Bisco Products, Inc. (BISCO). Data pertaining to the gap size and distribution


in methods of encapsulation, sample geometry, and handling frequency.
had been obtained by National Nuclear Corporation.(NNC) under.contract to CECO.


Additionally, the coupons had been subjected
The licensee had retained Northeast Technology Corporation (NETCO) to interpret


to about 5 times more radiation
the data. NETCO prefaced their assessment as preliminary, noting that avail- able data was limited, but concluded that the gap formation mechanism may be


than is associated
related to large local stresses in the Boraflex from fabrication-induced re- straint within the rack and to tearing and shrinkage of the material..


with the average fuel rack position.
The average gap size is 1-1/2 inches, with the largest 4 inches..   The gaps


Subsequent
occur in the.upper two-thirds of the cell length.        -
                    709010085


examination
IN 87-43 September 8, 1987 These gaps are inferred from anomalies in "blackness" testing results by NNC.


of full-length
The existence of a gap in the Quad Cities neutron absorber panel has been


panels disclosed two results: in one panel examined for effects of the water environment
confirmed by underwater neutron radiography conducted by Nusurtec, Inc.


but exposed to negligible
CECO also discussed the effects these gaps might have on the approved safety


gamma radiation, there was no degradation
analysis for the spent fuel storage racks. CECO used conservative assumptions


of the Boraflex.In another panel exposed to significant
for gap size, gap location, and fuel burnup. Considerable margin in k-eff


gamma radiation, 1-2 percent of the surface showed a gray discoloration
appears to be available before the licensing limit of 0.95 would be approached.


at the edges, similar to the degradation
In July 1986, Wisconsin Electric Company, the licensee at Point Beach 1 and 2, reported to the NRC that test coupons of Boraflex material had shown consider- able degradation under high radiation. However, the licensee asserted that


of the coupons.Discussion:
this result did not represent the actual condition of Boraflex used in its
The concern is that separation


of the neutron-absorbing
spent fuel storage racks because of differences in methods of encapsulation, sample geometry, and handling frequency. Additionally, the coupons had been


material used in high density fuel storage racks might compromise
subjected to about 5 times more radiation than is associated with the average


safety. Although Quad Cities reports that its racks, even with gaps in the Boraflex as large as 4 inches, can meet the criticality
fuel rack position. Subsequent examination of full-length panels disclosed


criterion
two results: in one panel examined for effects of the water environment but


of k-eff less than or equal to 0.95, this may not be the case for larger gaps or for other plants. A list of the 31 sites using Boraflex is given in Attachment
exposed to negligible gamma radiation, there was no degradation of the Boraflex.


1. Related information
In another panel exposed to significant gamma radiation, 1-2 percent of the


is given in"Behavior
surface showed a gray discoloration at the edges, similar to the degradation


of High-Density
of the coupons.


Spent-Fuel
Discussion:
The concern is that separation of the neutron-absorbing material used in high


Storage Racks," EPRI NP-4724, Electric Power Research Institute, August 1986.Efforts to understand
density fuel storage racks might compromise safety. Although Quad Cities


the gap formation
reports that its racks, even with gaps in the Boraflex as large as 4 inches, can meet the criticality criterion of k-eff less than or equal to 0.95, this


have revealed several topics on which information
may not be the case for larger gaps or for other plants. A list of the 31 sites


is needed. Accordingly, the material supplier (BISCO) and the Electric Power Research Institute (EPRI) have undertaken
using Boraflex is given in Attachment 1. Related information is given in


research programs to collect this information.
"Behavior of High-Density Spent-Fuel Storage Racks," EPRI NP-4724, Electric


Some of their objectives
Power Research Institute, August 1986.


are described
Efforts to understand the gap formation have revealed several topics on which


below.The BISCO program aims to establish
information is needed. Accordingly, the material supplier (BISCO) and the


with increased
Electric Power Research Institute (EPRI) have undertaken research programs


accuracy the relationship
to collect this information. Some of their objectives are described below.


between radiation
The BISCO program  aims to establish with increased accuracy the relationship


dose and size changes. The program also evaluates
between radiation  dose and size changes. The program also evaluates the


the potential
potential effects  of handling and restraint, during and subsequent to the fuel


effects of handling and restraint, during and subsequent
rack fabrication, on gap formation.


to the fuel rack fabrication, on gap formation.
The EPRI program will correlate data from utilities' neutron absorber coupon


The EPRI program will correlate
surveillance programs. EPRI will further examine data obtained from CECO, as


data from utilities'
well as from BISCO and other sources, to improve the understanding of possible
neutron absorber coupon surveillance


programs.
or actual gap formation models, including the effects of rack fabrication


EPRI will further examine data obtained from CECO, as well as from BISCO and other sources, to improve the understanding
methods and irradiation damage mechanisms. The EPRI Program will also attempt


of possible or actual gap formation
IN 87-43 September 8, 1987 to model the specific Quad Cities experience considering absorbed gamma dose as a


models, including
function of axial elevation, neutron absorbing sheet restraint, and fractional


the effects of rack fabrication
change in length.


methods and irradiation
The effect of rack design and manufacturing methods on the consequences of


damage mechanisms.
stress, temperature, and chemical environment to irradiated Boraflex is uncer- tain. Recent blackness test results at Turkey Point, who uses a Westinghouse


The EPRI Program will also attempt
spent fuel storage rack, did not indicate the presence of gaps in the Boraflex.


IN 87-43 September
The research programs are designed to evaluate each consequence and, In partic- ular, to improve the understanding of stress caused by method of attachment of


8, 1987 to model the specific Quad Cities experience
the Boraflex panel to the stainless steel wall of the cell. -
Together, these programs are designed to improve the industry understanding of


considering
the safety implications of the observed gaps in the Boraflex neutron absorber


absorbed gamma dose as a function of axial elevation, neutron absorbing
component of the OAT high-density spent-fuel storage racks at Quad Cities.


sheet restraint, and fractional
No specific action or written response is required by this information notice.


change in length.The effect of rack design and manufacturing
If you have any questions about this matter, please contact the Regional


methods on the consequences
Administrator of the appropriate regional office or this office.


of stress, temperature, and chemical environment
hares E. Rossi, Director


to irradiated
_    _  -    -                        Division of Operational Events Assessment


Boraflex is uncer-tain. Recent blackness
test results at Turkey Point, who uses a Westinghouse
spent fuel storage rack, did not indicate the presence of gaps in the Boraflex.The research programs are designed to evaluate each consequence
and, In partic-ular, to improve the understanding
of stress caused by method of attachment
of the Boraflex panel to the stainless
steel wall of the cell. -Together, these programs are designed to improve the industry understanding
of the safety implications
of the observed gaps in the Boraflex neutron absorber component
of the OAT high-density
spent-fuel
storage racks at Quad Cities.No specific action or written response is required by this information
notice.If you have any questions
about this matter, please contact the Regional Administrator
of the appropriate
regional office or this office.hares E. Rossi, Director_ _ --Division of Operational
===Events Assessment===
Office of Nuclear Reactor Regulation
Office of Nuclear Reactor Regulation


Technical
Technical Contacts:      Vern Hodge


Contacts: Vern Hodge (301) 492-8196 Albert D. Morrongiello
(301) 492-8196 Albert D. Morrongiello


(309) 654-2227 Attachments:
(309) 654-2227 Attachments:
1. List of Plants Using Boraflex Structures
                                                                              Attachment 1
1. List of Plants Using Boraflex                                               IN 87-43 Structures in the Spent Fuel Pool                                      September 8, 1987
2. List of Recently Issued NRC Information Notices LIST OF PLANTS WITH BORAFLEX


in the Spent Fuel Pool 2. List of Recently Issued NRC Information
STRUCTURES IN THE SPENT FUEL POOL


Notices Attachment
1. Arkansas 1,2                        16.  Peach Bottom 2.3
                      2. Beaver Valley 1                      17.  Pilgrim


1 IN 87-43 September
3. Diablo Canyon 1,2                    18.  Pt. Beach 1,2
                      4. Calvert Cliffs 2                    19.  Pr. Island 1,2
                      5. Farley 1,2                          20.  Quad Cities 1,2*
                      6. Fermi 2*                            21.  Rancho Seco*
                      7. Ft. Calhoun                          22.  River Bend


8, 1987 LIST OF PLANTS WITH BORAFLEX STRUCTURES
8. Ginna                                23.  Robinson 2
                      9. Grand Gulf 1,2*                      24.  Summer*
                      10. McGuire 1,2                          25.  Trojan


IN THE SPENT FUEL POOL 1. Arkansas 1,2 2. Beaver Valley 1 3. Diablo Canyon 1,2 4. Calvert Cliffs 2 5. Farley 1,2 6. Fermi 2*7. Ft. Calhoun 8. Ginna 9. Grand Gulf 1,2*10. McGuire 1,2 11. Millstone
11. Millstone 1,2,3                      26.  Turkey Pt. 3,4
                      12. Nine Ni. Pt. 1,2                     27.  Waterford 3
                      13. North Anna 1,2                       28. Seabrook 1,2
                      14. Oconee 1,2,3                        29. Watts Bar 1,2
                      15. Oyster Creek*                       30. Comanche Peak 1,2
                                                              31.   Harris


1,2,3 12. Nine Ni. Pt. 1,2 13. North Anna 1,2 14. Oconee 1,2,3 15. Oyster Creek*16. Peach Bottom 2.3 17. Pilgrim 18. Pt. Beach 1,2 19. Pr. Island 1,2 20. Quad Cities 1,2*21. Rancho Seco*22. River Bend 23. Robinson 2 24. Summer*25. Trojan 26. Turkey Pt. 3,4 27. Waterford
*Plants having spent fuel storage racks fabricated by Joseph Oat Corporation.


3 28. Seabrook 1,2 29. Watts Bar 1,2 30. Comanche Peak 1,2 31. Harris*Plants having spent fuel storage racks fabricated
/                                                        \_J    Attachment 2 IN 87-43 September 8, 1987 LIST OF RECENTLY ISSUED


by Joseph Oat Corporation.
INFORMATION NOTICES 1987 Tnfnrwmtinn                                    n.._ --
                                                                                    uasu    or


/ \_J Attachment
Noti c  No.    Subfect                          Issuance        Issued to


2 IN 87-43 September
87-42          Diesel Generator Fuse            9/4/87          All nuclear power


8, 1987 LIST OF RECENTLY ISSUED INFORMATION
Contacts                                          reactor facilities


NOTICES 1987 Tnfnrwmtinn
holding an OL or CP.


n.._ --Noti c No.87-42 87-41 87-40 87-39 87-38 87-37 87-36 87-35 Subfect Diesel Generator
87-41         Failures of Certain Brown        8/31/87         All nuclear power


Fuse Contacts Failures of Certain Brown Boveri Electric Circuit Breakers Backseating
Boveri Electric Circuit                           reactor facilities


Valves Routinely to Prevent Packing Leakage Control of Hot Particle Contamination
Breakers                                          holding an OL or CP.


at Nuclear Power Plants Inadequate
87-40          Backseating Valves Routinely      8/31/87        All nuclear power


or Inadvertent
to Prevent Packing Leakage                        reactor facilities


Blocking of Valve Movement Compliance
holding an OL or CP.


with the General License Provisions
87-39          Control of Hot Particle          8/21/87        All nuclear power


of 10 CFR Part 31 Significant
Contamination at Nuclear                          reactor facilities


Unexpected
Power Plants                                      and spent.fuel


Erosion of Feedwater
storage facilities
 
Lines Reactor Trip Breaker.u1etinghouse
 
Modal OSm4I6_Failed to Open on Manual Initiation


from the Control Room uasu or Issuance Issued to 9/4/87 All nuclear power reactor facilities
holding an NRC


holding an OL or CP.8/31/87 All nuclear power reactor facilities
license or CP.


holding an OL or CP.8/31/87 All nuclear power reactor facilities
87-38          Inadequate or Inadvertent        8/17/87       All nuclear power


holding an OL or CP.8/21/87 All nuclear power reactor facilities
Blocking of Valve Movement                        reactor facilities


and spent.fuel
holding an OL or CP.


storage facilities
87-37          Compliance with the General      8/10/87        All persons specifi- License Provisions of                            cally licensed to


holding an NRC license or CP.8/17/87 All nuclear power reactor facilities
10 CFR Part 31                                  manufacture or to


holding an OL or CP.8/10/87 All persons specifi-cally licensed to manufacture
Initially transfer


or to Initially
devices containing


transfer devices containing
radioactive material


radioactive
to general licensees, as defined in 10 CFR


material to general licensees, as defined in 10 CFR Part 31.8/4/87 All nuclear power reactor facilities
Part 31.


holding an OL or CP.7/30/87 All nuclear power--mactui fEacz11 ties -holdthg an OL or CP eploying W DS-416 reactor trip Breakers.OL a Operating
87-36          Significant Unexpected          8/4/87         All nuclear power


License UNITED STATES CP a Construction
Erosion of Feedwater Lines                      reactor facilities


Permit NUCLEAR REGULATORY
holding an OL or CP.


COMMISSION
87-35          Reactor Trip Breaker.            7/30/87        All nuclear power


WASHINGTON, D.C. 20555 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE. $300 FIRST CLSS MAIL POSTAGE
u1etinghouse Modal OSm4I6_                  - -mactui fEacz11 ties -
                                                  Failed to Open on Manual                        holdthg an OL or


* FEES PAID USNIIC PERMIT No. 0-67 IN 87-43 September
Initiation from the Control                      CPeploying WDS-416 Room                                            reactor trip Breakers.


8, 1987 to model the specific Quad Cities experience
OL a Operating License


considering
UNITED STATES            CPa Construction  Permit


absorbed gamma dose as a function of axial elevation, neutron absorbing
FIRST CLSS MAIL


sheet restraint, and fractional
NUCLEAR REGULATORY COMMISSION                                                                                      POSTAGE


change in length.The effect of rack design and manufacturing
* FEES PAID


methods on the consequences
WASHINGTON, D.C. 20555                                                                                              USNIIC


of stress, temperature, and chemical environment
PERMIT No. 0-67 OFFICIAL BUSINESS


to irradiated
PENALTY FOR PRIVATE USE. $300


Boraflex is uncer-tain. Recent blackness
IN 87-43 September 8, 1987 to model the specific Quad Cities experience considering absorbed gamma dose as a


test results at Turkey Point, who uses a Westinghouse
function of axial elevation, neutron absorbing sheet restraint, and fractional


spent fuel storage rack, did not indicate the presence of gaps in the Boraflex.The research programs are designed to evaluate each consequence
change in length.


and, in partic-ular, to improve the understanding
The effect of rack design and manufacturing methods on the consequences of


of stress caused by method of attachment
stress, temperature, and chemical environment to irradiated Boraflex is uncer- tain. Recent blackness test results at Turkey Point, who uses a Westinghouse


of the Boraflex panel to the stainless
spent fuel storage rack, did not indicate the presence of gaps in the Boraflex.


steel wall of the cell.Together, these programs are designed to improve the industry understanding
The research programs are designed to evaluate each consequence and, in partic- ular, to improve the understanding of stress caused by method of attachment of


of the safety implications
the Boraflex panel to the stainless steel wall of the cell.


of the observed gaps in the Boraflex neutron absorber component
Together, these programs are designed to improve the industry understanding of


of the OAT high-density
the safety implications of the observed gaps in the Boraflex neutron absorber


spent-fuel
component of the OAT high-density spent-fuel storage racks at Quad Cities.


storage racks at Quad Cities.No specific action or written response is required by this information
No specific action or written response is required by this information notice.


notice.If you have any questions
If you have any questions about this matter, please contact the Regional


about this matter, please contact the Regional Administrator
Administrator of the appropriate regional office or this office.


of the appropriate
Charles E. Rossi, Director


regional office or this office.Charles E. Rossi, Director Division of Operational
Division of Operational Events Assessment


===Events Assessment===
Office of Nuclear Reactor Regulation
Office of Nuclear Reactor Regulation


Technical
Technical Contacts:  Vern Hodge


Contacts:
(301) 492-8196 Albert D. Morrongiello
Vern Hodge (301) 492-8196 Albert D. Morrongiello


(309) 654-2227 Attachments:
(309) 654-2227 Attachments:
1. List of Plants Using Boraflex Structures
1. List of Plants Using Boraflex
 
in the Spent Fuel Pool 2. List of Recently Issued NRC Information
 
Notices*SEE PREVIOUS CONCURRENCES
 
0// /87*OGCB:DOEA:NRR
 
*AC/ECEB:DEST:NRR
 
*RI:QUAD *PPMB:ARM
 
*t/dGCB:DOEA:NRR
 
CVHodge CMcCracken
 
AMorrongiello


===TechEd CHBerlinger===
Structures in the Spent Fuel Pool
08/20/87 08/26/87 08/25/87 07/17/87 08/24/87 IN 87-XX t 'August xx, 1987 to model the specific Quad Cities experience


utilizing
2. List of Recently Issued NRC Information Notices


absorbed gamma dose as a function of axial elevation, fractional
*SEE PREVIOUS CONCURRENCES


change in length and neutron absorbing sheet restraint.
0// /87
*OGCB:DOEA:NRR *AC/ECEB:DEST:NRR    *RI:QUAD      *PPMB:ARM *t/dGCB:DOEA:NRR


The effect of rack design and manufacturing
CVHodge        CMcCracken          AMorrongiello  TechEd    CHBerlinger


methods on the consequences
08/20/87      08/26/87            08/25/87      07/17/87 08/24/87


of stress, temperature, and chemical environment
IN 87-XX


to irradiated
t 'August


Boraflex is uncer-tain. Recent blackness
xx, 1987 to model the specific Quad Cities experience utilizing absorbed gamma dose as a


test results at Turkey Point, who uses a Westinghouse
function of axial elevation, fractional change in length and neutron absorbing


spent fuel storage rack, did not Indicate the presence of gaps in the Boraflex.The research programs are designed to evaluate each consequence
sheet restraint.


and, in partic-ular, to improve the understanding
The effect of rack design and manufacturing methods on the consequences of


of stress caused by method of attachment
stress, temperature, and chemical environment to irradiated Boraflex is uncer- tain. Recent blackness test results at Turkey Point, who uses a Westinghouse


or entrapment
spent fuel storage rack, did not Indicate the presence of gaps in the Boraflex.


of the Boraflex panel to the stainless
The research programs are designed to evaluate each consequence and, in partic- ular, to improve the understanding of stress caused by method of attachment or


steel wall of the cell.Together, these programs are designed to improve the industry understanding
entrapment of the Boraflex panel to the stainless steel wall of the cell.


of the safety implications
Together, these programs are designed to improve the industry understanding of


of the observed gaps in the Boraflex neutron absorber component
the safety implications of the observed gaps in the Boraflex neutron absorber


of the OAT high-density
component of the OAT high-density spent-fuel storage racks at Quad Cities. To


spent-fuel
date, the NRC has not received information to prompt a more immediate address- ing of this issue.


storage racks at Quad Cities. To date, the NRC has not received information
No specific action or written response is required by this information notice.


to prompt a more immediate
If you have any questions about this matter, please contact the Regional


address-ing of this issue.No specific action or written response is required by this information
Administrator of the appropriate regional office or this office.


notice.If you have any questions
Charles E. Rossi, Director


about this matter, please contact the Regional Administrator
Division of Operational Events Assessment


of the appropriate
regional office or this office.Charles E. Rossi, Director Division of Operational
===Events Assessment===
Office of Nuclear Reactor Regulation
Office of Nuclear Reactor Regulation


Technical
Technical Contacts:    Vern Hodge


Contacts:
(301) 492-8196 Albert D. Morrongiello
Vern Hodge (301) 492-8196 Albert D. Morrongiello


(309) 654-2227 Attachments:
(309) 654-2227 Attachments:
1. List of Plants Using Boraflex Structures
          1. List of Plants Using Boraflex


in the Spent Fuel Pool 2. List of Recently Issued Information
Structures in the Spent Fuel Pool


Notices*SEE PREVIOUS CONCURRENCES
2. List of Recently Issued Information Notices
 
*SEE PREVIOUS CONCURRENCES


D/DOEA:NRR
D/DOEA:NRR
Line 558: Line 415:
_r~d~t-_(_CERossi
_r~d~t-_(_CERossi


6 b0 On08/ /87 OGCB:DOEA:NRR
6           b0                                           On08//87 OGCB:DOEA:NRR   AC/ CEB:DEST:NRR      Rr:QUAD        *PPMB:ARM C/OGCB:DOEA:NRR4 CVHodge          CMcCracken          AMorrongiello  TechEd    CHBerlinger CP6
          084;0/87        o8/aIb/87            08/;S787        07/17/87  08Lpt/87


AC/ CEB:DEST:NRR
IN 87-XX


Rr:QUAD *PPMB:ARM
July xx, 1987 of maximum gap size, on which the determination of k-eff rests. MaJor uncer- tainties in this picture include isotropy of volume changes, damage mechanism, and influence of stress, temperature, and chemical environment.


C/OGCB:DOEA:NRR
Volume changes are assumed isotropic. If untrue, the presently estimated


4 CVHodge CMcCracken
maximum gap size would be significantly affected.


AMorrongiello
The radiation damage mechanism is uncertain. Crosslinking leads to shrinkage, whereas scissioning leads to increased friability of the material. In the


TechEd CHBerlinger
absence of low dose data, it is presently assumed that crosslinking damage is


CP6 084;0/87 o8/aIb/87
proportional to dose; thus it is thought that crosslinking is about complete at
08/;S787 07/17/87 08Lpt/87 IN 87-XX July xx, 1987 of maximum gap size, on which the determination


of k-eff rests. MaJor uncer-tainties in this picture include isotropy of volume changes, damage mechanism, and influence
1-2 E 10 rads. The degraded Point Beach coupons were given a dose of this


of stress, temperature, and chemical environment.
magnitude, however the essentially nondegraded Point Beach panels and Quad


Volume changes are assumed isotropic.
Cities panels and representative positions in spent fuel pool storage racks are


If untrue, the presently
associated with doses from 3 to 6 times smaller than this range of values.


estimated maximum gap size would be significantly
Stress, temperature, and chemical environment may influence the estimate of


affected.The radiation
maximum gap size and hence pool criticality. In particular, to improve the


damage mechanism
understanding of stress, the EPRI program will determine the dependence of gap


is uncertain.
formation on the method of attaching the Boraflex panel to the stainless steel


Crosslinking
wall of the storage rack cell.


leads to shrinkage, whereas scissioning
Together, these programs are designed to improve the industry's understanding


leads to increased
of the safety implications of the observed degradation of Boraflex.


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


of the material.
If you have any questions about this matter, please contact the Regional


In the absence of low dose data, it is presently
Administrator of the appropriate regional office or this office.


assumed that crosslinking
Charles E. Rossi, Director


damage is proportional
Division of Operational Events Assessment


to dose; thus it is thought that crosslinking
is about complete at 1-2 E 10 rads. The degraded Point Beach coupons were given a dose of this magnitude, however the essentially
nondegraded
Point Beach panels and Quad Cities panels and representative
positions
in spent fuel pool storage racks are associated
with doses from 3 to 6 times smaller than this range of values.Stress, temperature, and chemical environment
may influence
the estimate of maximum gap size and hence pool criticality.
In particular, to improve the understanding
of stress, the EPRI program will determine
the dependence
of gap formation
on the method of attaching
the Boraflex panel to the stainless
steel wall of the storage rack cell.Together, these programs are designed to improve the industry's
understanding
of the safety implications
of the observed degradation
of Boraflex.No specific action or written response is required by this information
notice.If you have any questions
about this matter, please contact the Regional Administrator
of the appropriate
regional office or this office.Charles E. Rossi, Director Division of Operational
===Events Assessment===
Office of Nuclear Reactor Regulation
Office of Nuclear Reactor Regulation


Technical
Technical Contacts:  Vern Hodge


Contacts:
(301) 492-8196 Albert D. Morrongiello
Vern Hodge (301) 492-8196 Albert D. Morrongiello


(309) 654-2227 Attachments:
(309) 654-2227 Attachments:
1. List of Potentially
1. List of Potentially Affected Plants
 
Affected Plants 2. List of Recently Issued Information
 
Notices OGCB:DOEA:NRR


RI:QUAD PPMB:ARM C/OGCB:DOEA:NRR
2. List of Recently Issued Information Notices
 
D/DOEA:NRR


CYHodge AMorrongiello
OGCB:DOEA:NRR        RI:QUAD          PPMB:ARM C/OGCB:DOEA:NRR      D/DOEA:NRR


TechEd CHBerlinger
CYHodge              AMorrongiello  TechEd     CHBerlinger         CERossi


CERossi 07/ /87 07/ /87 07/11/87 07/ /87 07/ /87}}
07/ /87             07/ /87         07/11/87 07/ /87               07/ /87}}


{{Information notice-Nav}}
{{Information notice-Nav}}

Revision as of 03:02, 24 November 2019

Gaps in Neutron-Absorbing Material in High-Density Spent Fuel Storage Racks
ML031130349
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, 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, Skagit, Marble Hill, Crane
Issue date: 09/08/1987
From: Rossi C
Office of Nuclear Reactor Regulation
To:
References
-nr IN-87-043, NUDOCS 8709010085
Download: ML031130349 (7)
v • d • e


- >

I

Q

SSINS No.: 6835 IN 87-43 UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON D.C. 20555 September 8, 1987 NRC INFORMATION NOTICENO. 87-43: GAPS IN NEUTRON-ABSORBING MATERIAL

,INHIGH-DENSITY SPENT FUEL STORAGE

RACKS

Addressees

All nuclear power reactor facilities holding an operating license or a con- struction permit.

Purpose

This notice is to alert recipients to a potentially significant problem per- taining to gaps identified in the neutron absorber component of the high- density spent fuel storage racks at Quad Cities Unit 1. The safety concern is

that certain gaps might excessively reduce the margin of nuclear subcriticality

in the fuel pool. The NRC expects that recipients will review this notice for

applicability to their facilities and consider actions, if appropriate, to

preclude a similar problem occurring at their facilities. However, suggestions

in-this notice do not constitute NRC requirements; therefore, no specific

action or written response is required..

Description of Circumstances

On May 1, 1987, Commonwealth Edison Company (CECO), the licensee at Quad Cities

1 and 2, presented data to the NRC regarding gaps measured in Boraflex,.a

neutron-absorbing material used in the high-density fuel storage racks manufac- tured by the Joseph Oat Corporation (OAT). Boraflex is a trade name for a

boron carbide dispersion in an elastomeric silicone matrix manufactured by

Bisco Products, Inc. (BISCO). Data pertaining to the gap size and distribution

had been obtained by National Nuclear Corporation.(NNC) under.contract to CECO.

The licensee had retained Northeast Technology Corporation (NETCO) to interpret

the data. NETCO prefaced their assessment as preliminary, noting that avail- able data was limited, but concluded that the gap formation mechanism may be

related to large local stresses in the Boraflex from fabrication-induced re- straint within the rack and to tearing and shrinkage of the material..

The average gap size is 1-1/2 inches, with the largest 4 inches.. The gaps

occur in the.upper two-thirds of the cell length. -

709010085

IN 87-43 September 8, 1987 These gaps are inferred from anomalies in "blackness" testing results by NNC.

The existence of a gap in the Quad Cities neutron absorber panel has been

confirmed by underwater neutron radiography conducted by Nusurtec, Inc.

CECO also discussed the effects these gaps might have on the approved safety

analysis for the spent fuel storage racks. CECO used conservative assumptions

for gap size, gap location, and fuel burnup. Considerable margin in k-eff

appears to be available before the licensing limit of 0.95 would be approached.

In July 1986, Wisconsin Electric Company, the licensee at Point Beach 1 and 2, reported to the NRC that test coupons of Boraflex material had shown consider- able degradation under high radiation. However, the licensee asserted that

this result did not represent the actual condition of Boraflex used in its

spent fuel storage racks because of differences in methods of encapsulation, sample geometry, and handling frequency. Additionally, the coupons had been

subjected to about 5 times more radiation than is associated with the average

fuel rack position. Subsequent examination of full-length panels disclosed

two results: in one panel examined for effects of the water environment but

exposed to negligible gamma radiation, there was no degradation of the Boraflex.

In another panel exposed to significant gamma radiation, 1-2 percent of the

surface showed a gray discoloration at the edges, similar to the degradation

of the coupons.

Discussion:

The concern is that separation of the neutron-absorbing material used in high

density fuel storage racks might compromise safety. Although Quad Cities

reports that its racks, even with gaps in the Boraflex as large as 4 inches, can meet the criticality criterion of k-eff less than or equal to 0.95, this

may not be the case for larger gaps or for other plants. A list of the 31 sites

using Boraflex is given in Attachment 1. Related information is given in

"Behavior of High-Density Spent-Fuel Storage Racks," EPRI NP-4724, Electric

Power Research Institute, August 1986.

Efforts to understand the gap formation have revealed several topics on which

information is needed. Accordingly, the material supplier (BISCO) and the

Electric Power Research Institute (EPRI) have undertaken research programs

to collect this information. Some of their objectives are described below.

The BISCO program aims to establish with increased accuracy the relationship

between radiation dose and size changes. The program also evaluates the

potential effects of handling and restraint, during and subsequent to the fuel

rack fabrication, on gap formation.

The EPRI program will correlate data from utilities' neutron absorber coupon

surveillance programs. EPRI will further examine data obtained from CECO, as

well as from BISCO and other sources, to improve the understanding of possible

or actual gap formation models, including the effects of rack fabrication

methods and irradiation damage mechanisms. The EPRI Program will also attempt

IN 87-43 September 8, 1987 to model the specific Quad Cities experience considering absorbed gamma dose as a

function of axial elevation, neutron absorbing sheet restraint, and fractional

change in length.

The effect of rack design and manufacturing methods on the consequences of

stress, temperature, and chemical environment to irradiated Boraflex is uncer- tain. Recent blackness test results at Turkey Point, who uses a Westinghouse

spent fuel storage rack, did not indicate the presence of gaps in the Boraflex.

The research programs are designed to evaluate each consequence and, In partic- ular, to improve the understanding of stress caused by method of attachment of

the Boraflex panel to the stainless steel wall of the cell. -

Together, these programs are designed to improve the industry understanding of

the safety implications of the observed gaps in the Boraflex neutron absorber

component of the OAT high-density spent-fuel storage racks at Quad Cities.

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

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate regional office or this office.

hares E. Rossi, Director

_ _ - - Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Vern Hodge

(301) 492-8196 Albert D. Morrongiello

(309) 654-2227 Attachments:

Attachment 1

1. List of Plants Using Boraflex IN 87-43 Structures in the Spent Fuel Pool September 8, 1987

2. List of Recently Issued NRC Information Notices LIST OF PLANTS WITH BORAFLEX

STRUCTURES IN THE SPENT FUEL POOL

1. Arkansas 1,2 16. Peach Bottom 2.3

2. Beaver Valley 1 17. Pilgrim

3. Diablo Canyon 1,2 18. Pt. Beach 1,2

4. Calvert Cliffs 2 19. Pr. Island 1,2

5. Farley 1,2 20. Quad Cities 1,2*

6. Fermi 2* 21. Rancho Seco*

7. Ft. Calhoun 22. River Bend

8. Ginna 23. Robinson 2

9. Grand Gulf 1,2* 24. Summer*

10. McGuire 1,2 25. Trojan

11. Millstone 1,2,3 26. Turkey Pt. 3,4

12. Nine Ni. Pt. 1,2 27. Waterford 3

13. North Anna 1,2 28. Seabrook 1,2

14. Oconee 1,2,3 29. Watts Bar 1,2

15. Oyster Creek* 30. Comanche Peak 1,2

31. Harris

  • Plants having spent fuel storage racks fabricated by Joseph Oat Corporation.

/ \_J Attachment 2 IN 87-43 September 8, 1987 LIST OF RECENTLY ISSUED

INFORMATION NOTICES 1987 Tnfnrwmtinn n.._ --

uasu or

Noti c No. Subfect Issuance Issued to

87-42 Diesel Generator Fuse 9/4/87 All nuclear power

Contacts reactor facilities

holding an OL or CP.

87-41 Failures of Certain Brown 8/31/87 All nuclear power

Boveri Electric Circuit reactor facilities

Breakers holding an OL or CP.

87-40 Backseating Valves Routinely 8/31/87 All nuclear power

to Prevent Packing Leakage reactor facilities

holding an OL or CP.

87-39 Control of Hot Particle 8/21/87 All nuclear power

Contamination at Nuclear reactor facilities

Power Plants and spent.fuel

storage facilities

holding an NRC

license or CP.

87-38 Inadequate or Inadvertent 8/17/87 All nuclear power

Blocking of Valve Movement reactor facilities

holding an OL or CP.

87-37 Compliance with the General 8/10/87 All persons specifi- License Provisions of cally licensed to

10 CFR Part 31 manufacture or to

Initially transfer

devices containing

radioactive material

to general licensees, as defined in 10 CFR

Part 31.

87-36 Significant Unexpected 8/4/87 All nuclear power

Erosion of Feedwater Lines reactor facilities

holding an OL or CP.

87-35 Reactor Trip Breaker. 7/30/87 All nuclear power

u1etinghouse Modal OSm4I6_ - -mactui fEacz11 ties -

Failed to Open on Manual holdthg an OL or

Initiation from the Control CPeploying WDS-416 Room reactor trip Breakers.

OL a Operating License

UNITED STATES CPa Construction Permit

FIRST CLSS MAIL

NUCLEAR REGULATORY COMMISSION POSTAGE

  • FEES PAID

WASHINGTON, D.C. 20555 USNIIC

PERMIT No. 0-67 OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE. $300

IN 87-43 September 8, 1987 to model the specific Quad Cities experience considering absorbed gamma dose as a

function of axial elevation, neutron absorbing sheet restraint, and fractional

change in length.

The effect of rack design and manufacturing methods on the consequences of

stress, temperature, and chemical environment to irradiated Boraflex is uncer- tain. Recent blackness test results at Turkey Point, who uses a Westinghouse

spent fuel storage rack, did not indicate the presence of gaps in the Boraflex.

The research programs are designed to evaluate each consequence and, in partic- ular, to improve the understanding of stress caused by method of attachment of

the Boraflex panel to the stainless steel wall of the cell.

Together, these programs are designed to improve the industry understanding of

the safety implications of the observed gaps in the Boraflex neutron absorber

component of the OAT high-density spent-fuel storage racks at Quad Cities.

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

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate regional office or this office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Vern Hodge

(301) 492-8196 Albert D. Morrongiello

(309) 654-2227 Attachments:

1. List of Plants Using Boraflex

Structures in the Spent Fuel Pool

2. List of Recently Issued NRC Information Notices

  • SEE PREVIOUS CONCURRENCES

0// /87

  • OGCB:DOEA:NRR *AC/ECEB:DEST:NRR *RI:QUAD *PPMB:ARM *t/dGCB:DOEA:NRR

CVHodge CMcCracken AMorrongiello TechEd CHBerlinger

08/20/87 08/26/87 08/25/87 07/17/87 08/24/87

IN 87-XX

t 'August

xx, 1987 to model the specific Quad Cities experience utilizing absorbed gamma dose as a

function of axial elevation, fractional change in length and neutron absorbing

sheet restraint.

The effect of rack design and manufacturing methods on the consequences of

stress, temperature, and chemical environment to irradiated Boraflex is uncer- tain. Recent blackness test results at Turkey Point, who uses a Westinghouse

spent fuel storage rack, did not Indicate the presence of gaps in the Boraflex.

The research programs are designed to evaluate each consequence and, in partic- ular, to improve the understanding of stress caused by method of attachment or

entrapment of the Boraflex panel to the stainless steel wall of the cell.

Together, these programs are designed to improve the industry understanding of

the safety implications of the observed gaps in the Boraflex neutron absorber

component of the OAT high-density spent-fuel storage racks at Quad Cities. To

date, the NRC has not received information to prompt a more immediate address- ing of this issue.

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

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate regional office or this office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Vern Hodge

(301) 492-8196 Albert D. Morrongiello

(309) 654-2227 Attachments:

1. List of Plants Using Boraflex

Structures in the Spent Fuel Pool

2. List of Recently Issued Information Notices

  • SEE PREVIOUS CONCURRENCES

D/DOEA:NRR

_r~d~t-_(_CERossi

6 b0 On08//87 OGCB:DOEA:NRR AC/ CEB:DEST:NRR Rr:QUAD *PPMB:ARM C/OGCB:DOEA:NRR4 CVHodge CMcCracken AMorrongiello TechEd CHBerlinger CP6

084;0/87 o8/aIb/87 08/;S787 07/17/87 08Lpt/87

IN 87-XX

July xx, 1987 of maximum gap size, on which the determination of k-eff rests. MaJor uncer- tainties in this picture include isotropy of volume changes, damage mechanism, and influence of stress, temperature, and chemical environment.

Volume changes are assumed isotropic. If untrue, the presently estimated

maximum gap size would be significantly affected.

The radiation damage mechanism is uncertain. Crosslinking leads to shrinkage, whereas scissioning leads to increased friability of the material. In the

absence of low dose data, it is presently assumed that crosslinking damage is

proportional to dose; thus it is thought that crosslinking is about complete at

1-2 E 10 rads. The degraded Point Beach coupons were given a dose of this

magnitude, however the essentially nondegraded Point Beach panels and Quad

Cities panels and representative positions in spent fuel pool storage racks are

associated with doses from 3 to 6 times smaller than this range of values.

Stress, temperature, and chemical environment may influence the estimate of

maximum gap size and hence pool criticality. In particular, to improve the

understanding of stress, the EPRI program will determine the dependence of gap

formation on the method of attaching the Boraflex panel to the stainless steel

wall of the storage rack cell.

Together, these programs are designed to improve the industry's understanding

of the safety implications of the observed degradation of Boraflex.

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

If you have any questions about this matter, please contact the Regional

Administrator of the appropriate regional office or this office.

Charles E. Rossi, Director

Division of Operational Events Assessment

Office of Nuclear Reactor Regulation

Technical Contacts: Vern Hodge

(301) 492-8196 Albert D. Morrongiello

(309) 654-2227 Attachments:

1. List of Potentially Affected Plants

2. List of Recently Issued Information Notices

OGCB:DOEA:NRR RI:QUAD PPMB:ARM C/OGCB:DOEA:NRR D/DOEA:NRR

CYHodge AMorrongiello TechEd CHBerlinger CERossi

07/ /87 07/ /87 07/11/87 07/ /87 07/ /87


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