ML20117G832
| ML20117G832 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 09/03/1996 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20117G835 | List: |
| References | |
| NUDOCS 9609060002 | |
| Download: ML20117G832 (2) | |
Text
.
[ The number of GGNS specimen holders was determined per ASTM E185-73 (Ref. 3).
The three specimen holders.were designed, built and analyzed to Section III of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code), 1971 Edition, with Addenda through Winter 1972.
Each holder has 12 Charpy V-notch (CVN) specimens of the weld, base metal and heat-affected zone (HAZ) for a total of 36 specimens. A set of unirradiated specimens are kept, as well as archive material, for additional testing in order to provide baseline information.
GGNS is defined as an ASTM E185-73 Case "A" plant since the vessel has a shift in the reference null-ductility temferature (ART ) of will be exposed to a neutron fluence of less tha.,5x10',less jhan 100*F and n
n/cm over the design lifetime of the plant. The current testing schedule requires that the first specimen holder be removed at 8 EFPY, the second at 24 EFPY, and the testing and reporting is to be performed in accordance with the more recent l
ASTM E185-82 (Ref. 4).
If the ASTM E185-82 requirements were applied to wall fluence is 5x10}adetermine the schedu e the,first capsule should be withdrawn whenl n/cm, or when the ART The GGNS vessel wall is unlikely to r., reaches 50*F whichever is' first.
each the conditions described above during the design lifetime of the plant, therefore, early capsule withdrawal is not critical for continued operation of the plant.
In response to Generic Letter (GL) 92-01, Supplement 1 (Ref. 5), a study was performed by General Electric Company for the Boiling Water Reactor (BWR)
Vessel and Internals Project (VIP) on the copper levels present in BWR beltline materials (Ref. 6). The purpose was to verify plants with significant variation in the reported copper levels. GGNS was determined to be consistent with reported values with no significant variation l
in the reactor vessel material (e.g., 0.02-0.06% copper).
i The licensee used Regulatory Guide (RG) 1.99, Revision (Rev.) 2 to i
calculatetheshiftinRT[ials.and adjusted reference temperature (ART) values l
for all GGNg belt {ine matI The fluence used to evaluate the 32 EFPY ART was 2.5 x10- n/cm.
The resulting predicted values of RT shift indicate i
that the vessel will not experience a large shift over ves.7sel life. A l
comparison was made between calculated shift and fluence values and actual surveillance data from other BWR's in order to confinn the conservative predicted shift plus margin values that were used to modify the surveillance program schedule. The results for BWR/6's, including GGNS, show a small shift i
for capsules removed at EFPY similar to Grand Gulf's current schedule and at higher fluence levels. Based on the data, the measured shift for GGNS would be conservatively bound by the RG 1.99, Rev. 2 calculations.
?
The shift in RT, fracture toughness (K,).that results from surveillance testing thecrackarresI K
pressure-temperature (P-T) limits curves.. The, is used to calculate the i
i current P-T limits curves for GGNS are calculated with the 10 EFPY shift in RT 'ted using the conservative The limiting condition I
is the pressure test, and the P-T curve is calcuIa.
lower bound K,.
K, the static crack initiation fracture toughness, is l
i ic ENCLOSURE 9609060002 960903 PDR ADOCK 05000416 P
PDR m
i
r i
s 4,
4 i
approximately 2.4 times K,$, fracture toughness is not a significant concern which demonstrates the conservatism in the P-T limits calculation. Vesse j
for GGNS over the life of the vessel.
The BWR Owner's Group (BWROG) began a supplemental surveillance program (SSP)
.in the late 1980's that was designed to significantly increase the amount of i
BWR surveillance data in a systematic manner. The BWROG's reasons for beginning the program were the following:
There are a smaller number of capsules per plant and fewer BWRs than j
pressurized water reactors (PWRs)
)
There are not much BWR surveillance data at higher fluences, nor would there be for many years l
RG 1.99, Rev. 2 imposed some hardships on pressure testing for BWRs, some
=
j of which might be relieved if a better understanding of BWR embrittlement j
phenomenon were obtained.
Supplemental capsules were installed in Cooper and Oyeter Creek, and specimen j
withdrawal is planned for 1996, 2000, and 2002. The results will be the l
equivalent of 84 additional surveillance capsules compared to approximately 25 I
which have been tested. The materials used were selected to bound the range of chemistries in BWR beltline materials, and in.nost cases are BWR beltline i
materials. The GGNS surveillance plate and weld material, including the U
limiting material, are among the materials in the capsules. At least one of these materials is in each of the seven capsules in the SSP. Results will be l
developed which will provide information on all the GGNS plate and weld surveillance materials, and will be directly applicable to the GGNS t
i surveillance program, collected between 5x10'ppecifically, tg caps,ules, when tested, will have n/cm and 2x10 n/cm fluence, which bounds the end j
of life (EOL) fluence for the GGNS vessel.
4 Since the expected shift is low, the first surveillance program testing should be at a time when the majority of the shift in the vessel RT., has been achieved.
Early testing may yield shift in RT,_ values that are not distinguishable from the data scatter. Anomalous shift is not a major concern because, if it were to occur, the BWROG SSP will identify any greater than expected shift.
The staff used'pG 139 calculational methods to verify that the 8 EFPY fluence value-(2.2 x10 n/cm ) in combination with the low copper values (0.02-0.06%)
result in predicted values that are not distinguishable from thgdata scatter.
2 The staff also verified that the 24 EFPY fluence value (6.9 x10 n/cm ) would result in predicted values that are more likely to be distinguishable from the data scatter.
The licensee determined the revised surveillance schedule by examining the fracture toughness decrease as a function of shift, and used that shift to determine the appropriate EFPY for removal and testing of the first capsule.