ML20126C795
| ML20126C795 | |
| Person / Time | |
|---|---|
| Site: | Comanche Peak  |
| Issue date: | 12/18/1992 |
| From: | William Cahill, John Marshall TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.D.1, TASK-TM TXX-92628, NUDOCS 9212230218 | |
| Download: ML20126C795 (4) | |
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7t/ ELECTRIC December 18, 1992
% i!!!am J. Cahill. Jr.
Gene % e nev&nt U. S. Nuclear Regulstory Commission Attention:
Document Control Desk Washinot on, DC 20555
SUBJECT:
COMANCHE PEAK STEAM ELECTRIC STATION (CPSES) - UNIT 2 00CKET NO. 50-446 ADDITIONAL INFORMATION CONCERNING NUREG-0737, ITEM II.D.1 - PERFORMANCE TESTING OF REllEF AND SAFETY VALVES REF:
TV Electric letter logged TXX-92548 from Mr. William J. Cahill, Jr. to USNRC dated November 18, 1992 Gentlemen:
1 The referenced letter provided the information requested by the NRC concerning the CPSES Unit 2 pressurizer safety and relief line thermal hydraulic analysis (NUREG-0737, Item II.D.1).
The NRC staff reviewed this response and r(quested that additional inforrr tion be provided.
Attached is the requested additional information.
If there are any questions, please contact Manu C. Patel at (214) 812-8298.
Sincerely, William J. Cahill, Jr.
By:
J. S. Marshall Generic Licensing Manage.'
MCP/grp Attachment c-Mr. J. L. Hilhoan, Regivn IV Resident inspectors, CPSES (2)
Mr. B E. Hollan, N.1R 230037 9212230218 921218 g7c y
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- Attachment to.TXX 92628 Page 1 of 3 i
Following is the additional responses to TXX 92548 pertaining ~ tolthe pressurizer safety and relief valve analysis:
(4) Bendina Moments:
Did the calculations of bending moment on safety valves and'PORVs_at Comanche Peak 2 consider the combination of the~ effects of deadweight, thermal expansion, earthquake, and valve actuation loads?
CP5ES ResDonse:
All valve nozzle loads are evaluated for the combined effects Deadweight, Thermal, Seismic (OBE & SSE), and valve actuation (both-relief. valve and safety valve) as defined by the piping Design Specification 0-955125 and are acceptable.
(6) Extended Safety Valve Blowdown-The safety valve blowdown in the applicable-EPRI tests ranged from 4.8%
1 to 12.7%.
This indicates operation of the plant safety valves may result in blowdowns that exceed the design safety valve blowdown of 5%.
Provide sufficient information to show: (a) the extended safety valve blowdown will not cause voiding of the primary-systemfor degrade decay.
heat removal if voiding occurs,-(b) theLsafety valves will operate acceptably if-the extended safety valve blowdown:results-in filling the-pressurizer, and (c) the extended safety valve blowdown will not:
challenge plant safety systems.
l CPSES Resuonsg In order to address the three concerns listed above, an evaluation-was-performed to determine the impact that pressurizer safety valves 1with maximum blowdowns of 13% could have'on. the~ affected Comanche Peak Unit 2 -
licensing basis safety analyses.
The conclusions reached-by.the evaluation are as follows:
1)
An extended pressurizer -safety valve blowdown of up to' 13% will not cause_ voiding of the primary system-in.any-licensing basis-event.
2)
An extended pressurizer saf y valve blowdown of u'p to 13% will not cause pressurizer filling in any. licensing-basis event where the' pressurizer does not currently become' water solid.
3)
An extended pressurizer safety valve blowdown-of up to 13% will not challenge: any safety systems which-were not previously l
rhallenged'in the licensing-basis Safety analyses.
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- Attachment to TXX-92628 Page 2 of 3 (8c) Unit 2 Thermal-Hydraulic Analysis The answer describes the loading on the valves and pressurizer nozzle but does not address the discharge piping.
The higher pressure could accelerate the slug f aster in the piping near the pressurizer relief-tank.
Justify that the forces on this piping are not underestimated.
CPSES Response The response previously provided addressed the critically loeJed portions of the piping system.
The loadings produced in the oischarge header tend to decrease very rapidly due to the breakup of the water slug as it travels through the 12 inch pipe.
Subsequently, the stresses in this portion of the system are very low due to the relief valve discharge case (<1000 psi bending) and the small increase in pressure will have negligible impact.
(9) Structural Analysis:
(a)
The value f or n;tss point spacing is not given in the response.
(b)
The response does not'specifically state-that the Comanche Peak.
Unit 2 loads meet the allowables.
Can you make thisistatement?'
CPSES Resoonse:
(a)
The structural model for the TCX PSARV evaluation was developed using the PAGES (Piping Analysis Graphic Entry: System) computer.
program.
This program automatically selects mass spacing based on the pipe: size and the support locations. The-techniques used to develop the TCX model are the same as those used for the bench-marking analysis of the EPRI testing. including the use_of.
computer program PAGES.
'(b)-
All equipment and valve noczle loads have been shown to be-acceptable for all loading conditions as. identified in the CPSES Unit 2 Class 1 Stress Analysis Summary Report.
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' Attachment _to TXX-92628
.Page 3 of.3
. (10)-Hydraulic-Forcina function:
The response states thatLvariances in geometry'between the units are within NC1G 05 tolerances.
Do you have assurance that these tolerances do not affect the hydraulic forcing functions?
(i.e., is the-error-margin in the-forcing function calculation. sufficient to account for the variances in geometry that are allowed by NCIG-057)-
CPSES Resoonse:
Comparison of -the piping geometries f or Units 1 and 2 shows that the two layouts are_ mirror images of each other with only small. differences (approximately 6" or less) i n segment lengths, All other characteristics of the systems are the same (i.e.. valve properties, pipe sizes, temperatures and pressures).
These small differences in segment lengths do not have a significant impact on the hydraulic _
forcing functions, therefore the forcing functions developed for Unit 1 are applicable for Unit 2.
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