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ONITED STATES g g NUCLEAR REGULATORY COMMISSION
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Docket Nos. 50-329/330 i
MEMORANDUM FOR: Elinor Adensam, Chief j Licensing Branch No. 4
/ Division of Licensing i
THRU: /; James P. Knight, Assistant Director
- - s for Components and Structures Engineering Division of Engineering i
FROM: ,
George Lear, Chief Hydrologic and Geotechnical Engineering Branch Division of Engineering
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SUBJECT:
HYDROLOGIC ENGINEERING INPUT TO THE MIDLAND SER Plant Name: Midland Plant, Units 1 and 2 Licensing Stage: OL Responsible Branch: Licensing Branch No. 4, R. Hernan, PM Requested Completion Date: April 6,1982 i
. Enclosed is our Hydrologic Engineering Input for inclusion in the Safety Evaluation Report for the Midland Plant. This input was prepared by '
R. Gonzales of the Hydrologic Engineering Section.
There are several outstanding issues which will be addressed in subsequent j supplements to the SER. T.hese are:
- 1) Flood Protection of structures which have settled.
- 2) Adequacy of Dewatering System - this issue will be addressed in future OM hearings.
- 3) Ability of Cooling Pond Dikes to withstand the Probable Maximum Flood
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A camera-ready copy of Figure 2.4.1 was provided to R. Hernan, the PM, on _
April 2, 1982. .
~~f l George L
, Chief 8510000272 850930 Hydrologic and Geotechnical l BRUNNRN-602 PDR Engineering Branch i, Division of Engineering .
Enclosure:
As stated See page 2 for cc list ,
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Elinor Adensam ,
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- R. Hernan
i G. Lear ,
i J. Kane i L. Heller
]' M. Fliegel 4
i R. Gonzales t
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Hydrologic Engineering Summary Midland Plant i
Docket Numbers 50-329/330 Table of Contents 2.4 Hydrologic Engineering 2.4.1 Introduction
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2.4.2 Hydrologic Description 2.4.3 Flood Potential 2.4.3.1 Probable Maximum Flood (PMF) on the Tittabawassee River 2.4.3.2 Probable Maximum Flood (PMF) on Bullock Creek 2.4.3.3 Flooding due to Local Probable Maximum Precipitation (PMP) 2.4.4 Flood Protection Requirements 2.4.5 Cooling Water Supply 1.4.5.1 Normal Cooling Water Supply
- 4.5.2
. Emergency Cocling Water Supply 2.4.6 oundwater 2.4.6.1 Groundwater Description 2.4.6.2 Design of Dewatering System 2.4.6.3 Effects of Pipe Breaks on Dewatering System -
2.4.6.4 Dewatering System Monitoring Program 2.4.6.5 Design Basis for Subsurface Hydrostatic Loading 2.4.7 Accidental Releases of Liquid Effluents in Ground and Surface Waters
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HYDROLOGIC ENGINEERING INPUT TO ,
THE MIDLAND PLANT UNITS 1 AND 2 SER DOCKET NUMBERS 50-329 AND 50-330
. s 2.4 HYBRnt SGTr FNMTNFFDTMG 2.4.1 Ta+ rad"-+iaa
. The staff has reviewed the hydrologic engineering aspects of the applicant's design, design criteria and design basis of safety-related facilities for Midland. The acceptance criteria used as a basis for staf f evaluations are
- set forth in Sections 2.4-1 through 2.4-14 of the Standard Review Plan (SRP) b\s NUREG-0800. These acceptance criteria include the applicant General Design Criteria (10 CFR 100), and standards for protection against radiation (10 CFR 20, Appendix Br Table II). Guidelines for implementation of the requirements of the acceptance criteria are.provided in Regulatory Guidess
, ANSI Standards and Branch Technical Positions identified in SRP Sections 2.4-1 through 2.4-14. Conformance to the acceptance criteria provides the' bases for concluding that the site and facilities meet the requirements of Parts 20, 50 and 100 of 10 CFR with respect to hydrologic engineering.
2.4.2 uvdrntng4r n e r r i n+ i nn The Midland Plant is located directly south of Midland, Michigans on the .
southwest bank of the Tittabawassee River. Plant grade is at elevation .
634 feet above mean sea level (ft bst), some 43 f t higher than the normal .
river level. The headwaters of the Tittabawassee River are in north central From Michiganata/ointabout65 miles (mi) north of the Midland Plant.
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-z-there it meanders in a southeasterly direction for a distance of about 85 mi until it empties into the Saginaw River. - About 22 mi downstream of its confluence with the Tittabawasseer the Saginaw River flows into Lake i Huron. The drainage area of the Tittabawassee River above the Midland Plant encompasses about 2400 square miles (mego. Figure 2.4.1 shows the
- drainage basin and other hydrologic features of the Tittabawassee River.
The United States Geological Survey established a stream gaging stationi about 4700 ft upstream of the Midland Plante in March 1936. The maximum flow recorded since then is 34,000 cubic feet per second (cfs) and occurred on March 21r 1948. The maximum known discharge since at least 1907 reached a stage of 610 ft MSL with a peak discharge of 34,800 efs.
This occurred on March 28r 1916. The minimum recorded flow is 39 cfs and the average flow at Midland is about 1650 cfs.
The topography of the Tittabawassee River drainage area lacks pronounced relief and is characterized by Lakes and swampy eeeas. Less than half of the drainage area is forested. There are four existing hydroelectric power plant reservoirs on the Tittabawassee River above the Midland Plant. ALL of these have dams of earth construction with concrete spillways.
Bullock Creek is a small south side tributary that flows into the Tittabawassee River just upstream of the plant. This streams which drains an area of about40mf2[r had to be rerouted to accommodate construction of the plant
, fitL area.
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The applicant provided hydrologic descriptions of the site which the staff reviewed in accordance with procedures in SRP Sections 2.4.1 and 2.4.2. The staff concludes that the information is sufficient and meets g the requiremer.ts of GDC-2 and 10 CFR Part 100 with respect to general .
hydrologic descriptions.
4 2.4.3 m nna pn+.n+4at In assessing the flood potential at the siter the applicant analyzed
- three possible types of flooding: (1) A probable maximum flood (PMF).
on the Tittabawassee River with concurrent f ailure of upstream dams (2) a PMF on Bullock Creek, and (3) flooding due to local probable maxicum precipitation (PMP). Flood events considered not applicable to the Midland plant included surger seiche, tsunami and ice flooding.
The staff reviewed the material presented by the applicant and performed independent evaluations as described in SRP Sections 2.4.2, 2.4.3, 2.4.4, 2.4.5, 2.4.6 and 2.4.7. The staff concludes that the three types of
- flooding considered by the applicant meet the guidelines of R.G.1.102 and are the design bases flood events that the Midland Plant must be able to withstand in order to meet the requirements of GDC-2 of Appendix A to 10 CFR Part 50. -
2.4.3.1 penhaht Mav4mim M and an th- 74t+=hau==ea- #4uar i
t The PMF is defined as the most severe precipitation induced flood reasonably j possible in the region. In Section 3.4 of the SER-CP dated November 12, 1970, I the staff tentatively approved of the applicant's computational procedures l
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Figure 2.4.1 Hydrologic Features 1
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_4 for determining a PMF at the site and committed to review the applicant's calculation of PMF Levels during construction of the plant to assure that computational procedures had been properly employed. Based on our review ,
I of the applicant's analysess we now conclude that the procedures used .
are appropriate and that hydrologic and hydraulic parameters have been
- properly evaluated and applied.
For the Tittabawassee Rivers the applicant estimated a PMF diseharge of ,
- 248,000 :fs. The effects of failure of the four upstream power dams were then evaluated and the Tittabawassee River PMF was increased to 262,000 cfs to account for this failure. In evaluating failure of the .
upstream power dams, the applicant assumed that aLL four dams would be
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' overtopped by a PMF and would fait successively downstream. To allow
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for this " domino effects" the applicant assumed that the total maximum storage behind all four dams would be concentrated at'Sanford Dam which It was is the furthest downstream and thus closest to the Midland site.
then assumed that Sanford Dam would be overtopped and that a breach would develop in a low area of the crest of Sanford Dam which would grow progressively due to the erosiveness of the water flowing through the breached section. A dam break hydrograph was developed usino the maximum discharge through the f ailed dam and a volume equal to the total storage -
of the four failed dams. The resultant dam break floods with a peak .
discharge of 210,000 cfs and a volume of 167,000 acre-feet (af), was then routed downstream a distance of about 10 mi to the vicinity of the l
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Midland Plant. The analysis showed that by the time the dam break flo6d would arrive at the Midland Plante its peak would have attenuated from 210,000 cfs to about 60,000 cfs. Howevers the applicant conclu'ded that I the routed dam break flood would peak prior to the main PMF so that only about 14,000 cfs would coincide with the PMF peak of 248,000 cfs at the o
site. Thus, the total flow in the Tittabawassee river including the effects of dam f ailures was estimated to be 262,000 cfs. The applicant determined that a discharge of 262,000 cfs, in the Tittabawassee Riverr
. would result in a stillwater level of about 630.4 f t mst (rounded off to, 631 f t mst) in the vicinity of the plant.
The applicant also determined that because of a constriction in the Tittabawassee' Rivers flood waters would pond just upstream of the plant. Wind blowing across this ponded water could generate waves which could cause water levels to exceed the stillwater level of 631 ft mst. The applicant estimated that wind waves could result in runup levels as high as 635.5'ft mst. Since this is 1.5 ft higher than plant grader the applicant concluded that openings in safety related structures and components will have to be flood protected to elevation 635.5 ft mst.
This is discussed in Section 2.4.4.
The The sta.ff has reviewed the analysis presented by the applicant.
criteria used in the staff's review include sections 2.4.2, 2.4.3 and 2.4.4 of the SRP and GDC-2 of Appendix A to 10 CFR Part 50. The staff concludes that the failure mode assumed for Sanford Dam may not be
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conservative because the dam could fail in such a manner that the peak of the routed das failure hydrograph (60r000 cfs) could coincide with I
the PMF peak of 248r000 cfs. If this were to occure the peak flow past the plant would be 308,000 cfs instead of the 262,000 cfs .
determined by the applicant. Using this larger flows the staff
- independently determined that a flood of this magnitude would result in a level of about 631.5 ft mst which is 0.5 ft higher than the level determined by the applicant. Howevers the concurrent wind wave runup calculated by the staff is not as high as determined by the applicant.
The Coastal Engineering Research Centeri publisher of the reference used by the applicant to compute wind wave runupe recently revised its method for wave forecasting. Using this new methods the staff estimates that wind wave runup would be about 0.9 ft lower than estimated by the applicant. Thus although a flood of 308,000 cfs would result in a stillwater level about 0.5 ft higher than estimated by the applicant for a discharna of 262r000 cf s, the lower winfave runup would more than offset the increase in the stillwater level. The staff, thereforer concludes that a maiimum flood. level.of.635i5 ft mste;as computed.by:the applicant, is conservative and meets the criteria suggested in Regulatory
. Guide 1.102, " Flood Protection for Nuclear Power Plants." The staff ,
further concludes that protection of the plant to elevation 635.5 feet .
mst will meet the requirements of GDC 2 with respect to floods on the Tittabawassee River.
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2.4.3.2 Penh=hl= M=v4-"= Finad aa R" ' f ar 6 ce==k The applicant developed a PMF on Bullock Creek'to determine if this event
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would result in a higher water Level at the plant than the Tittabawassee :
River PMF Level. The Bullock Creek PMF was estimated at 32,600 cfs.
Computations were then made to determine the maximum water level which
- would result, assuming a concurrcnt 100 year flood in the Tittabawassee River. This analysis showed a water level in Bullock Creek of 620 ft mst. This flood level is lower than the Tittabawassee River PMF Level J
described in Section 2.4.3.1 above. .
The staff reviewed the material presented by the apptfc' ant ahd made independent analyses and evaluations. The procedures used by the staff are described in SRP Sections 2.4.2 and 2.4.3. The stafI. concludes that a flood level estimate of 620 ft mst for a PMF on Bullock Creek is conservative and thereforer is acceptable. The staff further concludes that, with respect to a PMF on Bullock Creeks the Midland Plant meets the requirements of GDC 2.
'a-' o ah=h'- M- 4-"- *-- 4a4+=+4^a (puoi 2.4.3.3 E'aadiaa n "- + a An onsite storm drainage system wiLL convey runoff from a 100 year storm .
away from the power plant structures. More severe rainfall such'as a PMP event wiLL exceed the capacity of the onsite storm drainage system.
At the request of the staf f, an analysis of the effects of a PMP event on safety related structures and components was made by the applicant.
It was conservatively assumed that all storm drains would be blocked I _ _ _ . _
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during a PMP event and that there would be no loss of water due to infiltration or retention. This analysis showed that ponded water depths will remain below the lowest door elevations of nearby safety . g related structures. .
- The applicant also analyzed the effect of a PMP event on roofs of safety related structures. Ponded PMP levels on building roofs were determined by routing rainfall through parapet openings. This analysis showed that.
- ponding depths on roofs of safety related structures wiLL range from.0.4 ft to about 1.4 ft. (Ponding depths are shown in Q&R Table 2.4-2 of the FSAR). The applicant has stated that building roofs can withstand the loads induced by these estimated ponded water depths.
The staf f has reviewed the applicant's analysis using the procedures described in SRP Sections 2.4.2 and 2.4.3. Based on this reviewe the staff concludes that a local PMP event will not cause water to enters safety related structures. The? staff further concludes that during a PMP evente ponded water levels on roofs of safety related structures will remain at or below the levels determined by the applicant.
.The staff concludes that with respect to a local PMPs the Midland Plant ,
meets the criteria of Regulatory Guides 1.59 and 1.102 and the requirements of GDC-2.
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As described in subsection 2.4.3.1r wind waves could result in water levels as high as 635.5 ft mst,1.5 ft above plant grade elevation of L 634 ft mst. Entrances to the auxiliary building are at elevation 634.5 ft mst which is 1 ft lower than the maximum wave runup level. The applicant proposes to protect these entrances by watartight doors or by removable A
watertight barriers which wiLL be installed before flooding occurs.
technical specification and emergency flood protection proceduris will describe the actions to be-taken to assure that watertight doors are properly closed and watertight barriers are installed prior to a TLood event.
Using the procedures described in SRP Sections 2.4.8 and 2.4.10r the staff has reviewed the flood protection design submitted by the applicant. The staff concludes that the flood protection design for structures whose entrances will be protected by watertight doors or watertight barriersi is acceptable and meets the requirements of GDC-2.
The staff has also reviewed the proposed flood protection technical specification. The procedures in SRP section 2.4.14 and 16 were used in this review. The staff concludes the technical specification does not meet the requirement of Section 50.36 of 10 CFR :Pa'rt 50 because.it does not .
define the conditions under which watertight doors will be closed or watertight barriers wiLL be put in place. Resolution of this item wiLL be described in a supplement to this SER. 1 I
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-10 Other safety related structures which could be affected by site flooding include the diesel generator building (DGB) and the service water pump '
structure TSWPS). Entrances to these structures have a design elevation i
635 ft, 8 in., which is 3 in. above the maximum calculated water level of waves generated during a PMP. This design is acceptable and meets the requirements of GDC-2. Howeverr both the DGB and the SWPS have experienced some settlement so it is possible that entrances to these structures are no longer above elevation 635.5 ft mst. The staff ^will require that all
, entrances to the DGB and the SWPS and any other'safetyerelated structures ,
that may be expected to settle, be at or above 635.5 ft mst or that other engineerfpfeaturesbeprovidedtoprecludeflooding. All safety-related structures must be flood protected to elevation 635.5 ft mst unless it can be shown that flooding of any structure will not affect the safe operation of the plant. Resolution of this outstanding issue will be provided in a supplement to this SER.
To resist the erosive effects of flood waters in the Tittabawassee Riverr the outer slopes of the cooling pond dikes are protected with riprap (stone) to the 100 year flood Level of 614 ft mst. Seeded turf is provided bstween this elevation and the t'op of the diker elevation 632 ft mst. Although the dike is not classified as a seismic Category I structurer damage or failure of portions of the dike could affect the operability of the emergency cooling water reservoir (ultimate heat sink).
Before the staf f can complete its flood review as per SRP Section 2.4.8,
the applicant must perform an analysis of the effects of the Tittabawassee River PMF on the cooling pond dikes. If this analysis shows that the dikes wiLL be eroded by flowing waters overtopped or otherwise damaged i during the PMFr the applicant must then submit for staff reviews the results of its analysis shewing..what effect damage to the dikes wiLL have
- on the emergency cooling water reservoir. Resolution of this outstanding issue wiLL also be addressed in a supplement to this SER.
- Rased on the information provided by the applicants the staf f is unable to determine that flood protection of the Midland Plant cooling pond dikes meets the requirements of GDC-2.
2.4.5 eratin, um+.- e, ,,, i u A cooling pond with a volume of about 12r600 acre feet Caf) and a surf ace (34 area of about 880 acres,has been constructed south of the station. This pond wiLL receive and store water from the Tittabawassee River for use during both normal and emergency operation. To provide a source of emergency cooling water in the event the cooling pond dikes should fails a secondary or emergency pond has been excavated, below the normal level of the main pondi in the northeast corner of the pond.
The staff has reviewed the material presented by the applicant using the procedures described in SRP 2.4.11 and concludes that the two water sources (the main pond and the emergency pond) meet the guidelines of R.G.1.27i D
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" Ultimate Heat Sink for Nuclear Power Plantsi" with regard to providing a high level of assurance that at least one cooling water source will be ava'itable for emergency operation of the plant. l 2.4.5.1 Normat continn Water Eueoly Although the main cooling pond has a volume of 12,600 acre-feet, only about 7r900 acre-feet are considered useable. This volume is sufficient to provide water for full. plant operation during a 100 day drought without
. having to withdraw water from the Tittabawassee River. .
Using the procedures described in SRP Section 2.4.11, the staff concludes that the main cooling pond provides a highly reliable source of cooling
. water such that the emergency pond will be used only on a very infrequent basis. The staff concludes that the requirements of GDC-44 with respect to normal operating conditions have been met.
2.4.5.2 Fnoenenev rnnlinn Water Runnly The emergency cooling pond provides cooling water for use in the service water system in the unlikely event that the main cooling pond dikes should fait and t'he main cooling pond should be' lost. It is of Seismic Category I design and is excavated in the cold leg of the main cooling pond. It has a normal depth of 8 feet below the bottom of the main coolin'g pond and a surface area of about 39 ac. Thecapacityisapproximately1.18xid)/
f $[ (272 ac-f t) which is sufficient for at least 30 days of cooling.
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. l Emergency cooling water -wiLL be withdrawn from a submerged pump bell in the service water pump structure. Heated water wiLL be discharged back to the pond through the service water discharge structures which are .
Located at the south end of the pond. The configuration of the ponde with the withdrawal near the bottom at the north end and the discharge
- near the surface at the south ends wiLL promote efficient cooling by i
stratifying the water into hot and cold layers.
- The applicant analyzed the ability of the emergency cooling pond to provide a 30-day supply of cooling water for the plant at or below the design basis temperature of 105 F, under the most severe meteorological conditions of record. The applicant's analysis predicted a maximum pond temperature of 105.3 F and a maximum 30 day evaporation of 2.6 x id@/f f$d Although the predicted temperature exceeds the design basis temperature by 0.3 Fr the applicant has stated that due to the short interval that the service water design temperature is exceeded, the design of the emergency cooling pond is considered to meet the criteria of R.G.1.27, Ultimate He'at Sink for Nuclear Power Plants.
Using the methods discussed in NUREG-0693, " Analysis of Ultimate Heat Sink Cooling Ponds" and NUREG-0733, " Analysis of Ultimate Heat Sink .
Spray Pondsr" and the criteria in R.G.1.27, the staff also analyzed
, the performance of the emergency cooling pond. The pond was conservatively modeled as a well mixed pond with a volume of 1.18 x 10f f 4}/r rather than r- - ,, -,, ~ -- .,--- , - - - - - , ,
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_14 a stratified pond as was assumed by the applicante in order to account l 1
for the possibility of short-circuiting of hot and cool water in the pond which would lead to a lower cooling rate and a higher responsiveness to . I
- thermal loads. Meteorological data were taken from Midland-Saginawr Michigan for the period 1949-1980. The staff predicted that the highest temperature of water withdrawn for the plant would be 98.8 F. The maximum 30 day pond water loss predicted by the staff would be about 1.76 x id@/ f47'r which is about 15 percent of the pond volume. The adequacy of the
_ meteorological data base used by the staff was determined by a compa,rison of the Midland-Saginaw data with onsite data for the years 1975 to 1976.
It was determined that the Midland-Saginaw data were more severe for this period than the onsite datar and probably overestimate the pond temperature and water loss by about 0.5 F and 2400 f$}/respectively.
Both the maximum temperature predicted by the staff and' the water lost fro'm the pond were less than those predicted by the applicant. The major reason for the discrepancies between the applicant's and the staff's analyses are:
- 1. The applicant used more conservative cooling and evaporation formulations in the pond model; and -
- 2. The applicant used the 67 year data ' base of Lansing Michigan while the staff used the 31 years of data for Midland - Saginawr Michigan. The Lansing data base is both longer ande according to the applicante more severe than the Midland-Saginaw data.
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y Using procedures described in SRP Section 2.4.11r the staff concludes that the emergency cooling pond is capable of supplying a minimum of 30 days of p
emergency cooling water to the plant at or below the design basis temperature and therefore meets the guidelines of R.G.1.27, " Ultimate Heat Sink for Nuclear Power Plants" and the requirements of GDC-44.
- As described abover water from the emergency cooling pond will be withdrawn by pumps in the service water pump structure (SWPS). Since-this structure
- is located in the cooling ponds it will be subjected to wind wave ac.tivity.
The applicant calculated the water levels and resulting hydrodynamic loads that could be induced on the SWPS by wind wave runup under extreme i
c ondit ions. This analysis showed a potential wave runup of about 637 ft mst and a hydrodynamic load of about 4,800 lb per ft. The. staff has reviewed the material presented by the applicant and has performed an i
independent analysis. Based on this, the staff concludes that the applicant's estimate of wave runup and resultant loads is conservative and therefore acceptable. Procedures and guidance discussed in SRP Section 2.4.5 were used by the staff in its review.
The SWPS could also be affected by ice blockage or ice loads so the applicant performed a study to determine what impact ice formation would have on the safe operation of the SWPS.
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During normal and emergency operation of the planti hected water will be discharged into the cooling pond so it is not expected that significant amounts of ice will accumulate at the SWPS. Any surface ice formation in, i the vicinity of the SWPS would not affect its operation because the water .
entrance is about 34 ft below the normal water level of the cooling pond.
. Although significant amounts of ice are not expected to accumulate on the SWPSr the applicant calculated the ice loads that would be induced on the SWPS in the event the plant was not in operation. The applicant, states
- that the SWPS is designed to withstand the ice and static loads that.
would be induced by a 30 in layer of ice assuming that the cooling pond level is at a normal water level of 627 f t mst.
The staff has reviewed the analysis presented by the applicant. The .
procedures used by the staff are discussed in section 2.4.7 of the SRP.
Based on this reviews the staff concludes that ice formation in the vicinity of the SWPS will be minimal at most and will not affect the operation of the SWPS. Thus the staff concludes that the Midland Plant meets the requirement of GDC 2 with respect to icing effects on safety related structures.
In section 10.0 of the SER-CP dated November 12, 1970, the staff stated .
that the applicant would be required to monitor the pond for sitting and .
if necessary to dredge it periodically. In compliance with this requirement the applicant has proposed a technical specification which defines surveillance requirements and limiting conditions for operation of the pond.
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The staff has reviewed the technical specification proposed by the applicant and concludes that the requirements of Section 50.36 of 10 CFR Part 50 have been met with regard to assuring that potential ;
sitting of the pond does not impact on its safe operation.
- 2.4.6 Groundwater 2.4.6.1 Groundwater Descriotion The Midland Plant is located near the center of the Michigan Basini a
- broad, shallow structural basin of Paleozoic sedimentary rocks up to.
14,000 ft thick. These rocks are covered by unconsolidated Pleistocene glacial drift that. regionally is about 200 to 300 ft thick. The unecnsolidated deposits beneath the site have been subdivided into five Lithologic units as shown in Table 2.4.7 of the FSAR. There are two groundwater systems located beneath the Midland Plant within these lithologic units; an isolated perched groundwater table in the surficial sands and a deeper confined aquifer. A layer of essentially impervious clay about 150 ft thick separates these two groundwater systems.
The quantity of water in the surficial sands is limited and is not a source of domestic or other supply in the site area. Recharge is mainly by infiltration of precipitation and from streams and ponds. The ,
groundwater gradient in the surficial sands is toward the T4ctabiwassee River. There are no wells located in the surficial sands between the plant and the Tittabawassee River.
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The confined aquifer is not recharged in the site area because of the presence of the thick clay layer that overlies it. The most likely
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recharge source is from distant areas where the aquifer ~ sand and gravels -
either outcrop or are connected with other aquifers. In the site arear ,
it is believed that the regional aquifer'has a nearly flat gradient sloping generally northeast.
During the site investigations the applicant inventoried 146 water wells.
~ within a 3 mile radius of the plant. All of these wells draw water from the confined aquifer or from a deeper bedrock aquifer. 57 water wells were identified within the site boundaries. Of theser only one has not
.been sealed. This well is being utilized during' construction and will be sealed when construction is complete. In additions two new construction wells have been installed. These wiLL also be sealed upon completion of construction. Groundwater will not be used by the Midland Plant during operation. There are no present or projected groundwater users within the plant boundaries nor between the plant and the Tittabawassee River.
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At the construction permit stager it was anticipated that the perched groundwater table beneath the plant would rise to a level about equal to .
that of the cooling ponde elevation 627 ft mst. As expectede this has ,
occurred. Howevers the applicant now proposed to lower the perched i l
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groundwater level during operation of the plant. Lower groundwater levels are necessary because of the presence of' loose sands beneath certain ,
safety-related structures which potentially could Ligueff during a: Safe 8 Shutdown Earthquake (SSE). An extensive boring program has identified loose sands in the vicinity of the Diesel Generator Building (DGB), the
- Railroad Bay Area (RBA) of the Auxiliary Buildingr the Service Water Pipes (SWP) and the Diesel Fuel Tanks (DFT). In the vicinity of the
, DGBr the RBA and the SWPr loose sands were located in the fill above I - elevation 610 ft mst. In the vicinity of the DFT, loose sands were .
Located below the foundation mat at approximately elevation 600 ft mst.
3 The applicant has proposed reinoval of the loose sands and rebedding i of the SWP in the area of the Circulating Water Intake Structurer where
! this condition exists, to eliminate this problem. The relatively thin layer of loose sand beneath the DFT has been shown to be an isolated pocket and is not considered to present a liquefaction problem. A full discussion on the evaluation of the liquefaction problem wiLL be provided in Section 2.5.4 of a supplement to this SER.
i To lower groundwater levels in the vicinity of the DGB and the RBA, the applicant proposes to install a permanent dewatering system. Although elevation 610 ft mst is the maximum design water level underneath these structures during operation of the plants the applicant proposes to l I
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Lower and maintain groundwater levels at or below elevation 595 ft est beneath the DGB and the RBA. This wiLL allow the plant to continue to operate for some period of time in the event that there is a malfunction , i
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of the dewatering system. .
- 2.4.6.2 Design of Dewatering System -
In designing the permanent dewatering systems the applicant considered several potential sources which could cause high water levels beneath the
- plant. Sources considered were: (1) Seepage from the Cooling Ponde.
(2) flooding in the Tittabawassee Riverr (3) seepage f rom Dow Chemical's tertiary treatment pond which is located just west of the Midland Plant and (4) infiltration from precipitation. The staff reviewed the applicant's analyses using the procedures in SRP section 2.4.12 and concludes'that these four sources represent a'll the credible causes of highwater beneath the plant which must be considered in the design of the permanent dewIatering system.
The design criteria for cooling pond dike construction called for excavation of a cutof f or inspection trenche along the entire length of the dike. This trench was to fully penetrate the surficial sands into
.either lacustrine clay or glacial till (see FSAR Figure 2.5-46). Assuming that the dikes were constructed as designede seepage from the pond should .
be minimals except in areas where the cutof f trench is missing, such as adjacent to structures located within the dikes.
O 9
To locate areas of recharge from the cooling pond and to determine the hydraulic relationships between the natural and backfill sandse several pumping tests were conducted. These tests showed that seepage from the i cooling pond is minimal except in the area surrounding the Circulating Water Intake Structure (CWIS) and the Service Water Pump Structure
- (SWPS) where water is seeping into the plant fill through the natural and backfill sands.
- The staff has reviewed the applicant's submittats and agrees that most of the seepage from the cooling cond is through the sands in the vicinity of the CWIS and the SWPS.
Another source of potential recharge is the Tittabawassee River. Howevers any potential recharge from this source will be minimized by the plant fill dike which surrounds the plant fill area (see FSAR ~ Figure 2.4-46).
The design of this dike is simliar to the cooling pond dikes except in areas where a bentonite slurry trench had to be installed within the diker because the dike cutoff trench did not penetrate into the impervious materials (FSAR Figures 2.5-46r 2.5-51 and 2.5-52 and figure 24-13 of the 10 CFR 50.54(f) responses).
Normally the water level in the Tittabawassee River is lower than the permanent dewatering design level of 595 feet. The mean annual river
\
l elevation is 591.3 feet (see response to 10 CFR 50.54(f) question 24-f).
During floods, water levels in the river can rise as high as elevation 631 l
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feet for a Probable Maximum Flood (PMF). Howevers the duration of a flood of this magnitude is limited. Water Levels in the Tittabawassee River for a PMF would remain above elevation 610 feet for only about 6.5 days ,
(see FSAR figure 2.4-23). Because of the limited duration of high water Levels and because of the presence of the dike surrounding the plant
- fill arear the staff concludes that the Tittabawassee River is not a potential source of significant recharge to the plant fill.
- Bullock Creek was also considered as a potential source of recharge..
However since the bottom of this creek is at elevation 592 feet, which is 3 feet lower than the design level of the permanent dewatering systemi it wiLL not be a source of seepage into the plant fill.
The third cotential source of recharge that was considered is Dow Chemical's tertiary treatment pond which is located just west of the Midland Plant.
~
The maximum water level in this pond is 614 feet. It is located about 1130 feet west of the plant. Any seepage from this ponde in an easterly direction toward the plants would be interrupted by the relocated Bullock Creek and would be carried' to the Tittabawassee River. (See Figure 52-1 of the 10 CFR 50.54(f) responses). Based on thi,sr the staff concludes
.that the Dow Pond wiLL not be a source of recharge to the plant fill. .
A fourth potential recharge source is infiltration of precipitation. The Midland Plant site will be graded so that runoff from precipitations or any other sturcer will not pond to a significant degree. Runoff will
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- e flow into the plant site drainage system which wiLL direct runoff to the Tittabawassee River, Bullock Creek, the cooling pond or to the parking tot which is located southwest of the plant. (See Q&R figure 2.4-2 f which was submitted by the applicant in response to NRC safety review question 371.10). This wiLL minimize ponding of water at the site and
- reduce the amount of water available to infiltrate into the plant fill.
The applicant has estimated that two wells have sufficient capacity to pump any water that infiltrates into the ground. These two wells are
- in addition to the 22 area wells which are also part of the permanent dewatering system which is described below. In its analysisi the applicant assumed that 25% of the average annual precipitation will infiltrate into the ground. The staff does not agree that the applicant's analysis is conservative because rainfall of greater intensity could occur.
The probable maximum precipitation (PMP), which is the rainfatt for which there is virtually no risk of exceedances is about 13 inches in a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> pe riod. Howevers the staff incependently determined that even if the entire 13 inches of rainfall were to infiltrate into the plant fills there is sufficient storage capacity in the plant fill below elevation 610 feet so that even if the area wells did not operater the infiltrated water would not raise the groundwater level above elevation 610 feet.
Based on this very conservative analysis, the staff concludes that infiltration of surface runoff will not be a significant source of recharge.
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Design of the permanent dewatering system provides for two sobsystems.
The first subsystem will consist of a double Line of interceptor wells to ;
I be located around the Circulating Water Intake' Structure (CWIS) and the . p Service Water Pump Structure (SWPS). 'The second subsystem wiLL consist .
of area wells which will be located throughout the plant fitt area. In i
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- addition to theser numerous permanent observation wells, piezometers and monitoring wells wiLL also be installed throughout the plant fitt area.
! - The applicant has determined that 20 wells are required to intercept and 1
remove the water seepingf' rom the cooling pond. Howevers to provide l nearly uninterrupted service should one ca more of the primary interceptor I
i wells break down, a second Line of 20 back up interceptor wells wiLL be
]
l- installed behind the 20 primary interceptor wells.
i i
j In designing the interceptor weLLsr the applicant initially used a 1
! permeability df 31 feet / day. (See 10 CFR 50.54(f) response 24-b).
l Subsequently the permeability was reduced to 17 feet / day (See 10 CFR 50.54(f) response 47-3). The 31 feet / day was the maximum value determined by the pumping tests. This value was determined from a pumping tests which was conducted to obtain information for design of
.the temporary dewatering system which was to be installed adjacent to the , ,
1 Unit 2 feedwater isolation valve pit. 17 feet / day was determined from .
the permanent dewatering pump test performed in weLL PD-15 which is closer I
to the seepage source. Tables 24.1, 24.3 and 47.1 of the 10 CFR 50.54(f) i
.
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la ' . -
responses list values of permeability which were determined using both field and laboratory tests. Table 47-1 shows two values which are greater than 17 feet / day; however, these values are not for wells located near 4 the source of seepage. They are for wells which are located south of the Diesel Generator Building. Table 24.3 presents permeability values determined from grain size analysis. The highest permeability shown in this table, for a well located in the vicinity of the CWIS and the SWPS is 125 feet / day.' Although this value is considerably higher than the
, 17 ft/ day used in design, the staff believes that permeabilities .
determined from in-situ field tests cre much more reliable than laboratory tests based on grain size. This is because soit permeability is influenced not, only by grain size but also by soit compositions orientation and distribution of soit particless void ratio and degree of saturation.
Anin-situfieldtest(isabettermeasureofalltheseparametersthan one that considers only grain size. Therefore, the staff concludes that a permeability of 17 feet / day is appropriate for use in design of the permanent dewtering system as outlined in Branch Technical Position HGEB-1 in Section 2.4.12 of the SRP.
The staff has reviewed the applicant's an'alysis and performed independent evaluations. The staff agrees that 40 wells located as close as possible i
to the CWIS and the SWPS are sufficient to intercept the seepage from the cooling pond and to provide sufficient redundancy should part of the dewatering system malfunction or fait.
Although the interceptor well system wiLL effectively intercept seepage from the cooling ponds it wiLL not remove all of the water that is alre'ady stored in the plant fill. The applicant proposes to accomplish this by ,
installing 24 area wells in the plant fill. Once th'e groundwater which is already in storage is removed, the area wells wiLL be needed only to maintain groundwater levels at or below 595 ft mst in the vicinity of the Diesel Generator Euilding and the Railroad Bay area by intercepting any water that is not collected by the interceptor wells or water ,
infiltrating from precipitation and pipe leakage. The staff has rev,iewed the applicant's analysis and agrees that 24 area wells are suf ficient to maintain wate.- Levels in the vicinity of the DGE and the RBA below elevation 610 ft mst under normal conditions.
The applicant has stated that 'the dewatering system is not seismic Category I because it is not required to operate during or after a'sa'fe shutdovn ear'thquake. The applicant estimated that in the event of a complete failure of the dewatering systems it would take at least 60 days before water levels below the DGB and the RBA would rise to elevation 610 ft. This would al. low sufficient time to repair and/or replace any damaged portio.
6f the dewatering system. To verify thise the staff requested and the applicant cenducted a recharge test.
In conducting this teste water levels beneath the DGB were Lowered to elevation 595 ft mst. ALL dewatering well pumps were then turned off and water levels were allowed to rise normally. After 60 days, the highest water levet recorded was in the vicinity of the DGB. This level was e
8
1 . ...
- elevation 606.% fi ms t. .The staff has reviewed the applicant's analysis using SRP Section 2.4.12 and Branch Technical Position HGEB-1. The _
staff concludes that in the event of a complete failure of the dewatering ,
system, there would be at least 60 days before water levels would rise to elevation 610 ft est beneath the DGB. Water levels at the RBA would
- rise more slowly because it is further away from the source of water, the cooling pond.
- 2.4.6.3 Ffear+= nf Pine Breaks .
At the request of the staff, the applicant considered breaks in underground piping and the effects these breaks would have on the ability of the permanent dewatering system te maintain water levels below elevation 610 ft mst in the vicinity of the DGB and RBA. This was done to show compliance with Branch Technical Position HGEB-1 of SRP Section 2.4.12.
Several non-seismic underground circulating water discharge lines are located to the east and west of the DGB, about 18 ft below its base mat.
These lines rest on natural sand in which the cewatering system will normally control the groundwater level to elevation 595 ft msl. The applicant performed an analysis of 'a postulated failure of the 8 ft diameter Unit 2 circulating water discharge line (CWDL) because this is the largest pipe near a critical structure. The applicant in its analysis assumed that the size of the pipe break would be equal to the cross-sectional area of the pipe. The applicant then estimated that the flow ratethroughthisbreakintothebackfillsandwouldbeabout3000fy& day l
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(16 gpm) and that the precominate flow would be downward through the natural sand on which the pipe is located. The applicant estimated that I it would take a maximum cf about 3 days, after -the pipe break for the ,
gruundwater level at the nearest area dewatering well to rise sufficiently above elevation 595 ft mst so that the well pump would activate and begin to pump out the water from the pipe break. Shortly after this, other dewatering wells would also activate and' assist in pumping. During the 3-day period between the time the pipe breaks and the nearest well ,
- activatesi the groundwater level at the edge of the DGB would rise tp about elevation 607 ft mst which is 3 f t below the critical elevation of 610' mst. Since the capacity of each area dewatering well is 15 gpm and the maximum flow rate from a pipe break was estimated by the applicant to be about 16 gpm which would disperse in_ all directionse one well is sufficient to prevent groundwa'ter from rising significantly above elevation
! 607 ft mst.
The staff has reviewed the applicant's analysis using' criteria and procedures from Branch Technical Position HGEB-1 of SRP 2.4.12. The staff concludes that the size of the pipe break assumed by the applicant is conservative and that in the event of a break of this size in the CWDL, which is located about 5 feet east and about 18 feet below the DGB, .
water levels along the east edge of the DGB could rise to an elevation of i about 607 ft mst before area . wells, would activate and begin removing I
water from the pipe break. The staff notes that should the area wells 1
( be inoperable at the time of a pipe break, water levels beneath the DGB I
could rise above elevation 607 ft mst. Howeverr were this to occure the
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permanent dewatering monitoring systems which is described in Section 2.4.6.4r would detect the rising groundwater levels and appropriate actionse to be defined in a technical specificationi could be taken ,
before groundwater levels rose above elevation 610 ft mst.
. The staff notes that the top of the CWDL is at elevation 610 ft mst; thereferer water levels would not be expected to rise significantly above this elevation due to a CWDL pipe break.
Another non-seismic Category pipe analyzed by the applicant for a postulated failure was the condensate storage -line (CSL). This line is a 20 in diameter pipe encased in concrete which runs from the condensate storage tank underneath the Diesel Generator Building to the Turbine Building. The condensate storage tank has a maximum capacity of 300,000 gallons. The applicant stated that if the CSL were to break such that the entire 300,000 gallon inventory in the condensate storage tank drained out through' the break, and remained only in an area directly beneath the DGBr the resultant groundwater rise would not exceed elevation 610 ft mst even if the area' wells did not operate.
The staf f has reviewed the applicants analysis using the criteria' and procedures in SRP Section 2.4.12 and Branch Technical Position HGEB-1.
The staff agrees that a postulated break in the condensate storage line would not result in groundwater levels above elevation 610 f t mst.
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The staff concludes that failure of either a Circulating Water Discharge Line or a Condensate Storage Line wiLL not result in groundwater Levels above the design level of 610 ft mst. However, the staff wiLL require i verification from the applicant that there are no other pipes whose failure could affect the dewstering system's ability to maintain. water Levels
~
. below elevation 610 ft mst beneath safety related structures.
2.4.6.4 n.um+.rina Mnn4tnrina Prooram ,
- The applicant has proposed a monitoring system consisting of six monitoring wells with continuous recorders and warning devices, 28 observation wells and four piezometers. The monitoring wells wiLL be located at strategic locations; two at the Diesel Generator Buit' ding, two at the Auxiliary Building and two in the Circulating Water Intake Structure / Service Water ,
1 Pump Structure area. These monitoring wells will be inspected on a weekly basis to verify the operation of the recording and warning systems. The observation wells and piezometers wilL be located throughcot the plant fill area.
The staff has reviewed the applicant's analysis and the locations of the monitoring weLLsr observation wells and piezometers. The staff
.is unable to determine whether the monitoring system is adequate to detect ,
any unexpected rise in groundwater levels because the applicant has not .
identified the extent of the areas to be dewatered to elevation 595 ft mst.
The applicant has been requested to provide a dewatering control plan which 9
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will identify the specif.ic areas to be dewatered to elevation 595 ft est me and the monitoring wells and/or piezometers which wiLL be used to assure that this level is maintained. Resolution of this issue wiLL be presented ,
in a supplement to this SER.
. A technical specification will describe procedures to be taken in the event that water levels exceed elevation 595 ft mst in the areas to be dewatered to this elevation. Although this technical specification
- has not been submitted for staff reviews the applicant has provided a description of the items to be addressed. The staff has reviewed the applicant's submittal and concludes that in addition to the items already described, the technical specification must also define the maximum elevations to which water levels in the dewatered areas wiLL be -
allowed to rise above elevation 595 ft mst before plant shutdown is initiated. In addition, the technical specification must also identify the specific wells (dewatering, monitoringr and/or observation) and piezometers which wiLL be used to determine this shutdown elevation.
The staff cannot conclude that the proposed dewatering monitoring system meets the criteria of Branch Technical Position HGEB-1 of SRP 2.4.12 or the requirements of Section 50.36 of 10 CFR Part 50.
, _ 1
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l 2.4.6.5 n==4aa ameie far R"h="rf=r. uvarn +2t4r inaa<nn l All safety-related structures, systems and components have been designed !
to withstand the hydrostatic loadings which would result from water. levels ,
as high as the Probable Maximum Flood as described in Section 2.4.3.1. ;
Since this water level is higher than any present or potential groundwater Level the staff' concludes that the applicable ' criteria of SRP Section 2.4.12 and the requirements of GDC-2r with respect to subsurface hydrostatic loadings, have been met. ,
2.4.7 Accidental Releases of Linuid Ef fl uente in Gennnd and Rnrfare Water.
SRP Section 2.4.13 sets forth criteria and procedures for the analysis of accidental releases of liquid effluents in ground and surface waters.
Using theser the staf f analyzed postulated failures of the Boron Recovery System Receiver Tank and the B'oric Acid Concentrate Tank to determine the potential for radioactive contamination of. surface and ground water sup' plies. As described in Section 15.7.3r these tanks were selected for
~
analysis because they contain the highest potential concentrations.
The Boron Recovery System Receiver Tank is located in the auxiliary building 5 bout 50 feet below plant grade. A failure of this tank would result in contaminants spilling out into the auxiliary building. In order for contaminants to leak out of the auxiliary buildings there would have to be cracks in the auxiliary building floor or exterior walls. It is highly unlikely that there would be cracks in the auxiliary building large O
I l
enough to allow significant water leakage because the auxiliary building is.of seismic Category I design. Howeverr if there were large cracksi and .
^
no action was taken to clean up the liquid spil'Li contaminants would leak I
out into the clay strata underneath the~ auxiliary building. This clay is essentially impervious and is about 150 ft thick so it is highly unlikely that the underlying confined aquifer would be affected. To verify thise the staff performed an analysir assuming that the entire inventory of the Boron Recovery System Receiver Tank enters the groundwater regime.
. This analysis showed that c'oncentrations of aLL nuclides at the nearest ,
water well would be less than one~ percent of the limits shown in Table II of Appendix B in 10 CFR Part 20.
The Boric Acid Concentrate Tank is located in the auxiliary building at elevation 634.6 ft mst which is just above a plant grade elevation of 634 ft mst. Failure of this tank would result in a liquid spill which could run :out on the plant yard through the railroad bay area. The plant onsite drainage sy' stem would intercept the spill and route. it to the cooling pond. After being diluted in the cooling ponde the spill would enter the Tittabawassee River in the plant blowdown if no actions 4
were taken to intercept contaminated wate'r. The staff's analysis showed that the concentration of all nuclides in the Tittabawassee River.~resulting from an assumed Boric Acid Concentrate Tank spill would also be less than one percent of the limits shown in Table II' of Appendix B in 10 CFR 1
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Based on these analyses, the staff concludes that postulated accidental spills of radioactive Liquids will not result in concentrations above 10 CFR Part 20 Limits for any surface or groundwater supply. Thus the -
I requirements of 10 CFR Part 100 with respect to potential surface and ,
groundwater contamination have been met by the Midland Plant.
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-3 5-l 2.4 References i U.S. Army Corps of Engineers, Coastal Engineering Research Centers ..
" Coastal Engineering Technical Note CETN-I-6, Revised Method for Wave Forecasting in Shallow Waters" March 1981.
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g L & y en feed ring-type feedwater waterhammer experienced in recirculating type steam Eenbe ors v _ aj w .
h this t N j
Tf n4s8 lobeneric 3. " item doesO t apply}e,o Mid and.
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cy:t; , Je; Qa .. in omrd=x ith th; ;;' M-- -. .;; !;ter, Cuida 1. 2L i p .29 xd the .ev ... ui. v i GDC 2, ^ , 5, , " , ;ad "O. TLs = ia i ." , -
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0 10.4.9 Auxiliary Feedwater System lowing section is the staff's evaluation of the Midland y feedwater sys e . This evaluation is pres n two parts: Part I is the evaluation of the AFL' iteria of the SRP. Part II is the evaluation of the AFWS agai e criteria d after the TMI-2 accident, whi enumerated in the NRC generic letter o 4, 1980 and id ied as Item II.E.1.1 of NUREG-0660 and NUREG-0737.
-10.4.3.1
^
f .senouss C lt;ri: _ y TE 7-The staff reviewed the Midland auxiliary feedwater system against the acceptance criteria of SRP Section 10.4.9. ThesecriteriaaregGDC2[asrelatedtostruc-tures housing the system and the system itself being capable of withstanding
[ the effects of natural phenomena such as earthquakes d e: ;da ,,..w . . . .n ,
f g\ end fia , with respect to structures housing the system and the system itself being capable of withstanding the effects of external missiles and internally generated missiles, pipe whip, and jet impingement forces associated gs with pipe break , as related to the capability of shared sys ms and compo-jp.'l nents important to safety to perform required safety functions; 9, as related to the design capability of system instrumentation and controls for prompt hot
]
shutdown of the reactor and potential capability for subsequent cold shutdow4 j QC,sStt-44,toensure(k)thecapabilitytotransferheatloadsfromthereactorsystem l to a heat sink under both normal operating and accident conditions, (I) redun-dar$cy of components so that under accident conditions the safety function can be performed assuming a single active component failure (this mav be coincident Dn, Tso.4-9 with the loss of offsite power for certain events), and ( the capability to isolate components, subsystems, or piping if required so that the system l 02/21/82 10-24 MIDLAND SER SEC 10 l Fo / A-s 5 8 53 .:
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- a pSERT.
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- / safety function will be maintained; as related to design provisions made
, to permit periodic inservice inspection of system components and equipment; C*C46, as related to design provisions made to pemit appropriate functional testing of the system and components to ensure structural integrity and leaktightness, operability, and performance of active components, and capability I oftheintegratedsystemtofunct][onasintendedduringnormal, accident condition ;W+^-' C ifu 1.25, ;; r ':ted te t'e ;=? it; ;.shutdown,and e.p cm . m = tic,c,.y.. _.me.. .c. m ,, . u.. .. .s. ..<. 4 :,,; ,
41;;di$waisvu vf 5y5ts;; CO;p=: Fir; E U ** "*l2+"A +^ d*cinn nrnufe4aac ,
m:d: f;r senue? '-itiati^a cf ??ch prc+ecti Y e ?cti^"; l 1"?, : 7 l t;d i i'^
p toct4ca ef structi_irae cyct.ac and cannonente 4-crt=t b . iciy in v- 6ue ef.f+ L un ficouing, 1.117, e5 . lated te tree pi dwwi,lvn vf A.-st...., ,y=iems, 8"A "^""0 Et r.t; *;pu. i.an 6 Lu saiciy is um I,ne eTTects of tornado missiles; anu BI"; "00 0 1, ;; r:1 ted t; tru k; #- 'ia" *ad =adar=+= -"" gy pipios a.r L ~
cutMde suniainmenL[Nao lu-1, as resatea to auniiary iccu J-. ;7 dr :
- cd pe r s'ipply di"a~ 't;.
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The following evaluation discusses the implementation of the above acceptance criteriag g fo s re p Section 10.4.g.
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.d *! The AFWS is designed to supply an independent source of water to the steam generators during normal plant startup, shutdown, and layup erations and in the event of a loss of main feedwater supply (see Figure 10 . The major r
components of the Midland AFWS are two 100 pprcent-capacity essential safety-grade pumps, one steam turbine driven and one motor driven. Both pumps l
[f . function in a transient or accident condition, but only the motor-driven pump j is used during plant startup or normal plant cooldown. The normal AFWS water supply is provided by the condensate storage tank. The deaerator storage ,
tanks or the condenser hotwell may also be used to supply water to the AFWS durin h t stAndb1 orm.+,
normal plant cooldown. A ismic Category I makeup
- t. b I. 4.ir.w ceen uve supply 4to the auxIfiary pump suction is provided y the service water system in the event that the condensate storage tank or other sources of water are not available. 6 - L > E A' [ R #
02/21/82 10-25 MIDLAND SER SEC 10 l l
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INSERT 0 Based on our review 6f the condensate and feedwater system, we conclude that the system meets the requirements of General Design Criteria 2, 4, 44, 45 and 46 as they relate to protection against natural phenomena, missile and '
environmental effects (including water hansner), decay heat removal function, ;
inservice inspection and testing. The system also meets the guidelines of Regulatory Guide 1.29 with respect to seismic classification. We, there-fore, conclude that the system is acceptable.
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Acceptability is based on meeting Position C.1 of Regulatory Guide 1.29 for safety-related portions of the system and Position C.2 for nonsafety-related portions. Protection against other natural phenomena is evaluated in Section 3.4 (flooding) and 3.5 (missiles) of this SER; INSERT 10.4.2 The basis for acceptance for meeting this criterion is set forth in Sections 3.5 and 3.6 of this SER.
INSERT 10.4-3 Acceptability is based on meeting BTP RSB 5-1, " Design Requirements of the Residual Heat Removal System " with regards to cold shutdown from the control room using only safe crade equipment, INSERT 10.4-4 BTP ASB 10-1, " Design Guidelines for Auxiliary Feedwater System Pump Drive ar.d Power Supply Diversity fer Pressurized Water Reactors" shall be used in meeting these criteria.
INSERT 10.4-5 In meeting this criterion the plant Technical Specifications should specify that the monthly AFW system pump test shall be performed for each AFW pump on a staggered test basis.
INSERT P In' meeting these criteria, the recommendations of NUREG-0611 " Generic Evaluation of Feedwater Transients and Small Break Loss-of-Coolant Accidents in Westinghouse-Designed Operating Plants," and NUREG-0635, " Generic Evaluation of Feedwater Transients and Small Break Loss-of-Coolant Accidents in Com- ,
bustion Engineering-Designed Operating Plants," shall also be met. An -5 acceptable AFWS should have an unreliability in the range of 10-4to 10 per demand based on an analysis using methods and date presented in NUREG-0611 and NUREG-0635. Compensating ~ factors such as other methods of accomplishing the safety functions of the AFWS or other reliable methods for cooling the reactor core during abnormal conditions may be considered to justify a larger unavailability of the AFWS.
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INSERT Q ,
l.' An evaluation against the generic recommendations of NUREG-0611 and 0635.
- 2. The evaluation of system reliability based on the applicant's I
reliability study.
- 3. An evaluation of the design basis for the flow capability for the system.
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I INSERT R
~
With the exception of the emergency (Class 1E) power supply to the essential motor driven AFW pump, the AFWS is not shared between units and, therefore, the requirements of General Design Criterion 5 are not applicable. The power supply sharing is discussed further in this SER section. Acceptability !
of the power supply sharing is discussed in Section 8.3 of this SER.
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TM a fi ies reviewed the FSAR to vert.*y the acceptability of the AFWS design with respect to its operating characteristics, classification, and provisions for inservice inspection and functional testing. i Minimum performance requirements for the AFWS have been identified and are No'r sufficient for the various functions of the system. This is discussed in more detail in the following paragraphs of this section of the report.
The AFW pumps take emergency suction from two sources. The normal source is the nonseismic Category I condensate storage tank (CST). If the CST is unavailable because of a tornado or seismic event, the operator is notified by low pressure alarms on the pump suction, and an automatic switchover to the seismic Category I tornado protected service water system (SWS) occurs. One service water train supplies each AFW pump. Upon initiation of service water, the affected train (s) is (are) automatically isolated by power-operated valves
[ from the nonseismic Category I piping leading to the CST, condenser hotwell,
\
and deaerator storage tank. Che*ck valves are also provided to prevent backflow to the CST, condenser hotwell, and deaerators.
Each SWS train is isolated from the other SWS train by redundant seismic Category I motor-operated valves powered from separate essential busses so that a single failure of one AFW train does not affect the other. A normally closed, fail close, seismic Category I power-operated valve is provided in the crosstie between the main feedwater system and the AFW motor-driven pump train.
The above features provide sufficient isolation to ensure that system function is not impaired in the event c a failure of a nonessential component. Based e
on the above, the staff concludes that the system meets the isolation requirements of G0Cf44 [ k h IbibIM.,C k h !'$t -
Gti.ukpl.M.
The essential portions of the AFWS are designed to seismic Category I requirements and Quality Group C requirements up to the containment isolation valves, and with Quality Group B specifications from the upstream side of these valves to the steam generators. Based on the above, the staff concludes 02/21/82 10-27 MIDLAND SER SEC 10 l
l
that the AFWS meets the requirements of GDC 2 and n ':., .
...no. es of Regulatory GuideA' ?E aad 1.29 with respect to ^"?'i+y nea T " seismic classification.
f S testing and inspection are included in the system design. Each AFWS pump is equipped with a recirculation line to the condensate storage tank for periodic functional testing purposes. Periodic testing of the AFWS pumps and -
jysGlt) valvesisidentifiedintheplantTechnicalSpecifications.fBasedonthe above, the staff conclud
- 10. 4 - b W1AL ^4hwvm ed._ N that w he system meets otott+oI.2S' wvn.U,.s- the requirements of GDC 46 Awithrespecttofunctionaltest g.
The AFWS components are located in accessible areas to permit periodic inservice inspection in accordance with ASME Code Section XI. Based on this, the staff concludes that the system meets the requirements of GDC 45 regarding design provisions for inservice inspection.
10.4.9.1.2 Natural Phenomena, Pipe Breaks, and Cracks f' W /4, a Thehf-has reviewed the AFWS design for protection against the effects of natural pher.omena, pipe breaks, or cracks in fluid systems outside containmert, single system component failures, loss of an onsite motive power source, or loss of offsite power.
Protection against failure of nonseismic Category I plant features is provided.
Failure of nonseismic Category I systems, components, or structures will not adversely affect AFWS function. All essential AFWS components are located in seismic Category I structures and are provided with protection against failure I
of nonseismic Category I compon,ents. .
iti.c' re, +ha e+=## e c .id;; .'..' tt,;
AFWS r'acina =:t: th'Eq'Idrised: . GDC 2 with eacnae+ +a pect:ctic, ago;n=i.
N 'fects of earthq :k : b^ ::: he ::fety--=1=+=ri nnetiane - e ' :ig.;d te En 4 "i C P2+ag^yI7-;I*^ rat'/in seemedsarn with Dncitinn P 1_
af Danois+acy u gnism__ ..on, 1 __;
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"^:itiO . C.2 uf EcMy Gusuc 1. C . -
Protection against missiles, tornadoes, and floods is provided. Essential portionsoftheAFWSarelocatedinthetornado-missilefnd-floodproof 02/21/82 10-28 MIDLAND SER SEC 10 l
l
.- f auxiliary building. The normal water sup k provided by the condensate storage
[ tank, deaerator storage tank, or the condenser hotwell are not tornado-missile Q protected.W h 'h- avan + a' t.',; h,;; cJ 16 .~. l .~..tu. muu pr u 6edeu .aier te r:0, th: cr tiaa e' the "! weeld 6 ;J;;; tic:"y t. ;...Tw. i wu to The
,tnrna-nentactori service watar ry t:: ;.pe. luw pump suu ivi. y....... w.n. ueni wi+h +ha nresence of an a m ;;; _ti :f,...i. The essential components of each AFWS train are housed in separate compartments which provide protection against internally generated missiles. (See Sections 3.4.1, 3.5.1.1, and 9.3.3 of this report for further discussion.) T 6 ; L ff - ..J A . tim t .. . T !: i: p. ;,;;;;;d fra= "aa* f ne-i;;, . . . . .. .!';; ;..d ::t: th: ';ri -- a+' c' CCC 0 ...d L r.d tr.; ;_id:li.. . vi neguia6uiy ou.
" . 'A.102 gd %:. ct d Tec
' el T.& . Cree dlsaS& s\ ls w ef ~ I
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tow /,a a - 12, (. , o 6 eel )
The essential AFWS trains may be used during startup and shutdow therefore, excert they arefev
" :th
- . 6.m yn,i s tbom.tly der <4st stm I,sa,;c.;; m ged as high r.=t.~.
energy lmes, and pipe breaks were pos uga e7,in the,.J,,,.yo%f;)s
. WS. Protection against high-energy pipe breaks in the AFWS is provided by separation of equipment. Essential portions of the AFWS are protected against the effects of high- and moderate energy line breaks in other systems. These
/ include the effects of pipe whip, jet impingement, and flooding. High energy
\'
piping systems are not located in the area of essential AFWS components. (See j Section 3.6.1 of this report for further discussion of protection against the effects of pipe breaks.) Environmental qualification with respect to pipe breaks is discussed in Section 3.11 of this SER. The essential components of each AFWS train are housed in separate watertight compartments for internal flood protection. Valves are installed in the floor drain lines for each essential AFWS pump room to prevent backflooding of the rooms. The staff concludes that the essential portions of the AFWS are protccted against the effects of pipe whip, jet impingement, andAfl oding assAciated,with pgg
% breaks and meet the requirements of GDC 4.d M ';;2M 5:'e#
- 3-1 " +h
+ +m nino -+
et r Sca,___.p_
,um rsa nurjesg ,,, e _ -1 m, v 1 m . w/ .g.
For either normal operating or accident conditions, tile AFWS is designed to provide sufficient feedwater to the steam generators to transfer the reactor coolant system decay heat to the main condenser or, if the condenser is unavailable, to the atmosphere through the atmospheric dump valves or the power-operated atmospheric vent valves.
02/21/82 10-29 MIDLAND SER SEC 10
INSERT 10.4-6 The Technical Specifications require that with one AFM pump and associated flowpath inoperable that the inoperable system be restored to operable l within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> or be in hot shutdown within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The system is tested monthly on a staggered test basis to assure both pumps are operable I and that each valve is in its correct position. At least once per 18 months, during shutdown, the automatic features of the system are verified operable including pump starts, valve operation and level control. The motor driven pump is used for plant startup, such that a separate flow verification test of the AFW system following an extended cold shutdown is not required (GS-6 of NUREG-0611 and NUREG-0635). An independent operator will perform valve lineup checks following testing or maintenance in addition to the valve lineup check made according to procedures for returning the system to service following maintenance or testing. This meets the guidelines of Recommendation GS-6 of NUREGs-0611 and 0635 with respect to flow path verification and independent operator valve lineup checks.
. C)
d ..
INSERT 10.4.7 In'the event of failure of the nontornado-protected, nonseismic Category I condensate-quality water sources, transfer to the seismic Category I service water system occurs automatically on low pump suction pressere. [We required the applicant to verify by test or analyses that AFW pump damage would not occur during the switchover interval due to the temporary loss of NPSH. Resolution of this item is currently under review by the applicant and we will report our evaluation of the resolution in a supplement to this SER. In the meantime, we cannot conclude that the requirements of GDC 2 and the recommendations of NUREGs 0611 and 0635 are met with respect to protection against natural phenomena and protection of the pumps due to loss of suction pressure.]
i l
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p .. w. m& y, & n QheAFWScanfunctionasrequiredintheeventofalossofoffsitepower.
g The turbine-driven pump receives main steam from both steam generators through a dc powered motor-operated valve on each steam supply line. These valves are normally closed and open on receip,t of ,anj uxiliary feedwater actuation signal (AFWAS). The steam supply linQ6e TocatTdIgistream of the main steam isolation valves. The AFWS pump turbine exhausts to atmosphere. The turbine-drivenandmotor-drivenpumplevelcontrolvalvesareacNwered through inverters from the dc bus, normally closed, and open on receipt of an AFWAS. The motor-driven pump can be powered from an onsite diesel generator vital ac bus. Each auxiliary feedwater pump discharge header is isolated from the steam generator it feeds by a vital ac-motor-operated valve in parallel with a dc-motor-operated bypass valve.
The AFWS consists of two trains, one supplying each steam generator. As indicated above, the AFWS trains are powered from redundant and diverse sources > o.cA4yM M B W 65 6 M d .
The AFW pump discharge headers are provided with a double crossover piping
( arrangement for system redundancy. Each crossover line contains a normally closed power-operated valve. If either AFW train fails to supply the necessary feedwater to its associated steam generator, the AFW p.mp of the other train would then supply feedwater via the crossover piping.
Double isolation of main feedwater from the AFWS during normal optration is provided. Steam supply to the tu -driven pump is provided froa both steam generators through separate or-operated valves. Redundant isolation is l provided for all essential portions of the AFWS from nonessential portions and systems. I e AutomaticAFWSfunctionisr$ovidedintheeventofamainsteamlineormain l feedwater line rupture. TE AFWS is equipped with a redundant feed-only good generator (FOGG) interlock system that operates to automatically isolate flow to a faulted steara generator and automatically direct flow to the intact steam generator. The steam generator with the break is detected by measuring the pressure difference between the two steam generators. When the pressure l
02/21/82 10-30 MIDLAND SER SEC 10 l
l
. J ..
I difference exceeds a set point, AFW is terminated to the low press re stea .
L M N; crNL M A A.%tL.% aa. pm"^'-
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- w.7. c y.kk'. A h 73 fw%.:/ .
Each AFWS pump is designed to provide 100 percent of the flow necessary for v.r,4., 4=. p wh pt root%
T ~ ~ -)
decay heat removal over the entire range of reactor operation, including all postulated design-basis accidents. A minimum of 175,000 gal of water in the condensate storage tank for each unit is reserved by Technical Specifications.
This volume adequately accommodates the plant at hot standby for approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> followed by a 6-hour c Idow to 80'F (decay he t removal syst N* -' -
IM *-
- cut-intemp)er5ae)
+-. % t i.r. - % -) .hs,eL..~ f. Mms p%.
The staff has recently determined reliability safety goals necessary for an AFWs to be acceptable with respect to GDC 44. As set forth in SRP Section 10.4.9, for an AFWS to have adequate heat transfer capability and component redundancy, the system must have an unreliability in the range of 10 4 to 10 5 per demand. As discussed in further detail below, the Midland AFWS unreliabil-ity is unacceptably high. Therefore, to meet the requirements of GDC 44, the staff requir that the applicant provide, for ea 5 unit, a third pump of AFW
\
that is capable of providing at least the minimum flow nece$sary to the g .
generators for decay heat removal during a loss of offsit7 I LTT
... __...._,_.m._,.m-
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The turbine-driven de powered AFWS pump train provides a diverse means of
_ f.
ensurirg feedwater supply to the steam generators independent of all offsite p or onsite ac power sources for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. The turbine-driven pump bearings do
" not require cooling from an ac-dependent source, and the pump can operate
[ without area forced ventilation for the 2-hour period. Actuation and control
- of this train are provided from the vital dc power source. Based on the above, h the staff concludes that the system meets the power diversity position of BTP
[ M i&* 4// M M.
ASB 10-1M tist msw so.4-e m ow_MA The turbine-driven and motor-driven AFW pumps automatically s receipt f a p*I
[fthesafetygradeAFWA ing AFW actuation, control of steam generator level is accomplished using4AFW control valves in each AFW loop. Control signals for each AFW 1evel control valve are supplied by redundant and inde-pendent Class IE level transmitters on the associated steam generators. In 02/21/82 10-31 MIDLAND SER SEC 10
_ , *..---- . . - . _ . . - _ . . . , , ._, , _ . . , , _ _ _ . , , . _ , . , , _ . - , , . _ - . . , , _ - . _ _ . - , , . -7.._.
E
INSERT 10.4-8 w .
AFWAS is initiated by any of several possible signal inputs: low pressure in either steam generator, a low water level in either steam generator, a reactor building high-pressure signal, loss of three out of four reactor coolant pumps, loss of both main feed pumps, a Class lE undervoltage, presence I
of an emergency core cooling actuation signal (ECCAS), or a manual trip.
i.
e e
6 I
l l
- + + -,,,ew- e-, _ __
addition to automatic initiation, AFW equipment may be manually actuated from I the control room or from the auxiliary shutdown panel. Based on the above, ;
the staff concludes that the system design provides instrumentation and control l i for prompt initiction of a shutdown fin accordance with the requir nts of '
EO Y GDC A)U 19c L -1Lkm Cr-O
& k~tAA.O
7.s Eks.,A.
CE W N A>
- v. i
^^"?-O E O W f' E *(
f^ ^M M*
- n 'l +- ) =_En%&
ye aie1 ::p:bi'i+y tn initiato and ennten1 th= a re ;- ; ==d unlune --f tg.
is-NstE either AFW5 train is v.udd;d '- +h" ~ -trel .vv- anu in sne auxi naty 57,td;;nannal - Based nn +'#:, 6ne staTT concluoes T.nat Lne sysium J 65 the
": ;l iniciation provisions vi Ew3 late.y -hw 1.02.
The AFWS for each unit is completely independent 4y from the AFWS for the other unit except for the backup secondary water source provided by the safety grade service water system (SWS). Although the SWS is shared between units, it contains two redundant independent trains. Each SWS train is capable of siriultaneously supplying the emergency feedwater requirements of both units.
Therefore, a failure of one train of the SWS will not prevent the safe shutdown
[ and cooldown of either unit. Based on the above, the staff concludes that the AFWS meets the requirements of GDC 5 with respect to sharing of structures, systems, and components.
MM L ouaiiiary i cu ter ;y;t:: ' c'"d-c all components m"d -a"4 p at frna the GT (inctild'in' g~vaWes anif' cross connections) up to and incluoing 6ne sun.. ;t8anc wt%-the -h generators Raced nn the review nf the applicant's proposed m
' usa *jr su iteT'ia$itJn I,a;c;, =ad enfato clacciflemtian Me th m Q 8ter System, and sysicm pw Turm8Mee-PeQ"i": 't ? d""4 "O ^^""?l, "ha^" mal- -
A'Y} -SCCideni suou a i s uisa , is'au 26 ail curiciuuca 6sia 6 6srw us,i@. d tI.; ;-mi 'i2G "
f a A q + - g r + -- 2nd ennnnetinn cuttame is in ennformanen wit _h ^ m._ " , ... * ; ; * . . ' ;
--'"'"'-: __ . ....:. = Uuc z, 4, d, 19, es, anu ^;, :nd ::t: t': " rid;-
7
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l 02/21/82 10-32 MIDLAND SER SEC 10
t "r red i.., Uie muienu idw5 is noc acceptaoie wi u . ..,gt +a cne 44, J t aiois wiii s epv, 6 un Liu
...v'uw.uu vi un s ma ue r i n a s upp i
<ro --
,....m t; ' W 10.4.9.2 Auxiliary Fe 3,4c y dr WM,edwater A System l- d Reliability Review t
The
._r--- ~~ h. 1 aff has reviewed the Mi land Units 1 and 2 AFWS against the reouirements ofthe}pril 24, 1980 '
, which corresponds to Item II.E.1.1 of NUREG-0660 and N !G-0737.
10.
9.2.1 Introduction and Background The TMI-2 accident and subsequent investigations and studies highlighted the importance of the AFWS in the mitigation of transients and accid ents. As part of its assessment of the THI-2 accident and related implications for operating plants, the staff evaluated the AFWS for all operating plants having a NSSS designed by Westinghouse (NUREG-0611) or Combustion Engineerigg (NU .
The staff evaluations of these system designs are in the REGfalongwith the staff's recommendations for each plant and the concerns that led to each d-recommendations.
The objectives of the evaluation were to: (1) identify necessary changes in AFWS design or related procedures at the operating facilities to ensure the continued safe operation of these plants, and (2) to identify other system characteristics of the AFWS that, on a long-term basis may require system modifications. ,
To accomplish these objectives, the staff
, (1) reviewed plant-specific AFWS designs against the SRP (2) assessed the relative reliability of the AFWS under various loss of feedwater transients (one of which was the initiating event of THI-2) and other postulated failure conditions by determining the potential for AFWS failure as a result of common causes, single point vulnerabilities, and human error.
In accordance with the requirements of Item II.E.1.1 of NUREG-0660, the staff has applied the generic results and recommendations from the above described reviews for operating plants to the Midland AFWS and has reviewed the detcilad 02/21/82 10-33 MIDLAND SER SEC 10 a
l
,4HA. M4woeswoul-ity evalua ion ubmitted b the applicant. TF- "
Mid1 nd AFWS,.
9hMW reliabigJL MJ **6_ Ausp , A. bl, v at, *,,s. 1 #2 &
M.# ,
e ,. o .r c 10.V.9.
In a letter dated February 23, 1981, the applicant provided a report entitled
" Midland Plant Auxiliary Feedwater System Reliability Analysis." This analysis '
evaluated the AFWS reliability for the three postulated transients and accident scenarios identified for study in the staff's April 24, 1980 letter utilizing fault-tree methodology. Overall numerical system unavailability for the three cases was determined using the NRC g Edfailureratedatabase. Results of the applicant's analysis indicated that the Midland AFWS ranked in the medium reliability range for case 1, Loss of Main Feedwater; for case 2, Loss of Offsite Power; and for case 3, Loss of All AC Power. This ranking is based upon a comparison of the results of reliability assessments of the AFWS designs in all operating PWRs. AFWS unreliability in the medium range, 10.s to 10 4 per demand, is not in accordance with the licensing criteria in SRP Section 10.4.9. An AFWS should have an unreliability in the range of 10 4 to 10 5 per demand in order to be acceptable wit *i respect to the heat transfer ar.d redun-dancy requirements of GDC 44. Thereforo,thestaffrequireebthattheapplicant
(
provide for each unit a third AFW pump that is capable of providing at least the minimum flow necessary to the steam gerteratorA for decay heat removal during a
. opvoyW,L,a- o,m, .y gaa.us (-a x dewy bdIysoM 4[{1Y (M C 2 h N u M M n. .
- e. -
ff./# -->The staff has reviewed the applicant's deterministic co AFWS against SRP Section 10.4.9 and BTP ASB 10-1 and finds that the AFWS design is in compliance, except with respect to GDC 44, as discussed above. Environ-mental qualification of the AFWS is discussed in Section 3.11 of this SER.
Short-term recommendations GS-2, GS-5, GS-7, GS-8, and GL-1 in the staf f's April 24, 1980 letterwerenotincludedinthisevaluationbecahtheyeither do not apply or are covered by the long-term recommendations included in this SER.
M The staff has reviewed the applicant's response to the require in Enclosure 2 i of the staff's April 24, 1980 letter regarding the design basis for AFWS flow requirements. The applicant provided this informatio evision 33 the FSAR.
02/21/82 10-34 HIDLAND SER SEC 10
vt Lt ;te'f conclude that the applicant's design basis for AFWS flow requirements is acceptable.
Le f-P=r+dfconclude/thattheit.plementationoftherecommendationsidentified from the above reviews has improved the reliability of the Midland AFWS, although, as noted above, he reliability of the Midland AFWS is not considered g adequate. The applicant ett incorporate all applicable short- and long-term recommendations of the April 24, 1980 letter prior to receipt of the operating license.
10.4.9.2.2 Implementation of Staff Recommendations Short-Term Recommendations Recommendation GS-1 The licensee should propose modifications to the Technical Specifica-tions to limit the time that one AFW system pump and its associated
(
flow train and essential instrumentation can be inoperable. The outage time limit and subsequent action time should be as required in current Technical Specifications; i.e., 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />, 6 respectively.
In response, the applicant indicated in FSAR Appendix 10A.3 that the proposed Midland Technical Specification, Section 3.7.1.2, applies. This Specification limits plant operation with one AFWS train out of service to 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> and the subsequent action time to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />. The staff concludes that this Technical gpecificationisincompliancewithitsrecommendationandis,therefore, acceptable.
Recommendation GS-3 The licensee has stated that it throttles AFW system flow to avoid water hammer. The licensee should reexamine the practice of throttling AFW system flow to avoid water hammer. The licensee should verify that the AFW system will supply on demand sufficient 02/21/82 10-35 MIDLAND SER SEC 10
INSERT 10.4-9 !
By letter dated March 1,1982, the applicant provided a revised reliability ~*
study for the AFWS that placed the Midland system in the high range of 10
-5 The revised study was based on three major proposed to 10 uhreliabili ty.
These are: The changes in the AFWS design and Technical Specifications.
motor driven pump would have the capability to be powered from both emer-gency buses; the limiting conditions for operation in the plant Technical Specifications would be changed such that one AFWS pump could only be out for 48 hours5.555556e-4 days <br />0.0133 hours <br />7.936508e-5 weeks <br />1.8264e-5 months <br /> in lieu of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> before shutdown begins; the basic criterion for the reliability study was changed of core uncovery to allow
-[We have reviewed the applicant's proposed changes time for manual actions.
and conclude they are not an acceptable alternative to a third AFW pump.
This conclusion is based on the possible reduction in overall reliability of the emergency buses due to the cross-connect feature and a reduction of the defense-in-depth goal by not using steam generator dryout as a basic criterion for the AFW system reliability analyses. Based on the above we conclude that the AFW system is not in compliance with GDC 44 with respect to heat transfer capability and redundancy.]
e o
1
.0 \
g i
initial flow to the necessary steam generators to assure adequate decay heat removal following loss of main feedwater flow and a reactor trip from 100 percent power. In cases where this reevalua-tion results in an increase in initial AFW system flow, the licensee should provide sufficient information to demonstrate that the required l
initial AFW system flow will not result in plant damage due to water hammer.
In response, the applicant indicated in FSAR Appendix 10A.3 that the Midland AFWS does not rely on throttling of AFW flow for protection against waterhammer.
Based on the applicant's response, the staff concludes that Recomme dation S-3 is not applicable to Midland. ( h _d M h M3 M b N ,-- -c ,w ~ :E r, n 3 h 1 &.
Recommendation GS-4 ( [
Emergency procedures for transferring to alternate sources of AFW supply should be available to the plant operators. These procedures
(
should include criteria to inform the operator when, and in what order, the transfer to alternate water sources should take place.
The following cases should be covered by the procedures:
(1) The case in which the primary water supply is not initially available. The procedures for this case should include any operator actions required to protect the AFW system pumps against self-damage before water flow is initiated.
(2) The case in which the primary water supply is being depleted.
The procedures for this case should provide for transfer to the alternate water sources prior to draining of the primary water supply.
In FSAR Appendix 10A.3 the applicant indicated that an automatic transfer of the AFWS water supply from the condensate storage tank to the service water system is provided. The automatic transfer occurs on a low pump suction pressure signal coincident with the presence of an AFWAS. Therefore, it is not 02/21/82 10-36 MIDLAND SER SEC 10 l
l
o s, D o.
- - 'y .
\
\ \
t s t necessary to have emergency procedures for transferring to alternate sources of AFWsupplyJogthgc,aseif wh th
, , pripa,rf wat,er suppp , s g n g ly availablej thy ftifi~ finds the response to Part 1 of this recommendation acceptable.
I By letter dated June 4, 1981, the applicant indicated that the condensate storage tank low level alarm response procedure will provide for manusi switchover to alternate suction sources. The alarm response procedure will be issued prior to plant operation. The staff finds the response to Part 2 of this recommendation acceptable.
Recommendation GS-E i
The licensee should confirm flow path availability of an AFW system flow train that has been out of service to perform periodic testing or maintenance as follows:
(1) Procedures should be implemented to require an operator to
'(
i determine that the AFW system valves are properly aligned and a secord operator to independently verify that the valves are prope.1" aligned.
(2) The licensee should propose Technical Specifications to assure that prior to plant startup following an extended cold shutdown, a flow test would be performed to verify the normal flow path from the primary AFW system water source to the steam generators.
The flow test should be conducted with AFW system valves in their normal alignment.
By letter dated June 4, 1981, the applicant stated that Midland maintenance and test procedures require that valves be returned to their original position upon completion of maintenance or surveillance testing. Technical Specification 4.7.1.2.a.3 will be revised to require second independent valve lineup verifi-cation following maintenance or testing of the AFWS. The staff finds the applicant's response to this part of the recommendation acceptable, pending issuance of the Technical 4pecificationsty4t.
02/21/82 10-37 MIDLAND SER SEC 10
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By letter dated June 4, 1981, the applicant stated that Technical Specification 4.7.1.2 will be revised to require a flow path test every 18 months or after an extended cald shutdown. Extended cold shutdown will be defined as a cold shutdown equal to or greater than 30 days. The Technical Specification will 9* also specify the flow path as condensate storage tank to both steam generators g through the AFW nozzles using the moto M riven AFW pump. Verification will be by AFW flow indication and steam generator level. The Technical Specification will be revised prior to plant operation. The staff finds the applicant's response to this part of the recommendation acceptable pending issuance of the Technical Specifications.
Additional Short Term Recommendations Recommendation l
The licensee should provide redundant level indication and low level alarms in the control room for the AFW system primary water supply, to allow the operator to anticipate the need to make up water or transfer to an alternate water supply and prevent a low pump suction pressure condition from occurring. The low level alarm setpoint should allow at least 20 minutes for operator action, assuming that the largest capacity AFW pump is operating.
By letter dated June 4,1981, the applicant stated that a low level alarm is provided to warn the operator that the CST is approaching the minimum AFW volume required for a safe shutdown. A low level alarm will be provided from the plant computer to give the operator at least 20 minutes to assess the need for makeup water or transfer to an alternate water supply. The staff finds the response to this recommendation acceptable.
Recommendation (This recommendation has been revised from the original recommendation in our April 24, 1980 l etter.)
h #=$4 The licensee should perform a 48-hour endurance test on all AFW system pumps, if such a test or continuous period of operation has not been accomplished to date. Following the 48-hour pump run, the pumps l
1 02/21/82 10-38 MIDLAND SER SEC 10 J 1
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should be shut down and cooled down and then restarted and run for I hour. Test acceptance criteria should include demonstrating that the pumps remain within design limits with respect to bearing / bearing oil temperatures and vibration and that pump room ambient conditions (temperature, humidity) do not exceed environmental qualification r limits for safety-related equipment in the room.
In FSAR Appendix 10A.3 the applicant committed to perform a 48-hour endurance test on all AFWS pumps during startup testing. The applicant should document the results of the tests and include the following:
(1) a brief description of the test method and instrumentation used (2) a plot of bearing and bearing oil temperature vs time for each pump demonstrating that the temperature design limits were not exceeded #
(3) a plot of pump room ambient temperature and humidity vs time to lg [ demonstrate that the pump room ambient conditiosf do not exceed environmental qualification limits for safety-related equipment in the room (4) a statement confirming that the pump vibration limits were not exceeded J The staff concludes that the response to this recommendation is acceptable pending receipt of acceptable test results. If the results are not acceptable, the staff will require modifications and provide a safety evaluation regarding the tests and modifications.
Recommendation The licensee shoulo implement the following requirements as speci-fled by Item 2.1.7.b on page A-32 of NUREG-0578: " Safety grade indication of auxiliary feedwater flow to each steam generator shall be provided in the control room. The auxiliary feedwater flow instrument channels shall be powered from the emergency buses 02/21/82 10-39 MIDLAND SER SEC 10
i* .
consistent with satisfying the emergency power diversity require-ments for the auxiliary feedwater system set f orth in Auxiliary -
Systems Branch Technical Position 10-1 of the Standard Review Plan, Section 10.4.9."
In Appendix FIAR 10A.3 the applicant responded to this recommendation by stating that safety grade flow indication of AFWS flow to each steam generator is provided. This response is evaluated in Section 7.3 of this SER.
Recommendation Licensees with plants which require local manual realignment of 3 valves to conduct periodic tests on one AFW system train, ash @A
-4s-only one remaining AFW train available for operation should
> propose Technical Specifications to provide that a dedicated indi-vidual who is in communication with the control room be stationed at the manual valves. Upon instruction from the control room, this operator would realign the valves in the AFW system train from the
[ test mode to their operational alignment.
By letter dated June 4, 1981, the applicant stated that the Midland Technical pecificationsrequiretwoAFWtrainstobeoperableformodes1,2,and3.
During surveillance testing in modes 1, 2 yand 3, which requires local manual realignment of valves, an individual assigned to the test who is in communica-tion with the control room will be stationed at the manual valves. Upon instruction from the control room, this operator would realign the valves in the AFWS from the test mode to the operational mode. The staff finds the response to this recomendation acceptable.
Long , Term Recommendations Recomendation GL-2 Licensees with plant designs in which all (primary and alternate) water supplies to the AFW systems pass through valves in a single flow path should install redundant parallel flow paths (piping and valves).
02/21/82 10-40 MIDLAND SER SEC 10
Licensees with plants in which the primary AFW system water supply passes through valves in a single flow path, but the alternate AFW system water supplies connect to the AFW system pump suction piping downstream of the above valve (s), should install redundant valves parallel to the above valve (s) or provide automatic opening of the valve (s) from the alternate water supply upon low pump suction pressure.
The licensee should propose Technical Specifications to incorporate appropriate periodic inspections to verify the valve positions.
AttheMidlandplant,thenormalAFWsourceisteCS(. Water from this tank passes through valves in a single flow path subsequently divides and hpliessuctiontoeachAFWpump. Downstream of these valves in the primary water source flow path, each AFW pump is provided with a separate supply line with double isolation valves from the secondary water source. The valves between the secondary water supply and the AFW pump suction ooen automatically jresew e.
upon a low pump suction pressure signal coincident with the r m .t of an AFWAS. The Midland Technical Specifications also provide for periodic inspections to verify the AFWS valve positions. The staff finds tne response to this recommendation acceptable.
Recommendation GL-3 "At least one AFW system pump and its associated flow path and essential instrumentation should automatically initiate AFW system flow and be capable of being operated independently of any AC power source for at least two hours. Conversion of DC power to AC power is acceptable."
The FSAR indicates that the turbine-driven AFW pump and its associated flow path and essential instrumentation automatically initiate AFWS flow and are capable of being operated independent of any ac power source for at least 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. The staff has reviewed this information and confirms that the turbine-driven AFWS pump train is available to supply emergency feedwater independent ,
i 02/21/82 10-41 MIDLAND SER SEC 10
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I of onsite or offsite ac power supplies. Based on its review, the staff concludes that this recommendation is satisfied by the Midland AFWS design.
4 Recommendation GL-4 1 i ?
j Licensees having plants with unprotected normal AFW system water j
supplies should evaluate the design of their AFW systems to deter-
- mine if automatic protection of the pumps is necessary following a j seismic event or a tornado. The time available before pump damage, the alarms and indications available to the control room operator, and the time necessary for assessing the problem and taking action ;
shoul be considered in determining whether operator action can be j reli on to prevent pump damage. Consideration should be given to providing pump protection by means such as autoastic switchover of the pump suctions to the alternate safety grade source of water, automatic pump trips on low suction pressure, or upgrading the I normal source of water to meet seismic Category I and tornado protection requirements.
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- At the Midland plant the normal AFW source is nonsafety grade. The safety grade I source is provided by the SWS to the suction of each AFW pump. Switchover of the AFW pump suction to the 4WS is accomplished automatically using a two-out-of-four low pump suction pressure logic concurrent with the presence of an AFWAS. To prevent spurious opening of the service water valves as a' result of normal transients, the low suction pressure must persist for 4 seconds before it l
initiates opening of these valves. Approximately 2.5 seconds is required for valves to reach the 50 percent-open position, which is the point at which full flow will be established. The staff requires that the applicant ensure that the AFW pumps can survive the low suction pressure condition for the approxi-I mately 7 seconds required to effect the water source transfer.
l In a meeting with the applicant on April 30, 1981, the staff requested that the applicant evaluate the need for installing a low suction pressure pump trip to protect the AFW pumps in the event that the normal (nonseismic, nontornado) water source is lost while the AFWs is operating in a h al made (that is, pumps running without the presence of an auxiliary feedwater 02/21/82 10-42 MIDLAND SER SEC 10
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Recommendation GL-
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The licensee should upgrade the AFW system automatic initiation signals and circuits to meet safety grade requiremer.ts.
In response to this recommendation, the applicant indicated in FSAR Appendix 10A.3thatthepresentAFfautomaticinitiationsignalsandcircuitsare safety grade. The evaluation of the design is in Section 7.3 of this SER.
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