ML20041F084
| ML20041F084 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 03/12/1982 |
| From: | Devincentis J PUBLIC SERVICE CO. OF NEW HAMPSHIRE, YANKEE ATOMIC ELECTRIC CO. |
| To: | Miraglia F Office of Nuclear Reactor Regulation |
| References | |
| SBN-231, NUDOCS 8203160174 | |
| Download: ML20041F084 (19) | |
Text
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I sanaa sTA m IPUEBLIC SERVICE
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Companyof New Hampshw e 1671 Worcester Road j
Framinoham, Massachwsetts 01701 (617)- 872 8100 dld U March 12,1982 SBN-231 O
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2 C::.:n n.,, - ~ ru nd " H f'i United States Nuclear Regulatory Commission
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Wa shi ng ton, D. C. 20555 7
s Attention:
Mr. Frank J. Miraglia, Chief Licensing Branch #3 Division of Licensing Re fe rences :
(a ) Construction Permits CPPR-135 and CPPR-136, Docket Nos. 50-443 and 50-444 (b) USNRC Letter, dated February 12, 1982, " Request for Additional Information," F. J. Miraglia to W. C. Tallman S ul,j ec t :
Responses to 230 Series RAIs; (Ceosciences Branch)
Dear Sir:
We have enclosed responses to the cubject RAIs, which you forwarded in Re f e re nce (b).
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Very truly yours, 1
YANKEE ATOMIC ELECTRIC COMPANY Jbh5b l'
.hohnDeVincentis' Project Manager JDV: ALL: dad O Y l
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230.3
. The probability of exceeding the CBE during the operating life of (2.5.2.7) the plant should be discussed.
RESPONSE
Our original responso to RAI 230.3 was based on sourec areas-that were generalized for_New England and not specific to the Seabrook site. - As a result of the recent New Brunswick and New Hampshire earthquakes, which occurred subsequent to the original response to RAI 230.3, we plan on having our consultant revise this-response using Seabrook site specific information as appropriate.
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RAI Q230.4 At the level of the seismic Category I electrical manholes, duct banks, and service water piping that are located in structural backfill, des-cribe the level and time history of acceleration that are appropriate for the Safe Shutdown Earthquake, given a 0.25g-anchored Reg. Guide 1.60 design spectrum for bedrock. Discuss and justify the procedure used to -
determine the SSE ground motion in the structural backfill and the degree of uncertainty in this d'etermination.
Include in your discursion a des-cription of the material properties and seismic wave transmission charac-teristics of the backfill.
Identify any fill or backfill that underlies any part of the foundation of any seismic Category I structures, as identi-fled in Table 3.2-1 of the FSAR, and discuss the implications of such fill on the SSE design levels for those structures.
RESPONSE
The information requested is addressco in FSAR Subsections 3.7(B).l.4,
- 3. 7 (B). 2.4, 3. 7 (B). 3.12 and 2.5.4. 5.
Additional specific details are provided in response to questions Q220.17 and Q241.7.
All structures identified in Table 3.2-1 of the FSAR except electrical manholes, duck banks, and service water piping are placed on competent bedrock or fill concrete extended to competent bedrock.
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230.5 In Section 2.5 of the FSAR you state "the design response spectra are provided based on an earthquake of 10 to 15 seconds d ura tion... ". Justify your duration estimate in light of historical accounts of the 1755 Cape Ann event that report strong shaking lasting several minutes.1 Identify the definition of 4
duration that you are using. Discuss possible differences in duration on bedrock and on structural backfill at the level of the Seismic Category I electrical manholes, duct banks, and service
-water piping.
RESPONSE
The 10 to 15 seconds duration of motion is that which is estimated to exceed.05g (Bolt, 1973, 1981). The account given by Winthrop (1755) is perceived motion. The ability to perceive ground motion is a function of its frequency and duration (Nicholls et al.,
1971; Siskind et al., 1980); in general, the higher frequencies and longer durations are associated with lower thresholds of perceptible motion. At frequencies of 1 to 4 hertz, it is estimated that the threshold of perceptibility would be between
.00lg and.008g; 6 to 50 times lower than the.05g chosen as the strong motion duration.
Because of the early hour of the morning (approximately 4:15 A.M.)
and the lack of man-made background noise in 1755, Professor
'Jinthrop undoubtedly perceived the motion at the low end of the threshold of perceptibility and, as he has described, felt several phases of motion and not just that associated with the strong motion (Shear or Lg).
This is consistent with the duration of perceptible motion from other earthquakes as stated by Bolt (1973,
- p. 1307); "the long period vibrations taken with the aftershocks add to the human propensity to exaggerate the duration of shaking (humans can feel a.001g).
Some people in the Alaska earthquake reported feeling motions for 150 seconds (Kachadoorlan and Plafker, 1967)".
The seismic motion in the offsite borrow supporting Seismic Category I electrical manholes, duct banks, and service water pipes will be damped out within 2 seconds after the_end of the SSE bedrock seismic motion.
This duration was determined by assuming that motion in the offsite borrow was essentially stopped when the amplitude of motion was less than 10% of the amplitude at the end of the earthquake. The decay of. amplitude af ter the end of the earthquake is defined by (Richart, et al. 1970):
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2nD
= n Z2 ll - D
-y where 21=
Amplitude at end of earthquake Z2=
Amplitude after n cycles of damped free vibration n=
Number of cycles after end of earthquake D=
Percentage of critical damping
Using~D = 5%, seven (7) cycles are required to reach the 10%
amplitude level. The natural period of vibration for the greatcat thickness of of fsite borrow, based on the SilAKE analysis described in Subsection 2.5.4.10.b, is less than T = 0.25 sec.
This results 4
in a duration of seismic motion in the offsite borrow of less than 2 seconds after the end of bedrock motion. For thinner layers-of offsite borrow, the duration of motion will be less than calculated above.
References I
1.-
Bolt, B. A.,1973, Duration of Strong Ground Motion:
Fifth World
. Conference Earthquake Engineering, Rome.
2.
Bolt, B.
A.,
1981, Interpretation of Strong Ground Motion Records:
State-of-the-Art for Assessing Earthquake llazards in the United States, Miscellaneous Paper S-73-1, No. 17.
3.
Nicholls, et al., 1971, Blasting Vibrations and Their Effects on Structures: United States Department of the Interior, Bureau of Mines Report of Investigations, No. 656.
4.
Siskind, et al., 1980, Structure Response and Damage Produced by Ground Vibration from Surface Mine Blasting: United States Department of the Interior, Bureau of Mines Report of Investigations.
5.
Winthrop, John II,1757, An Account of the Earthquake Felt. in New England
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and the Neighboring Parts of America, on the 18th of November 1755, In a letter to Tho. Birch, D. D. Secret, R. S. by Mr. Professor Winthrop of Cambridge in New England:
Philosophical Transactions, v. 50, p. 1-18.
6.
Kachadoorlan,. R. and Plafker,1967, Effects of the Earthquake of March 27, 1964 on the Communities'of Kodiak and Nearby Islands:
U.S. Geological Survey Paper 542-F.
7.
Richart, F. E; Woods, R. D.; and Itall,.J. R.; 1970, Vibrations of Soils and Foundations, Prentice-Hall, Inc., Englewood Cliffs, New Jersey.
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230.6 Regarding your response to Question 230.3 on probability of -
exceeding the OBE during the operating life of the plant. Provide the input parameters chosen for the McGuire (1976) seismic hazard i
program and discuss the sensitivity of the results upon the uncertainties in the parameters.
Discuss the effect of the Franklin, New Hampshire event-of January 18, 1982 and other recent events upon the calculated probability of exceeding the OBE.
RESPONCE:-
See response to RAI 230.3.
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Question 230.7 Update your historical record of regional earthquakes up to and including, at least, the time of occurrence of the Franklin, New Hampshire event of January 18, 1982.
Discuss the correlation of this and other recent events with geologic structure or tectonic provinces and their significance with respect to the OBE and SSE.
Discuss the effect of any strong motion data obtained from the New Hamsphire event and other recent events upon empirical strong motion relationships used in determining the OBE and SSE.
Response
The data required to update the historical record of regional earthquakes are presently assembled.
It should be noted that finalized locations for New England are only available through March 1981, and through the end of 1978 for Canada.
Preliminary locations, subject to changes, are only available through PDE; (Preliminary Determination of Epicenters-USGS).
In the past, these have not been included in FSAR.
The New Hampshire event of January 18, 1982 (EST) has been given a preliminary location at 43.5N, 71.6W by the USGS in PDE 3-82.
Aftershocks data collected by W ston Observatory, Weston e
Geophysical and M.I.T. are presently being analyzed.
The occurrence of the New Hampshire event appears to confirm that the tectonic structure, described in the Boston
Edison docket, to which the 1940 Ossippee earthquakes were associated, is indeed active.
The epicentral location of the January 18, 1982 event is coincident with the intersection of two lineaments of small microcarthquakes detected by a local network operated for almost two years around Ossippee, New llampshire by Boston Edison Company (see figure).
These lineaments are in close spatial correlation with an aeromagnetic anomaly of similar shape.
See the aeromagnetic data (proprietary) filed at the NRC by Boston Edison Co.npany.
The applicant has not as yet obtained strong motion data for this earthquake sequence'and has separately petitioned the NRC for any help they may be able to provide in obtaining such data.
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Question 230.8 Discuss the correlation of the Central New Brunswick sequence of events beginning January 9, 1982 with geologic structure or tectonic provinces and the significance of these events with respect to the OBE and SSE.
Present all available information for these events on locations, depths, focal mechanisms, and correlation with past seismicity.
Discuss the the effect of any strong motion data resulting from these events upon empirical strong motion relationships used in determining the OBE and SSE.
Response
At present geophysical and geological data available for the New Brunswick area is being assembled.
These data will be analyzed and modeled to produce a basis for making a correlation of the earthquakes to geologic structure, if possible.
Assembling, analyzing and interpreting the data will take several weeks.
Present information indicate that the magnitude of the New Brunswick earthquake is less than 6 (m ).
This would not b
impact the design spectra for the SSE at Seabrook.
The OBE is not influenced by the occurrence of the New brunswick earthquake.
Current information for the New Brunswick earthquake is still preliminary.
The request for information will be
. completed as finalized data become available.
A summary of preliminary information is as follows:
- 1. A preliminary analysis by the Earth Physics Branch in Ottawa (EPB) of a 3-day subset of aftershocks confirms the epicentral location given in PDE-2-82 (Preliminary Determination of Epicenters-USGS) for the three largest shocks.
It also finds focal depths varying from 0 to 10 km, and a 5 km by 5 km epcentral area.
- 2. A preliminary fault plane solution by the EPB suggests high angle dipping nodal planes, oriented slightly east of north, and north of west, and an equal amount of strike and dip motion.
The applicant has not as yet obtained strong motion data for this earthquake sequence and has separately petitioned the NRC for any help they may be able to provide in obtaining such data.
Question 230.9 Section 2.5.1.2 a.
8 describes the geology of the Circulating Water System tunnels as interpreted from core borings and seismic data.
It is our understanding that the actual bedrock conditions as revealed by the tunnels is very similar to that interpretation.
Other than a brief geological reconnaissance of portions of the tunnels, the staff has no.
basis to independently assess the actual geologic conditions, a.
In order that we may complete our evaluation of the geology within the site visit, provide the geologic maps of the tunnels and any discussion of the geology.
Highlight any revisions in the original geological interpretations based on preconstruction investigations.
b.
On page 2.5-41, section (c) a statement is made that no throughgoing fault has been identified or inferred by the boring investigations.
During the staff's reconnaissance of the tunnels there was at least one geclogic feature observed which could be interpreted as a throughgoing fault.
The feature referred to is the badly disintegrated dike and/or f ault gouge in the discharge tunnel located about 1000 feet east of the divergence of the two tunnels, and again along strike in the intake tunnel.
Although not seen during the site visit, it is our understanding that other similar features were mapped.
Is it still your conclusion that there are no throughgoing faults in the tunnel area?
Please include the bases for your conclusion.
c.
On page 2.5-44, same section, you state that the geologic structures which controlled the downward migration of weathering solutions in three zones cannot be estimated:
(1) beneath northwest shore of Commons Island; (2) beneath tidal flats northwest of Commons Island; and (3) beneath Hampton Harbor west of Hampton-Seabrook Bridge.
Did geologic mapping of the tunnels indicate the cause of the extreme weathering at these (and other) locations?
Response
230.9.a Three figures, numbers 230.9-1, 230.9-2 and 230.93, are provided to show the. geology.of the tunnels.
Figures 230.9-1 and 230.9-2 show for the intake and i
discharge tunnels, respectively, geologic profiles.(5x f
vertical exaggeration), schematic plan diagrams, and histograms describing tunnel-support requirements (both as-built and preconstruction predictions), water inflow, mole advance rates, and bedrock joint spacing.
Figure 290.9-3 is a geologic plan map of the circulating water system tunnels, showing rock types and mapped faults.
The information presented on these figures
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summarizes the significant data mapped in detail by project geologists during the course of tunnels excavation.
Detailed field notes and large-scale L
geologic map compilations of tunnels geology are stored
. at the site.
A summary report, supplemented with numerous data tables and descriptive figures, is currently being prepared to describe the tunnels geology in detail.
Revisions in the original preconstruction geological interpretations of the tunnels geology, as generated from detailed mapping within the tunnels, do not suggest modifications of significance to the site.
The modifications have merely involved relo:ating geologic contacts to the east or west of the locations previously estimated by inference from widely-spaced borings data combined with the geophysically-defined topography of the bedrock surface.
Several areas of mixed metasedimentary/ igneous rock types were found in the tunnels which the widely-spaced borings investigations failed to intersect.
Zones of l
apparently closely-jointed or deeply weathered rock l
l seen in borings were found during tunnels excavation 1
consistently to be of less lateral extent and of l
greater rock competence than interpreted from l
l preconstruction investigations.
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230.9.b The initial question of throughgoing faults at the site related to an east-west thrust fault which is shown for the area on the geologic map of New Hampshire
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(Billings, 1956).
Borings investigations at the site and along the tunnel alignments indicated that the
. fault does not exist.
Mapping in the tunnels has demonstrated that the contact between the Newburyport pluton and the Merrimack group metamorphic rocks, earlier depicted as a through-going thrust fault, is an intimately-interfingering intrusive contact.
Detailed mapping during construction has identified 104 faults in the tunnel excavations and 61 faults in the site excavations.
The system and styles of site faults are described in detail in the FSAR, with the conclusion that all are considered to be localized deformations.
The systems and styles of tunnel faults closely resemble those of the site faults in their orientations, widchs, displacements and mineralization, and we conclude that they are also localized, non-throughgoing deformations.
The fault identified in Question 230.9.b as located about 1,000 feet east of the divergence of the two tunnels crosses the discharge tunnel at Station 114+05, where it strikes N33*E, dips 79'NW and contains gouge.
No evidence was found to indicate the direction of throw on the fault.
Projected on strike to the northeast, the fault, if continuous, would intersect l
i the intake tunnel near Station 120+00, about 900 feet northeast of the discharge tunnel.
At Station 120+21 in the intake tunnel, a diabase dike 8 inches thick i
j strikes across the tunnel nearly parallel with the l
. attitude of the discharge tunnel fault.
The dike and adjacent metasedimentary country rocks are bleached, but the thin dike is intact and does not contain gouge.
The apparent relationships between the fault and the dike at these tunnel locations resemble those observed at similarly northeast-trending faults A-1A and SI-l in the site excavation, where diabase intruded along pre-existing fault planes.
Each of these site faults is a minor, discontinuous structure.
230.9.c W athering degradation was found in the tunnels to be e
considerably less than that suggested by the borings investigations,-and the broad zones of weathering inferred from the borings were not encountered in that form.
As shown on Figures 230.9-1 and 230.9-2, in areas where the bedrock surface is at a low elevation, the underlying bedrock was found in the tunnels to be more closely jointed, permitting the more rapid migration of ground water.
These conditions enhance the advance of weathering degradation.
Beneath the northwest shore of Commons Island and the tidal flats in that area, the generally greater weathering effects coincide with the presence there of micaceous metasedimentary rocks.
A lense of similar micaceous rock coincides with another zone of inferred deep weathering beneath Hampton Harbor to the west of the Hampton-Seabrook bridge.
While sof ter and more
. micaceous, the rock at these locations is not severely
. weathered.
No substantial weathering was found in the tunnels at the earlier-inferred zone of deep weathering immediately to the west of the Hampton-Seabrook bridge.
Bedrock weathering encountered in the intake tunnel between Stations 119+70 and 120+25 coincided with the intersection of a hydrothermally-altered northeast-striking diabase dike and a moderately-dipping, north northwest-striking fault.
This is also a location where the bedt :k surface is at a relatively low elevation.
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1 Question 230.10 Considerable geological and seismological research has been carried out in New England during the past few years by state geological surveys, universities, consulting firms and the USGS.
Many of the publications reporting the results of this research have been published after docketing of the FSAR.
Many of these publications are referenced in the N".0,
- 1981, NUREG/CR-2131, New England Seisciotectonic Study, FY 1979.
Others appear in various earth science publications.
Update the FSAR' to include an assessment of the most recent earth sciences research as to their significance to the geologic and seismic safety of the site.
Response
The FSAR will be updated to 1982 to include a bibliography of reports as requested as well as a comment on their potential to modify any regional or site geologic or seismological considerations.
The applicant and its consultants' are aware of and maintain a library of current published data and reports, and to the best of their knowledge, none of the uncited publications bear significantly on any conclusion drawn for the Seabrook site.
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