ML20244E438
| ML20244E438 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 06/16/1989 |
| From: | Hairston W GEORGIA POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-88-01, GL-88-1, HL-517, NUDOCS 8906200340 | |
| Download: ML20244E438 (7) | |
Text
w m r;.. m as,
N' m e,s m.
h%
<y i.
T 8; t
} [ ll t
( w.
- I ; ij ill r
,4,
- r..
? w-
-e 1
- ,,,_ M f y
NY Ct s liiblO fN I
f i.
uv1 i
HL-517' 0128V l
June 16, 1989 l
l U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C.
20555
]
PLANT HATCH - UNITS 1, 2 I
NRC DOCKETS 50-321, 50-366 OPERATING LICENSES DPR-57, NPF-5 l
PROPOSED RHCU WELD EXAMINATIONS l
PER GENERIC LETTER 88-01 i
Gentlemen:
i
- On June 30, 1988, Georgia Power Company (GPC) responded to Generic Letter' (GL) 88-01, "NRC Position on IGSCC in BHR Austenitic Stainless i
Steel Piping."
Included in our response was a request to exclude from examinations, the non-safety-related reactor water clean-up (RWCU) piping located downstream (outside containment) of the double isolation valves.
By letter-dated October 24, 1988, - the NRC denied this exclusion due to l
lack of justification. On April 5,1989, GPC met with the NRC to. discuss l
the hardship involved with inspecting all these additional welds.
Based H
on the discussion. agreement was reached to perform a sample inspection plan, with - the understanding that we predetermine our flaw evaluation criteria for scope expansion prior to the outage, and provide the criteria to the NRC for their review.
~The enclosure presents our proposed examination plan and the flaw evaluation criteria for the j
subject piping.
You may contact this office at any time if you have questions.
I I
2 Si.1cerely.
1
/@.d __ _ o C
.1 W-W. G. Hairston, III GKM/eb J
Enclosure:
Proposed RHCU Held Examinations Per Generic Letter 88-01
)
c:
(See next page.)
j 890620034o 890616 PDR ADOCK 05000321 p_
-1.
i U.S. l Nuclear: Regulatory Comission June:16,-1989-Page Two p
1.
- c
- ;Georcia Power Comitny n
Mr. H.. C. Nix, Geinral Manager - Nuclear Plant Mr. - L.. T.. Gucwa, Fanager Engineering and Licensing - Hatch
-GO-NORMS 1
U.S. Nuclear Reaulatory Commission. Washinoton. D.C.
Mr. L. P. Crocker, Licensing Project Manager - Hatch U.S. Nuclear Reaulatory Commission. Reaion II Mr.~ S. D. Ebneter, Regional Administrator Mr. J. E. Menning, Senior. Resident Inspector - Hatch 0128V
______.__-_____m___._____
,0
- 1. :
ENCLOSURE PLANT HATCH UNITS 1, 2 NRC DOCKETS 50-321, 50-366 OPERATIAG LICENSES DPR-57, NPF-5 PROPOSED RHCU HELD EXAMINATIONS PER GENERIC LETTER 83-01 I
_Our June 30, 1988 letter requested excluding approximately 130 reactor water clean-up (RNCU) welds (combined number of welds for both units) from the ultrasonic testing (UT) requirements of Generic Letter (GL) 88-01 and NUREG-0313, Revision 2.
The subject piping welds are located outside primary containment and are not considered part of the reactor l
coolant primary pressure boundary.
. Our relief request was based on three considerations:
(1) The piping is isolable.
Two, upstream, automatically-actuated isolation valves close l
upon a variety of initiation signals indicative of a leak or break; (2) l ALARA considerations.
The estimated personnel exposure for inspection i
and related activities would range from 0.4 to 6 rem per weld, depending on location; and (3) The piping is not safety-related and has never been 1
part of our ASME Section XI Program. The NRC initially denied our relief request by letter dated October 24, 1988.
This relief request does not pertain to the Class I portions of the RHCU piping, which have been replaced.
These. welds would be considered Category G welds per GL 88-01 (non-resistant, not inspected material) because they have not been ultrasonically examined previously.
Therefore, in accordance with the
. generic letter, all of the subject Unit 2 RNCU welds would have to be inspected during the 1989 maintenance / refueling (H/R) outage and all the j
Unit I welds exaained during the 1990 outage.
Inspection of all these welds would approximately double the number of UT examinations for intergranular stress corrosion cracking (IGSCC)-susceptible welds otherwise required by GL 88-01.
i On April 5, 1989, GPC personnel met with the NRC staff to discuss the l
burden associated with inspection of the subject welds and verbally i
agreed to a sample examination plan. The following paragraphs detail our augmented inspection plan for the RHCU piping welds outside the outboard isolation valve.
Specifically, the number and location of the selected
. welds in the subject piping, and flaw evaluation criteria for scope expansion are discussed.
Held Selection A review was performed to determine the RHCU weld population which may be most susceptible to IGSCC. Seven Unit 2 RHCU welds (approximately 10% of l
t the applicable weld population) have been selected for ultrasonic testing (UT) inspections.
The selection of the seven welds was determined based 0128V HL-517 E-1
f.
I i
l f
ENCLOSURE (Continued)
PROPOSED RHCU WELD EXAMINATIONS PER GENERIC LETTER 88-01 on accessibility, ALARA considerations, and IGSCC susceptibility.
Figure 1 shows a schematic of the Unit 2 RHCU piping.
GPC plans to inspect two 6-inch diameter welds and three 4-inch diameter welds between the outboard isolation valve (F004) and the entry to the regenerative heat exchanger.
The regenerative heat exchanger is a counter flow heat exchanger which allows heat from the hot reactor fluid inlet flow to be transferred to the fluid being returned to the reactor after filtering.
After leaving the regenerative heat exchangers the operating temperature of the fluid has dropped considerably on the inlet side of the system.
Two 4-inch welds will be examined on the fluid return side after exiting the regenerative heat exchanger.
To summarize, five welds will be examined on the hot leg inlet side of the regenerative heat exchanger, and two welds will be examined on the hot leg outlet side.
Studies have shown that IGSCC is more likely in piping which operates at higher temperature.
Expansion of scope to include another seven welds will depend on the results of the initial inspection relative to the flaw evaluation criteria discussed below.
Flaw Evaluation Criteria Held inspection and disposition of crack-like indications (e.g., overlay design) will be in accordance with Generic Letter 88-01/NUREG-0313, Revision 2 guidance.
Scope expansion criteria will not be in accordance with the GL.
Reportable indications for the purpose of scope expansion will be based on the ' leak-before-break criteria described below, in lieu of those of NUREG
- 0313, Revision 2.
The subject piping is not considered safety-related and can be isolated.
The welds in this piping were not radiographer and have not been included in our ASME Section XI Program.
This means that reliable baseline data on the welds is not availsble.
Our intent is to use these criteria to determine unacceptable cracking for the purpose of scope expansion.
Structural Integrity Associates (SIA) was retained by GPC to assist in the development of the scope expansion criteria.
The conclusion of this effort is that any axial flaws, or single circumferential flaw with length less than approximately 30% of the circumference would tend to leak before breaking, and thus would not be a cause for concern if they were present in uninspected welds in this non-safety system.
The allowable flaw length depends on the magnitude of the applied stress.
A review of the stress report for the subject piping (including the seven welds selected for inspection),
indicates that the applied stresses are bounded by the range of stress 0128V HL-517 E-2
ENCLOSURE (Continued)
PROPOSED RNCU HELD EXAMINATIONS PER GENERIC LETTER 88-01 level reported in Table 1.
Table 1 shows the allowable flaw length as a function of applied stress and pipe
- diameter, generated using a
conservative set of material properties.
The proposed criteria of Table 1 is independent of flaw depth, since flaw growth through-wall in small diameter piping is predicted to be rapid.
The tendency observed in numerous cracking incidents in small BWR lines (112 inch diameter) is for local through-wall growth (due to asymmetries in the stress pattern) rather than for uniform growth around the circumference.
Thus, industry experience supports these leak before break arguments.
In summary, when the identified flaws in the inspection sample are axial, or when a circumferential flaw in the weld is shorter than the lengths identified in Table 1,
expansion of the inspection sample is not required.
(It should be noted that any detected flaw indication [or multiple circumferential indications] near the length in Table 1 would be evaluated on a case-by-case basis, to determine if sample expansion is required )
If our initial examinations identify one or more welds with flaws larger than the above criteria, GPC will either examine an additional seven welds as indicated by the above criteria, or discuss our findings with the NRC. The additional welds will be selected considering the magnitude of applied stresses in those welds related to Taule 1, as well as the susceptibility criteria used to select the original sample, plus any new information gained from the initial examinations.
If one or more welds in the subsequent examinations have flaws longer than that identified in Table 1,
the inspection scope would not be automatically expanded.
At that point, GPC would discuss, with the NRC, our resolution plan relative to the subject piping.
If the subsequent welds do not have flaw indications as large or larger than Table 1, GPC will plan to inspect an additional 7
welds during the next maintenance / refueling outage and follow similar guidelines regarding flaw evaluation and scope expansion.
Plant Hatch Unit 2 has a maintenance / refueling outage scheduled to commence around September 1, 1989.
Similar RHCU IGSCC inspections on Unit I would occur during the Spring of 1990 refueling outage.
1 0128V HL-517 E-3
1 4
-.-., L*~
j Nn j-I ENCLOSURE'(Continued)
TABLE'1 Permissible Flaw Lenaths vs.-Stress
~For Non-Safety Grade RHCU Pinina Held Inspections 6" Pipe 4" Pipe Applied Stress Critical Length Critical Length.
(KSI)-
(% of Circumference)
. % of Circumference)
(
.14.1 18.4%-
21.0%
9.4 29.6%
32.4%
4.7 47.3%
49.0%
Notes:
1.
Criteria is independent of flaw depth.
'2.
A detected flaw indication (or multiple small indications) near the size indicated by this table will be evaluated on a case by case basis..
0128V HL-517 E-4
_ = = _ _ _
f, ~~
)
3 D-L GE 0
I A
8 6
uNM x
2 2
E 0
8 0
8 E R T.
B 3
8 D
/
. [
u
= R
=
H F
O T
[
I IDD R/ m ~
E FF 0
)
3
)
S R 5
D E G L G x
E N A V AH f
0 9
C 0
3 x 7
A c 6 4
1 E
G R.
1 1
1 a
L 0
L T.
N m '
0 5
E B
8 8' E H
I L
. l a
" I
=
= R 8
P 3e NE I
hU fPd l
GE P
1 I
n R
7 aa 0
U 6
S 4
D C
(
L V
E A
V f4 R
a 4
l g
X.
1 2
9S 2D E
(L R
AE U
1V TG 1
IF I
q N
y 43 g
g U
I H
A B
M M
1
]
0 M
C 0
O C
C-T
'4 4
R 9 S
t 5
D P
6 P
6 A
N 2 L
M 1
M i
A U
H U
I
(
(
P t
T
. E g
P L
A V E
E f
R 9 U
U aA 0
EP 4 1
C C
V V
%R f
D A.
gm i
EE R
CS o
G s S 9
m oD D
6 n
I A
.L
(
s.
f S
AE rV n
f D
3 0
L t
u I
0 E
69 9
n C
G V Y
5 n
R 3
a A
t M
ca I
R 4
i P
0 <2' n
F>1 0
7 LE 104 0
FD g
'