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:Q


COMMISSION
- >
I


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


D.C. 20555 September
===UNITED STATES===
NUCLEAR REGULATORY COMMISSION


8, 1987 NRC INFORMATION
===OFFICE OF NUCLEAR REACTOR REGULATION===
WASHINGTON D.C. 20555


NOTICENO.
===September 8, 1987===
NRC INFORMATION NOTICENO. 87-43:
GAPS IN NEUTRON-ABSORBING MATERIAL


87-43: GAPS IN NEUTRON-ABSORBING
,IN


MATERIAL ,IN HIGH-DENSITY
HIGH-DENSITY SPENT FUEL STORAGE


SPENT FUEL STORAGE RACKS
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.


problem per-taining to gaps identified
The NRC expects that recipients will review this notice for


in the neutron absorber component
applicability to their facilities and consider actions, if appropriate, to


of the high-density spent fuel storage racks at Quad Cities Unit 1. The safety concern is that certain gaps might excessively
preclude a similar problem occurring at their facilities. However, suggestions


reduce the margin of nuclear subcriticality
in-this notice do not constitute NRC requirements; therefore, no specific


in the fuel pool. The NRC expects that recipients
action or written response is required..


will review this notice for applicability
==Description of Circumstances==
:
On May 1, 1987, Commonwealth Edison Company (CECO), the licensee at Quad Cities


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


and consider actions, if appropriate, to preclude a similar problem occurring
neutron-absorbing material used in the high-density fuel storage racks manufac- tured by the Joseph Oat Corporation (OAT).


at their facilities.
===Boraflex is a trade name for a===
boron carbide dispersion in an elastomeric silicone matrix manufactured by


===However, suggestions===
Bisco Products, Inc. (BISCO).
in-this notice do not constitute


NRC requirements;
===Data pertaining to the gap size and distribution===
therefore, no specific action or written response is required..
had been obtained by National Nuclear Corporation.(NNC) under.contract to CECO.


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


of Circumstances:
the data.
On May 1, 1987, Commonwealth


Edison Company (CECO), the licensee at Quad Cities 1 and 2, presented
NETCO prefaced their assessment as preliminary, noting that avail- able data was limited, but concluded that the gap formation mechanism may be


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


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


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


material used in the high-density
-
709010085


fuel storage racks manufac-tured by the Joseph Oat Corporation (OAT). Boraflex is a trade name for a boron carbide dispersion
IN 87-43 September 8, 1987 These gaps are inferred from anomalies in "blackness" testing results by NNC.


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


silicone matrix manufactured
confirmed by underwater neutron radiography conducted by Nusurtec, Inc.


by Bisco Products, Inc. (BISCO). Data pertaining
CECO also discussed the effects these gaps might have on the approved safety


to the gap size and distribution
analysis for the spent fuel storage racks.


had been obtained by National Nuclear Corporation.(NNC)
===CECO used conservative assumptions===
under.contract
for gap size, gap location, and fuel burnup.


to CECO.The licensee had retained Northeast
Considerable margin in k-eff


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


Corporation (NETCO) to interpret the data. NETCO prefaced their assessment
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.


as preliminary, noting that avail-able data was limited, but concluded
===However, the licensee asserted that===
this result did not represent the actual condition of Boraflex used in its


that the gap formation
spent fuel storage racks because of differences in methods of encapsulation, sample geometry, and handling frequency.


mechanism
===Additionally, the coupons had been===
subjected to about 5 times more radiation than is associated with the average


may be related to large local stresses in the Boraflex from fabrication-induced
fuel rack position.


re-straint within the rack and to tearing and shrinkage
Subsequent examination of full-length panels disclosed


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


The average gap size is 1-1/2 inches, with the largest 4 inches.. The gaps occur in the.upper
exposed to negligible gamma radiation, there was no degradation of the Boraflex.


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


of the cell length. -709010085 IN 87-43 September
surface showed a gray discoloration at the edges, similar to the degradation


8, 1987 These gaps are inferred from anomalies
of the coupons.


in "blackness" testing results by NNC.The existence
Discussion:
The concern is that separation of the neutron-absorbing material used in high


of a gap in the Quad Cities neutron absorber panel has been confirmed
density fuel storage racks might compromise safety. Although Quad Cities


by underwater
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


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


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


by Nusurtec, Inc.CECO also discussed
"Behavior of High-Density Spent-Fuel Storage Racks," EPRI NP-4724, Electric


the effects these gaps might have on the approved safety analysis for the spent fuel storage racks. CECO used conservative
Power Research Institute, August 1986.


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


for gap size, gap location, and fuel burnup. Considerable
information is needed.


margin in k-eff appears to be available
Accordingly, the material supplier (BISCO) and the


before the licensing
Electric Power Research Institute (EPRI) have undertaken research programs


limit of 0.95 would be approached.
to collect this information.


In July 1986, Wisconsin
Some of their objectives are described below.


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
The BISCO program aims to establish with increased accuracy the relationship


under high radiation.
between radiation dose and size changes.


However, the licensee asserted that this result did not represent
===The program also evaluates the===
potential effects of handling and restraint, during and subsequent to the fuel


the actual condition
rack fabrication, on gap formation.


of Boraflex used in its spent fuel storage racks because of differences
The EPRI program will correlate data from utilities' neutron absorber coupon


in methods of encapsulation, sample geometry, and handling frequency.
surveillance programs.


Additionally, the coupons had been subjected
EPRI will further examine data obtained from CECO, as


to about 5 times more radiation
well as from BISCO and other sources, to improve the understanding of possible


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


with the average fuel rack position.
methods and irradiation damage mechanisms. The EPRI Program will also attempt


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


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


of full-length
change in length.


panels disclosed two results: in one panel examined for effects of the water environment
The effect of rack design and manufacturing methods on the consequences of


but exposed to negligible
stress, temperature, and chemical environment to irradiated Boraflex is uncer- tain.


gamma radiation, there was no degradation
Recent blackness test results at Turkey Point, who uses a Westinghouse


of the Boraflex.In another panel exposed to significant
spent fuel storage rack, did not indicate the presence of gaps in the Boraflex.


gamma radiation, 1-2 percent of the surface showed a gray discoloration
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


at the edges, similar to the degradation
the Boraflex panel to the stainless steel wall of the cell.


of the coupons.Discussion:
-
The concern is that separation
Together, these programs are designed to improve the industry understanding of


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


material used in high density fuel storage racks might compromise
component of the OAT high-density spent-fuel storage racks at Quad Cities.


safety. Although Quad Cities reports that its racks, even with gaps in the Boraflex as large as 4 inches, can meet the criticality
No specific action or written response is required by this information notice.


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


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
Administrator of the appropriate regional office or this office.


1. Related information
hares E. Rossi, Director


is given in"Behavior
_
_
-
-


of High-Density
===Division of Operational Events Assessment===
Office of Nuclear Reactor Regulation


Spent-Fuel
Technical Contacts:
Vern Hodge


Storage Racks," EPRI NP-4724, Electric Power Research Institute, August 1986.Efforts to understand
(301) 492-8196


the gap formation
===Albert D. Morrongiello===
 
(309) 654-2227 Attachments:
have revealed several topics on which information
1. List of Plants Using Boraflex
 
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
===Structures in the Spent Fuel Pool===
2. List of Recently Issued NRC Information Notices


spent fuel storage rack, did not indicate the presence of gaps in the Boraflex.The research programs are designed to evaluate each consequence
===Attachment 1===
IN 87-43


and, In partic-ular, to improve the understanding
===September 8, 1987 LIST OF PLANTS WITH BORAFLEX===
STRUCTURES IN THE SPENT FUEL POOL


of stress caused by method of attachment
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


of the Boraflex panel to the stainless
8.


steel wall of the cell. -Together, these programs are designed to improve the industry understanding
Ginna


of the safety implications
9. Grand Gulf 1,2*
10.


of the observed gaps in the Boraflex neutron absorber component
McGuire 1,2
11. Millstone 1,2,3
12.


of the OAT high-density
===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


spent-fuel
18. Pt. Beach 1,2
19. Pr. Island 1,2
20. Quad Cities 1,2*
21. Rancho Seco*
22. River Bend


storage racks at Quad Cities.No specific action or written response is required by this information
23. Robinson 2
24. Summer*
25. Trojan


notice.If you have any questions
26. Turkey Pt. 3,4
27. Waterford 3
28. Seabrook 1,2
29. Watts Bar 1,2
30. Comanche Peak 1,2
31. Harris


about this matter, please contact the Regional Administrator
*Plants having spent fuel storage racks fabricated by Joseph Oat Corporation.


of the appropriate
/
\\_J


regional office or this office.hares E. Rossi, Director_ _ --Division of Operational
===Attachment 2===
IN 87-43


===Events Assessment===
===September 8, 1987===
Office of Nuclear Reactor Regulation
LIST OF RECENTLY ISSUED


Technical
===INFORMATION NOTICES 1987===
Tnfnrwmtinn


Contacts: Vern Hodge (301) 492-8196 Albert D. Morrongiello
n.._
--
Noti c


(309) 654-2227 Attachments:
No.
1. List of Plants Using Boraflex Structures


in the Spent Fuel Pool 2. List of Recently Issued NRC Information
87-42
87-41
87-40
87-39
87-38
87-37
87-36
87-35 Subfect


Notices Attachment
===Diesel Generator Fuse===
Contacts


1 IN 87-43 September
===Failures of Certain Brown===
Boveri Electric Circuit


8, 1987 LIST OF PLANTS WITH BORAFLEX STRUCTURES
Breakers


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
===Backseating Valves Routinely===
to Prevent Packing Leakage


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
===Control of Hot Particle===
Contamination at Nuclear


3 28. Seabrook 1,2 29. Watts Bar 1,2 30. Comanche Peak 1,2 31. Harris*Plants having spent fuel storage racks fabricated
===Power Plants===
Inadequate or Inadvertent


by Joseph Oat Corporation.
===Blocking of Valve Movement===
Compliance with the General


/ \_J Attachment
===License Provisions of===
10 CFR Part 31


2 IN 87-43 September
===Significant Unexpected===
Erosion of Feedwater Lines


8, 1987 LIST OF RECENTLY ISSUED INFORMATION
Reactor Trip Breaker.


NOTICES 1987 Tnfnrwmtinn
u1etinghouse Modal OSm4I6_


n.._ --Noti c No.87-42 87-41 87-40 87-39 87-38 87-37 87-36 87-35 Subfect Diesel Generator
===Failed to Open on Manual===
Initiation from the Control


Fuse Contacts Failures of Certain Brown Boveri Electric Circuit Breakers Backseating
Room


Valves Routinely to Prevent Packing Leakage Control of Hot Particle Contamination
uasu or


at Nuclear Power Plants Inadequate
Issuance


or Inadvertent
Issued to


Blocking of Valve Movement Compliance
9/4/87


with the General License Provisions
===All nuclear power===
reactor facilities


of 10 CFR Part 31 Significant
holding an OL or CP.


Unexpected
8/31/87


Erosion of Feedwater
===All nuclear power===
reactor facilities


Lines Reactor Trip Breaker.u1etinghouse
holding an OL or CP.


Modal OSm4I6_Failed to Open on Manual Initiation
8/31/87


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


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


holding an OL or CP.8/31/87 All nuclear power reactor facilities
8/21/87  


holding an OL or CP.8/21/87 All nuclear power reactor facilities
===All nuclear power===
reactor facilities


and spent.fuel
and spent.fuel
Line 385: Line 384:
storage facilities
storage facilities


holding an NRC license or CP.8/17/87 All nuclear power reactor facilities
holding an NRC


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


or to Initially
8/17/87


transfer devices containing
===All nuclear power===
reactor facilities


radioactive
holding an OL or CP.


material to general licensees, as defined in 10 CFR Part 31.8/4/87 All nuclear power reactor facilities
8/10/87 All persons specifi- cally licensed to


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
manufacture or to


License UNITED STATES CP a Construction
===Initially transfer===
devices containing


Permit NUCLEAR REGULATORY
radioactive material


COMMISSION
to general licensees, as defined in 10 CFR


WASHINGTON, D.C. 20555 OFFICIAL BUSINESS PENALTY FOR PRIVATE USE. $300 FIRST CLSS MAIL POSTAGE
Part 31.


* FEES PAID USNIIC PERMIT No. 0-67 IN 87-43 September
8/4/87  


8, 1987 to model the specific Quad Cities experience
===All nuclear power===
reactor facilities


considering
holding an OL or CP.


absorbed gamma dose as a function of axial elevation, neutron absorbing
7/30/87


sheet restraint, and fractional
===All nuclear power===
-
-mactui


change in length.The effect of rack design and manufacturing
fEacz11 ties -
holdthg an OL or


methods on the consequences
CP eploying W DS-416 reactor trip Breakers.


of stress, temperature, and chemical environment
===OL a Operating License===
UNITED STATES


to irradiated
===CP a Construction Permit===
NUCLEAR REGULATORY COMMISSION


Boraflex is uncer-tain. Recent blackness
===WASHINGTON, D.C. 20555===
OFFICIAL BUSINESS


test results at Turkey Point, who uses a Westinghouse
PENALTY FOR PRIVATE USE. $300


spent fuel storage rack, did not indicate the presence of gaps in the Boraflex.The research programs are designed to evaluate each consequence
===FIRST CLSS MAIL===
POSTAGE


and, in partic-ular, to improve the understanding
* FEES PAID


of stress caused by method of attachment
USNIIC


of the Boraflex panel to the stainless
PERMIT No. 0-67


steel wall of the cell.Together, these programs are designed to improve the industry understanding
IN 87-43 September 8, 1987 to model the specific Quad Cities experience considering absorbed gamma dose as a


of the safety implications
function of axial elevation, neutron absorbing sheet restraint, and fractional


of the observed gaps in the Boraflex neutron absorber component
change in length.


of the OAT high-density
The effect of rack design and manufacturing methods on the consequences of


spent-fuel
stress, temperature, and chemical environment to irradiated Boraflex is uncer- tain.


storage racks at Quad Cities.No specific action or written response is required by this information
Recent blackness test results at Turkey Point, who uses a Westinghouse


notice.If you have any questions
spent fuel storage rack, did not indicate the presence of gaps in the Boraflex.


about this matter, please contact the Regional Administrator
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 appropriate
the Boraflex panel to the stainless steel wall of the cell.


regional office or this office.Charles E. Rossi, Director Division of Operational
Together, these programs are designed to improve the industry understanding of


===Events Assessment===
the safety implications of the observed gaps in the Boraflex neutron absorber
Office of Nuclear Reactor Regulation


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


Contacts:
No specific action or written response is required by this information notice.
Vern Hodge (301) 492-8196 Albert D. Morrongiello


(309) 654-2227 Attachments:
If you have any questions about this matter, please contact the Regional
1. List of Plants Using Boraflex Structures


in the Spent Fuel Pool 2. List of Recently Issued NRC Information
Administrator of the appropriate regional office or this office.


Notices*SEE PREVIOUS CONCURRENCES
===Charles E. Rossi, Director===
Division of Operational Events Assessment


0// /87*OGCB:DOEA:NRR
===Office of Nuclear Reactor Regulation===
Technical Contacts:  
Vern Hodge


*AC/ECEB:DEST:NRR
(301) 492-8196


*RI:QUAD *PPMB:ARM
===Albert D. Morrongiello===
(309) 654-2227 Attachments:
1. List of Plants Using Boraflex


*t/dGCB:DOEA:NRR
===Structures in the Spent Fuel Pool===
2. List of Recently Issued NRC Information Notices


CVHodge CMcCracken
*SEE PREVIOUS CONCURRENCES


AMorrongiello
0// /87
*OGCB:DOEA:NRR *AC/ECEB:DEST:NRR


===TechEd CHBerlinger===
*RI:QUAD
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
*PPMB:ARM *t/dGCB:DOEA:NRR


absorbed gamma dose as a function of axial elevation, fractional
CVHodge


change in length and neutron absorbing sheet restraint.
CMcCracken


The effect of rack design and manufacturing
AMorrongiello TechEd


methods on the consequences
CHBerlinger


of stress, temperature, and chemical environment
08/20/87
08/26/87
08/25/87
07/17/87 08/24/87


to irradiated
IN 87-XX


Boraflex is uncer-tain. Recent blackness
t 'August


test results at Turkey Point, who uses a Westinghouse
xx, 1987 to model the specific Quad Cities experience utilizing absorbed gamma dose as a


spent fuel storage rack, did not Indicate the presence of gaps in the Boraflex.The research programs are designed to evaluate each consequence
function of axial elevation, fractional change in length and neutron absorbing


and, in partic-ular, to improve the understanding
sheet restraint.


of stress caused by method of attachment
The effect of rack design and manufacturing methods on the consequences of


or entrapment
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 or


of the safety implications
entrapment of 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. To


storage racks at Quad Cities. To date, the NRC has not received information
date, the NRC has not received information to prompt a more immediate address- ing of this issue.


to prompt a more immediate
No specific action or written response is required by this information notice.


address-ing of this issue.No specific action or written response is required by this information
If you have any questions about this matter, please contact the Regional


notice.If you have any questions
Administrator of the appropriate regional office or this office.


about this matter, please contact the Regional Administrator
===Charles E. Rossi, Director===
Division of Operational Events Assessment


of the appropriate
===Office of Nuclear Reactor Regulation===
Technical Contacts: Vern Hodge


regional office or this office.Charles E. Rossi, Director Division of Operational
(301) 492-8196
 
===Events Assessment===
Office of Nuclear Reactor Regulation
 
Technical
 
Contacts:
Vern Hodge (301) 492-8196 Albert D. Morrongiello


===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===
2. List of Recently Issued Information Notices


Notices*SEE PREVIOUS CONCURRENCES
*SEE PREVIOUS CONCURRENCES


D/DOEA:NRR
D/DOEA:NRR
Line 558: Line 569:
_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


AC/ CEB:DEST:NRR
Rr:QUAD


Rr:QUAD *PPMB:ARM
*PPMB:ARM C/OGCB:DOEA:NRR4 CVHodge


C/OGCB:DOEA:NRR
CMcCracken


4 CVHodge CMcCracken
AMorrongiello TechEd


AMorrongiello
===CHBerlinger CP6===
084;0/87 o8/aIb/87
08/;S787
07/17/87
08Lpt/87


TechEd CHBerlinger
IN 87-XX


CP6 084;0/87 o8/aIb/87
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.
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
Volume changes are assumed isotropic. If untrue, the presently estimated


of stress, temperature, and chemical environment.
maximum gap size would be significantly affected.


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


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


estimated maximum gap size would be significantly
proportional to dose; thus it is thought that crosslinking is about complete at


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


damage mechanism
magnitude, however the essentially nondegraded Point Beach panels and Quad


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


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


leads to shrinkage, whereas scissioning
Stress, temperature, and chemical environment may influence the estimate of


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


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


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


In the absence of low dose data, it is presently
wall of the storage rack cell.


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


damage is proportional
of the safety implications of the observed degradation of Boraflex.


to dose; thus it is thought that crosslinking
No specific action or written response is required by this information notice.


is about complete at 1-2 E 10 rads. The degraded Point Beach coupons were given a dose of this magnitude, however the essentially
If you have any questions about this matter, please contact the Regional


nondegraded
Administrator of the appropriate regional office or this office.


Point Beach panels and Quad Cities panels and representative
===Charles E. Rossi, Director===
Division of Operational Events Assessment


positions
===Office of Nuclear Reactor Regulation===
Technical Contacts:
Vern Hodge


in spent fuel pool storage racks are associated
(301) 492-8196


with doses from 3 to 6 times smaller than this range of values.Stress, temperature, and chemical environment
===Albert D. Morrongiello===
(309) 654-2227 Attachments:
1. List of Potentially Affected Plants


may influence
2. List of Recently Issued Information Notices


the estimate of maximum gap size and hence pool criticality.
OGCB:DOEA:NRR


In particular, to improve the understanding
RI:QUAD


of stress, the EPRI program will determine
PPMB:ARM C/OGCB:DOEA:NRR


the dependence
D/DOEA:NRR
 
of gap formation
 
on the method of attaching


the Boraflex panel to the stainless
CYHodge


steel wall of the storage rack cell.Together, these programs are designed to improve the industry's
AMorrongiello TechEd
 
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
CHBerlinger


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}}

Latest revision as of 10:35, 16 January 2025

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


Q

- >

I

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

,IN

HIGH-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:

1. List of Plants Using Boraflex

Structures in the Spent Fuel Pool

2. List of Recently Issued NRC Information Notices

Attachment 1

IN 87-43

September 8, 1987 LIST OF PLANTS WITH BORAFLEX

STRUCTURES 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 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 3

28. Seabrook 1,2

29. Watts Bar 1,2

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.._

--

Noti c

No.

87-42

87-41

87-40

87-39

87-38

87-37

87-36

87-35 Subfect

Diesel Generator Fuse

Contacts

Failures of Certain Brown

Boveri Electric Circuit

Breakers

Backseating Valves Routinely

to Prevent Packing Leakage

Control of Hot Particle

Contamination at Nuclear

Power Plants

Inadequate or Inadvertent

Blocking of Valve Movement

Compliance with the General

License Provisions of

10 CFR Part 31

Significant Unexpected

Erosion of Feedwater 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 OL or CP.

8/31/87

All nuclear power

reactor facilities

holding an OL or CP.

8/31/87

All nuclear power

reactor facilities

holding an OL or CP.

8/21/87

All nuclear power

reactor facilities

and spent.fuel

storage facilities

holding an NRC

license or CP.

8/17/87

All nuclear power

reactor facilities

holding an OL or CP.

8/10/87 All persons specifi- cally licensed to

manufacture or to

Initially transfer

devices containing

radioactive material

to general licensees, as defined in 10 CFR

Part 31.

8/4/87

All nuclear power

reactor facilities

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 License

UNITED STATES

CP a Construction Permit

NUCLEAR REGULATORY COMMISSION

WASHINGTON, D.C. 20555

OFFICIAL BUSINESS

PENALTY FOR PRIVATE USE. $300

FIRST CLSS MAIL

POSTAGE

  • FEES PAID

USNIIC

PERMIT No. 0-67

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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