ML20006E462
| ML20006E462 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 12/07/1989 |
| From: | Shelton D TOLEDO EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| 1740, TAC-M75327, NUDOCS 9002230240 | |
| Download: ML20006E462 (6) | |
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TOLEDO
%ss EDISON A Centenw Energy Cwwww DONAU) C. SHELTON vce Prescert-,ms (41D)P49 2300
. Docket Number 50-346 License Number NPF-3 Serial Number:1740 December 7, 1989 United States Nuclear Regulatory Commission Document Control Desk Vashington, D. C. 20555
Subject:
Proposed Alternative to ASME Section XI Requirements for Volumetric and Surface Examinations of Reactor Vessel Nozzle to Pipe Velds (TAC Number M75327)
Gentlemen LASME Boiler and Pressure Vessel Code,Section XI requires that an outside diameter (OD)l surface and volumetric examination be conducted of the velds at the terminal' ends of piping runs connected'to vessels.- This examination includes the reactor vessel inlet, outlet and core flood-nozzles to pipe velds. The required examinations vill be performed during the Davis-Besse Nuclear Power Station (DBNPS) sixth refueling outage, currently scheduled for Spring 1990. In order to maintain as-low-as-reasonably-achievable (ALARA) exposure associated with these examinations, this letter requests approval of an alternate examination method.
The detailed description and justification for the proposed alternative from the ASME Code requirement is provided in the Attachment.
ASME Section XI currently requires both a volumetric examination of the inner 1/3 thickness of the veld and a OD surface examination of the veld. The volumetric examination is performed from the inside diameter (ID) of the nozzle using the Babcock and Vilcox (B&V) Automated Reactor Inspection System (ARIS) tool. -The surface examination-is performed using a manual magnetic particle examination from the OD veld surface. Due to the high radiation levels at the nozzle locations, Toledo Edison is proposing that an ultrasonic examination of the OD veld surface be performed from the ID of the nozzle using the ARIS tool.
This examination. technique was demonstrated at the B&V Lynchburg, Virginia facility on August 9, 1989 at which NRC representatives were present. The examination technique which was demonstrated is described in the Attachment.
.9002230240-891207 E
PDR: ADOCK 05003346 6
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-THE TOLEDO EDISON COMPANY.
EDISON PLAZA 300 MADISON AVENUE TOLEDO, OHIO 43652 i
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Dock;t Number 50-346 i
License Number'NPF-3' i
2 Serial Number 1740
.Page 2' This proposed alternative is submitted pursuant to 10CFR50.55a, Paragraphs (a)(3) and (g)(5)(iii). Toledo Edison requests NRC approval of this proposed alternative by January:31,.1990 in order to facilitate scheduling of i
the examinations during-the sixth refueling outage.
Should further'information be required, please contact Mr. R. V. Schrauder,.
Manager-Nuclear. Licensing, at (419) 249-2366.
Very truly yours, j
GBK/ssg
's Attachment cc A. B. Davis, Regional Administrator, NRC Region III P.-M. Byron,.DB-1 NRC Senior Resident Inspector T. V. Vambach, NRC/NRR DB-1 Senior Project Manager t
State of Ohio i
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?.L.DockotNhber50-346 L,g,
Lic;ts) Nu ber NPF-3 i
Serial Number 1740 Page 1 PROPOSED ALTERNATIVE TO ASME CODE REQUIRED EXAMINATIONS e
ASME Code Required Examinations Components: Reactor Vessel Inlet, Outlet, and Core Flood Nozzle to Pipe Velds 36" Outlet Reactor Vessel Nozzle (X) to Pipe Veld (FV111A) 36" Outlet Reactor Vessel Nozzle (Z) to Pipe Veld (FV111B) 28" Inlet Reactor Vessel Nozzle (Z/V) to Pipe Veld (FV56B) 28" Inlet Reactor Vessel Nozzle (X/Z) to Pipe Veld (IV113B) 28" Inlet Reactor Vessel Nozzle (X/Y) to Pipe Veld (FV56A) 28" Inlet Reactor Vessel Nozzle (V/X) to Pipe Veld (FV113A)
Core Flood Nozzle Pipe to Nozzle Veld V-axis Core Flood Nozzle Pipe to Nozzle Veld Y-axis Function:
Provides for reactor coolant circulation through the reactor vessel and Emergency Core Cooling System (ECCS) core flood system injection into reactor vessel ASME Class:
ASME Section XI, Class 1, Circumferential Pipe Velds - greater than 4-inch Nominal Pipe Size Examination Requirements:
Volumetric and surface examination of velds at terminal ends of piping runs connected to vessels.
Reference ASME Code Section XI, 1977 Edition through the Summer 1978 Addenda Basis for Proposed Alternative The Toledo Edison Company's DBNPS inservice inspection examination plan has
.been prepared in accordance with the requirements of ASME Section XI, 1977 Edition through the Summer 1978 Addenda.
In accordance with the requirements of TableLIVB-2500-1 (Category B-J) of ASME Section XI, the reactor vessel nozzles to reactor coolant and core flood pipe velds require both a volumetric examination of the inner 1/3 thickness of the veld and a OD surface examination of the veld. The volumetric examination is performed from the ID of the nozzle using the B&W ARIS tool and the~ surface examination requires a manual magnetic particle examination from the OD surface. Due to the high radiation levels at the nozzle locations, Toledo Edison is proposing that an ultrasonic examination of the OD veld surface be performed from the nozzle ID using the ARIS tool in lieu of the required surface examination from the OD using the magnetic particle technique. To justify this proposed alternative, a demonstration of the opposite surface flav detection capabilities utilizing state-of-the-art examination techniques and equipment was performed at the B&W s
Lynchburg, Virginia facility on August 9, 1989.
The purpose of the demonstration was to define the capabilities of detecting the minimum size (through vall dimension) reflector originating at the opposite (OD) surface which could be detected during an actual ARIS
- . '. Dockdt Nu:ber 50-346 2g Lic;nsa Number NPF-3 Serial Number 1740 7
Page 2 examination from the ID of the nozzle.
Although the ARIS tool itself could l
not be used for this demonstration, a robotic arm manipulator was used that simulates the ARIS scanning motions which would be used to perform the actual UT examination.
In order-to determine the opposite surface flav detection capabilities a test block was fabricated that contained a series of axial and circumferential OD notches ranging in depth from.024" to.353".
(see notches A through R on Draving Numbers 1189493 B-1, Figure 1).
The test block reflector design was based on ASME Section XI acceptance criteria for surface planar flaws. All notch sizes used for the purpose of this demonstration were considered as acceptable surface planar flaws per Section XI acceptance criteria.
The block was submerged in water to simulate the actual field application and was subsequently scanned with a contact 45 degree L-vave dual element transducer.
Examination criteria such as scan direction, scan motions, and transducer vere duplicated as closely as possible to the actual examination which vill be performed using ARIS.
Scanning was performed in both the circumferential and axial directions to detect the reference notches.
The essential examination parameters required to reproduce these results vill be incorporated, as required, into the technical procedure which vill be utilized for the onsite examination.
These parameters include a 45 degree, medium damped, 2.25 mHz, 1.25", dual element, L-vave transducer focused at a 2" depth; scanned both parallel and perpendicular to the veld with scanning speed not to exceed 4" per second; indexing performed using a maximum of 2" index increment and a sample interval of at least.050".
Data was acquired and analyzed using the B&W state-of-the-art data acquisition and imaging system (ACCUSONEX). The ultrasonic system was calibrated using the side drilled holes to establish a calibrated sweep range with a Distance Amplitude Correction (DAC) Curve. The gain level for the DAC curve was used as a reference for the gain adjustment during this benchmark demonstration.
To_ lower the recording threshold the DAC curve was adjusted to a 20% full screen height (FSH) flat recording threshold. The test block was then scanned-several different times at increased gain levels until all of the notches A through R vere detectable. The result was that all the notches were detectable at a gain level of 24 dB above reference with a recording threshold of 20% FSH.
Due to the lov material noise of the carbon steel test block, excessive noise signals were not encountered allowing the use of such high gain levels.
The seanning sensitivity to be used for actual field examination vill be determined in a similar manner using notches of various dimensions installed in the calibration block for the nozzle-to-pipe velds.
Table I shows the relationship of the notch dimensions to the maximum allovable flav size permitted in this material.
ASME Section XI acceptable standard IVB-3514 was used to make these determinations.
Sizing scans looking for tip diffracted signals were performed on the opposite surface reflectors. The same transducer which was used for detection was used for the sizing scans. Tip diffracted signals were detected with good reliability for sizing data on the notches equal to or greater than 10%
T; e
/(, Dock;t Nu:ber 50-346 Lic:ns] Number NPF-3 Serial Number 1740 i
Page 3 through vall. Tip signals for the reflectors at 5% through vall were detected but did not provide the resolution required to accurately size this small of a reflector.
t Further improvements are being made to increase the sizing capability and accuracy of such reflectors using the tip diffraction. flav sizing technique.
Some of these improvements include increasing the transducer frequency and shortening the length of the transducer elements.
L t
As a further enhancement for detection capabilities Toledo Edison and B&W are evaluating the placement of real defects in the mockup since the cracks are e
generally much more difficult to detect and size than EDM notches or side o
drilled holes in the materials involved in these velds.
The surface examination has been estimated to require approximately 40 manhours for preparation of each of the reactor vessel inlet, outlet and core flood nozzles to pipe velds and an additional 10 manhours of inspection time.
Because of the location of the. nozzles, radiation levels are anticipated to be a total exposure of 60 to 90 man-rem.
Since the installation of shielding in the nozzle area is impractical, these inspection requirements are not considered practical for use at DBNPS.
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[*
ja. Docket Number 50-346 Lic:ns] Number NPF-3 Serial Number 1740 Page 4 TABLE 1
' AXIAL NOTCHES Maximum (1)
(a)
A11ovable Notch Length.
Depth a/1 a/t' a/t A
.380"
.125"
.33 5.2%
13.8%-
B
.375"
.062"
.17 2.6%
10.9%
.C
.376"
.024"
.06 1.0%
8.6%
D
.623"
.251"
.40 10.5%
13.8%
E
.623"
. 124"
.20 5.2%
11.7%
F
.623"
.050"
.08 2.1%'
9.1%
G
.826"
.175"
.43 14.7%
13.8%
r H
.826"
.175"
.21 7.37%
12.0%
I
.826"
.043"
.05 1.87%
8.6%:
'CIRCUHFERENTIAL NOTCHES J
.375"
.130"
.35 5.4%
13.8%
K
.376"
.065"
.17 2.7%
10.9%
L
.375"
.031"
'. 08 1.3%
9.1%
M
~
.624"
.255"
.41 10.6%
13.8%
N
.625"
.129"
.21 5.4%
12.0%
0
.627"
.054"
.09 2.3%
9.2%-
P
.826"
.352"
.43 14.7%
13.8%
0
.823"
.177"
.22 7.4%
-12.3%
R
.825"
.072"
. 09 3.0%
9.2%
t'=2.4" Maximum allowable length for a flav detected by e. surface examination is 0.68" l
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