ML20212A795
| ML20212A795 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 07/21/1986 |
| From: | Bailey J GEORGIA POWER CO. |
| To: | Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| GN-1006, NUDOCS 8607290130 | |
| Download: ML20212A795 (7) | |
Text
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si Georgia Power Cornpany Project Management Post Offic] Box 282 Waynesboro Georgia 30830 P*
Telephone 404 724 8114 404 554-9961 Vogtle Project July 21, 1986 Director of Nuclear Reactor Regulation File: X7BC35 Attention: fir. B. J. Youngblood Log: GN-1006 PWR Project Directorate #4 Division of PWR Licensing A U. S. Nuclear Regulatory Commission Washington, D. C. 20555 NRC DOCKET NUtiBERS 50-424 AND 50-425 CONSTRUCTION PERMIT NUMBERS CPPR-108 AND CPPR-109 V0GTLE ELECTRIC GENERATING PLANT - UNITS 1 AND 2 SEISMIC SEPARATION BETWEEN COMP 0NENTS
Dear fir. Denton:
During a meeting with members of the NRC staff on June 4,1986, Georgia Power Company was requested to transmit to the NRC the Vogtle Electric Generating Plant (VEGP) program on Seismic Separation between Components. The attachment to this letter describes the VEGP program.
If your staff requires any additional information, please contact me.
Sincerely, J. A. Bailey Project Licensing lianager JAB /wkl Attachment xc:
R. E. Conway NRC Regional Administrator R. A. Thomas NRC Resident Inspector J. E. Joiner, Esquire D. C. Teper B. W. Churchill, Esquire W. C. Ramsey M. A. liiller (2)
L. T. Gucwa B. Jones, Esquire Vogtle Project File G. Bockhold, Jr.
N cP k [ h K 05000424 o 860721 1
A i
VEGP PROGRAM ON SEISMIC SEPARATION BETWEEN COMPONENTS VEGP safety-related components are designed for safe shutdown earthquake (SSE) loads using conservative assumptions and procedures.
The support spacing and lateral stiffness provided by these component supports result in relatively rigid systems and thus small seismic displacements during a seismic event.
In addition, since, in general, these components are individually supported, their separate installation results in physical separation.
However, in order to provide objective evidence that adequate seismic separation exists or to demonstrate the acceptability of localized potential interactions, a finalization program has been developed.
The VEGP finalization program on seismic separation addresses, resolves and documents potential seismic interaction of safety-related components as described in the following paragraphs.
In addition to this finalization program, there are other related VEGP finalization programs that are performed for different purposes (e.g.,
site verification of safety-related equipment qualification program, hazards finalization i
program, and final piping system design verification program) from l
which the pertinent results and/or observations with respect to seismic separation are integrated.
Components such as instruments, control
- panels, fans and fan compartments,
- motors, piping in line-mounted devices (e.g.,
valve operators and their appurtenances), actuators for dampers, equipment appurtenances, switchgear, motor control
- centers, batteries, etc.,
are verified through walkdowns to have been installed with adequate physical clearance with respect to seismic separation.
Where inadequate clearance is identified with respect to seismic separation, it is evaluated and resolved by Engineering on a case-by-case basis.
Wall-mounted equipment such as transformers, emergency lighting panels, switches, local control stations, etc., are, in general, provided with clearance for accessibility and maintenance.
Electrical cable tray and conduit runs are specificed to be installed to avoid conflict with access to, operation or maintenance of, or removal of electrical or other equipment.
Therefore, potential seismic interaction of this equipment with other components is considered unlikely.
However, these wall-mounted components are selectively walked-down in congested areas (particularly in areas with extensive field routed commodities) to i
ascertain that the installed conditions are adequate with respect to seismic separation.
Containment liner plate is an important safety feature since it provides a leak tight barrier.
Thus, the umponents or elements in close proximity to the liner plate system are installed with adequate separation.
A walkdown is performed for the containment liner plate system to verify that the installed conditions are adequate with respect to seismic separation.
e-l Some. components such as heat exchangers, tank filters, fire and tornado F
dampers, coolers, air handling units (excluding the fan compartment) terminal boxes, etc., are also installed with adequate separation because of operational and maintenance provisions.
In addition, these components exhibit one or more of the following characteristics:
rugged in nature, functionally passive, or enclosed in metal casing.
Because of these j
attributes, their functionality is unlikely to be affected by low energy seismic interactions with neighboring components.
However, as in the j
case of wall-mounted equipment, selective walkdowns are performed in l
congested areas (particularly in areas with extensive field routed l
commodities) to ascertain that the installed conditions are adequate l
with respect to seismic separation.
t In the case of ASME piping systems, and B31.1 main steam and main feedwater systems, the VEGP final piping system design verification program (79-14 walkdown) requires the verification of separation around i
the piping.
The.walkdown evaluation procedure requires that any 1
infringement on the required separation space be evaluated on a l
case-by-case basis to ensure that adequate. separation is available j
to accommodate piping thermal growth and piping seismic movement.
The i
scope of this verification includes-valve operators and their t
appurtenances, and pumps and pump motors associated with these piping i
systems.
The non-safety related commodities and equipment in seismic Category 1 building:, in areas where safety-related equipment are located, are supported to assure their structural integrity during' a seismic event.
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This precludes compromising the integrity of a safety-related system or component by failure of a non-safety related component during a 1
seismic event (i.e.,
seismic 2/1 interaction).
Exceptions to this l
design provision are allowed only in selected areas where it has been determined that no safety-related equipment can be affected.
l Furthermore, hazards walkdowns are performed in rooms containing safety-related equipment to review the potential for seismic 2/1 i
interactions.
Unacceptable potential interactions are resolved either 1
by analysis, component upgrades, providing barriers or relocations.
Finally, components such as electrical cable trays, conduits, HVAC ducts, instrument lines, piping, and their supports have no active elements and are made of steel materials, and thus structrual integrity ensures their functionality.
However, in the event that an element of these components or their supports might -be in close proximity to 1
l or even in contact with each other, these components will accommodate i
such impact during an SSE and remain functional.
This is because any i
seismic interaction will entail low energy impacts due to small seismic i
velocities, and these interactions could be elastic or may result in local inelastic deformation.
Therefore, potential seismic interaction j
is not a concern for. these components.
In order to provide the analytical bases for this position, a generic parametric study was i
performed. A summary of this parametric study was performed.
A summary of this parametric study is contained in the enclosure.
It should be noted that while the results of this study are applicable to all l
piping, seismic separation for ASME piping and B31.1 main steam and main feedwater systems designed to seismic Category 1 requirements i
)
is verified during the VEGP final piping system design verification program (79-14 walkdown) as discussed earlier.
The parametric study considered typical potential interactions which represent conservative as-built cases.
The parametric study was based on the conservative assumptions that successive multiple impacts will occur with peak velocities.
Also, it was assumed that no elastic margin existed prior to impact, In addition, maximum mass ratios were also considered.
Under these conservative assumptions, limited yielding would take place with a maximum required ductility of about five.
Considering that the inelastic deformation is local, such an interaction is acceptable and will not adversely effect the functional requirements of the passive systems involved.
Local inelastic deformation serves as the energy dissipator during the low-energy impact and significant forces are nct transmitted to the other parts of the system or to the supports.
In summary, the VEGP program on seismic separation systematically responds to pertinent issues of potential interaction between safety-related components and neighboring components.
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Enclosure
SUMMARY
OF PARAMETRIC STUDIES ON SEISMIC INTERACTION EFFECTS BETWEEN COMP 0NENTS i
Introduction Safety-related components such as cable trays, conduits, HVAC ducts, instrument lines, piping, and their supports are designed to withstand safe shutdown earthquake (SSE) loads using conservative design assumptions and procedures.
The support spacing and lateral resistance provided by these component supports result in relatively rigid systems, and thus small seismic displacements.
In addition, these are passive components made of steel, and thus structural integrity ensures their functionality.
Since, in general, these components are individually supported and in the case of electrical cable trays, HVAC ducts and piping, and their associated supports, are uniquely located on the design drawings to preclude interference with other elements and components, their installation results in physical separation.
However, there could be isolated cases where a component or its support might be in close 4
proximity to (or even in contact with) another component.
In such cases, interaction is considered possible between adjacent components i
and/or their supports during a seismic event.
This document summarizes the results of parametric studies that were performed to demonstrate the ability of a component to remain functional during and after seismic interactions with a neighboring component.
Seismic Interaction Seismic interaction between components is a low eneregy impact event due to the small velocities involved.
Two oscillating components with small or no gap between them can experience multiple impacts during an SSE.
The impacts could be either elastic (disengagement after impact) or plastic (maintaining contact for some time after impact).
In addition, the seismic behavior of a component including impact effects could be either elastic or inelastic, depending on the seismic margin available in the original design of the component.
These parametric studies consider the possible pertinent combinations.
Methods of Analysis Potential seismic interaction was modeled as an impact event with two impacting components idealized as single degree-of-freedom systems with elastic or inelastic properties.
Utilizing the energy balance technique, the principle of conservation of momentum and the concept of coefficient of restitution, closed form solutions for the impact event were obtained.
i
Selection of Parameters In addition to the type of impacts (elastic or plastic) and the type of structural behavior of the components (elastic or inelastic), the effects of seismic interaction depend on the following parameters:
a.
Existing seismic gap b.
Number of impacts during an SSE c.
Mass ratio between the components d.
Stresses from other concurrent operating loads e.
Available margins in the elastic strengths of the components f.
Available inelastic deformation capability (available ductility) of the components.
g.
Damping ratio h.
Coefficient of restitution All of these parameters were evaluated by reviewing the typical designs of VEGP components and their supports.
Small seismic gaps are assumed to entail many impacts between two neighboring components during an SSE.
The parametric studies evaluate conservatively the cumulative effects of multiple impacts by assuming 4
that the two components experience five successive impacts with peak velocities of approach.
These parametric studies consider possible variations in the mass ratio (small mass divided by the large mass) between the two impacting components.
Accordingly, the full range from 0 to 1 for the mass ratio is considered.
In order to maximize the required ductility during an inelastic seismic impact, stresses from dead and other operating loads acting concurrently with an SSE are assumed to be zero.
Thus, the existing stresses prior to impact are assumed to be entirely due to SSE.
In addition, it is assumed that there is no margin in the elastic strength of a component to accommodate seismic impacts.
A low structural damping ratio of 5% is assumed for the impacting components made of steel materials.
This is a conservative assumption since the high local stresses and local yielding will produce higher damping.
The coefficient of restitution for elastic impacts between the components can vary from 0.5 to 0.8.
A value of 0.65 is used in the parametric studies.
J The potential seismic interaction effects between VEGP components are enveloped by the above set of parameters considered in the studies.
Results of Analyses The impact effect on a component was calculated as a percentage of 4
'the SSE effects without impact.
Accordingly, seismic impacts between two identical components could increase their peak SSE response, in the direction away from each other, by 60% if the components remain 4
j elastic.
If the components do not remain elastic, the calculated maximum
~
required ductility for the identical components to accommodate seismic impacts was shown to be 1.7.
If the seismic impacts occur between two non-identical components, the small (with.less mass) component could experience substantial increase to its peak SSE response in the direction away from the larger component.
The maximum required ductility for such cases was shown to be 5.3.
A large ductility will lead to a large permanent set, thus i
increasing the gap between the components and alleviating the effects i
of subsequent impacts.
Since the components involved can readily.
accommodate a ductility requirement of five and since the inelastic deformation is local, such an interaction is acceptable and will not i
adversely affect the functional requirements of the passive systems involved.
i
- Thus, the components can accommodate seismic interactions while i
maintaining their structural integrity and hence their functionality.
l
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Local Effects The blunt contact surfaces of components may experience locally high 2
stresses and inelastic deformations from seismic impacts.
- However, the functional capabilities of the components will not be affected, j
as demonstrated by the following example:
If a 3/4" diameter conduit supported at 8' intervals is impacted at j
its midspan by a massive pipe support during an SSE, the resulting i
local crimp and ovalization in the conduit"will be less than 7%.
The corresponding maximum reduction in cross-sectional area of the conduit is less than 1%.
Thus, the functionality of cables which occupy typically less than 60% of the conduit cross-sectional area will not be compromised.
I Conclusion q
i The results of these parametric studies performed for VEGP demonstrate l
that components such as electrical cable trays, conduits, HVAC ducts, instrument lines, piping, and their supports will remain functional during and after seismic interactions with neighboring components.
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