ML20043F758
| ML20043F758 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 06/07/1990 |
| From: | Devine J GENERAL PUBLIC UTILITIES CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 5000-90-1938, GL-88-01, GL-88-1, NUDOCS 9006180091 | |
| Download: ML20043F758 (6) | |
Text
...
y f
OPU Nuclear Corporation i
N Imr One Upper Pond Road Parsippany, New Jersey 07054 201-316-7000 TELEX 13&482 Writers Direct Dial Numbet June 7, 1990 5000-90-1938 i
U. S. Nuclear Regulatory Commission Attention:
Document control Desk Mailing Station P1-137 Washington, DC 20555 Gentlemen subject: Oyster Creek Nuclear Generating Station (OCNGS)
Docket No. 50-219 Generic Letter 88-01 References GPUN Ltr. 5000-89-1712, Dated 1/31/89 GPUN Ltr. 5000-90-1891, Dated 2/21/90 NRC Ltr., Dated 4/17/90 i
We have reviewed your most recent letter, concerning compliance with GL 88-01, and our inspection plans for the upcoming cutage (13R). We will submit revised inspection plans for 13R for staff review by August 1990.
In answer to your request for information regarding GPUN compliance with the subject generic letter, we have addressed herein the items identified by the NRC staff.
Staff Position:
1.
The licensee's position not to amend the Technical Specifications (TS) to include a statement on In-service Inspection (ISI) as required in GL 88-01 is not acceptable.
Response
GPUN will be revising Sur previous response to GL 88-01 and will submit a Technical Specification change Request consistent with this response during the upcoming refueling outage, scheduled for completion in the Spring of 1991.
9006180091 900607 PDR ADOCK 05000219 P
PDC C320674 1
GPU Nuclear Corporation is a subsidiary of General Public Utilities Corporation n -.
+
w e
4 G(NERIC LETTER 88-01 o
PAGE 2 i
l 1
Staff Position:
2.
The Licensee's position to reduce the frequency of piping inspections based on the implementation of hydrogen water chemistry (HWC) is not acceptable.
The staff has learned through reports that piping weld cracking has occurred at two nuclear power generating facilities which have been I
operating with HWC.
The staff has some concerns regarding the effectiveness of HWC in mitigating IGSCC. Therefore, the staff is not granting inspection credit based on the implementation of HWC at this time until the staff's concerns are resolved.
Response
I GPU Nuclear will not reduce the frequency of piping inopsetions at this time. However, a reduced inspection frequency may be requested in the future, based on industry experience with HWC, and/or BWR Owners Group (BWROG's) findings and recommendations concerning HWC.
i Staff Position 3.
The licenses position to reduce the frequency of inspections on stress i
improved treated welds is not acceptable.
Response
GPUN will comply with the NRC staff's recommendation not to reduce the e
frequency of inspections on SI-treated welds.
However, we believe that SI of small bore (dia. equal or less than 12") ICSCC Category D welds would j
increase the integrity of piping even without post SI-inspection.
3 Therefore, these welds (GPUN Category C/D) will not be downgraded to Category G welds, as defined in Section 5.3.1.7 of NUREG 0313, Revision 2.
These welds will remain as Category D welds and will be inspected'in accordance with the requirements of GL-88-01.
I Staff Positions i
4.
The licensee did not justify the reduction in the frequency of inspections i
of welds classified as IGSCC Categories C, D, E, and G.
The licensee should revise the inspection schedules for these welds in accordance with GL-88-01 and all IGSCC Category G welds should be inspected during the next scheduled refueling outage (13R).
Response
The reason for reducing the frequency of inspections was based on taking credit for hydrogen water chemistry (HWC).
As discussed in Response 2, GPUN will not take any credit for HWC during 13R.
Therefore, there will be no reduction in the frequency of inspections of welds classified as IGSCC
. categories C, D, and E.
C320674 i
i
0
'{
}
CENERIC LETTER 88-01 f
PAGE 3 CPUN will comply with the NRC staff's recommendation except the IGSCC Category G welds of recirculation safe ends and Reactor Water Clean-Up (RWCU) welds cutboard of the second isolation valves.
Eight (8) of the sixteen (16) recirculation safe end category 0 welds will be stress l
5 improved and inspected during 13R. The remaining 8 welds will be stress improved and inspected during 14R. Additionally, only 10% of tho RWCU welds outboard of the second isolation valves will be inspected during l
13R.
If indications are characterized as IGSCC in the RWCU sample, CPUN r
will approach the staff on their disposition and any plans for sample expansion.
r Staff Positient l
5.
The licensee's position classifying as uninspectable five casting-to-casting welds in the Recirculation System is not acceptable.
There are techniques available in the industry to inspect castings and the i
castings should be inspected in accordance with CL 88-01 Resoonset The staff's concerns about inspection of casting-to-casting welds have been discussed between GPUN and EPRI NDE center.
The techniques developed to date have been able to detect cracks with size larger than 50% through-wall thickness in centrifugal cast stainless steel (CCSS).
The grain structure in the CCSS is much more uniform than that found in statical cast stainless steel.
It is the lack of uniformity that affects the ability to perform a reliable examination for small cracks such as IGSCC.
Therefore, we consider that there is no NDE technique available that would reliably detect IGSCC and meet the requirements of CL 88-01 and NURCO 0313, Rev. 2.
EPRI is' working on developing screening methods to determine acoustic characteristicefoi castings and the resultant methods for performing reliable examinations. GPUN will develop plans to inspect casting welds i
when acceptable techniques are available.
Since no meaningful results would be generated by the current NDE methods, inspection of these casting l
welds during 13R would not be in the interests of reducing radiation exposure.
Staff Positions 6.~
The licensee's position concerning sample expansion based on systems rather than by IGSCC category as required in GL 88-01 is not acceptable.
Response
GPUN will accept the NRC staff's recommendation with the following exceptions:
C320674
v o
o GENERIC LETTER 88-01
}
PAGE 4 3-(a) Svatem Safe-Ends If flaws are detected in nny of the reactor coolant safe-ends, on'y those safe-end welds residing within the affected system i
will be included within the examination expanded sample.
Since the majority of the safe-end welds are made of Inconel and their joint configurations are different from that of the-remaining pipe welds, we believe it is appropriate to treat the system safe-end welds as a separate group.
(b) RWCU Welds Located Outboard of the Second Isolation Valves As discussed in Response 4, only 10% of the RWCU welds' located outboard of the second isoletion valves will be inspected during 13R. GPUN would approach the staff on their disposition I
and any plans for sample expansion should ICSCC be found in the initial sample welds.
(c) Samole Expansion for " Suspect" Welds
" Suspect" welds are those that required extensive examination
=in order to disposition wolds as not containing indications of i
For example, in 11R, there wvere eight recirculation system welds that required additional examinations that led to the conclusion, at that time, that the indications were characteristic of root condition, geometry, and/or.
counterboro.
Experience at other plants showed that these-conditions often resulted in subsequent examinations concluding that the indications were really characteristic of IGSCC.
Therefore, our initial sample of six welds in 12R was selected from the eight " suspect" welds of 11R.
Two of the six were dispositioned in 12R as containing IGSCC.
,i There were no substantial changes in location or signal characteristics from the 11R to 12R examinations.
Since our sample expansion required examination of an additional six welds, the two remaining 11R " suspect" welds, plus'four others, were examined. One of the two remaining 11R " suspect" welds was determined to contain ICSCC. This' finding resulted in examination of the remaining 49 Category C Recirculation system welds.
No additional indications of IGSCC were detected.
Based upon the above sequence, we consider that our approach to weld selection was based on sound engineering and EPRI -
qualified NDE examiners' judgement. Therefore, we consider that the following sample expansion requirement for " suspect" welds to be technically sound and ALARA conscious Should indications of IGSCC be detected in welds considered to be " suspect," as defined above, sample expansion will include only other " suspect" welds, if any, in a number-equal to the initial sample.
Further indications of IGSCC in the second sample will require examination of all remaining " suspect" welds.
1 C320674
m O
i '
GENERIC LETTER 88-01 PAGE 5 (d) Remainina Welds (Recirculation, Core Sorav. Shutdown Coolina, Isolation Condenser Inside and Outside Drvwell, RWCU Inside the Second foolation Valve, and closure Head Picinc.)
It is proposed that should flaws be detected in welds of a specific category, as defined in GL 88-01, then an equal number of welds will be examined within that category in the first expansion sample.
Should flaws be detected in the second expansion sample, all welds in that specific category will be examined.
Staff Position 7.
The licensee's position of considering flaw evaluation having no constraint on plant restart is not acceptable.
The licensee should revise its position and follow the staff's position in GL 88-01 reporting requirements which requires NRC approval of flaw evaluations and/or repairs in accordance with IWB 3640 and IWA 4130 before resumption of operation.
I
Response
GPUN agrees with the NRC staff position concerning flaw evaluations and will obtain NRC approval of the evaluations and/or repairs prior to restart.
Staff Position 8.
The licensee's position of not ultrasonically inspecting the RWCU piping welds outboard of the secondary containment Isolation valves (CIV) after 13R refueling outage is not acceptable. The licensee should ultrasonically inspect at least 10% of the welds outboard of the secondary CIV during each refueling outage.-
Response
We accept the staff position concerning ultrasonic inspections of at least 10% of RWCU piping welds outboard the secondary CIV for the 13R outage.
Also, we tentatively plan to inspect a further 10% of RWCU
. piping welds during future refueling outages,-pending results of 13R inspections and subject to possible inspection reduction as may be allowed by the.use of HWC.
l C320674 j
M.
c.
s-s j; Le = i CENERIC LETTER 88-01 L
PAGE 6 i
If you have any questions regarding this matter, please contact Mr. Michael Laggart, Manager, BWR Licensing at (201) 316-7968.
l Very truly yours, l
t
[
\\
~
a.k.Ed t
s.
J. C. DeVine, Jr.
Vice President & Director i
Technical Functions 0
JCD/BP/crb (C320674)
/
cc Administrator
{
Region I U. S. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 NRC Resident Inspector Oyster. Creek Nuclear Generating Station Forked River, NJ 08731-Mr. Alex Dromerick, Jr.
U. S. Nuclear Regulatory Commission Hall Station P1-137 i
Washington, DC 20555 L
n
,k
[
r r
9 b
o a
i i
. C320674 e
e
<m.
t--
,