Information Notice 1995-17, Reactor Vessel Top Guide and Core Plate Cracking
UNITED STATES
NUCLEAR REGULATORY COMMISSION
OFFICE OF NUCLEAR REACTOR REGULATION
WASHINGTON, D.C. 20555 March 10, 1995 NRC INFORMATION NOTICE 95-17: REACTOR VESSEL TOP GUIDE AND CORE PLATE
CRACKING
Addressees
All holders of operating licenses or construction permits for boiling water
reactors (BWRs).
Purpose
The U.S. Nuclear Regulatory Commission (NRC) is issuing this information
notice to alert addressees that significant cracking has been observed in the
weld regions of the reactor vessel top guide and core plate in an overseas
BWR. It is expected that recipients will review the information for
applicability to their facilities and consider actions, as appropriate, to
avoid similar problems. However, suggestions contained in this information
notice are not NRC requirements; therefore, no specific action or written
response is required.
Description of Circumstances
During the 1994 inservice inspection of the Wuergassen BWR in Germany, significant cracking was visually observed in the reactor vessel top guide and
core plate. The cracks were circumferentially oriented along the weld regions
and were located in the rim areas of the top guide and the core plate (see
figure in Attachment 1). The top guide and the core plate were made of
niobium stabilized austenitic stainless steel (SS) (equivalent to American
Iron and Steel Institute Type 347 SS) and were post-weld heat treated during
fabrication. The Type 347 SS material had a relatively high carbon content
and a minimum niobium-to-carbon ratio. Samples of this material had passed a
standard sensitization test. Significant cracking was also found in the core
shroud, which was made of the same material. The root cause of the observed
cracking is still under evaluation.
Discussion
Early in 1991, minor cracking not associated with a weld was observed in a
cross beam of the top guide in a domestic BWR (Oyster Creek). Subsequent
monitoring and assessment of the cracking showed that the structural integrity
of the top guide was maintained. The cracking observed in the overseas BWR is
considered significant because it was the first time cracking was found in the
ring weld regions of the reactor vessel top guide and core plate.
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IN 95-17 March 10, 1995 On November 22, 1994, General Electric (GE) issued Rapid Information
Communication Services Information Letter No. 071, "Top Guide and Core Plate
Cracking," which discussed the cracking event reported in the overseas BWR.
The overseas BWR had accumulated approximately 13 years of hot operating time
and the average conductivity of the reactor water during the worst five fuel
cycles had been 0.22 microsiemens per centimeter [0.56 micromho per inch].
Althouyh the overseas BWR was not a GE BWR and the GE-design BWRs have several
different configurations of the top guide and core plate assemblies, there are
similarities in the designs. For example, GE noted that welds existed in GE
BWRs (domestic BWRs) in areas that were cracked in the overseas BWR. In the
overseas non-GE BWR, Type 347 austenitic SS was used for fabricating the top
guide and the core plate, instead of Type 304 austenitic SS, which was used in
domestic BWRs. GE has tested Type 347 SS for its resistance to intergranular
stress corrosion cracking (IGSCC). On the basis of tests, GE has concluded
that sensitized Type 347 SS has a susceptibility to IGSCC equivalent to that
of sensitized high carbon Type 304. When Type 347 SS is not sensitized, it
has a susceptibility to IGSCC equivalent to that of Type 304L SS that is not
sensitized. GE concludes that domestic BWRs with a similar amount of hot
operating time may expect cracking to occur in the top guide and the core
plate.
The BWR Vessel and Internals Project (BWRVIP), by letter of January 3, 1995, reported the GE evaluation of the safety significance of this cracking event
as it pertains to domestic BWRs. The nonproprietary portion of the BWRVIP
letter is given in Attachment 2. A BWRVIP report for all internals, discussing IGSCC susceptibility ranking, safety consequences, inspection
scopes and methodologies, flaw evaluation, repair strategies and mitigation of
degradation is expected in the latter half of 1995.
The NRC staff will monitor the inspections of top guides and core plates in
the industry. The staff is evaluating the safety implications of cracking in
these areas to determine whetner additional generic communication is needed.
Related Generic Communications
On September 30, 1993, the NRC issued Information Notice (IN)93-79, "Core
Shroud Cracking at Beltline Region Welds in Boiling-Water Reactors," in
response to the discovery of cracking of the core shroud welds at Brunswick
Unit 1 plant. Following the additional, discovery of core shroud cracks at
Dresden Unit 3 and Quad Cities Unit 1 in 1994, the following additional
generic communications were issued: 1) IN 94-42, "Cracking in the Lower
Region of the Core Shroud in Boiling-Water Reactors," on June 7, 1994;
2) Supplement 1 to IN 94-42 on July 19, 1994; and 3) Generic Letter 94-03,
"Intergranular Stress Corrosion Cracking of Core Shroud in Boiling Water
Reactors," on July 25, 1994.
IN 95-17 March 10, 1995 This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Project Support
Office of Nuclear Reactor Regulation
Technical contacts: W. H. Koo, NRR E. M. Hackett, NRR
(301) 415-2706 (301) 415-2751 T. A. Greene, NRR
(301) 415-1175 Attachments:
1. Figure, "Location of Cracking in
Top Guide and Core Plate"
2. Letter from BWR Vessel and Internals
Project to U.S. Nuclear Regulatory Commission,
"Request for Information Regarding the Impact
of BWR Core Plate and Top Guide Ring Cracking,"
January 3, 1995
3. List of Recently Issued NRC Information Notices
- 4'z~~sse#1? J1&/ s
Attachment 1 IN 95-17 March 10, 1995 Guide
Rim
Top
I
'I
crack
Reactor
Shroud.
Vesssel
Core Plate Rim
Support Ring 0-.
Not t Scale
Figure 1. Location of Cracking In Top Guide and Core Plate
WV Attachment 2 B3WRVI~ wwrovgrMarch IN 95-17
10, 1995 BWR Vessel & pages
Internals Project _ Issue Management and Resolution
January 3, 1995 U.S. Nuclear Regulatory Commission
Washington, D.C., 20555 Attention: Document Control Branch
SUBJECT: Request for Information Regarding the Impact of BWR
Core Plate and Top Guide Ring Cracking
In response to a request for information on the subject, the BWRVIP
is providing the
information in this letter on relevant design aspects of BWR core plates
and top
guides and the impact that recently discovered outer ring cracking
could have on the
safety performance of these components.
In order to provide this response on an expedited basis, the information
below has
not been reviewed by all BWRVEP utility members. GE has based
the information
presented here on top level drawings, such as reactor assembly drawings, in most
cases. There may be cases where field modifications occurred during
fabrication
which are not shown on the reactor assembly drawings. Any such
modifications
would improve the component condition relative to that reported
here, so the
information here is expected to be conservative. However, individual
utility reviews
of plant-specific configurations may reveal some minor differences
from the
information presented here.
CORE SUPPORT PLATE
The safety function of the core support plate is to provide lateral support
and
positioning for the control rod guide tubes, which in turn support
all but the
peripheral fuel assemblies, such that control rods can be inserted
and the core can be
cooled following an accident. While there may be minor differences
in core plate
designs from plant type to plant type and plant to plant, the design
characteristics of
importance relative to the ring weld cracking issue are essentially
the same for all
plants. A description of a typical core plate follows. The core plate
consists of a 2 inch thick circular plate with CRD guide tube holes about 11 inches
in diameter. A
cylindrical rim is welded under the plate (full penetration), and
the rim-plate
structure is reinforced underneath with a gridwork of beams
and bars. The core
plate is secured to the core plate flange of the shroud by multiple
(from 36 to over 70,
depending on the plant) preloaded stainless steel studs (see example
in Figure 1).
There is aligner pin hardware, which provides some lateral restraint
between the
+o-tk
Reply To: J. T. Beckham, Jr., BWRVIP Chairman, Southern
1ff
Nuclear Operating Co., 42 Inverness
Center Parkway, Bifmingham, AL 35242 * (205) 877-7279
- Fax: (205) 802-0393
K ' Attachment 2 Januarv 3, 1995 IN 95-17 USNRC March 10, 1995 Page 2 pages
core plate and shroud, but the discussion here is focused on the presence of the
preloaded studs.
The preloaded studs provide a large compressive load holding the core plate in
place relative to the shroud. Friction between the core plate ring and shroud flange
is sufficient to prevent lateral motion of the machined surfaces during a seismic
event. The friction factor of a stress corrosion crack in the ring weld would be
significantly higher, so even assuming through-wall cracking of the ring weld, the
core plate would maintain its full design capability to resist displacements due to
vertical delta-P and seismic loads and due to lateral seismic loads.
TOP GUIDE
Review of GE documents indicates that there are five basic top guide configurations.
Table 1 lists the US BWRs under each configuration. The configurations are
described in terms of their lateral support capability, which is the key issue for top
guides. Sketches and descriptions of each configuration are provided in
attachments, as follows:
Attachment I: BWR/2 Attachment 2. Aligner Pin Assemblies Only (BWR/3,4)
Attachment 3: Aligner Pin Assemblies Plus Reinforcement Blocks (BWR/3,4)
Attachment 4: Aligner Pin Assemblies Plus Wedges (BWR/4,5)
Attachment 5: BWR/6
Potentialfor Vertical Displacement
In considering a seismic event, vertical seismic plus operating delta-P loading would
not overcome the weight of the top guide. Based on recent TRACG analyses for a
loss of coolant accident (LOCA) event, LOCA delta-P loads would not overcome the
top guide weight. While time has not permitted a rigorous analysis of combined
seismic plus LOCA vertical loads for all plants, it is expected that such a combination
will not overcome the top guide weight For example, recent TRACG results for a
BWR/4 show a LOCA delta-P of about 1 psi. This represents an upward load of
about 25% of the top guide beam weight Therefore, a vertical seismic acceleration
of about 0.75g would be required to overcome the top guide weight For plants with
hold-down bolts, there would be even more margin against top guide vertical
displacement.
The discussion above applies to an intact. as-designed top guide. If complete ring
weld cracking were assumed, the top guide assembly would still react to vertical
loads as a single, effectively intact component, because there are about 200 welded
pins connecting the top plate to the bottom plate through the beam connections.
januarv 3,1995 YAttachment 2 USNRCL IN 95-17 Page 3 March
Page 3 10,
of 1995
7 pages
Therefore, the ring weld cracking raises no new concerns relative to vertical top
guide displacement.
Potentialfor Lateral Displacement
The top guide provides lateral support for the fuel during a seismic event, transferring the load from the fuel to the shroud. The means by which the lateral
load is transferred to the shroud depends on the plants top guide configuration, described in the Attachments. Likewise, the impact of ring weld cracking depends
somewhat on the top guide configuration. Each configuration is addressed below.
BWR/2 Plants (Attachment 1)
The BWR/2 top guides are supported laterally by four vertical aligner pin
assemblies plus eight lateral support brackets. The brackets are welded to the
shroud and are sized to be within 1/16 inch of the top guide ring. Ring weld
cracking does not degrade the capability of this combination of lateral supports.
The lateral support brackets are welded to the shroud with intermittent fillet welds;
the associated creviced geometry could be SCC susceptible. However, there are no
applied loads during operation, and the fillet weld residual stresses are considerably
less severe than the residual stresses associated with weld geometries like the ring
weld. It is extremely unlikely that enough of the redundant lateral support
components would be sufficiently cracked to allow top guide displacement during a
seismic event.
BWR/6 Plants and BWR/4,5 Plants with Wedges (Attachments 4 and 5)
The BWR/6 equivalent of the top guide, commonly called the grid, is quite different
in design. The grid is integral with the upper shroud (comparable to the portion
above H3). The grid/upper shroud assembly is bolted to the lower shroud with
about 80 preloaded studs. The mechanical joint transfers the fuel seismic load from
the grid into the shroud. There is no grid weld comparable to the ring weld in the
top guides. Thus, the subject cracking is not an issue for BWR/6.
For some BWR/4s and all BWR/5s, lateral support wedge assemblies were added
between the top guide and shroud to increase the seismic structural margin of the
top guide. These wedges, numbering between 24 and 32 around the top guide
perimeter, provide mechanical lateral restraint to supplement that of the aligner pin
assemblies. Ring weld cracking does not degrade the capability of this combination
of lateral supports.
The mating piece of the wedge assembly attached to the shroud is fillet welded, so
there is some limited potential for SCC. However, it is extremely unlikely that
3' 19Attachment 2 January 3, I995 pN 95-17 USIRC iMarch 10, 1995
Page 4 pages
enough of the redundant lateral support components would be sufficiently cracked
to allow top guide displacement during a seismic event.
BWR/3 Plants and Remainingi, BWR/4 Plants (Attachments 2 and 3)
The BWR/3 plnts and those BWR/4s not addressed above were designed such that
the aligner pin hardware reacts the lateral seismic loads. Reinforcing blocks added
in some plants increase the seismic loading capacity of the aligner hardware, but that
arrangement still relies on the structural integrity of the aligner hardware welded to
the shroud.
For these plants, ring weld cracking has a small, acceptable impact on the top guide
margin preventing lateral displacement. The evaluation below discusses the impact
of ring weld cracking, and then proceeds through several levels of hypothetical
component degradation and system responses to show that even for extremely
unlikely worst case scenarios safe shutdown would be achieved.
If the weld in the top guide ring were cracked:
The top guide beams attach to the outer ring assembly by pins in the top and bottom
plates, which are connected by the ring containing the suspect weld. The load from
fuel movement during a seismic event is transferred to the beams, then to the top
and bottom plate via the pin connections. If the ring weld were completely cracked, the full load would have to be transferred through the pin connections to the bottom
plate, then to the aligner pin hardware and finally to the shroud (in the case where
there are no supplemental restraints like wedges). The load path from the fuel to the
shroud bypasses the outer ring, if it were fully cracked, as long as the pins to the
bottom plate remain intah. There are typically around 100 pins connecting the
redundant beam structure to the bottom plate, so it is expected that, while some pins
might shear, loads would redistribute and the overall structure would stay intact
Therefore, cracking in the ring would have an acceptably small impact on the top
guide's ability to transfer the seismic load to the shroud.
Alignment pin hardware integrity:
The cracking of the ring weld indicates, as expected, that the environment in the top
guide region is aggressive. It is possible that the aligner pin hardware could
experience SCC. However, the likelihood of SCC being extensive enough that
seismic loads could cause top guide lateral motion is quite low, for several reasons:
1. The aligner pin hardware is welded to the top guide and shroud with fillet welds
or partial penetration groove welds. While some aligner brackets have crevices, most aligner pin hardware have welds all around, precluding crevice SCC. The
amount of connecting weld is typically sufficient so that the pin is the highest
stressed part of the alignment hardware during a seismic event. Thus, some SCC
Januarv 3, 1995 Attachment 2 IN 95-17 USNRC March 10, 1995 PageS pages
could be tolerated before the connecting welds would have the highest stresses, and even more SCC could be tolerated before the welds would separate by shear.
2. The aligner hardware is redundant; there are four aligner pins in the top guide.
For any given direction of seismic acceleration, three or four aligners would carry
some of the top guide load. Thus, there would have to be significant degradation
in most or all of the aligner hardware sets to allow top guide movement
3. For plants with vertical aligner pins, the arrangement of the aligner pin hardware
is such that for any direction of seismic acceleration, one or two sets of alignment
pin hardware would be partially or fully blocking top guide movement, even if
cracking had occurred. The top guide bottom plate and some beams would have
to deform around the alignment pin hardware during the seismic event, which
would limit displacements.
4. For plants with horizontal aligner pins, the hardware is attached by unareviced
fillet weld arrangements. Fillet welds generally develop smaller shrinkage
residual stresses than partial or full penetration welds like the ring weld and
shroud welds. Thus, the likelihood of SCC at these connecting welds is lower
than for the ring weld. A VT inspection of the alignment pin hardware at
Brunswick 1 was conducted when the shroud cracking was discovered (H3 was
extensively cracked) and no cracks were observed at the bracket fillet welds.
5. For plants with reinforcing blocks, the blocks are attached to the top guide, providing additional bracing on either side of the shroud bracket which engages
the aligner pin. If the aligner pin hardware attached to the top guide were to fail, the reinforcing blocks and intact shroud bracket would prevent top guide
motion. However, if the shroud bracket welds failed, the top guide could move
to the extent described in (3) above.
If the aligner pin hardware were cracked:
If several sets of aligner pin hardware were significantly cracked (quite unlikely)
and a design basis seismic event occurred (very unlikely), the remaining alignment
pin hardware fillet weld ligaments might separate by shear. For those plants with
hold down bolts, the bolts would have to fail before the top guide could move
laterally a significant amount. In some plants, the core spray sparger brackets
welded to the shroud would contact the top guide after limited displacement In the
extreme case, the top guide could move 4 to 5 inches before contacting the shroud.
Control rod insertion has been tested successfully for fuel channel static
displacements of up to 1.2 inches at the center of the channel length. This condition
has conservatively been extrapolated to a top guide displacement of 2.4 inches for
shroud repair discussions. Considering that the top guide displacement and control
rod insertion would be occurring during a dynamic seismic event, it is reasonable
to
January 3, 1995K> Attachment 2 USNRC IN95-17 Page 6 March 10, 1995 pages
expect that fuel motion would allow insertion more readily than would a static
situation. Dynamic tests of rod insertion with fuel motion have shown that
comparable insertion results could be achieved with dynamic fuel displacement
about 2.5 times the static displacement This information supports engineering
judgment that control rods would insert with a top guide lateral displacement of six
inches, which is greater than the displacement of the top guide contacting the
shroud.
If the top guide displacement occurred and control rods did not insert:
While the cumulative likelihood of the combination of events which must occur to
reach this condition is extremely unlikely, the outcome is still safe shutdown. If
control rods did not insert, standby liquid control would still be available. Failure of
control rods to insert is covered in plant Emergency Operating Procedures, and
operators are trained to respond to such scenarios. There is no scenario, including
any involving loose parts, where failure of top guide hardware, top guide
displacement or failed control rod insertion would disable the standby liquid control
system.
CONCLUSIONS
All 36 operating US BWRs have core plates with hold-down bolts. Core plate ring
weld cracking has an insignificant impact on core plate displacements under delta-P
and seismic loading.
The top and bottom plates of top guides are connected in a redundant way so that
ring weld cracking has an insignificant impact on the top guide response to vertical
loads, whether or not hold-down bolts are present.
Twenty BWRs have lateral support configurations where ring weld cracking has an
insignificant impact on top guide lateral load capability.
Sixteen BWRs have top guides where lateral loads are reacted by alignment pin
hardware. For these, ring weld cracking can have a small, but acceptable, impact on
top guide lateral load capability.
A number of additional hypothetical top guide component failures and associated
system responses are evaluated, with the conclusion in all cases being that safe
shutdown would be achievable.
Januarv 3, 199s
Attachment 2 USNtmc
Page
IN 95-17 Page 7 7March 10, 95
7 pages
The BWRVIP is using this information to incorporate appropriate
core plate and top
guide inspection and, if needed, evaluation/repair guidelines
into the overall vessel
and internals program, and will update the NRC on continuing
development and
implementation of this program.
If you have any questions, please contact Vaughn Wagoner, Technical Chairman of
the BWRVIP Assessment Subcommittee, at (919) 546-7959.
Sincerely, ACr
Carl Terry, Executive Chairman
BWRVIP Assessment Subcommittee
c: D.S. Brinkman, NRC Senior Project Manager
J. T. Beckham, Jr., BWRVIP Chairman
S. LaBruna, BWRVIP Vice Chairman
R.A. Pinelli, BWROG Chairman
KP. Donovan, BWROG Vice Chairman
BWRVIP Assessment Subcommittee Members
Attachment 3 IN 95-17 March 10, 1995 LIST OF RECENTLY ISSUED
NRC INFORMATION NOTICES
Information Date of
Notice No. Subject Issuance Issued to
95-16 Vibration Caused by 03/09/95 All holders of OLs or CPs
Increased Recirclation for boiling water reactors.
Flow in a Boiling Water
Reactor
95-15 Inadequate Logic Testing 03/07/95 All holders of OLs or CPs
of Safety-Related Circuits for nuclear power reactors.
95-14 Susceptibility of Con- 02/28/95 All holders of OLs or CPs
tainment Sump Recircula- for nuclear power reactors.
tion Gate Valves to
Pressure Locking
95-13 Potential for Data 02/24/95 All holders of OLs or CPs
Collection Equipment to for nuclear power reactors.
Affect Protection System
Performance
95-12 Potentially Nonconforming 02/21/95 All holders of OLs or CPs
Fasteners Supplied by for nuclear power reactors.
A&G Engineering II, Inc.
95-11 Failure of Condensate 02/24/95 All holders of OLs or CPs
Piping Because of 'rosion/ for nuclear power reactors.
Corrosion at a Flow- Straightening Device
95-10 Potential for Loss of 02/10/95 All holders of OLs or CPs
Supp. 1 Automatic Engineered for nuclear power reactors.
Safety Features
Actuation
95-10 Potential for Loss of 02/03/95 All holders of OLs or CPs
Automatic Engineered for nuclear power reactors.
Safety Features
Actuation
95-09 Use of Inappropriate 01/31/95 All holders of OLs or CPs
Guidelines and Criteria for nuclear power reactors.
for Nuclear Piping and
Pipe Support Evaluation
and Design
OL = Operating License
CP = Construction Permit
IN 95-17 March 10, 1995 This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
/s/'d by BKGrimes
Brian K. Grimes, Director
Division of Project Support
Office of Nuclear Reactor Regulation
Technical contacts: W. H. Koo, NRR E. M. Hackett, NRR
(301) 415-2706 (301) 415-2751 T. A. Greene, NRR
(301) 415-1175 Attachments:
1. Figure, "Location of Cracking in
Top Guide and Core Plate"
2. Letter from BWR Vessel and Internals
Project to U.S. Nuclear Regulatory Commission,
"Request for Information Regarding the Impact
of BWR Core Plate and Top Guide Ring Cracking,"
January 3, 1995
3. List of Recently Issued NRC Information Notices
DOCUMENT NAME: 95-17. IN
- See previous concurrences
OFC *EMCB:DE *EMCB:DE *C/EMCB:DE *PUB:ADM
NAME WHKoo:wk:adl RAHermann JRStrosnider Tech ED
DATE _ 01/09/95 I01/09/95 01/09/95 J01/18/95 OFC
NAME
DATE
- OECB:DOPS
TGreene
01 2// a
-
_ *C/OECB:DOPS
RDennig
j01/26/95 I1*OECB:DOPS
RKiessel
02/21/95 f1*C/OECB:DOPS
AChaffee
02/27/95 OFC w1prsp
NAME mes
DATE 103 l /95 OFFICIAL RECORD COPY
IN 95-XX
March xx, 1995 On September 30, 1993, the NRC issued Information Notice (IN)93-79, "Core
Shroud Cracking at Beltline Region Welds in Boiling-Water Reactors," in
response to the discovery of cracking of the core shroud welds at Brunswick
Unit 1 plant. Following the additional discovery of core shroud cracks at
Dresden Unit 3 and Quad Cities Unit 1 in 1994, the following additional
generic communications were issued: 1) IN 94-42, "Cracking in the Lower
Region of the Core Shroud in Boiling-Water Reactors," on June 7, 1994;
2) Supplement 1 to IN 94-42 on July 19, 1994; and 3) Generic Letter 94-03,
"Intergranular Stress Corrosion Cracking of Core Shroud in Boiling Water
Reactors," on July 25, 1994.
This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Project Support
Office of Nuclear Reactor Regulation
Technical contacts: W. H. Koo, NRR E. Hackett, NRR
(301) 504-2706 (301) 504-2751 T. Greene, NRR
(301) 415-1175 Attachments:
1. Figure, "Location of Cracking in
Top Guide and Core Plate"
2. Letter from BWR Vessel and Internals
Project to U.S. Nuclear Regulatory Commission,
"Request for Information Regarding the Impact
of BWR Core Plate and Top Guide Ring Cracking,"
January 3, 1995
3. List of Recently Issued NRC Information Notices
- See previous concurrences DOCUMENT NAME: S:\DOPS SEC\TOPGUIDE.INF
OFC *EMCB:DE *EMCB:DE *C/EMCB:DE *PUB:ADM
NAME WHKoo:wk:adl RAHermann JRStrosnider Tech ED
DATE 01/09/95 01/09/95 01/09/95 j01/18/95 OFC *OECB:DOPS _ *C/OECB:DOPS *OECB:DOPS *C/OECB:DOPS
NAME TGreene RDennig RKiessel AChaffee
DATE 01/26/95 ]01/26/95 j02/21/95 102/27/95 OFC ID/DOPS
NAME BGrimes
DATE / /95 OFFICIAL RECORD COPY
IN 95-XX
January xx, 1995 This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Project Support
Office of Nuclear Reactor Regulation
Technical contacts: W. H. Koo, NRR E. Hackett, NRR
(301) 504-2706 (301) 504-2751 T. Greene, NRR
(301) 415-1175 Attachments:
1. Figure, "Location of Cracking in
Top Guide and Core Plate"
2. Letter from BWR Vessel and Internals
Project to U.S. Nuclear Regulatory Commission,
"Request for Information Regarding the Impact
of BWR Core Plate and Top Guide Ring Cracking,"
January 3, 1995
3. List of Recently Issued NRC Information Notices
/9: *-
DOCUMENT NAME: G:\TAG\TOPGUIDE.INF 14*1'1E IP- J
- 'Zo nrovinuo cnncurrences 714 J
OFC *EMCB:DE *EMCB:DE *C/EMCB:DE *PUB:ADM -14.1.&
NAME WHKoo:wk:adl RAHermann JRStrosnider Tech ED
DATE 01/09/95 01/09/95 01/09/95 01/18/95 OFC *OECB:DOPS *C/OECB:DOPS " POECB:DOP
TGreene RDennig JSh KRKiessel Of
NAME
DATE 01/26/95 01/26/95 / // l I
OFC C/f Ae PSD/DOPS ,_
NAME AChSffle]~ I BGrime29efiA
DATE tr /rL'\95 / /95 I -'t---- --- -- ---
' - --- nrnn
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UH-ILIAL KtLUKU W rY
IN 95-XX
January xx, 1995 This information notice requires no specific action or written response. If
you have any questions about the information in this notice, please contact
one of the technical contacts listed below or the appropriate Office of
Nuclear Reactor Regulation (NRR) project manager.
Brian K. Grimes, Director
Division of Project Support
Office of Nuclear Reactor Regulation
Technical contacts: W. H. Koo, NRR E. Hackett, NRR
(301) 504-2706 (301) 504-2751 T. Greene, NRR
(301) 415-1175 Attachments:
1. Figure, Location of Cracking in
Top Guide and Core Platen
2. Letter from BWR Vessel and Internals
Project to U.S. Nuclear Regulatory Commission, Request for Information Regarding the Impact
of BWR Core Plate and Top Guide Ring Cracking,"
January 3, 1995
3. List of Recently Issued NRC Information Notices
DOCUMENT NAME: G:\TAG\TOPGUIDE.INF
- See previous concurrences
OFC *EMCB:DE *EMCB:DE *C/EMCB:DE *PUB:ADM
NAME WHKoo:wk:adl RAHermann JRStrosnider Tech ED
DATE 01/09/95 01/09/95 01/09/95 01/18/95 OFC OECB:DOPS CWAP OECB:DOPS C/OECB:DOPS
NAME TIreene >v Renld RKiessel AChaffee
DATE 1 /Z(/95 l/> ,/95 / /95 / /95 OFC D/DOPS
NAME BGrimes
DATE / /95 OFFICIAL a ______COPY
OFFICIAL RECORD COPY
I
Office of Nuclear React;r Regulation
Technical contact(s): William H. Koo, NRR, (301) 504-2706 Edwin M. Hackett, NRR, (301) 504-2751 Attachments:
(1) Letter from BWRVIP to U.S. Nuclear Regulatory Commission, "Request for
Information Regarding the Impact of BWR Core Plate and Top Guide Ring
Cracking," dated January 3, 1995
(2) List of Recently Issued NRC Information Notices
- See Drevious concurrences
OFC *DE:EMCB *DE:EMCB *DE:EMCB l PUB:ADM ]
NAME WHKoo:wk:adl RAHermann JRStrosnider Tech ED
DATE [ 01/09/95 01/09/95 101/09/95 / ///95 OFC C/OECB:DOPS C/OECB:DOPS D/DOPS
NAME RDennig AChaffee BGrimes
DATE
_- - - _
/ /95 . .__.
/ /95 / /95
[OFFICIAL RECORD COPY] DOCUMENT NAME: G:\TAG\TOPGUIDE.INF
cycles wX0.22 pS/cm. indicated that the subject eirseas BWR t not a GE
BWR, but the designs the top guide and core plate ae similar. GE also
noted that similar ids existed in GE BWRs (domestic BWRs). In domestic BWRs
Type 304 austenit stainless steel (SS) was used for fabricating the t
guide and the cae plate, instead of Type 347 austenitic stainless sta1 which
was used in th overseas non-GE BWR. GE has tested Type 347 SS for ts
resistance to intergranular stress corrosion cracking (IGSCC). B ed on the
tests GE --- that Type 347 stainless stee has a susice ti ity to IGS5%?
equiv~alent to that of Type 304L stainless steel en no seni ze and is
equivalent to high carbon Type 304 stainless steel when sens zed. As stated
in the subject RICSIL, GE expects that azOhfa, cracking ma occur in the top
guide and core plate of the domestic BWRs which have a siilar amount of hot
operating time. GE indicated that there are several diferent configurations
of the top guide and core plate assemblies in the GE esigned BWRs. The BWR
Vessel and Internals Project (BWRVIP) by letter of anuary 3, 1995jreported /
GE's evaluation of the safety significance of th cracking event pertaining
to the domestic BWRs. The non-proprietary por on of the BWRVIP's letter is V
provided in the attachment.
The NRC staff will closely monitor the in ections of top guides and core
plates in the industry. The staff is e luating the safety implications of
such cracking and will determine if a itional generic communication is
necessary. N
This information notice require no specific action or written response. Ifi
you have any questions about e information in this notice, please contact
(one of) the technical cont (s) listed below or the appropriate Office of
Nuclear Reactor Regulation NRR) project manager.
Brian K. Grimes, Director
Division of Operating Reactor Support
Office of Nuclear Reactor Regulation
Technical ntact(s): William H. Koo, NRR, (301) 504-2706 Edwin M. Hackett, NRR, (301) 504-2751 Atta en ns: -
(1) etter from BWRVIP to U.S. ulatory Comm ssion,"Request for
Information Regarding the I of BWR Core Plate and Top Guide Ring
Cracking," dated January 3, 1995
(2)List of Recently Issued NRC Information Notices
- see previous concurrences I t
OFC EMCB:DE SC/EMCB:DE C104 H PUB:ADM
NAME WHKoo* RAHermann* {~osnider Tech ED
DATE 01/09/95 01/09/95 ,/ I , , X__
OFC C/OEAB:DORS C/OGCB:DORS D/DORS
NAME AChaffee GMarcus BGrimes
DATE / I / / / j/
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- U-I-ILA no'Y
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t FFILIAL RMCKU LUPYJ UUCUMtNI NAMt: b:\KUU\IUPGUlUt.1Nt