ML14169A072
| ML14169A072 | |
| Person / Time | |
|---|---|
| Site: | Arkansas Nuclear, FitzPatrick  |
| Issue date: | 06/19/2014 |
| From: | Entergy Operations |
| To: | Office of Nuclear Reactor Regulation |
| References | |
| Download: ML14169A072 (61) | |
Text
Seismic Hazard Reevaluation June 19, 2014
IPEEE Questions Arkansas Nuclear One James A Fitzpatrick
Arkansas Nuclear One IPEEE Was W theth Emergency E D/G F Fuell oilil ttank k and d 4160 v Switchgear upgraded to 0.30 g?
Explain E l i why h th there iis some iinconsistency i t b between t section ti 4.7 of the March submittal compared to RAIs from the IPEEE
Arkansas Nuclear One IPEEE Was W theth 4160 v S Switchgear it h upgraded d d to t 0.30 0 30 g?
?
4160 Volt Switchgear 2A-3 2A 3 and 2A 2A-44 Walk down performed during 2R12 outage 3rd set of plug welds observed versus 2 Reevaluated with 3 sets of welds Switchgear HCLPF to >0.30
>0 30 g Documented in 96-SQ-2001-01 R. 0
Arkansas Nuclear One IPEEE Was the Emergency D/G Fuel oil tank upgraded to 0.30 g?
Diesel Generator Fuel Oil Tank 2T-57A&B
- Re-evaluated
- Tanks qualified to 0.30 g
- Documented in 95-SQ-2521-01 revision 0
- Documented in GL 97-02 Completion Letter
Arkansas Nuclear One IPEEE Explain p whyy there is some inconsistency y between section 4.7 of the March submittal compared to RAIs from the IPEEE.
RAI Response A ffault tree was constructed by removing the components not on the IPEEE safe shutdown list March submittal AA fault tree was developed from the detailed plant fault tree, taking no credit for components on the IPEEE SSEL March submittal is in error ANO - Unit 1 IPEEE meets the requirements of Section 3.2.5.8 of NUREG-1407
J A Fitzpatrick IPEEE J.A.
How is the HCLPF calculation for the block walls in the IPEEE adequate?
How was relay chatter addressed?
Was W EPRI-6041 EPRI 6041 usedd for f Category C t II SSCs SSC iin th the Turbine Building?
J A Fitzpatrick IPEEE J.A.
How is the HCLPF calculation for the block walls in the IPEEE adequate?
NRC Bulletin 80 80-11 11 and A-46 A 46 walk walk-downs downs 3 walls subsequently installed 4 walls ll strengthened t th d EPRI NP-6041-SL Evaluating damping value used
J A Fitzpatrick IPEEE J.A.
How was relay chatter addressed?
Relay Chatter JAF was a Focused IPEEE 144 Outliers Outlier Seismic Verification Sheets ((OSVS)) form for each outlier were filled out.
All outliers were resolved in 1998 However, SPID required new relay evaluation JAF has committed to perform a new relay evaluation
J A Fitzpatrick IPEEE J.A.
Was W EPRI-6041 EPRI 6041 used d ffor C Category t II SSCs SSC in i T Turbine bi Building?
YES Class I potions designed to both 0.08g for OBE and 0.15g for DBE Class II portions governed by 0.08g design.
Class II OBE design controlling for preventing a collapse affecting Class I portions for DBE Table 2-3 of EPRI NP-6041 is applicable
Soil Properties Indian Point Energy Center
Indian Point Energy Center The new Ground Motion Response Spectra (GMRS) developed by EPRI and the NRC has some differences.
The source of the differences are the result of different properties assumed for the site amplification.
EPRI used the historical hard rock values which would result in no amplification.
NRC used a softer rock value
Indian Point Energy Center Located west of the Hudson River in Buchanan, New York The Th siteit h houses ththree reactors; t
Indian Point Unit No. 1 (SAFSTOR MODE)
Indian Point Units Nos.
Nos 2 & 3, 3 two Pressurized Water Reactors Site Area bedrock is rock of the Manhattan Formation, Limestone, and marble
Indian Point Energy Center The circa 1980 EPRI-SOG Summary Report indicates that the units were founded on basement rock with the site underlain by ypphillite and limestone Table 5-1 indicates hard limestone below 17 ft with a 7 ft layer of decomposed decomposed rockrock The regional rock units generally consist of gneiss,, schist,, granite, g g , quartzite, q , and marble,, all typically associated with high Vs. (Shear Wave Velocity)
Indian Point Energy Center Building the three nuclear units required a significant amount of rock removal.
Rock blasting was used to fragment and remove the rock to below foundation levels. Native rock elevations in the plant area varied from approximately Elev Elev. + 80 ft ft. to Elev Elev. + 20 ft ft.
towards the western part of the site.
Foundation ou da o e elevations e a o s foro the e sa safety e y related e a ed structures are, in general, 30 feet or more below grade/top of the rock. (final blasted elevation of rock)
Indian Point Energy Center There were no quantifications for the compressional (p-wave) or shear wave velocities Estimates were based on information suggesting that, for the Indian Point site, shear wave velocities in excess of 9200 fps are appropriate NOTE:
NOTE 9200 FPS = 2,804.16 2 804 16 mps
Indian Point Energy Center Typical Wave velocities
Indian Point Energy Center RECENT INFORMATION The 2010 and 2011 EPRI Reports relied upon the EPRI-SOG information The Indian Point Nuclear Generating Station site is considered a hard-rock site because the shear-wave velocity at the surface is > 9200 fps. This is consistent with the hard-rock ground motion equations used here for rock conditions (EPRI, (EPRI 2004).
2004) Therefore, Therefore no site-site specific amplification calculations were made, and hard-rock hazard curves are used to determine the spectra.
Indian Point Energy Center RECENT EXCAVATION IN THE FUEL STORAGE BUILDING A single failure proof crane had to be installed Anchoring A h i the th crane required i d excavating ti th the rock k
Rock removal:
No blasting allowed Extremely difficult Numerous diamond drill bits were broken Rock samples were categorized as marble.
Indian Point Energy Center RECENT SOIL INVESTIGATIONS AT INDIAN POINT SITE 2005 thr thru 2007 Installation of groundwater monitoring wells Seismic Survey Work to facilitate movement of Spent Fuel Dry Casks Independent Spent Fuel Storage Installation of concrete pad
Indian Point Energy Center In 2006 a seismic survey was performed at a location approximately 600 feet south of Indian Point 3 VC GPR measurements obtained depth to bedrock Seismic S i i refraction f ti surveys to t predict di t compressional i l wave velocities in the fill and at the top of the rock Spectral Analysis of Surface Waves (SASW) data obtained using the ReMI Methods The rock profile in the area is highly fractured and is not representative p of the rock characteristics in the plant area.
Fractures in rock result in reduced compressional and shear wave velocities
Indian Point Energy Center Indian Point Energy Center Large g discontinuities in the rock elevation.
AGS noticed several characteristics of the rock b
beneathth th the site.
it FiFirst, t the th topography t h off the th bedrock interface ranged from flat to highly variable over relatively y short distances. There were a few locations where the bedrock interface disappeared and was located greater than 40-45 feet below ground surface(bgs) surface(bgs). This occurred on Line 1 from stations minus10 to 40, and on Line 5 from stations 12 to 30.
Indian Point Energy Center Indian Point Energy Center Indian Point Energy Center (RQD) Rock Quality Designation is and indicator as to the degree of fragmentation in the rock Compare Monitoring Well logs along a line close to the southern part of the plant, i.e.,MWs-41,43,44,45,46, and 47 MWs 48 (and 40), which represent a line in the general area south of the Warehouse (where MW-48 is located).
Indian Point Energy Center MW RQD and Notes RQD values of 13, 23, and 58.
MW RQD 48 Fracture zone 41 85 100 85-100 Elev. 25 ft to Elev. 37-6 ft.
43 73-100 Fracture zone:
44 80-100
- Elev.
El 28 tto 31 ft 45 97-100
- Angular fragments Elev.
46 68-100 29.5 ft to 32 ft 47 95 100 95-100 40
- Elev. 35 ft to Elev. 38 ft.
- 35 ft to Elev. 37 ft
- Closely Cl l spaced d fractures f t Elev. 71-4 to 71-9 ft.
Indian Point Energy Center Monitoring Well Map
Indian Point Energy Center Based on the significant fracturing in the MW closest to the seismic survey lines, it is apparent that the area suffered significant erosion and stress levels that caused significant rock fragmentation and discontinuities.
Estimates E ti t as to t the th wave velocities l iti away ffrom this area of significant discontinuities should be used for o Indian d a Point.
o
Indian Point Energy Center WORK PERFORMED BY GZA TO INSTALL MONITORING WELLS 23+ boreholes installed in the plant area Rock generally characterized as white MARBLE.
The Rock Quality Designation (RQD):
improves with depth improves with distance away from the fragmentation caused by blasting and weathering generally in the 80 to 100 range Presence P off bedrock b d k ffractures t ( hi h iincludes (which l d ttransverse ffractures) t )
higher near the bedrock surface decreases with depth in the area of the Site The RQDs are affected by y drilling g techniques, q , core breakage g during g handling, stress-relief and air slaking, the presence of thinly bedded or closely jointed zone, and the extensive blasting at the site.
Attempts to correlate the RQDs with compressional or shear wave velocities would be questionable at best.
Indian Point Energy Center WORK PERFORMED BY TECTONIC AT THE FUEL STORAGE BUILDING Eight borings were made inside the FSB and along the road to the FSB.
Four of the borings are in the FSB, just south of the Spent Fuel Pool Samples from borings B-1 and B-2 used to perform unconfined compressive strength tests B-1 was taken at a depth of 9.5 to 10 B-2 was taken at a depth of 11 to 12 The RQDs at the sample locations were 66 and 55 55, respectively respectively, indicating significant fragmentation effects from the adjacent blasting Results of the unconfined compressive strength testing on the two rock core samples l yielded i ld d strength h varying i from f approximately i l 10 10,000 000 to 20,000 pounds per square inch. These unconfined compressive strengths generally correlate to strong to very strong rock conditions.
Indian Point Energy Center WORK PERFORMED BY TECTONIC AT THE FUEL STORAGE BUILDING A seismic refraction study was performed along a 235 ft. long array along the road leading east from the FSB Geophones FSB. G h were placed l d fifive (5) ffeett apartt along l
the array.
The Tectonic Report p indicates that the rock q quality y
increases with depth.
The upper portion of the rock in this area is significantly fragmented as a result of the blasting for the FSB to the north and blasting for the Primary Auxiliary Building to the south.
Indian Point Energy Center Th P-wave The P velocities l iti along l th the ttop off th the rock k vary ffrom 12,500 fps to 13,900 fps.
Indian Point Energy Center WORK PERFORMED BY TECTONIC AT THE ISFSI PAD The ISFSI pad required the placement of a carefully engineered fill with properties that match the ones used in performing the Dry Cask drop analyses.
y Up to five (5) feet of rock had to be removed to facilitate the placement of the engineered fill Rock removal was by mechanical means, significantly affecting the rock upper portion.
Indian Point Energy Center WORK PERFORMED BY TECTONIC AT THE ISFSI PAD Engineering Properties
Indian Point Energy Center WORK PERFORMED BY TECTONIC AT THE ISFSI PAD Seismic Refraction Arrays
Indian Point Energy Center WORK PERFORMED BY TECTONIC AT THE ISFSI PAD Included the characterization of the underlying y g rock Included seismic refraction studies along six (6) arrays Results from the seismic refraction work were used to verify the predictions as to depth to bedrock Some anomalies existed with the sixth array Estimates as to the compressional wave velocities obtained from the Line 6 array should not be considered
Indian Point Energy Center SEISMIC REFRACTION Estimates the rock compressional wave velocities along the interface between the engineered fill and the top of the rock The top of the rock layer is weathered and more f
fragmented t d Measured compressional wave velocities along weathered rock surface do not represent the wave velocities at a depth in the range of 30 ft.
below the top of the rock
Indian Point Energy Center The mean of the low bound compressional wave velocities from Arrays 1 through Array 6 is 13,217 fps.
The mean of the upper bound compressional wave velocities from Arrays 1 through Array 6 is 15,633 fps.
The overall mean of the compressional wave velocities measured at the ISFSI pad for the rock upper portion is 14,425 fps.
Fractures, more prevalent in the upper portions of the rock, result in a reduction in the compressional (Vp) and shear wave (Vs) velocities through the rock Velocities measured by Tectonic represent compressional wave velocities through fractured and weathered rock in the top section of the rock and do not represent wave velocities representative of locations 30 feet below the rock surface.
Indian Point Energy Center Tectonic observed that: The The presence of bedrock fractures (which includes transverse fractures) is reported to be higher near the bedrock surface and to decrease with depth in the area of the Site (Tectonic, 2004).
Based on the above observations, observations it may be inferred that the wave velocities measured by Tectonic represent reduced compressional wave velocities through fractured rock and that at depths of 30 ft. or more below the rock surface, the improved rock quality results in higher wave velocities.
velocities For the purpose of estimating compressional wave velocities away from the fractured, and weathered, rock surface, we shall assume the compressional wave velocity at the foundation level off safety f related structures is equal to the mean value off the wave velocities for the ISFSI arrays, i.e. Vp = 14,425 fps.
Indian Point Energy Center CONCLUSION The site sits on hard rock historic documents site it excavation ti workk applicable well data Use of selective site data is inappropriate perimeter well data ISFS Pad surface data
Seismic Screening Indian Point Energy Center
Indian Point Energy Center IP3 was screened in as a Priority 1 plant for an SPRA since the consideration of the more recent re-assessment of the IPEEE was not considered.
The original IPEEE analysis in 1995 was performed to meet the minimum Review Level Earthquake (RLE).
The actual capacity of the plant is much higher.
Demonstrated in recent re-assessment of IPEEE
Indian Point Energy Center In 2010/2011 the NRC used values for plant p capacity extracted from the IP3 IPEEE report submitted in 1997.
This resulted in the NRC determining a very conservative SCDF estimate of 1.0E-04 per year, or 1 in 10,000 reactor-years.
reactor years.
NRC has evaluated and stated any plant with a SCDF value lower than 1.0E-04 per year (or 1 in 10 000 reactor-years) 10,000 t ) is i acceptable.
t bl
Indian Point Energy Center Using the improved plant capacities developed by a Seismic review team a reassessment of the SCDF estimate was performed in April 2011.
This report IP-RPT-11-00012 (ML13183A280) was transmitted to the NRC by June 2013 letter NL-13-084 NL 13 084 (ML13183A279).
With the use of the improved plant capacities and EPRI updated 2010 hazard curves; A new SCDF was estimated at 7.1E-06 per year (or 1 in 140,845 reactor-years).
Indian Point Energy Center Assessment Approach Understanding the current seismic risk to the station, in terms of SCDF.
Identifying potential conservatisms within the IP3 IPEEE submittal information used by the NRC in the SCDF calculation.
Making IPEEE component fragility values more realistic.
The team computed fragility values for a sample of components that are high contributors to risk using original component design documents
Indian Point Energy Center Reducing g conservatism in the USGS seismic Hazard Curves.
the USGS seismic hazard calculations did not include Cumulative Absolute Velocity (CAV) filtering and ground motion incoherence, which tend to reduce the acceleration values.
Developing a more realistic SCDF using the revised fragilities and hazard curves.
It should be noted that the original PRA computer model Seismic S i i HHazardd IIntegration t ti P Program (SHIP) iis nott available il bl to be modified and an alternate approach was developed
Indian Point Energy Center Identification of Low Capacity Components in dominant sequences Seismic-induced loss-of-offsite power (LOSP) and the subsequent loss of on on-site site AC power from all three emergency diesel generators.
Loss of secondary side cooling due to depletion of the condensate storage tank and failure of RHR shutdown cooling due to the seismic event.
Loss of component cooling water (CCW) or containment fan coolers due to a seismic event.
Indian Point Energy Center Indian Point Energy Center The improved values for the median capacity (Am = 1.27g),
and composite uncertainty (c = 0.4) 0 4) calculated by the review team resulted in a SCDF estimate of 9.4E-06 per year (1 in 106,383 reactor-years) associated with the currentt USGS H HazarddCCurves which hi h represents t a significant reduction from the GI-199 reported SCDF estimate (1.0E-04 per year or 1 in 10,000 reactor-years) and d iis a much h more realistic li i estimate i off the h seismic i i risk.
i k It should also be noted that using the improved fragility (Am
= 1.27g, g, and c = 0.4 ) along g with the 2010 EPRI updated p
seismic Hazard Curves instead of the USGS curves further reduces the SCDF value to 7.1E-06 per year (or 1 in 140,845
, reactor-years) y )
Indian Point Energy Center The IPEEE and its reassessment were reviewed for adequacy utilizing the guidance provided in Section 33.3 3 of the SPID (EPRI, 2013a). A detailed description of the results of the IPEEE adequacy review is included in A
Appendix di B off th the M MarchhSSubmittal b itt l (ML14099A111) .
The results of these reviews have shown, in accordance with the criteria established in SPID (EPRI, 2013a) Section 3.3, that the IPEEE and reassessment of the IHS are adequate to support screening of the updated seismic hazard for Indian Point Unit 3. The review also concluded that the risk insights obtained from the IPEEE are still valid under the current plant configuration.
Indian Point Energy Center Scaling the Review level earthquake (RLE)
Am = 0.975g c = 0.30 HCLPF = Am x e - (2.3264 x c ) = 0.975 x e - (2.3264 x 0.30 )
= 0.975 x 0.4976 = 0.485g Scaling factor 0.485/0.23 = 2.11
Indian Point Energy Center Conclusion Based on the results of the screening evaluation, IIndian di Point P i t Unit U it 3 screens-outt off a risk i k evaluation.
Unit 2 will perform its SPRA in group 1 and should show adequate margin based on initial results from Unit 3.
SUMMARY
Ensure a complete understanding of the NRC questions.
ti IPEC is a hard rock site.
IP3 Updated IPEEE should be used to evaluate the new GRMS.
IP3 should be screened out of an additional risk assessment since it has already been performed.
Additional confirmation of safety provided by ESEP.
If additional dditi l time ti is i needed d d to t review i the th IPEEE IP3 should be categorized as a Conditional Priority 3 p
plant.