ML20209D278
| ML20209D278 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 08/20/1984 |
| From: | Reiter L Office of Nuclear Reactor Regulation |
| To: | Thadani A Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML20209C800 | List:
|
| References | |
| FOIA-87-6 NUDOCS 8408280374 | |
| Download: ML20209D278 (5) | |
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UNITED STATES
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8 NUCLEAR REGULATORY COMMISSION n
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,E WASHINGTON, D. C. 20555
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AUG 2 01984 MEf10RANDUM FOR: Ashok Thadani, Chief Reliability and Risk Assessment Branch Division of Safety Technology
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THRU:
, James P. Knight, Assistant Director for
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Components & Structures Engineering Division of Engineering FROM:
Leon Reiter, Acting Chief Geosciences Branch Division of Engineering
SUBJECT:
PRELIMINARY REVIEW 0F THE EXTERNAL EVENTS ANALYSES IN THE SEABROOK STATION PROBABILISTIC SAFETY ASSESSf1ENT (PSA)
Staff from DE and DSI have completed their initial review of the external events analyses in the Seabrook PSA. Attached to this memorandum is a list of staff reviewers and oetailed review corcents and questions to be transmitted to the Seabrook applicants. This review was coordinated by P. Sobel.
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-s Leon Reiter, Acting Chief Geosciences Branch Division of Engineering
Enclosures:
As stated
- 1. Seabrook PSA Reviewers
- 2. Review Comments and Questions I
cc:
R. Vollmer J. Chen J. Knight L. Heller F. Rowsome R. Pichumani Fo2n - F7-ce <-
S. Brocoum A. Masciantonio L. Reiter C. Ferrell g//]
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R. Frahn J. Stang T. Sullivan R. Jachowski l
S. Davis J. Fairebent P. Sobel R. Anand I
fi. Chokshi R. Klecker N
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Docket Nos. 50-443/444 Seabrook Station Nuclear Power Plant Reviewers for External Events Probabilistic Safety Assessment Area of Review Responsible Branch Assigned Reviewer Seismic GSB/SGEB/MEB/EQB P. Sobel/N. Chokshi, J. Chen/R. Pichumani A. Masciantonio Aircraft Crash SAB C. Ferrell Fire ChEB J. Stang External Floods EHEB R. Jachowski Hazardous Chemical SAB C. Ferrell (TruckCrash)
Wind / Tornado METB/SGEB/ASB J. Faircbent/
N. Chokshi/
R. Anand Turbine Missile MtEB R. Klecker DE
Contact:
L. Reiter/P. Sobel l
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P Staff Coments and Questions on Seabrook Station Probabilistic Safety Assessment
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Comments and Questions on Seabrook PSA Seismic Hazard Analysis 1.
In the seismicity analysis, earthquakes identified with an epicentral intensity but without a magnitude estimate were converted to a body-wave magnitude using an equation derived specifically for New England by Weston Geophysical Corporation. As noted in the attached internal staff memorandum, the staff questions the validity of the Weston epicentral intensity to magnitude equation. Provide a response to the concerns in the attached memorandum.
2.
Two of the four equations used to estimate acceleration at the site as a function of magnitude and distance from the epicenter (AI and AID) were derived from intensity attenuation observed during earthquakes in New England (C. Klimkiewicz, personal communication, 1982). Figure 15 on PSA page F.1-44 shows the AI and AID attenuation equations indicate lower hazard than the Campbell or Nuttli and Herrman attenuation equations. The AI and AID ground acceleration equations also predict lower near source accelerations for the same magnitude. Why would near source magnitude (for the gssumeb)forthesetwoequations?
same m be lower in the east compared to the west, as you have Describe the bases for these 6ttenuation equations.
3.
.In the PSA seismic. analysis, peak acceler'ations have upper bound limits based on sustained acceleration. This practice has been a i
concern for the staff in past PRA reviews. Has any new basis for this practice been developed since the study by Kennedy described-in the PSA? What is the effect of untruncated calculations in the i
seismic analysis?
4.
T'he s'tructural engineerino part of the PSA uses a site-specific spectrumfromBernreuter{NUREG/CR-1582). This spectral shape depenas, however, on earthquake magnitude and distance to the source. Compare the spectral shape used in the PSA to the more recent site specific spectra developed in the Seabrook SER by LLNL.
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5.
You have assumed in your fragility analysis that the majority of seismic risk results from earthquakes that have magnitudes between 5.3 and 6.3.
What is the basis for this assumption?
6.
As part of an ongoing joint NRC Office of Research and Office of Reactor Regulation effort, the staff is assessing the seismic hazard for all nuclear power plants east of the Rocky Mountains.
The results for the first ten sites are discussed and displayed in NUREG/CR-3756. The Seabrook site is included in the next set of sites and we will forward the results to you as soon as they are available.
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!T d' NUCLEAR REGULATORY COMMISSION (f.dg.j t
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kEt10RANDUMFOR: Retert E. Jackson, Chief Geosciences Branch, DE T'RU:
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Leon Reiter, Leader' H
Seismology Section, GSB, DE FR0;W Jeff Kimball, Seismologist Seismology Section, GSB, DE SUSJECT:
REVIEW CF WESTON GEOPHYSICAL liAGNITUDE TO EPICENTRAL INTEi!SITY EQUATION FOR THE NORTHEAST At the January 5, 1984 meeting with the Millstene applicant the staff was presented with seismicity comcarisons*between the Millstone site area and the r,'ew Brunswick earthquake epicentral regicn. These
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ccmparisons ' utilized an ccoirical ccrrelation, derived by Weston Gecphysical Cero., between magnitude and epicentral intensity.~ This ecuation is necessary if recurrence statistics are to be based ucen
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magnitude and if the entire historic earthcuake data set is to be useo.
Histor;ic earthcuakes with only epicentral intensities ' list'ed are cerverted to equivaient nagnitude using this empirical correlation.
In adcition to the use of this correlation at ISillstone,i.leston has used this relationship in seismic hazard studies and PRA's.
The purpose of this memorancum is to evaluate this correlation and compare it to others (Street and Lacroix,1979, f:vttii and Herr ann,1978) for the northeast United States. - An evaluation of.this relationship will aid in a better understanding of, the absolute numbers in these probabilistic-studies.,
The data set used b'y Weston i's"recrocuced here as Table 1. Least squares
~
regression has been performed verifying the Weston ecuation for this data set.
Figure 1 shows the basic data and the graphed equation of l
Weston, Nuttli and Herrmann (1978) and Street and Lacroix-(1979). The t:uttii and Street equations have been used by the staff in the past. As shewn in figure 1 the largest difference is these equations is for intensities TVil=V and less, where the Westen equation predicts lower l
magnitudes compcred to the others. This is important when' developing recurrence relationships because the slope of the recurrence curve is dependent on the proportion of. data in each magnitude range.
Subsets of the data in Table 1 have been investigated to determine if trrrnds in the da d.xist which may explain the above noted differer.ces.
The regression ecu,.- n: of the verious subsets are listed in Table 2 i
and shown in figurr'i ? and 3.
Figure 2 ccmpares the Weston equatien and the data set divicH into two time intervals while figure 3 compares the data set divicec nto threc magnitude intervals.
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S~sveral trends.in the above discussed fi..gures tre worth noting.. The two_
/ 'Iike intervals when studied separately appear to show a time bias. -Fo r a,given magnitude earthquake higher epicentre.1 intensities have been assioned more becently. This may be due to a difference in how magnitudes are' determined or an increased awareness by both the resecrch' community and the public. The older events 5 ave Mbig's listed by Street a'n'd Lacroix (1979) while the more recent events have magnitudes (Mn) listed in the NEUSSN. Bulletin..As discussed by Herrmann (1983) Mn may not ecual tAbig. One other explanation may be in how epicentral intensity is determined.
It is very difficult to evaluate whether this has char.ged with time.
if Another trend in the data, displayed in figure 3, is that the slope of the regression curve steepens as more lower cagnitude data is incluced.
The steepening of the slope tends to lower the equivalent magnitude for the lower intensitics. An explanation for this may be that, for the smaller magnitudes, only the anomalous intensities appear in the bulletins. For example, the majority of magnitude 2.0 eerthouakes are not felt yet this is oct taken into acccunt in the Weston analysis.
Both ::uttii Pnd Herrmann (1978) and Street and Lacroix (1979) based their regression on the larger earthquakes and thus avoided the 'p0ssible problem of deternining how to assign zero intensity for the smaller earthcuakes. The subset of the Weston data set using magnitude 3 5 t: ~
6.6 crocuces an ecuation very similar to Street and Lacroir (1979). The Westen data set tppears to give two large a weight to the reportec l
epicentral intensities for magnitudes less than about 3.5.
Based upon the aoove discussion i* is recommended that a copy of this memorcndum be sent via the Millstone project manager to the applicant
' and.thei.r. consul.ttnts who have used the discussed relationships for bcth
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the hazard. analysis (Dam,es & Moo'rd reort) and the Millstone /Rew.
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Brunswick seismicity.r.ecurrents comparisons.
I am available to.neet l
uith the appl ~icant and their consultant to discuss both.this.demor'an6am and potential implications regarding conclusions reacheo on material l
submitted on the Millstone docket.
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Jef' Kimball, Geophysicist Seismology Section Geosciences Branch, DE cc:
R. Jackson' A. K. Ibrahim L. Reiter P.. P.c t hma n S. Broccum J. Kinball B. Ocolittle E. J. Youngbinnd F
ggg g g jgg4 TAB LE l EART.9 QUAKES USED TO DETERMINE RELATIONSHIP OF
- m[-MAGNITUD'E TO' EPICENTRAL ~ INTENSITY IN THE NORTHEAST YR*
MO 'DA LAT.
N.
LONG.
W.
Io mb 1924. 09 30 47.60 69.70 VII-VIII 5.5 1925 03 01 47.60 70.10 IX 6.6 1929 08 12 42.87 78.35 VIII 5.2 1931 04 20 43.40 73.70 VII 4.7 1935 14 01 46.78 79.07 VII
- 6. 2 1938 08 23
'40.10 74.50 1/
3.9 1939 10 19 47.80 70.07 VI 5.6 1940 01 28 41.63 "
70.80 V
2.6 1940 12 20 43.80 71.30 VII
- 5. 4 1943 01 14 45.30 69.60 V
4.4 1944 09 - 05 '
44.97 74.90 VIII 5.8 1947 12 28 45.20 69.20 V
4.4 1949 10 05 44.80 70.50' V
4.5 1951 09 03 41.25 74.25 V
3.8 1957 04 26 43.60 69.80 VI 4.8 1963 10 16 42.50 70.80 v
1.9 1963 10 30 42.70 70.80 IV-V
- 2. 4 1964 04 01
- 43. 60 71.50 IV 1.8 1964 06' 26 43.30 71.90 V
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- 2. 6 1966 01 01 42.80 78.20 VI 4.7 1967 06 13 42.90 -
78.20 VI 3.9 1967 07 01 44.40 69.90 IV 2.9 1967 07 01 44.38 69.87 V
3.4 1968 10 19 45.30 74.12 V
3.2
'. 1969
.06.13 _ _
43.30
,, 78.22 IV 2.5 1973 06 13 45.39 71.03 VI
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1975 09 02
'. 43, 20 69.74 IV
- - 3. 3 1976 04 15 44.24 70.14 II-III
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2.4 1976
- 04. 24 41.46 72.49 IV
- 2. 2 1976 05 10 41.54 71.01 V
2.7 1976 07 13 45.18 74.10 III-IV 2.9 1976 10 23 47.82 69.79 V
4.2 1977 08 08 49.77 67.05 IV 3.9 1977 12 20 41.82 70.76 IV 3.1 1977 12 20 41.84 70.70 III
- 2. 4 1977 12 25 43.20 71.64 IV 3.- 2 1978 01 04 44.07 70.55 III-IV 3.0 1979 01 29 44.83 73.19 II 2.8 1979 04 23 43.04 71.24 III-IV 3.1 1979 12 30 41.16 73.72 III
- 2. 2 1980 04 03 48.69 68.05 IV 4.1 I
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PROBABILISTIC SAFETY ASSESSMENT SEABROOK STATION STRUCTURAL AND GEOTECHNICAL ENGINEERING BRANCH REQUEST FOR ADDITIONAL INFORMATION Based on the preliminary review of the structural fragility and geotechnical aspects (Chapter 9 and Appendix F) of Probabilistic Safety Assessment (PSA) report submitted by the applicant, the following additional information is needed to complete the review.
Structural Engineering Aspects 1.
Provide supporting calculations for fragility data presented in Table 4-3 through Table 4-16 of Appendix F.
Also, provide fragility calculations for components (7), (11), (13), and (23) of Table 9.2-3.
2.
In several recent PRAs (e.g. Millstone), sliding failure mode of. Category I structures have been found to be critical in that it affects the inter-connected piping.
Exolain, why such a failure mode has not been considered at Seabrook.
3.
Section 2.1.3 of Appendix F states that the non-category I building are separated fran the category I structures by seismic gaps and that they were either designed to Category I criteria or their failure would not affect Category I structures. It is not clear that the above statement is still valid for accelerations higher than SSE. Please provide detailed basis for the judgenent that the failure of the non-category I structures would not affect Category I structures.
s,
Discuss, whether or not the tank wall flexibility has been considered in 4.
~
the fragility determination. In past, design calculations for tanks have been based on rigid wall assumption in many cases.
Geotechnical Engineerina Aspects Provide the fragility calculation for the safety related electrical duct 1.
bank and manholes.
2.
Section 6.6.3.2.2 Loss of Service Water:
How is the fragility of the service water system affected when subjected to:
- 1) ground movements due to tectonic strain adjustments,
- 2) lapses in quality of construction, 3)lackofmaintenance/ inspection,and
- 4) degradation by weathering?
How does the unavailability value for the service water supply compare to the unavailability experience value for municipal water supply sources? Justify any substantial differences between these values.
- 3. Table 9.2.1 Seismic Capacity of Structures The median acceleration capacity shown on table 9.2.1 varies from about 2 to 10 gravities. For foundation accelerations with vertical components above 1 gravity, the structure can momentarily lose contact with the ground; after a period of free-fall, the t
l foundation of the structure would subsequently impact the ground.
l Have impact effects been considered in the " capacity" evaluations l
given in table 9.2.1? If not, why have these effects been l
disregarded?
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=
r am HECHANICAL ENGINEERING BRANCH REQUEST FOR ADDITIONAL INFORMATION SEABROOK STATION PROBABILISTIC SAFETY ASSESSMENT (SSPSA)
- 1. Provide an adequate assurance that all possible interaction of non-safety related structures or equipment with saftty related items has been investigated in the SSPSA study. A walk-through after completing the construction of the plant to evaluate all possible interaction of nonsafety related structures or equipment with safety related items is recommended.
- 2. Section 2.4 of Appendix F, " Seismic Analysis Details," of Reference 1 states that, "An inadequate data base exists upon which to determine explicitly the contribution of design and construction errors to most Seabrook structures and equipment seismic capacities.
In one exception to this, the possibility of a large throughwall flaw was consioared as a lower bound for generic piping." Provide additional information to describe hcw a large throughwall flaw in piping was considered in the SSPSA study.
- 3. In Section 4.17 of Appendix F of Reference 1, " Soil-Structure Interaction Effects," the applicant has stated that, "At the frequencies of maximum energy content, although a very small amount of uplift may occur, the direction of the input motion is reversed before any significant rocking motion can occur." The applicant has concluded in the above section that relative motion sufficient to cause piping failure is not considered a possible failure mode.
In addition, the applicant has not considered the structure sliding failure mode that was considered in the PRA studies of some other plants (e.g., Hillstone 3). Provide additional information including necessary computational results to justify the apparent conclusion that the above far -re modes do not contribute significantly to any adverse effects of anchor point motion on the piping.
O a
Equp,h ent Qualification Branch Preliminary Connents/ Questions on Seabrook Station Plan 1.
Please describe the methodology used to assure that all necessary systems and components have been considered and included in Table 9.2-2.
2.
Provide examples of the calculations and assumptions used to derive fragility curves for all components listed on Table 9.2-3.
I 3.
Please discuss the assumptions and methods used to analyze piping and conduit runs between buildings and at building interfaces.
4.
Please elaborate on the significance of deviation values of 0.0 in Table 9.2-2.
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SAB Questions and Comments on Seabrook Units 1 and 2 PSA Section 9.3 Aircraft Crash Analysis This analysis is similar to the applicant's previous risk analysis evaluation presented in the FSAR and evaluated by the NRC staff in Section 2.2 of the Seabrook SER (NUREG-0896). Both of these analyses conclude that aircraft crash risk as the result of activities in the vicinity of the Seabrook site is acceptably low and does not pose a threat to the safe operation of the plant.
We have reviewed Section 9.3 of the PSA and find it acceptable.
Section 9.7 Hazardous Chemicals and Transportation Events In Section 9.7, the applicant has detemined that the probability of a vehicle penetrating a bridge guard rail (on an onsite roadway) and damaging the busses for all offsite power is 2.5 X 10-3 per year.
This value exceeds the criteria of SRP Section 2.2.3.
The applicant should eneck the analysis to detemine if it is valid, and if so, should take preventative measures, such as strengthening the bridge rails and roadway guard rails to prevent trucks from damaging the electrical bus for offsite power from the three outside sources.
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METEOROLOGY QUESTIONS ON SEABROOK PSA The discussion of tornado wind hazard and frequency presented in Section 9.8 of the Seabrook PSA mirrors that provided in the report, "Seabrook Nuclear Power Plant Missile Analysis" (by Applied Research Associates, Inc., for the applicant, September 1983), which has been previously reviewed by the i
staff (see the April 12, 1984 memorandum from Gammill to Parr on " Tornado Occurrence Frequency for Seabrook"). As described in that review, the staff's independent analysis confirmed that the applicant has reasonably estimated the probabilities of extreme wind speeds associated with tornadoes. Also, as indicated in that review, the applicant did not consider the probabilities of extreme winds from non-tornado phenomena.
The discussion presented in Section 9.8 of the Seabrook PSA, alludes to winds associated with non-tornado phenomena, but fails to adequately consider such winds or to present sufficient bases for dismissing the effects of such winds. For example, the discussion on page 9.8-3, acknowledges that "some critical equipment outdoors" could "be damaged at windspeeds much below 360 mph" resulting in a " transient initiating event." The wind-generating phenomenon identified for this situation is
" weaker but more frequent tornadoes." However, windspeeds up to 150 mph may be more likely due to non-tornado phenomena, Provide an expanced discussion of the consideration of extreme winds o
generated by non-tornado phenomena, including sufficient bases for
an
. dismissing the effects of these winds, if applicable. Specifically, provide an expanded discussion of wind events capable of initiating transients.
Other extreme meteorological conditions should be addressed in the PSA, with sufficient bases presented for dismissing the effects of these conditions, if applicable. Table 10-1 of NUREG/CR-2300, "PRA Procedures Guide," identifies examples of such other meteorological ccnditions to be considered in probabilistic risk assessments.
Provide a discussion of the consideration of extreme meteorological o
conditions other than winds and tornadoes which may impact the design of auxiliary systems and components or which may result in transient initiat'ing events.
Some meteorological conditions resulting in transient initiating events may also result in impaired evacuation for emergency response. For example, extreme wind speeds affecting plant performance would also likely damage offsite structures, block roadways with fallen trees or debris, and disrupt notification and communication. Snow storms and/or ice storms could affect responses to an emergency situation, including significantly expanded evacuation times.
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4 3-o Provide a discussion of the impacts of meteorological conditions on consequence assessment, considering the possibility that some meteorological conditions could initiate transients, impair emergency response, and impede implementation of protective actions such as evacuation.
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