ML20198D392
| ML20198D392 | |
| Person / Time | |
|---|---|
| Site: | Catawba  |
| Issue date: | 12/14/1998 |
| From: | Gordon Peterson DUKE POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| GL-96-06, GL-96-6, TAC-M96794, TAC-M96795, NUDOCS 9812230075 | |
| Download: ML20198D392 (10) | |
Text
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i, Duk) Energy Corporation b.M-Catawba Nudear Station J
=
4800 Concord Road York, SC 29745
, Gary R. Peterson (803) 831-423i OFFICE Via 1%sident (803) 831-3426FM i
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December 14, 1998 U.
S. Nuclear Regulatory Commission ATTENTION:
Document Control Desk Washington, DC 20555-0001
SUBJECT:
Duke Energy Corporation Catawba Nuclear Station, Unit 1 & 2 Docket Nos. 50-413/414 Request for Additional Information Related to Generic Letter 96-06 Response (TAC Nos. M96794 and M969795)
Attached.please find Caatawba's response to the NRC Staff's Request;for Additional Information dated July 30, 1998 related to Duke's responses to Generic Letter 96-06 dated January 28, 1997 and> June 24, 1998.
Your letter of July 30, 1998 requested this information to be
. submitted by November 30, 1998.
However, there were several analyses that were needed to properly respond to the request and would'not.be completed in time to meet the November 30, 1998 date*.
This was discussed in a phone conversation on November 19, 1998 between Skip Copp, Catawba Regulatory Compliance, and Peter Cat'wba NRC Project Manager.
In~that conversation, Peter
' Tam, a
Tam indicated that a two week extension of the response date would be acceptable.
ThereLare no regulatory commitments contained in this response.
Questions regarding this response should be directed to Skip Copp
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at-(803)'831-3622.
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Peterson g
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Attachmant
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9812230075 981214 T
PDR ADOCK 05000413 S
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'U.S. Nuclear Regulato:y Commission
. December 14, 1998
.Page 2
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.L. A. Reyes L
U. S. Nuclear: Regulatory Commission l
' Regional Administrator, Region II Atlanta Federal Center 61;Forsyth St.,=SW, Suite 23T85 Atlanta, GA 30303 P.
S. Tam.
NRC Senior' Project Manager'(CNS)
U.
S.. Nuclear Regulatory Commission Mail Stop.0-14H25 Washington, DC 20555-0001-D. J. Roberts Senior Resident Inspector-(CNS)-
U. S. Nuclear Regulatory' Commission Catawba Nuclear Site l
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I Catawba Nuclear Station Response to NRC Request For Additional Information Dated July 30, 1998 Response to Generic Letter 96-06 l
REQUEST 1:
In the January 28 1997, submittal, Duke indicated that a total of j
three pipe segments in each unit were susceptible to thermally induced pressurization, which are isolated by soft seat plug i
valves.
Duke stated that testing has been performed that demonstrated that these valves would leak enough fluid to prevent overpressurizing the piping above the maximum Code-allowable l
pressure.
In order to complete its review of Duke's response, the' staff needs the following information for these penetrations:
l Describe the applicable design criteria for the piping and valves.
Include the required load combinations; Provide a drawing of the valve.
Provide the pressure at which l
the valve was determined to lift off its seat or leak and i
discuss the method used to estimate this pressure.
Discuss any sources of uncertainty associated with the estimated lift off or leakage pressure; Provide the maximum-calculated stress in the piping run based on the estimated lift-off or leakage pressure.
RESPONSE 1:
Background and General Description In the Catawba response dated Janucry 28, 1997, three containment isolation situations were identified where the system design pressure (but not the maximum Code allowable pressure), may be exceeded, all located on non-safety systems penetrating containment.
These penetrations or interconnected piping inside containment involve soft seat plug valves, where no overpressure protection device was required because original Criterion 2.d took credit for a combination of seat deformation, seat leakage, or stem seal leakage.
All three applications are non-safety related, and the associated system / valves are not required to be used/ reopened in any Erargency Procedure.
Item No. 48 (Penetration M-358)
Based on a design review to document the response to Generic l
Letter 96-06, Item No. 48 has been reclassified as meeting both l
Criteria 2.d and 2.c.
This penetration, therefore, is excluded from further consideration since Criterion 2.c. does not need i
f 1
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overpressure protection because it contains air, steam or gas during normal operation.
This penetration is used to drain the
' refueling canal following refueling, and is itself drained per procedure.
There is no procedure to refill the penetration with water, and it. remains unfilled until the next refueling outage.
Therefore, during normal operation, this penetration contains compressible gas rather than water.
Based on the preceding discussion, no detailed stress analysis data is provided for Item 48 (Penetration M358).
Plug valve leakage test results for the 4" plug valve, however, are included in the Plug Valve Leakage Test Summary Results Table 1 for completeness.
{
Description of test, location of leakage and discussion of test uncertainty A relief valve test bench was utilized in order to determine the pressure at which leakage would occur for each size plug valve.
Based on the Duke Piping Specification Tables.for the pipe sizes of interest, a maximum test pressure of 1900 psig was selected to bound.the lowest Code allowable pressure.
Each plug valve was flanged between Schedule 160 fittings, and pressure was raised in increments, with 5 minute hold time at each plateau, until external leakage occurred.
A test sheet was filled out recording the pressure and location of the leakage.
Results are summarized in Table 1.
TABLE 1 PLUG VALVE LEAKAGE TEST
SUMMARY
RESULTS Valve Valve Pen.
Leak Code Location &
Size Tag No.
Press Max Description in.
No.
psig psig 1/2 YM316 M-337 None N/A No leakage up to 1900 psig 3/4 YM319 M-337 None N/A No leakage up to 1900 psig 2
YM319 M-337 1100 2059 External leakage at body / bonnet, stem seal 3
NC213 M-216 1500 1955 External leakage at body / bonnet, stem l-seal 4
- FW11, M-358 730 N/A External leakage at FW71 body / bonnet Uncertainties include the condition of the installed valve's
- sleeve and stem seals as well as relaxation of the bonnet bolt torque.
The test valves were spare valves from the warehoune and 4
2
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t l
were factory ready for plant installation but not previously torqued or subjected to prior conditioning.
These valves from the factory would be expected to be in better condition than j
valves used in plant conditions.
However, the mode of leakage minimized the significance.of the sealing material.
The 2",
3",
and 4" plug valves all showed external body-to-bonnet joint leakage at pressure below the maximum test pressure.
The leakage appeared to be caused by stretching of the bonnet bolts.
The 1/2" and 3/4" valves did not exhibit either external or through valve leakage.
This is reasonable since the larger valve sizes have significantly larger bonnet diameter, resulting in more tension loading on the bonnet bolts.
The small valves have bonnet thickness that is significantly greater in relation to their body diameter, thus the same internal pressure load results in less tension loading on the bonnet bolts and less bending moment-in the bonnet.
While test uncertainty may result in some variability of the pressure at which leakage could be expected for an installed valve versus a test valve from the warehouse, the overall results show that plug valves 2" and over exhibit i
external leakage at the body to bonnet joint prior to maximum code allowable pressure.
This basis and the resulting margin is explained in relation to the calculated piping stress in the following paragraphs.
Item No. 1 (Penetration M-216)
Description The location of this penetration is shown on Reference 1, the Reactor Coolant System flow diagram.,
from the Tufline vendor catalog, is a schematic drawing that gives valve dimensions for the various body sizes.,
" External Seals", shows details of the external leak paths.
This non-safety related penetration is used for normal pressurizer relief tank (PRT)_ makeup.
It is therefore undesirable to drain the penetration or the header.
The safety related penetration piping consists of an outside motor operated valve and an inside check valve, through which water can expand unimpeded to the non-safety header inside containment containing a 3" Tufline plug valve (NC213).
There is also a fail-closed air-operated control valve in line to the PRT that normally initiates makeup flow, but which may fail closed when instrument air is isolated following the LOCA.
It has been shown by a combination of testing and analysis that the 3" Tufline plug valve has an external leakage path such that Code a.11owable pressure is not exceeded.
Design Criteria and Loading Combination The NC System piping containing penetration M216, that is subject to pressurization due to thermal heatup, is classified as Duke Class B & E piping as indicated on the Reactor Coolant System
(
flow diagram (Reference 1).
The applicable design criteria and i
l l
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j loading combinations for Duke Class B piping is documented in Table 3-96 of the Catawba Updated Final Safety Analysis Report
'(Reference 3).
Also, Updated Final Safety Analysis Report a
.Section-3.9.3.2.3 requires that " Functional Capability" must be maintained when piping is subjected to loads in excess of those for which " Upset" limits are specified.
The Reactor Coolant System is one of the essential piping systems that must satisfy this " Functional Capability" requirement.
The " Functional Capability" condition can be shown to be satiafied if stresses due to " Faulted" condition are demonstrated to be less than the
" Functional Capability" stress limit (generally 1.8S ) as h
outlined in-Section 3.9.3.2.3 of the Updated Final Safety l
Analysis Report.
The applicable design condition for the
" pressurization due to thermal heatup" case is considered
" Faulted", since it is a result'of pipe rupture.
For this evaluation, the stress due to internal pressure (from the thermal heatup condition) was combined with bending stress terms in the equation for " Functional Capability" and shown to satisfy that
)
requirement.
Maximum Calculated Stress in the Piping Run The design temperature for Class B portion of the piping is 240 degrees F.
The design pressure is 165 psia.
.The maximum calculated stress in the piping run (based on the valve estimated lift-off or leakage pressure) is provided below and is envelope of Unit 1 and Unit 2 results.
The " Functional Capability" condition was checked, substituting the 1500 psi leakage pressure for the design pressure with the following results:
Calculated Stress = 24.6 ksi Allowable Stress 1.8S 31.2 ksi 0 240 F
=
h This represents a 27% positive structural margin available for longitudinal pipe stresses.
Given the 240 degrees F Post-LOCA temperature, the maximum allowed internal pressure for satisfying ASME Code Equation for hoop stress (NC-3641.1) was calculated to be 1955 psig, which represents a 30% positive structural margin available for hoop stresses.
Thus, there is margin for considerable uncertainty in plug valve leakage pressure while remaining within Code allowable stress.
Item No. 96 (Penetration M-337)
Description j
Reference 2 shows the location of this penetration on the Makeup L
Demineralized Water System flow diagram.,
from the l'
dimensions for the various body sizes. Attachment 2, also from Tufline vendor catalog, is a schematic drawing that gives valve l
4
i, l
l the Tufline vendor catalog, shows details of the external leak paths.
This non-safety related penetration is used for normal demineralized water needs inside. containment.
The safety related penetration piping consists of an outside motor operated valve and an inside check valve, through which water can expand unimpeded to the non-safety header inside containment containing 1
a number of Tufline plug valves.
There is one normally open 2" plug valve in the header.
Normally closed plug valve sizes include 2",
3/4", and 1/2".
Water is used for makeup to various j
needs during normal operation, making it undesirable to drain the penetration or header.
It has been shown by a combination of l
testing and analysis that while the small plug valves do not leak, the 2" Tufline plug valve has an external leakage path such that Code allowable pressure is not. exceeded.
Design Criteria and Loading Combination The YM System piping containing penetration M337, that is subject l
to " pressurization due to thermal heatup", is classified as Duke l
Class B & G piping as indicated on Reference 2.
The applicable design criteria and loading combinations for Duke Class B piping is documented in Table 3-96 of the Catawba Updated Final Safety Analysis Report (Reference 3).-The applicable design condition l
ft.
the " pressurization due to thermal heatup" case is considered l
"Fadited", since it is a result of pipe rupture.
The applicable l
stress criteria for the " Faulted" condition is 2.4Sn.
L Maximum Calculated Stress in the Piping Run The design temperature for Class B portion of the piping is 120 l
degrees F.
The design. pressure is 165 psia.
The maximum calculated stress in the piping run (based on the valve estimated lift-off or leakage pressure) is provided below and is envelope of Unit 1 and Unit 2 results.
The " Faulted" condition was checked, substituting the 1100 psi leakage pressure for the l
design pressure with the following results:
l-Calculated Stress = 37.7 ksi Allowable Stress 2.4Sh = 41.6 ksi 9 240 degrees F l
This represents a 10% positive structural margin available for longitudinal stresses.
Given the 240 degrees F post-LOCA l
temperature, the maximum allowed internal pressure for satisfying L
ASME Code Equation for hoop stress (NC-3641.1) was calculated to
[
be 2059 psig, which represents a 87% positive structural margin l
available for hoop stresses.
Thus, there is margin for j
considerable uncertainty in plug valve leakage pressure while remaining within Code allowable stress.
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REQUEST 2:
In its submittal, Duke also indicated that the Equipment Decontamination (WE) piping has a design pressure of 8015 psia, which would withstand the pressurization due to heatup.
In order to complete its review, the staff needs the following information for these penetrations:
Provide the applicable design criteria for the piping and valves.
Include the required load combinations.
Provide a drawing of the piping run between the isolation valves.
Include the lengths and thickness of the piping segments and the type and thickness of the insulation; Provide the maximum-calculated temperature and pressure for the pipe run.
Describe, in detail, the method used to calculate these pressure and temperature values.
This should include a discussion of the heat transfer model used in the analysis and the basis for the heat transfer coefficients used in the analysis.
RESPONSE 2:
Item No. 46 (Penetration M-356)
There is a misunderstanding of the basis for not requiring an installed relief path or overpressure protection device for Item No. 46, Equipment Decontamination (WE) System (Penetration M356).
This misunderstanding may be due to extraneous information supplied with the January 28, 1997 submittal.
Pages 22 and 23 of the Catawba submittal list as one of the original criteria for not providing overpressure protection the following:
- 2. " Penetrations for which the overpressure protection feature is considered unnecessary, and thus is not provided include the following:
- f. Equipment Decontamination (WE) piping judged to be adequate to withstand heatup due to 8015 psia design pressure."
However, the final evaluation of the WE penetration begins with the description on page 27 of the Catawba submittal as follows:
"The following penetrations, designated as Overpressure protection Criterion 2.c, contain air, steam, or gas during 6
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normal operation, and therefore do not require additional overpressure protection because they are not subject to thermal 6xpansion of an incompressible fluid.
These penetrations are listed below for completeness.
Item Pen.
Description Design Contents No.
No.
(psig)
(fluid) 46 M356 Equipment Decon 8000 Air" Line Based on a design review to document the response to Generic Letter 96-06, this penetration was reclassified as meeting both Criteria 2.f. and 2.c.
No additional relief path or overpressure i
protection is needed because the WE System is not filled following Type C leak rate testing, and no procedure exists for operation of the system.
Therefore the WE System only contains compressible gas rather than water.
Additionally, a review of leak rate testing history (average 25 sccm Units 1 & 2) provide additional confidence that overpressure protection is not needed.
Based on the preceding discussion, the detailed information requested should not be necessary and is not provided for Item 46 (Penetration M356).
Item No. 49 (Penetration M-377) (Correction)
Item 49 was incorrectly designated on page 27 of the January 28, 1997 submittal as meeting Criterion 2.c (penetrations that contain air, steam, or gas during normal operation, and therefore do not require additional overpressure protection because they are not subject to thermal expansion of an incompressible fluid).
Item Pen.
Description Design Contents No.
No.
(psig)
(fluid) 49 M377 Refueling Cavity 50 Air Fill Line Based on a design review to document the response to Generic Letter 96-06, this penetration was reclassified as meeting l
Criterion 2.a.
Criterion 2.a applications are those penetrations for which the overpressure protection feature is considered I
unnecessary, and thus is not provided.
The penetration includes l
a check valve for the inside isolation valve, through which the l
pressure increase would be relieved to containment atmosphere through the open ended piping inside containment.
In this case, i
the downstream soft seated plug valve is aligned by procedure to be normally open.
Thus the fill line is open ended inside containment.
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l REFERENCES
- 1. Catawba Updated Final Safety Analysis Report Figure No. 5-3,
" Reactor Coolant (NC) System", showing Item 1 NC System
. penetration M-216,
- 2. Catawba Updated Final Safety Analysis Report Figure No. 9-45,
" Makeup Demineralized Water (TM) System", showing Item 96 YM System penetration M-337.
- 3. Catawba Updated Final Safety Analysis Report Table 3-96 Stress Criteria and Load Combination Requirements for Duke Class B, C,
and F Piping.
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