ML20009C606
| ML20009C606 | |
| Person / Time | |
|---|---|
| Site: | Surry  |
| Issue date: | 07/16/1981 |
| From: | Leasburg R VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | Harold Denton, Varga S Office of Nuclear Reactor Regulation |
| References | |
| 443, GL-81-14, NUDOCS 8107210255 | |
| Download: ML20009C606 (6) | |
Text
a 2
VIRGINIA EI.ncraic Axo POWER COMPANY RICilMOND, V1MOINIA 20 261 July 16, 1981 R. II. LEAssic =a Vaca Passionar
' Nt:ctaAan OraMATIONS Mr. Harold R. Denton, Director Serial No. 443 Office of Nuclear Reactor Regulation N0/LEN:ms Attn:
Mr. Steven A. Varga, Chief Docket Nos. 50-280 Operating Reactors Branch No. 1 50-281 Division of Licensing License Nos. DPR-32 U. S. Nuclear Regulatory Commission DPR-37 Washington, D. C.
20555 Gentlemen:
SEISMIC QUALIFICATION OF AUXILIARY FEEDWATER SYSTEMS SURRY POWER STAfION UNITS 1 AND 2 Attached is Vepco's response for Surry to NRC Generic Letter No. 81-14 on Seismic Qualification of Auxiliary Feedwater Systems.
Included in the attachment is Table 1, which was provided in the generic letter. By leaving this table blank, we are indicating seismic qualification of those listed items.
Also included in the attachment is a description of the methodologies and acceptance criteria ' used to support our conclusion of seismic q alifica-tion.
If you have questions or require additional information, please contact us.
Very truly yours, l-
_l y
,w R. H. Leasburgr Vice President - Nuclear Operations Attachment ec:
Mr. James P. O'Reilly, Director Office of Inspection and Enforcement g p$(
~
ho4s Region II s
l t
s 3I y
N M
/ /
o
,y ^
tw, 8107210255 810716 PDR ADOCK 05000280 l
P PDR
t 4
ATTACHMENT I SURRY POWER STATION RESPONSE TO ENCLOSURE 1 The design basis and methodology for seismic qualification of the Auxiliary Feedwater System is given in various sections of the FSAR.
The FSAR (Table 15.2.1-1) identifies the Condensate and Feedwater System as meeting the Class I seismic criteria including:
100,000 gallon Condensate Storage Tank Auxiliary Steam Generator Feed Pumps Piping, Valves and Supports From 100,000 gallon Condensate Storage Tank to Auxiliary Steam Generator Feed Pumps From Auxiliary Steam Generator Feed Pumps to Steam Generator Feed Lines Steam Generator Feed Lines Inside Containment to and including first Isolation Check Valve Outside Containment.
This table further indicates that these criteria are met for all instrumenta-tion and controls to operate and monitor operativa of critical system compo-nents, and all cable to critical components, instrunents, and controls.
l The Auxiliary Feedwater (AFW) system components are housed in the Reactor Con-tainment, the Main Steam Valve House Cubicle, and the Auxiliary Steam Genera-tor Feed Pump Cubicle; Table 15.2.1-1 identifies these structures as meeting the Class I seismic criteria.
The Condensate Storage Tank is a separately founded seismic Class I tank.
Furthermore, the FSAR (paragraph 8.2) defines design bases and acceptance criteria for electrical system components as follows:
"The electrical systems are designed to supply electrical power to all essential unit equipment during normal station operation and under incident conditions.
The electrical system components vital to unit safety, including the emergency diesel generators, are designed and protected as necessary so that their integrity is not impaired by potential earthquakes, high winds, floods or distur-l bances on the external electrical system. Cables, motors and other electrical equipment required for operation of the Engineered Safe-guards are suitably protected against the effects of either a nuclear system accident or a severe external environmental pheno-menon in order to ensure a high degree of reliability."
-g A.
The piping of the auxiliary feedwater system as identified in Table 15.2.1-1 of the FSAR is Seismic. Class I and has been included within the scope of seismic related Bulletins 79-02, 79-04, 79-14, and 80-11.
The concerns of Bulletin 79-07 have been addressed in ot.r program to respond to the order to Show Cause dated March 13, 1979.
All of the Seismic Class I piping at Surry within the scope of Bulletin 79-14 has been i
reanalyzed as a result of the Show Causc Order and Bulletin 79-14.
Documentation of these reanalyses is being completed, and the final reports are scheduled to be prepared by November 1981.
The Auxiliary Feedwater System was included in the scope of I.E.
B.
General methodologies for seismic Class I qualification of equipment are described in FSAR Section 15.2.4, the Seismic Design Report (SDR)*, and response to Question 4.14.
4 Seismic Analyses Methods Seismic analyses methods outlined in the FSAR and SDR include Static Analysis and Testing.
These analyses methods are further described in the FSAR Responses to Questions 4.10 and 4.11.
The methodology employed to qualify the Class I piping is described in Section 4.0 of the Seismic Design Review.
)
Electrical and control system equipment design is based on static accele-ration loads equals to peak resonant response since restraints, snubbers, etc. are not used to preclude resonance of electrical and control systems equipment (Response to Question 4.11.).
Typical protection system equipment is subject to testing under simulated seismic accelerations to demonstrate the ability to perform and complete its function.
Seismic testing conforms to guidelines referenced in the Response to Question 4.11.
The original design of a number of safety-related lines in Surry Units 1 and 2 had been performed using the SHOCK 2 computer ce%; the stress summation methodology of this code was determined to be unacceptable by the NRC in 1979.
The resulting Order to Show Cause of March 13, 1979 required those piping systems designed wi h these codes to be reanalyzed using an acceptable piping code.
As a result of this Show Cause Order and the subsequent Bulletin 79-14, virtually all of the piping and supports within the scope of 79-14, have been reanalyzed using the NUPIPE program. The piping was analyzed including the effects of thermal expan-sion, internal pressure stresses, and earthquake loads.
The reanalysis and modification program have verified that the Seismic Class I piping
(
meets the requirements of Section 15.2.4 of the FSAR, in accordance with the code of record, ANSI B31.1, 1955, with Code Case N-7.
l The conservatisms applied to the reanalysis of the piping systems for Surry have been extensively delineated in Section 7 of the VEPC0 submit-tal to the NRC of June 5, 1979 (Serial No. 453).
l i
l
- " Seismic Design Review, Equipment and Piping, fiurry Power Station," issued June 30, 1971 and revised September 15, 1971.
,_m.
y
~.~.,_,,m.
-,-,_,.,-,_m
..._..,..--r
a Seismic Input The Surry FSAR states in Section 15.2.4:
" Class I structures, systems, and compenents designed ' to resist seismic forces are listed in Table 15.2.1-1. The design is baaed on
.two separate seismic criteria: The Operational Basis. Earthquake (OBE) and the Design Basis Earthquake lDBE), as described in Section 2.5 and Appendix A.
Acceleration response spectra for each earthquake are given on Fig. 2.5-1 and 2.5-2."
Because the AFW System is identified in Table 15.2.1-1, it falls undet the above design conditions for seismic input as described in FSAR Section 2.5 and in the SDR Section 2.0.
In most cases for piping, Soil Structure Interaction Amplified Response Spectra (SSI ARS) were employed.
The acceptability of SSI was obtained in an NRC letter from D. Eisenhut dated May 25, 1979. The completion of
-documentation for the NRC staff review of SSI was provided by the report,
" Soil Structure Interaction in Development of Amplified Response Spectra for Surry Power Station - Units 1 and 2,"- dated June 8,1979.
In accor-dance with NRC letters of May 25, 1979 and November 15, 1979, the seismic inertial stresses and loads computed using the SSI-ARS were increased by factors of 1.5 for the DBE and 1.25 for the OBE cases, compounding the conservatisms in the seismic analysis.
Load Combinations The Response to Question 4.10 provides the criteria for combining modal responses in those cases where modal response spectrum analysis is used.
The ' load combinations which include seismic loads are discussed in FSAR Section 8.2 and Table 15.2.1-1.
Furthermore for piping, Section 15.2.4 stated:
i
" Seismic loading includes the horizontal or vertical responses acceleration or combinations of both where the effects, as measured by the separate acceleration components, of horizontel and vertical l'
accelerations are combined to produce maximum stress intensities, l
taking into - account any potential adverse effect due to phase of the separate accelerations."
The stress combinations and acceptance criteria are given in the follow-l ing equations from section 4.2 of the SDR:
()
Sp+SDL H
5 1.2 S (2) l.
Sp+Sgt + Sggg g
1.8 S (3)
Sp+SDL
- DBE H
(')
p THERMAL STRF"3 5 1.25 Sg + 0.25 SH I
I i
c.
.w.-.,-
.,m
.-y
,-,_r
L where:
' Longitudinal Pressure Stress S
=
p S
=
ea aad Stress DL Operational Basis Earthquake Stress S
=
OBE Design Basis Earthquake Stress S
=
DBE S
=
Basic material allowable stress at maximum (hot) temperature H
Basic material allowable stress at minimum (cold) temperature S
=
C Acceptance Criteria Maximum working stress limits permitted for Operating Basis Earthquake combined loading and the acceptance criteria for the Design Basis Earth-quake combined loading conditions are referenced in the FSAR Table 15.2.1-1 and Section 15.2.4.
Table 15.2.1-1 designates that the AFW System is designed to Class I seismic criteria. The legend to Table 15.2.1-1 further states:
"All Class I components and structures are designed to resist the operational basis earthquake within allowable working stresses. A check has been made to determine that failure will not occur with a design basis earth pake."
The acceptance criteria for components qualified by testing is no loss of function, as given in the FSAR Section 8.2.
l-i
.... g TABLE 1 SURRY POWER STATION I
AUXILIARY FEEDWATER SEISMIC QUALIFICATION (1) Pumps / Motors i'
(2) Piping i
(3) Valves /Act ators (4) Power Supplies (5) Primary Water"and Supply Path l
(6) Secondary Water and Supply Path *
(7) Initiation and Control System (8) Structures Supporting or Housing these AFW System Items
- Applicable only to those plants where the primary water supply or path is not provided, however, a seismically qualified alternate path exists.
O e
..