ML19344A331

Auxiliary Sys Branch Input to SER Citing Incomplete Pipe Break Analysis for Certain High Energy Piping Sys Outside Containment & Incomplete Design for High Density Storage Sys for Spent Fuel

ML19344A331
Person / Time
Site:	Midland
Issue date:	03/20/1979
From:	Office of Nuclear Reactor Regulation
To:
References
NUDOCS 8008120657
Download: ML19344A331 (48)

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_ Auxiliary Systems Branch Safety Evaluation Report Midland Plant Units 1 & 2 Docket Nos. 50-329/330 3.4 Water Level '(Flood) Design-Our review of the' Midland Plant protection against flooding included the applicant's design to protect safety related systems, structures and components from the effects of flooding, and the ability of the design to maintain the capability for a safe plant shutdown during a 4

design basis flood. General Design Criterion 2 " Design Basis for Pro-tection' Against Natural Phenomena" requires that structures, systems and components important to safety be' designed to withstand the effects -

of floods. The following evaluation describes the methods by which the Midland plant meets this criterion by demonstrating safe plant shutdown will not be precluded due to flooding.

The plant grade for the Midland Plant site is located it a minimum ele-vation of 634 feet which'is above the conservatively calculated probable maximum flood (PMF) level of 631 feet. Further information on the evalua-tion of the methods used to determine the probable maximum flood level can be found in Section 2.4 'of this report. All entrances to safety related structures are at elevation 634.5 feet or higher, and therefore, above the.PMF level. During a postulated PMF all safety related struc-tures are protected from flooding up to elevation 635.5 feet by sandbagging to protect against wind and wave effects. Sandbagging is an acceptable 1

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al cernative to " hardened protection"I and meets the guidelines Of pc31-

~ tions C.2.a. b, and c, Regulatory Guide 1.59, " Design. Basis Floods for

' Nuclear Power Plants" since sufficient warning time is available to imple-ment the sandbagging, and the sandbagging is not required for any flooding events-less than the PMF. 'Also, sandbagging is only necessary to protect against win. and wave effects, and aces not have to withstand the static forces of the PMF water level.

The sandbagging is also an alternative to pcs - on C.2.: F: t,aa:ce.>l Guide 1.59, which recommends "hardenea protection" for those structures, systems and components necessary for cold shutdown. We find this an acceptable alternative because the sandbaaoino is used where Dermanent Drotection is nnt considered feasible due to access requirements for trucks and train cars or personnel access doors which are already constructed. Midland has also provided a technical specification for the implementation of emergency pro-cedures to assure adequate-time and orocedures for sandbagging.

Further information on the evaluation of this Technical Specification and the sand-bagging can be found in Section 2.4 of this Report.

The external wall's of the auxiliary building and the containment are pro-tected from flood waters by a waterproof membrane up to elevation 632 feet.

These are _the only build'ngs that contain safety related equipment at levels below the'PMF. The safety.related service water structure also extends below the PMF level, but contains no components below the DMF that i:d d be a# ected b) ::d 4 ate 73 I: a <;ats : ::#

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'l" Hardened protection' as definea. in Regulatorv Guice i 59 means

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All. exterior construction joints of safety related structures are sealed with water stops to grade. level and piping penetrations are provided with watertight seals. Electrical penetration and personnel access between the turbine building and tr.e auxiliary building are provided with seals and watertight doors designed to withstand the hydrostatic loading associated with the turbine building flooded to elevation 634.5 feet. Since these flood protection metboas use barriers incorporated in:c -5e cesign of

- the plant, the design meets' the guidelines of Regulatory Guicies 1.59

" Design Basis Floods for Nuclear Power Plants" and 1.102 "Flcod Protec-

. tion for Nuclear Power Plants,'.' which recommend " hardened protection" including penetration !,eals, watertight.coors and constructicn joint seals.

The Midland plant is protected against flooding caused by local-precipitation by a site drainage system which is designed to remove v.ater buildup. caused by the probable maximum-precipitation (PMP). The drainage system removes precipitation from the roofs and the areas

. surrounding the safety related structures and conveys 'the water via sloped: drains to the cooling pond or the Tittabawassee Riv'er The site drainage system, and the locating of outside openings ter safety related structures above the plant grade, provide acceptable methods of

protecting ' safety related' equipment from the effects,0f flooding due

'to precipitation.

As a. result of our review, we conclude that the facility design meets the

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4 requirements of General-Design Criterion 2 and the guidelines of Regulatory Guides-1.59 and 1.102 as described above. On that basis, we ::enclude that the water ; level ;(flood) design ~ is acceptable.

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' 3.5 ' MISSILE PROTECTION-3.5.l'1 INTERNALLY-GENERATED MISSILES (OUTSIDE CONTAINMENT)

Protection against postulated internally generated missiles outside containment associated with plant operation, such as missiles generated by rotating or pressurized equipment,is provided by any one or a combina-tion of barriers, separation, restraint of potential missiles, strategic orientation and eouipment design. The primary means of providing cro-tection to safety related equipment is-through the use of plant physical arrangement. The majority of safety related systems are physically separated (within separate-compartments) from non-safety related systems and the redundant components of safety related systems are physically separated such that a patential missile could not damage both trains of the safety related system. Where separation is'not feasible, one of the other methods described above is used.

As recommended.by Regulatory Guide 1.13, " Spent Fuel Storage Facility Design Basis," the spent fuel is protected from internally generated missiles;by the fuel pool walls and by designing the fuel handling system such that a seismic event will not result in missile generation. The ultimate. heat sink is also protected 'from the effects of internally generated missiles in accordance with Regulatory Guide 1.27, " Ultimate Heat Sink," by having one ' pump of each train in a separate compartment, and an installed spare pump in a third compartment that can be used for either unit.

The applicant has provided;an analysis of the affects of potential sources of internal missiles in areas outside containment. Typical postulated missile sources include.6, inch boric acid evaporation system valves, 6 inch auxiliary steam genera *or valves, steam generator recirculation pump,

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.. service and component cooling water pumps and fuel-pool cooling pumos.

.We ha've reviewed the applicant's. analysis and agree that the postulated missiles are representative of typical missiles and that the applicant-has

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shown to our satisfaction that the affects of the potential missiles wil' not prevent safe plant shutdown.

Infornation regarding the evaluation of the design of the Midland plant for protection against turbine missiles can be found in Section 3.5.1.3 of this Reoort.

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We have-reviewed the adequacy of the aoplicant's design to maintain the capability for a safe plant shutdown in the event of an internally generated missile outside containment. We have concluded that through

- the use of separation, barriers, restraints, orientation and equipment design, the Midland plant-design is in confonnance with General Design Criterion 4 " Environmental and Missile Design Basis," as it relates to the systems being capable to withstand the effects of internally generated missiles outside containment.

- Based on our review as discussed above, we find that the design meets the guicelines of Regulatory Guide 1.13 and 1.27 and the require-ments of General Design Criterion 4.

We, therefore, conclude that the facility's-design against internally generated-missiles outside contain-ment is'e-eptable.

3.5.2 Structures,' Systems, and Com::enents to be Protected from Extere a

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Generateo Missiles Ceneral-Design Criterion 4. requires that all components essential to the Lsafety of the plant be protected from-the effects of externally generated

- mi ssiles'. 'All safety related-structures except portions of the auxiliary buil' ding 1 roof over the new fuel storage area are designed to withstand

>the effects of tornado generated missiles. All safety related systems 4l

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and components, with the exception of the borated water storage tank are located within tornado missile protected structures.or otherwise protected with barriers.

The evaluation of the adequacy of the design the Midland plant for the protection of safety related systems and components are include'd in the individual evaluations of this report for the systems or areas that require protection. 'As an example refer to Section 9.1.2 (New Fuel Storage) for the evaluation of the portion of the auxiliary building roof, mentioned above, that is not protected against tornado missiles.

The' evaluation ~ of the tornado' protection' for the borated wat 4r storage tank is located'in Section 9.3.4 " Chemical and Volume Control System."

Based on our evaluations and conclusions of' the individual systems a'nd components as put forth in the individual sections of this report, we conclude that the overall plant design meets the requirements of General Design Criterion 4 as it relates to torna'do missile protec-tion. For the evaluations of how the reouirements of Criterion 4 are met, for a particular section refer to the individual sections of this repo rt.

3.6.1 Protection Acainst Dynamic Effects Associated witn the Postulated Ruoture-of Pioino (Outsiae Containment)-

[The applicant has: not-completed the pipe break analysis for certain high Jenergy piping systems. outside containment. We will evaluate the results of the applicant's analysis after i.t has been submitted. 'We :will -socrt our. findings in-afsuoplement.]

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-*r 9.0 Auriliary Systems The. auxiliary systems evaluated in' this reoort which are necessary for safe plant shutdown include: the service water systems, comoonent cooling

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water system, ultimate heat-sink, portions of the makeup and purifica-tion system, chemical addition system, afety related chilled water system, and safety' related ventilation sy' stems.

Systems evaluated in this report necessary to assure safe handling of fuel and adequate cooling of the spent fuel include: new and spent' fuel storage facilities, the spent fuel pool cooling and purification system and the fuel handling system.

Other auxiliary systems evaluated in this report include: the equip-

-ment and. floor. drainage system, the compressed air system, condensate

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storage system, and the fire protection system. These systems have been evaluated since their failure could either be a direct or indirect source of. radioactive release to the environs or could have adverse

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effects on systems' necessary for safe shutdown.

We have also reviewed-other auxiliary systems that are not safety related to assure their failure would not prevent safe shutdown nor-result in a potential source of radiological release to the environment. These l

systems' include: the pressurizer relief tank, potable and sanitary wate7 system, demineralized water makeup system, non-safety related

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chilled water system andinon-safety related ventilation systems. - The

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acceptability of these systems was based on our review which determined that:

(a)~ where the system interfaces or connects to a seismic Category I system or component, normally. closed.or automatically operated seismic Category I isolation valves:are provided to physically separate the-non-essential ' portions from the essential system or component, and -(b) the failure of the non-safety related system or portions of the system will not preclude the operation of safety related systems or components located in close proximity. Based on our review of the above listed systems' design, piping and instrumentation diagrana, and plant layout drawings we conclude that since their failure will not result in radio-logical releases or damage to safety related equipment or prevent safe plant shutdown,- they are acceptable.

9.1 Fuel Storage and Handlinn 9.1.1

~New Fuel Storace Th'e new fuel storage racks are designed for dry storage of approximately, 70% of a full core load (124-assemblies). There are two new fuel storage pits' (one pit for each unit) equally sized to store one-half.the total of new fuel assemblies. The auxiliary building, which houses the fuel pitt andLracks for both units, and the pits and racks themselves are

' designed to seismic Category I requirements in accordance with Regulatory

- Guide 1.29:" Seismic Design Classification" and General Design Criterion 2

" Design. Basis for Protection Against Natural Phenomena."

The stainless steel'new fuel racks have a center-to-center spacing-of.

21. inches which ~is sufficient to maintain Kef' less than 0.'95 'even

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Q 9-the racks are flooded with unborated water. The fuel pits are also provided with drains to; reduce the likelihood of flooding of the fuel oits.

The 21-inch center-to-center spacing is also sufficient to maintain Keff equal to or less than 0.98, asstning optimum moderation, such as by -

aqueous foam. The spacing.between racks is such that a-fuel assembly cannot be inserted in other than a prescribed location, assuring that the-I-

21-inch spacing is not threatened. Therefore, the design meets General Design' Criterion 62, " Prevention of Criticality in' Fuel Storage.and Handling,"'

which requires that criticality be preventad by physical systems or oro-cesses,'oreferably by use of geomstrically safe configurations.

j In accordance with Section 9.1.1 "New Fuel Storage" of the Standard Review l

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' Plan, we requested the applicant to design' the racks to withstand the maxi-mum uplift forces that could be exerted by.the fuel handling system without an increase in Keff.

In Amendment 14, the applicant provided. verification l

that excessive forces could not be applied by the fuel handling system.and l

therefore Xeff would not be increased. All hookups to the new fuel assem-blies.with the fuel handling system are done directly by hand so that the handling system will.not be attached to the. racks. The new fuel racks are used only for storage of new fuel such that a fuel assembly cannot become stuck due to ' swelling as is possible with the spent fuel,- therefore, exces-sive forces cannot be transmitted to the fuel racks via the fuel-assemblies.

For these reasons,'we~ agree with the applicant that excessive fuel handling l-

- forces th'at would result in an increased Keff will not be transmitted to the new' fuel racks. Therefore, they._have an acceotable alternative 'to the standard l

l review plan l recommendation that theEnew fuel racks ~and the anchorages be designed 4

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to withstand the ' maximum uplift. forces that can be exerted by the foal handling system.

The new fuel storage area is -located in a portion of the auxiliary

-building that does 'not have a tornado missile protected roof. Therefore,

- no protection'of. the new fuel from vertical tornado missiles is pro-vided.. The applicant gives the following reasons why the'new fuel storage. area is not protected:

1; The new fuel is stored dry.and the pit is provided with drainage, and because there is no water, changing of the geometry due t'o external missiles will not result in criticality;

2.. There are no fission products in the new fuel, therefore there will be no radioactivity releared as a result of fuel damage.

We agree with the applicant's basis for no tornado vertical missile pro-tection, and since protection is provided against damage due to horizontal

- missiles, by locating the new fuel in-seismic Category I storage pits, we find that the, applicant's design is an acceptable alternative to Section I

9.1.l'of the Standard Review Plan, because 'the safety function (No-Criticality)

' is maintained.following a postulated tornado event. Therefore, General Design Criterion 62 " Prevention of Criticality in Fuel Storage and Handling,"'

.as related to the prevention of criticality in fuel storage systems, is met.

Based on.our review' of the new fuel storage design as described above.

-we find'that the' design meets the guidelines of Regulatory Guide l.29,

-and the ' requirements of General Design. Criteria 2 and 62 as described above.

'Je therefore conclude : hat the new ' fuel. storage system is ' acceptacie.

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- Spent Fuel Storace (In ' Amendment'15 the applicant proposed to increase' the spent fuel storage capacity from 1-2/3 cores to 5-2/3 cores. The design of the high density

. storage' system ~is'not complete. We will provide our evaluation after the

. applicant submits details of his final design.]

9. l'. 3.

' Soent' Fuel-Pool Coolinq and purification System 4

The spent fuel pool cooling and-purification system.is designed to maintain

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the water quality and clarity of the fuel pool water and to remove the -

decay heat generated by the stored spent fuel assemblies.

The Midland plant uses one storage pool for both units; therefore, one spent fuel-pool cooling and purification system is provided and-shared i-

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between units. -General Design Criterion 5 " Sharing of Structures,' Systems i

-- and Components," allows sharing. if it is -shown that such sharing will not

-significantly impair their ability to perfom their safety function,

' including shutdown' and cooldown'of both units -following an accident.

Because-a. failure of either cooling train will not prevent adeouate spent

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fuel cooling nor affect safe shutdown of either unit, the requirements of General Design Criterion 5 are met.

- The spent fuel pool cooling portion of'the system is designed to seismic Category I recuimments as. recommended by Regulatory Guides 1.13 " Quality.

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Group C',assification" and 1.-29 " Seismic Design Classification." It j

consists of _ two cooling trains one pump and; one heat exchanger per train, both_ of which are ocerated during nomal plant conditions.

'To meet the-guidelines of Regulatory ~ Guide 1.13 "Soent Fuel Storage

H pacility Design Basis," redundant seismic Category I sources of I

makeup water;are available from' the essentialLservice water _ system in

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addition to the nomal-makeup which is 'taken from the primary water storage tank. The fuel pool cooling system is arranged and provided with syphon breakers where necessary to prevent inadvertant draining of the fuel pool to less than ten feet above the fuel. Therefore. the require-ments ;of. General Design Criterion '61 " Fuel Storage and Handling and Radioactivity Control," as related to the design of the system to prevent significant reduction in fuel storage coolant inventory under accident conditions are met.

In Amendment 17, the applicant provided the results of the spent fuel

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decay heat load calculations for the revised storage capacity of.5-2/3 -

The calculations were perfonned assuming 6-month refueling inter-cores.

vals using the methods set forth in our Branch Technical Position ASB 9-2

" Residual Decay Energy for Light Water Reactors," and therefore' are acceptable. Since the increase in fuel storage capacity, from 1-2/3 to 5-2/3, increases the heat load by less than-10 percent, the design para-meters of'the spent fuel pool. cooling system were not required to be changed.as.a result of the high density storage. For the highest " normal" heat-load conditions, (4-2/3 nomal smi-annual refueling batches in the

- soent fuel pool, with the last batch placed in the pool 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> after.

reactor.shutddwn) two. trains of the spent fuel pool cooling system in opera-tinn will maintain ~ ocoliwater temperature below 125'F. With one

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train operating, the scent fuel nool cooling system will maintain pool water w,.

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temperature below:163*F.for the highest nomal storage conditions. This

_ temperature -is acceptable for these conditions.

For the highest "abnonnal"

, storage conditions (4-2/3 cores ~ of nonnal semi-annual r'efueling batches, plus one full. core ' unload placed in the pool 96 hours0.00111 days <br />0.0267 hours <br />1.587302e-4 weeks <br />3.6528e-5 months <br /> after reactor shutdown) the

. decay heat removal. system of the affected' unit can be used to supplement the spent fuel pool cooling system to maintain pool water temperature below 125'F.

The decay heat removal system will only be used to supplement the spent fuel pool' cooling system when a full core unload is necessary. The ability to remove decay heat with redundant components as described above meets the requirements of General Design Criteria 44 and 61 as they relate to the removal of decay heat' assuming a single active failure. The system meets =

the isolation requirements of General Design Criterion 44 by using seismic Category I isolation valves to separate non-safety related systens, such as the non-seismic purification portion of the system, from the safety relate'd portions.

By-providing. adequate accessibility to' conduct the required examinations in accordance with the ASME Code,Section XI, the safety related portions

'of the system can be periodically inspected as required by General D sign-e Criterion 45 " Inspection of Cooling Water System." Since the system is continuously operated, the requirements of General Design Criterion 46 " Test-ing of.Coolfr.; Water System" are met with regards to structural and leaktight-

- integrity and the operability o' the active comoonents in the system.

. The system is'. housed inLa cortion cf the seismic Category I' auxiliary build-

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ing.which is tornado missile croof aid flood croteted, therefore the fuel p

ocol cooling and curification syster is protected against natural 3 phenchena 1

in accordance with General Design Criterion.2 Sesign Basis 'for protection Againstnatural;ohenomena'."

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Based on our review as described above, we find that the spent fuel pool cooling and purification is in conformance with Branch Technical Position

. ASB 9.2 with respect to decay, heat. loads, is designed in accordance with Regulatory Guides 1.13 and 1.29, and meets the raquirements of General Design Criteria 2,-5, 44, 45, 46, 61 and 62. We, therefore, conclude' that the spent fuel. pool ' cooling and purification system is acceptable.

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9.1.4 Fuel Handling System (In Amendment 15, the applicant proposed to provide a single failure proof auxiliary building cask handling crane. The crane design has recently been

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submitted as a Topical Report and is under review. The applicant will also-provide further details of how portions of the systent not included in the Topical Report meet the guidelines of Regulatory Guide 1.104 " Overhead Handling i

Systems for Nuclear Power Plants." We will provide our evaluation after the review is completed.]

9.2 Water Systems j

9.2.1 Service Water Syst m l

The service water system (SWS) supplies auxiliary cooling water for essen-l l

tial-as weil at en-essential components throughout the plant. The SWS is L

shared between Units 1 & 2 and consists of five 100 percent capacity pumps connected to a header which is sectionalized into the A and B trains for each L

unit. One of the pumps is an installed spare that can be manually connected to i

ei ther' train. Train A suoplies half the safety related loads of each unit, while i

train 3 supplies the other half. Each train is powered from the Class lE cower system as recommended by Regulatory Guide 1.29. One of the two pumps fin each train.is 'nomally ocerated with the other cump in-automatic standby.

The standby cumo:will start upon loss of the operating pumo or an engi.neered

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safety features actuation signal. Ne single active failure will result in loss of cooling water to more than one safety:related component of one unit.

Since there is redundancy of all safety related components that are cooled by the SWS and a failure will not preclude safe shutdown of either unit, the sys-tem design meets General Design Criterion 5 with' regards' to sharing of safety related systems, which requires that the sharing shall not significantly impair their ability. to cerform their safety functions. Within the pump house struc-ture, the train A pumps of both units are located 'in one compartment and train

.B pumps of both units are located in a second compartment, and the installed spare pump is located within a third compartment. By this method of separa-tion.and compartmentalization, including the pumphouse structure designed to protect the pumps from tornado missiles, the requirements of GDC 4 " Environ-mental.and Missile Design Bases" are met with regards to protection against missiles.

In accordance with the guidelines of Regulatory Guides 1.26 "Qua*ity Group Classification" and 1.29 " Seismic Design Classification," the safety related portions of the system.are designed to Quality Group C, seismic Category I requirements. Portions of the system that supply cooling water to non-safety related systems.and components, such as to the turbine-building, are auto-matically isolated from the safety related portion of the system by seismic Category I. isolation valves-following an engineered safety features actua-

- tion signal. (ESFAS). Upon loss of oower all isolation valves fail in the safe position they would assume following an ESFAS. A single active failure of:

any cne isolation valve or SWS'oumo with or without offsite power will not affect the ability of the ' system to perfom its safety function because only one' redundant train could be affected. By oroviding the isolat1on cacabilities and redundancy. in conoonents described above, the recuirements of GCC 3

- Cooling Water" are net, including the single active 'ailure criterion.

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. Safety related heat loads that are served by the SWS, in accordance with L

GDC 44, with regards to heat transfer during normal and accident conditions-are: the containment recirculation air cooling units, emergency diesel generators,. component cooling water system, and the essential chilled water system. The SWS also serves as an automatic seismic Category I supply of water to the auxiliary feedwater system during accident conditions if the non-l seismic condensate storage tank is not available. Another safety related l

function of the service water system is to provide an alternate seismic-

- Category I supply of makeup water to the spent fuel pool.

The safety related pumps, valves, heat exchangers and piping of the system, _

to the extent practicable, are designed and located to f'acilitate periodic j

inspection as required by GDC 45 " Inspection of Cooling Water System." This is accomplished by providing adequate accessibility to conduct the required

' examinations in acccrdance with the ASME Code,Section XI.

l To meet the requirements of GDC 46, " Testing of Cooling Water System" the service water system is designed to include tne capability for testing l

- through the full operational sequences that brings the system into ope *ation l

l for. reactor shutdown and for loss-of-coolant accidents, including operation i

L of applicable portions of the protection system and the transfer between normal and emergency power sources. These tests have been included in the l

surveillance' requirements of the plant Technical Specifications.

The service water sys' tem heat load is normally rejected to the plant cooling pond which incorporates the seismic Category I emergency cociing pond as described'in Section 9.2.5 of this report. A design basis for the emergency cooling po'nd is not to exceed 96*F as an initial temperature for accident Lconditions. There are periods when the service water system heat load could not' be dissicated by the plant cooling pond without the pond exceeding 96*F, e

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'such as' during the mid-sumer months. During these periods the service water.

system heat loads will.be rejected to the atmosphere by non-safety related mechanical draft cooling towers and the plant cooling pond is isolated. For this latter mode of operation the SWS. supply and return automatically shif ts to the emergency ~ cooling pond in.the event of an engineered safety features

-(ESF) signal. We requested the applicant to verify no service water pump damage would occur and safe shutdown would not be precluded ~in event the macnanical-draft cooling towers were lost without the presence of an ESF signal.

As a result. in Amendment 8, the applicant provided safety grade low water level detecto'rs in the pump pit to automatically shift the water supply to the cooling pond, thereby, assuring a cooling water source for all postulated conditions.

The essential portion of the service water system meet the requirements of GDC 2 " Design Basis for Protection Against Natural Phenomena" since they

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are housed 'in seismic Category I, tornado missile protected structures, and all. components that could be affected by flooding are adequately protected

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against the probable maximum flood at discussed is Section 3.4 of this report.

Based on our review as described above, we find that the-service water sys-tem meets the guidelines of Regulatory Guides 1.26 and 1.29, and the require-ments of General Design' Criteria 2,' 4, 5, 44, 45 and 46. We, therefore, conclude that the servic'e water systen.is acceptable.

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9.2.2 Comoonent Cooling Water System The comoonent cooling _ water system (CCMS) provides an intennediate closed cooling loop for removing heat from reactor plant auxiliary systems'and

' transferring it to the service water system. Each unit has its own CCW

. system consisting of.two. independent.100 percent capacity closed loop flow

. paths.each supplied by one'CCW pump for safety related systems, and a L.

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comon ' supply to nonessential systems. This evaluation is applicable to the component cooling water system for either unit. Either of!the two redundant flow paths will meet the minimum engineered safety feature flow requirements during a design basis accident (DBA). A fifth full capacity CCW pump is provided and may be manually aligned to either of the independent loops for either unit by use of a normally isolated cross-connect between the two units' systems, should one of the pumps fail. These provisions assure adequate water supply and heat removal in the event of a single failure of a system corponent in accordance with General Design Criterion 44 " Cooling Water."

Essential portions of the CCW system are designed to Quality Group C, seismic Category I requirements as recommended by Regulatory Guides 1.26 " Quality Group Classification" and 1.29 " Seismic Design Classification" and are pro-tected against adverse environmental occurrences, such as tornaC es and floods by locating the system within the seismic C;tegory I auxiliary and reactor l

buildings, thereby meeting the requirements of General Design Criterion 2

" Design Basis for Protection Against Natural Phenomena."

The component cooling water system uses ' separation and compartmentaliza-tion, and is housed within the tornado missile proof auxiliary building to meet the requirements of. General Design Criterion 4 " Environmental and Missile Design Basis" regrMing dynamic effects associated with pipe whip, jet impingement and missiles. Each train is powered from a separate essential AC bus.

The'non-essential ~ ortions of the system are automatically o

isolated from the essential cortions of the system in the event of an engineered safety features (ESF) signal by seismic Category I isolation valves.

In the event of a single failure of an isolation valve, only one-

.of ne two 100 percent trains would :e affected.

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, applicant'provided at our request, automatic closure of the isolation in the event of a low surge tank level to protect both essential loops in the event'of a pipe break' or crack :in the common non-essential portion of

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the' system.' By oroviding the automatic isolation described above, the requirements of General Design Criterion 44, regarding isolution capability 4

and a single active failure are met.

t By.providing adequate accessibility to conduct the required examinations. in accordance with the ASME Code,Section XI the safety related pumps, valves..

heat exchangers and piping can be periodically inspected as required by General Desigri' Criterion 45 " Inspection of Cooling Water Systen."

To meet. the requirements of General-Design Criterion 46 " Testing of Cooling Water System," the CCW system is designed to include the capa-4 bility for testing through the full operational sequence that brings the system into operation for reactor shutdown and for loss-of-coolant acci-

. dents, including operation of applicable portions of the protection sys-4 tem and the transfer between-normal and emergency power sources. These tests are perfomed in accordance with the surveillance reautrements of

.the plant Technical Specifications.-

Based on our review as described above, we have determined tha.t the conoo-

- nent cooling waterisystem meets the~ guidelines.of. Regulatory ' Guide 1.25 Land 1.29, and the recuire ents of General; Design Criteria 2,- a, aa, 45 and-

25. We, 3here#: e, c:nclude 9at tne ::-cenen: cc 14ag water syste- e_

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design with the Regulatory Guides that were issued since the Construction As.a result of this spec al review, we provided a i

Permit was issued.

safety evaluation (March 2,1976) of the: ultimate heat sink with respect to Regulatory Guide 1.27.

During the review, we requested the appli-cant to-provide a heat removal transient analysis to demonstrate the UHS has' the capability to provide-adequate water inventory (30 day) supply and prcvide sufficient heat dissipation to keep SWS temperature within acceptable design limits in accordance with the guidelines of Regulatory' Guide 1.27. The analysis provided-by the applicant was not complete because actual station auxiliary heat loads were not available, and the applicant used a-:onservative safety marg n i

instead of the actual heat loads. That analysis showed that the maximum heat sink temperatures attained would be 3.5'F above the service water l.

~ system design temperature. We, therefore, concluded in our safety: evaluation-that during the OL review, we would require the applicant to demonstrate that all safety related equipment whose design temperature is exceeded would be able to function for as long as the emergency lasted, or we would require

.the plant Technical Specifications to include a power level lin tt to conform with position C.4 of Regulatory Guide 1.27, when the 'JH5 reached a cra-determi.ced tem erature.

TheEapplicant's final transient heat re.-oval analysis based en actual loads ar. lus'ag ).*, Tetneds set forth in our 3rasch tennicai : s'-ion ASB i-:

^ ;'ing" "Ces'fual. ~dcay Heat Energy. for Light Water.3.ea-Ors #0 c. rg Te r?

showed that the' actual design. temperature of.the service water systen may

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'. cance of such a small excess--temperature, we conclude that the. UHS meets position C.4 of Regulatory Guide 1.27'and no change in plant Technical Specifications 'is necessary.

In accordance with the guidelines of Regulatory Guide 1.27, the anplicant has'shown by analysis.that the UHS is capable of providing,' without makeuo, susficient cooling for at -least 30 days folicwing an accident in one unit and safe shutdown ~ and cooldown of the other unit. We have

.. reviewed the applicant's analysis 'and conclude his methods of analysis are acceptable and concur with his ' conclusions.

Based on our review described above, we have determined that the ultimate heat sink meets the guidel nes of Regulatory Guide.l.27 and our Branch

' Technical. Position ASB 9-2, and meets the requirements' of General Design Criteria 2, 4 and 5.

We, therefore, conclude that the ultimate heat sink

'is. acceptable.

L' 9.2.6 Condensate Storace Facilities The condensate storage facilities consist of two 300,000 gallon storage.

' tanks, ow;er unit, each.of which has one transfer oumo and one transfer jockey oumo. 145,000 gallons of each -tank is reserved for auxiliary feedwater supply, which is sufficient for maintaining the olant in hot shut-down.for 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> followed by a 6 hour6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> reactorf cooldown.

The condensate storage; facilities are not safety related -and are not-designed to seismic Catecory I recuirements and are not protected against tcenade missiles. The acclicant croposed to tarual'y' transfer :ne auxii1ary #eecwater s0::aly #rcr :ne ::ncensate

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e, storage tal.k to the service water system in~the event of failure ~of the condensate storage tank. At'our request, in Amendment 16.-

the-applicant provided an automatic switchover of the auxiliary feed-water from the condensate storage tank to the service water system (See Section -10.4.9 of this Report for an evaluation of the automatic switchover).

As a result of our review, we conclude that with the automatic switch-over to a: safety grade auxiliary feedwater suoply, the condensate

- storage facilities are. not safety related, and that fa'ilure of the sys-tem will not result in damage-to safety related equipment nor will it prevent safe plant-shutdown. We, therefore, conclude the condensate storage facilities are acceptable.

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9.3.1

. Comoressed Air Svstem' The compressed air system is shared.between the two units providing both instrument and service air from three air compressor trains, each including a compressor unit, intercooler, aftercooler and air receiver. The instru-ment air passes through a drying / filtering train while the service air goes directly to distribution.

' The-function of the compressed air system-is-not safety related; However,

- the pioing and valves Lat containment penetrations are designed to Quality l

Group'B, seismic Category I reouirements in accordance with Regulatory

- Guide 1.26 " Quality Group Classific'ation" and 1.29 " Seismic Design Classi-

- fication." All air operated valves.in safety related: systems are designed

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- to fail. in the safe position uoan loss of air. We have reviewed the

'a::li. cant's list of safety related air c:erated valves and the clant

- ?&ID's anc= conclude tna: :ne failure moces of these' valves are acceptacle.

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- and. valves at containment penetrations meet the guidelines of Regulatory Guides 1.26 and -1.29 as ' described above. and that failure 'of the compressed t air system ' willi not prevent safe plant t.hutdown. We, therefore, conclude

-that.the compressed air system.is acceptaole.

l

9. 3.3 '

Ecutoment and Floor Drainage System The eg'uipment and. floor drainege system (EFDS) accommodates drains;from potentially radioactive sources as well as non-potentially. radioactive sources.

The. system is designed to prevent potentially radioactive licuid wastes from draining to nonradioactive areas. This is accomolished by using separate drain systems for potentially radioactive and nonradioactive areas.

l The potentially radioactive waste system collects liquid waste,. including waste.resulting from oiping or' tank ruptures, from the containment, auxiliary building, and fuel storage areas and transfers the waste,;

deoending on -the source, to the licuid waste system drain tank, chemical waste receiver tanks, laundry drain tanks, or to the boron recovery sys-tem. The radioactive licuid waste system is further discussed in Section 11 of this report.. 0 rains from non-potentially radioactive sources, such as the turbine' buildino an.' Drocessisteam evaporator building are conveyed to sumjs and then oumoed to the' oil.uaste basin. The flocr drainage system fror" the ESF equioment rooms are provided with remotely coerated isola-tion valves which are located 'outside the area they serve. These isola-tion l valves 'are normally ; shut to prevent flooding of the ESF eouipment roomsidue to backflow through the ecuipment and floor drainage system.

Each ESF ecutoment room is' orovided with high water levelf detectors which l alar-in the control. room. 4cdiMonal ficcc crotecPon 'is: orovicec 'cr -

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. The _ equipment and floor drainage' system is-classified as non-safetyL relatied. However,.the piping and valv'es at containment-penetrations 'are designed to_ Quality Group B,-seismic Category I requirements in accordance-with Regulatory Guides 1.26 " Quality Group Classification" and 1.29.

" Seismic Design Classification."'

Based on our ~ review, we conclude that the equipment and floor drainage system is sufficient to protect safety related-areas and. components from

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flooding and to' prevent the inadvertent release of radioactive liquids

. to the: environs, meets the guidelines of Regulatory Guides 1.26.and 1.29 L

. as' described above, and that the system's failure will not prevent safe -

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. plant. shutdown ~. We, therefore, conclude that the system is acceptable.

9.3.4 Chemical and Volume Control' System.

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The chemical and volume. control ' system consists of the makeup and curi-

- fication (MVP) system,. chemical addition system,'and the boron recovery system (BRS). These systems are used to control and maintain reactor.

-coolant in'ventory Lto control the baron concentration in the reactor

- coolant through the' process of makeup and letdown; supply seal. injection to the reactor, coolant oumps; and to purify: the primary coolant by deminerali-

' zation.

-[We requested the applicant to demonstrate that a single active failure following.ailoss of offsite power will not result in reactor coolant-pump (RCP) seal' damage.

In Amendment.16, the apolicant committed to

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provide..an analysis of this event to determine the effects on the RCP seal integrity. The Midland plant is currently being reviewed for cold ~

shutdown capability using only safet.v grade equipment in accordance with Branch Technical-Position RSB 5-1. ' Refer to Section 5.4 of-this report for an ' evaluation of the CVCS system in this' regard. We will complete our evaluation of -the CVCS following our review of the applicant's analysis.1

' 9.4 -

Air Conditioning,' Heating, Cooling and Ventilation Systems 9.4.1

. Control' Room Area Ventilation System-There is-one connon control-room for Units 1 and 2.

The safety related por-tions of the control room area ventilation systen (CRAVS) consists of' the control room heating, ventilating, and air conditioning (HVAC) system;-

the switchgear and battery room HVAC system; and the control room-pressuri-p zation system. All of these systems are designed to seismic Category I requirements and, therefore, meet the guidelines of Regulatory Guide 1.29-

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" Seismic Design Classification."'

The CRAVS includes two supply / recirculation air handling unf ts, two recir-culation air filtration' trains, two makeup air filtration trains, four -

switchgear room' unit. coolers, four battery room. exhaust fans and unit coolers, and two pressurization tanks. Each of these comoonents has 100 percent ventilation capacity-for the areas they serve, tnereby meeting the single failure ~ criterion.

Jhara is a sinale common control room for the two Midland units. The control room HVAC system meets the requirements of General Design Criterion 5 "Sharing of Structures,= Systems. and Comoonents"- because a. single active:

failure will.2not imoair 'the system's safety function as-all safety related u

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componer.ts are' 100 percent-redundant. The switchgear and battery rooms -

emergency HVAC systems are lnot shared between units, since each individual

room has.its.own 100 percent capacity emergency cooling unit, and the battery rooms each have their own 100 percent capacity emergency exhaust '

cfan. j0uring normal operation the emergency HVAC systems for the battery rooms 'and switchgear rooms are not operating,'and the rooms are ventilated by the control room HVAC system.

During normal operation, one of the two ' air handling units operates to

. supply air of controlled temperature and humidity to the control-room, the cable spreading rooms, the switchgear rooms and the battery rooms..During accident conditions the individual cooling units for the switchgear rooms and battery rooms are automatically started to maintain these rooms within the design temperature limits for their respective eouipment. D'uring

. emergencies: the air.' handling units serve only-the control. room. The air handling units are1 designed to maintain the control: room within.the environ--

mental limits. required for operation of plant.ontrols and uninterrupted

- safe occupancy during all operational modes, including design basis acci-

- dent conditions as. required by General Design Criterion 19'" Control Roon."

This is accomplished.by isolating.the control room from the"outside and other plant areas and starting the recirculation air filtration trains.

The control room pressurization system is automatically initiated, following

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~ accidents, using pressurized air tanks'to pressurize the control.

room to prevent infiltration of radioactive gases, hazardous chemicals, oossible steam from a steam line break,Jor. smoke. The cressurization sys-teninas' sufficient'cacacity to maintain 1/S" 9.g. in the control room for a ceriod. of 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. The cressurization system is designed witn suffi-cient redundancy to perforn its safety funct.1on-folicwing any. single active es-

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failure. The: habitability of-the control room following accidents is evaluated'in Section 6.4 of this report.

.To meet the requirements of General Design Criteria 2 " Design Basis for Protection Against Natural Phenomena" and 4 " Environmental and Missile Cesign Basis," regarding natural phenomena and external missile protec-tion, the CRAVS outside air intakes are tornado missile protected and the rest of the system is located within the tornado proof, seismic Category I, flood protected auxiliary building. The CRAVS exhaust stack is also designed to. seismic Category I requirements and to withstand tornado missiles without loss of function. The system design meets requirements of General Design Criterion 4 regarding orotection against pipe whip and

' et. impingement and. internally generated missiles as evaluated in Sections j

3.6 and 3.5 of this report.

At our. request, -in Amendment 8, the applicant provided a -battery room exhaust system designed:to limit the concentration of hydrogen to below

'2 volume percent and to alarm in-the control room when battery room 'ven-tilation is lost. Hydrogen monitors are also provided'and will alarm in the control rvom if the battery room hydrogen concentration reaches 3 -

volume percent.

' Based on our review as described above.we have determined that the con-trol room area ' ventilation system meets the guidelines of Regulatory -

Ghidel1.29,~ and the requirements of General Design Criteria 2, 4, 5 and Criterion 19 as1 t' relates to'providing adequate protection to permit 1

access and occupancy of-the control room under accident conditions. We, therefore, conclude that the system design is acceptable.

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Spent Fuel Pool Area Ventilation System -

. The function ~of the. spent fuel pool -area ventilation system.'(SFPAVS) l

-13? to maintain a suitable' environment for equipment operation and to limit _ potential-radioactive release to the atmosphere during nonnal opera--

tion and postulated fuel handling accidents.

-.During normal operations _ the spent fuel.-storage area:is served by two inon-safety related, 50 percent capacity trains, and four unit coolers which I'

-maintain:a controlled environment suitable for oersonnel access and equip-j.

- ment operation.-- The system also filters the' air before discharging to the i

auxiliary building _ exhaust' stack. During emergenci.es, such as a fuel L

. handling accident that may result in high radioactive releases, redundant radia.

tion' detectors-in the.axhaust duct isoltta the normal ventilation system and automatically starts. a safety related standby exhaust. system. The standby exhaust system consists of two 1.00 percent capacity trains, each having an iir filtration-unit which meets Regulatory Guide 1.52.and an.

exhaust fan.. The standby exhaust system and redundant isolation valves from the normal _. ventilation system are designed to seismic Category I

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requirements and powered from. the Class lE power system as recomended l'

by Regulatory Guide 'l.29 " Seismic Design Classification." The guidelines l

of Regulatory Guide 1.13 " Spent Fuel-Storage Facility Design Basis" are r% because the system has the capability.to limit radioactive releases Eto' acceptable levels during normal l operation and following fuel handling -

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accidents by virtue of air. filtration and' maintaining.a negative cressure in the ' area to '. limit.exfiltration.

The safety,reiated )ortions-of:the' system are in accordance with General Nsign Criteria'2 " Design Basis.for Protection-Against Natural Phenomena"'

and a " Environmental and. Missile Design Sa' sis" regarding crotection against n

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Based;on our review of the spent-fuel pool area ventilation system _ we have detennined that-safety: related portions of the system meet the guidelines of Regulatory Guides 1.13 and 1.29, and the' requirements of General Design

' Criteria 2. and 4.

We, therefore -conclude that the system is' acceptable.

9.4.3 Auxiliary and Radwaste Area Ventilation System.

.The auxiliary and radwaste area ventilation system (ARAVS) is oresently desioned; to perfonn no safety functions as the applicant contends that it is required only during nonnal operation. The ' safety related areas that are served by the ARAVS' durino nonnal operation each contain their own safety related coolina units which-are used during emergencies and are evaluated in-Section 9.4.5 of this -

report.

[Although the ARAVS is not necessary for ' safe plant shutdown, leakage from some ESF rooms du to pump seal failure.following. a loss-of-

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e coolant accident could result in untreated radioactive releases to= the' environs. We reouired the apolicant to provide a safety grade system

'for: preventing these radioactive releases. The doses due to these radio--

active releases are evaluated-in Section 15.2 of this report. We will provide.our evaluation of the auxiliary and radwaste area ventilation -

system following resolution of this item.)

1 9.4.51

. Engineered Safety Features Ventilation System

. The~ engineered safety features ventilation system (ESFVS) is designed.to.

' maintain a suitable enviroament dur.ing; emergencies for the ESF equioment i-located in' the areas of. tne auxiliary building wnicn.auring nonnal operation are ~serveo 'oy cne auxiliary and rauwaste area ventilation systen.

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1The s'ystem has individual unit coolers which have chilled water cooling coils that receive water from the (safety-related) safeguards chiEled water

. system.

All' components of the. system are designed to seismic Category I require-ments as recommended by Regulatory Guide 1.29 " Seismic Design Classifica-tion." Each ESF area has ~at least one individual cooler that is pcwered from the same emergency bus as the equipment that it serves. This meets the single failure criterion since each ESF area or equipment room has a 100 percent capacity redundant counterpart. The requirements of Gereral Design Criteria 2 " Design. Basis for Protection Against Natural Phenomena" and 4 " Environmental and Missile Design Basis" regarding protection against natural phenomena, missiles, pipe whip and jet impingement forces are< met by locating the equipment in separate areas or rooms of the tornado missile protected portion of. the seismic-Category I auxiliary building.

During nonnal plant operation, the-auxiliary and radwaste area ventilation system provides ventilation of the ESF areas which is evaluated in Section i!-

9.4.3 of this report. The ventilation is supplemented as necessary to control temperature by the unit coolers which are controlled thermostatically.

A unit cooler also automatically starts whenever the ESF pump in its area is-started. The unit coolers may also be started remotely from the control room.

Based on our review asL described above we have detarmined that the engineered' safety features ventilation system meets the guidelines of Regulatory Guide

. l.29 and the' requirements of General-Design Criteria 2 and 4 We, there-

- fore, conclude that tne system is acceptable.

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' Other Safety Related Ventilation Systems Other safety related ventilation. systems are the diesel generator build-t-

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.ing HVAC system-and the service water pump structure HVAC system. There

. are four. separate diesel generator buildings at the Midland site, each of

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f which has its own l'00 percent. capacity; HVAC. system.. Each diesel genera-tor building HVAC system.is-started automatically when:its respective diesel

. starts.and is powered from the same emergency bus as its associated diesel f

generator. The system functions automatically to maintain temperature in

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the diesel building below.120*F during diesel operation and above 50*Fl when the -diesel is idle. Since each diesel generator has its own HVAC sys-tem, the design meets the single failure criterion.

There is one' service water pump structure for both units housing 5' essential service water pumps within 3 rooms.

( 2-c-1 split - see =Section ~ 9.2.1) Each pumplin'each room has its own HVAC supply system such that a single failure will ~ affect only one pump. -Each system is ' automatically started whenever its respective service water pump is started, and temperature is automatically controlled by exhaust damper.

-modulation and recirculation. Each system is powered from the same emer-gency bus.as its respective service water pump. The system is designed to

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maintain a temperature within the structure suitable for pump operation.

Safety related portions of both the diesel' generator HVAC system and the service water pump structure HVAC system are designed-to seism'ic Category i.

I~ requirements 'as recomended:by Regulatory Guide 1.29 " Seismic Design

.' Classification."" Both systems are also protected against tornado missiles, Thoused.in' seismic Category I structures which are protected against the l-

- design basis flood, and are adequately protected against internal missiles and pipe lbre'ak in;accordance with General; Design Criteria 2 " Design Basis'

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i JBased:on 'our; review we'have determined that the diesel generator build -

o Lin'g;andiservice water,'pumpistructure HVAC systems meet out single failure j criterion,: the guidelines of Regulatory Guide 1.29 'and the recuirements

.of_ General: Design Criteria 2 and 4. -Re, therefore, conclude that the-systems are adceptable, t-

, 9.5.lL Fire Protection Sy' stem

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[At' our ; request, the ' applicant has.provided 'a detailed fire hazards

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analysis _ and 'a comparison of his plant-design to Appendix A of our i

-Branch Techn$ cal Position ASB 9.5-1 " Fire Protection for Nuclear. Power-Plants." We are currently reviewing: their submittal and will, provide-our, evaluation. in,a. future supplement.]

.-10. 3 -.

Steam and' Power Conversion Systems -

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Main Steam Supply System

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This.sectiontof the report evaluates the safety-related portion of the main team system (outs' de containment):which includes the_ portion 'of the; system i

s between the containment 'up 'to. and including the main ' steam Tisolation valves.

.(MSIVS). : Portionsfof the main steam system downstream of the MSIV's are-1 evaluatedihere_ only-as ~ they:may affect. the-safety related portions: of' the -

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system in, the event of 'a main steam line break.

. In:accordance'with - the guidelines 'of ~ Regulatory Guides 1.~ 26 " Quality

.l TGroup; Classification" and 1.29?" Seismic DesignfClassification", those ll r

l portions ofjthe main steam system: frome the. steam _ generators _ up.to and

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Each~ unit providei steam from two steam generators via two 36-inch steam

_. lines _to a high pressure turbine for electrical power generation. During normal operation, steam'is 'also delivered from the steam lines of Unit 1

. through two 26-inch lines to a ;36-inch header and to -the-process steam evaporators where it is used to generate tertiary steam that is supolied to Dow Chemical Co.

- The~ Midland main steam system is'a unique design having cross-connects 1 between the two units downstream of'tha MSIV's, since the first priority in steam demand is the supply to Dow Chemical rather than electrical power generation. ' Sections 10.3.1 through 10.3.3 of this report describe the 4

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operating modes of the main steam systems for supplying steam for Dow.

- Process flow diagrams, Figures 10.3-1 through 10.3-6 of this report, show the interties between units and the valve lineup for the 4 modes of opera-tior for the main steam and' feedwaternsystems.

~During operating Modes 1 and 2, Unit I will supply process steam 4

plus the' Unit I turbine generator.

If a main steam line break were to occur upstream of an MSIV in Unit I while it was operating in Mode 1 or 2, a blowdown path from the unaffected steam generator would be available through the process steam system to the evaporator system if the MSIV.of the unaffected-steam generator failed to close. The applicant claimed that

.their MSIV's were single failure proof since all active comoonents were

. redundant. - We did not agree with.the applicant that their MSIV's could not failit6 close and required-that they revise the design such that a failure

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of. an'MSIV to close would not result in a blowdown of both steam generators of

Unit 1.

In Amendment :15, the _apolicant revised the design to include main steam line break closure signals to the process steam-isolation valves

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Theseiclosure signals are :necessary to 'orotect the plant only if the break -

- c is upstream ~cf the MSIV's. 'de'do ~not'Dostulate such a break as a result of

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aiseismic event because.that portion of. the main steam system is designed

'to seismic. Category I' requirements. Therefore, dependence on non-safety gradeLisolation1 valves is acceptable to protect against a' break upstream -

of an MSIV together.with.an assumed failure of the safety grade MSIV'on -the unaffected-steam' generator.

. During operating Modes :3 and 4, the Unit 2 steam generators are'supolying

.These-mo' es. are -used less fre-process steam.to the evaporator. building.

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-q'uently,'when the Unit 1 ' reactor is unavailable. During these modes, pro.

tection.agaf ast a Unit 2 steam line break-upstremn of an MSIV coincident with' a. failure to close of. the unaffected Unit 2 steam generator's MSIV-is a

provided in.the same manner as; operating Modes 1 and 2 as discussed pre-

-viously. However,' the Unit 2. steam system does not have backup MSIV's-because they;are not required' by state codes-(see Section 10.3.3). -The

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required protection is provided by the main staam -intertie isolation valves which close upon receipt of a-main steam line break' signal. ' We find this acceptable on' the.same basis that we described for Modes 1 and 2.

During M]de 4 operation the main steamisystems of the two units are

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. shared,'with the'. Unit 2 steam generator supplying steam tt the Unit.1

.turbi.ne generator. The Unit 1 NSSS is shut down with two MSIV's in

series isolating the Un.it 1' steam generators fecm the rest of the -

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steam system:and the Unit 2 turbine is shut down.and isolated from the-main steam. system by the turbine stop and centrol-valves.

General Design Criterion 5 " Sharing offStructures,. Systems and Com-ponents", allows sharing if it 'is _ shown that such sharing will not significantly impair their safety functions. In the event of an accident in one unit, an orderly ~ shutdown and-cooldown of-the remaining:

units must not be precluded. When the~ main steam systems are being sharea, Unit 1 is already -shutdown.and cooled down.. Therefore, if the sharing does r.ot affect the ability to perform the system's.

. safety-function in-the event ~of an accident in Unit 2. the require-

^ ments of General _ Design Criterion.5 are met. nurino times when the lain. steam system is shared, the Unit.2 steam supply system uses only the non-

-safety related portion of; Unit-l's' main steam system, from the outboard MSIV to the turbine. This-portion of-.the main steam system does;not per-form a_ny safety function or generate ary signals to close the MSIV's

or the main steam-intertie isolation valves. The main-steam line break instrumentation of Unit'2.still senses only the Unit 2 parameters to provi.de protection against a steam-line break. Similarly, for 4

all-~other accidents, the Unit 2 protection system and input parameters.

[

are'usedTto provide protection for. the Unit 2 plant by closing -the

" Unit' 2'MSIV.'s. We,-therefore, conclude _that the' requirements of Criterion (5'are mat since the' abi.lity to protect against design basis

~

accidents.!s;not imcaired by the sharing.

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The MSIV's and main steam intertie isolation valves are designed.to' l

c ose in five seconds upon receipt of a main steam isolation valve closure signal. The valves.are designed to stop steam from either direction. Failure of one MSIV to close, coincident with a steam line break, will not result in the uncontrolled blowdNn of more than one steam generator. To summarize our previous evaluations of a steam line t.eak upstream of an MSIV ara.a f 3ilure of the other MSIV. to close blowdown of'the affected steam generator is prevented by the closure of the non-seismic Category I main steam intertie isolation valves, turbine stop

. valves,' turbine bypass valves, and for Unit 1, tre backup MSIV's whicP

-serve-as an acceptabie backup for this accident.

Seismic Category I' safety valves and power relief valves arE provided

-for 'each steam generator ininediately outside the containment structure -

upstream of the main steam. isolation valves. The power relief valves are air operated and fail in the clored position on loss of air supply.

4 The power relief valves are also equipped with hand wheels to facilitate manuel operation if required.

In accordance with Branch Technical Position RSF c.1

" Design Requiremerts of the Residual Heat Removal System," which re-quires safe cold shutdown capability following an earthquake using

only safety grade equipmert, we reouired that the applicant perfonn manual testing of the power relief. valves to demonstrate that a controlled cooldown can ~be accomplished.

[The apolicant has not-committed to der #orm cnis test.]

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--38 1The safety related portion of the main steam lines, including the MSIV's 'are located'above the auxiliary buildino roof. At our recuest in Amend--

ment 9,. the applicant provided barriers to ort,wct. the safety re'-

~

.-lat'ed portions of the main steam linesand MSIV's from tornado missiles.

With the: addition of the tornado missile barriers the safety related portions of the main steam system meet.the requirements of General

~

Design Criteria 2'" Design Basis for Protection Against Natural. Phenomena" and 4" Environmental and Missile Design Basisi' Section '3.6' of this report-

~

evaluates the main steam system design with respect to hioh enerov oice break protection.

Based on our review, as dercribed above, we find that the main' steam system (outside containment) up.to and including the MSIV's meets the-

. guidelines of Regulatory Guides 1.26 and 1.29 and the requirements of..

We.therefore conclude that the General Design Criteria 2, 4 ard 5.

main steam system, ~outside ccntainment, up to and including the MSIV's is acceptable.

10.a

0ther Features

of the Steam and Power Conversion

~

The other features tof the steam anc power conversien systems evaluated

. in thisrecort are the safety related portions of the main feedwater system,- the auxiliary feedwater system, and the circulating water system.

.le havealso reviewed the condensate system, non-safety related oortions of -the 'eedwater syste.., :ne ::c:M: : enc :::wc:we anc akeL: syster,

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condensate cleanup-system,-and the' steam generator. recirculation system.

^Theicondensate cleanup systen. includes (the condensate demineralizer, f

system and the Lfeedwater chemical addition system. 'The failure of

'these systems' would not prevent safe plant shutdown-nor result in:poten-tial radioactive releases.

.The acceptability of Lthese systems 'was based on our review which deter-mined that: (a)lwhere the system? interfaces or connects to a seismic-

- Category _I? system'or component normally closed or automatically l

l

. operated seismic Category I isolation valves are provided, and (b) the failure of'these' systems will not preclude the operation of -

~

safety-related. systems' or components located-in-close prcximity.

We, find.that the design of the condensate system, nonisafety related L

portions of the feedwater system, cooling _ pond blowdown and makeup L

Tsystem'. condensate cleanup system and the steam generator recircula-l-

l~

tion system._ meet the above criteria, and, therefore, they are l

acceptable.

l 10.4.5. ' Circulatina Water System The circulating water system-is designed to renove the heat rejected from the. main condensers via the cooling pond. The circulating water system lis-not. required 1to maint'ain the reactor in a safe shutdown cona -

tion or mitigate'the. consequences of' accidents. However, it is the -liegest'

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At our request, in Amendment 3, the applicant provided an analysis.

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-of the effects of a complete rupture of 'the circulating water expan-Esion. joint at-the main' condenser. The analysis showed that the

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water' level'in the turbine building would rise at a rate of 1.05 feet per minute. ' Two level alarms provide indication in the contrcl room.

In~ the event of no operator. action the turbine building' could fill to grade-level.

. Flow paths to the outside.would limit the flooding to that level. Flooding ~ of the. turbine building to grade. level-as

-a result of the probable o maximum flood has -been evaluated and 'ound

- acceptable'in Section 3.4 cf this report. Since a failure 'of the cir-culating water. system'cannot result in more severe flooding than the design basis flood, we find the analysis acceptable.

Based on our review, we find that a failure of-the circulating water

. system will. not damage any safety related equipment or prevent safe plant shutdown. -We, therefore, conclude' that the circulating water l

l-system is acceptable.

10.4.7.

Main Feedwater System l

-The safety. related portions of the main feedwater system consist of a -

main feedwater isolation-valve outside containment and.a second main.

'feedwater. isolation valve inside containment, and the interconnecting

. piping up to the: steam generator.

Separate connections to the steam '

. generators are provided for' auxiliary; feedwater injection (Section 10.4.9 of this report).

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. The safety related portions of. the main feedwater system.from the steam:

. generator out to and including the outemost containment isolation valve are' designed.to Quality Group B, seismic Category I requirements in accordance witn Regulatory Guides 1.26 " Quality Group Classification" and 1.29 " Seismic. Design Classification."

All safety related portions of the main feedwater system are housed within the tornado missile proof auxiliary building and are therefore protected against ' natural phenomena in accordan'ce with General Design Criterion 2 " Design Basis for Protection Against Natural Phenomena."

The requirements of General Design. Criterion 4 " Environmental and Missile

- Design Basis" regarding missiles, pipe whio and jet imoingement are met l

as evaluated in Sections 3.5 'and 3.6 of this report.

i There' are certain modes of operation, described in Section 10.3.3. of this -

- report, which are unique to the Midland plant due to process steam demand to Dow Chemical. During one of these' modes the feedwater-systems are shared between - uni ts. Specifically, by manual ~ cross connection, steam from the Unit.2 steam generators may be routed to the Unit 1 turbine, and via part'of the Unit 1 feedwater system the condensate -is : returned to the Unit 2 steam generator. During this mode of. operation, General Design Criterion - 5 " Sharing of Structures,-. Systems and Components" allcws sharing if it is shown that;such : haring will not significantly impair the systems safety func-tions.

In -the event'of an accident in one unit, an ord rly shutdown and cool-down. of the remaining units must not b'e precluded. Because Unit 1 is already

shutdown' an'd cooled'down when this mode of operation is used, i_f the sharing does not af#ect the-ability of:the system to perfom its safety function, nen l:

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General Design-Criterion 5_is met. The Unit 2 main ~ feedwater system uses only-the non-safety 'related portion of Unit l's' feedwater system which performs'no safety function and does not generate any-protection signals toclose the main feedwater isolation valves. The safety related 70rtions of Unit'2's main feedwater system ~still serve Unit 2 and the isolation valves receive ESF signals from the Unit 2 detectors and protection cir-cuitry. The safety related portions of Unit.l's main feedwater system

~

are isolated.and not shared. We, therefore, conclude that the require-ments of GeneralDDesign Criterion 5 'regarding sharing of safety related

- systems -and components are met.

There are: two safety grade main feedwater isolation valves on each feed-water line which receive a signal to close in the event of a main steam or feedwater line break;. therefore, a single failure will not result in continued-feedwater supply 'to the affected steam generator. The

'feedwater system design, therefore, is not subject to the concern of generic Task A-22, "PWR Steam Line Break, Cora, Reactor Vessel and Con-

~

tainment Building Response," b%ause reliance is not placed on non-safety

- grade.feedwater system valves to mitigate the consequences. of 'a main

- steam' or 'feedwater line break.

~ A gen'eric concern-of. pressurized water reactors is feedwater hammer in the. feed--

liner;to the steam Jenerators.

Feedwater hammer may occur in PWR's witn a feed-

ring-in the steam generator when the feedring is drained and cold water is in-

' jected causing the stear. in tne feedring and feedwater if ne to c:ncense rapidly _

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Based on ouri review of th; main feedwater system, we find that the sys-tem's' design is-in accordance. with the guidelines of Regulatory Guides 1.26 and,1.29 and the requirements of General Design Criteria 2, 4 and 5.

We, therefore, conclude that the system is acceptable.

10.4.9 Auxiliary Feedwater System

- The auxiliary.feedwater (AFW) system is an engineered safety feature-i desianed to sucolv feedwater tn the staam nanavatnre during nor-mal operations, including startup, shutdown and hot standby, and'in the event of loss of main feedwater supply. The system provides feedwater for the removal nf. deca" heat from the reactor until the reactor coolant sys-tem decreases to a temperature (280*F tar Midland) wnere-tne cecay neot

~

• emoval systen may be placed'in operation.

The auxiliary feedwater. system consists of two 100 cercent-capacity pumps for_ each' unit, one turbine driven and one motor driven.

In response to our request, in Amendments-3 and S the aopiicant orovided design details i

1 o_ verify ~ diversity?in power supplies to each of the AFW systems in t

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accordance with' our Branch-Technical Position ASB 10-1 " Design Guide-lines for. Auxiliary Feedwater System Pump Drive and Power Supply Diver-sity for Pressurized Water Reactors." The turbine-driven pump-is avail -

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- able -to supply auxiliary feedwater independently of onsite or offsite AC power. Steam to.the turbine driven pump is taken from each of the steam l

generators via DC motor operated valves. There are two auxiliary feed-water isolation valves' arranged in parallel isolating the AFW discharge

- header from each steam generator, one' valve is AC operated, the other ir~

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DC operated. The flow control valves.and the header valves

- which crossconnect the discharge from the two pumos are motor operated and l

fail in the nonnal " throttled ooen" position on loss of power. The above diversity in power to pumps and valves assure an available source of auxiliary feedwater supply in the event of loss of all AC or DC power.

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The AFW system is nonnally lined uo' to take suction from the non-seismic condensate storage tank. In the event of an accident, this design' could letd to AFW pump damage due to low suction pressure in the event the non-safety grade storage tank were lost and the AFW pumps started. At our request, in Amendment 16, the applicant provided an automatic sther :nar manual.switchover of tne AFW pump sucticn to cath t v As of tne safety crode l.-

service wate-system. These motor operated valves are powered from the l

-same emergency bus as the SW pumps to which they are connected, thereby meeting the single failure criterion. The valves need not neet our power--diversity requirements ~because the condensate storage tank will

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. still be available following ~a complete loss of. AC or DC power. Since the condensate: storage tank'is 1

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also not tornado' missile protected, the automatic switchover is also necessary to assure.an automatic source of 'AFW in the event of a tornado. The AFW system is.

' designed to Quality Group C and seismic Category I requirements, in accordance with the. guidelines of. Regulatory Guides 1.26 " Quality Group Classification" and 1.29 " Seismic Design Classification."' With the addition of the automatic switch-over. to the. tornado protected, seismic Category I service water system, the system also meets the requirements of General Design Criterion-2 "Design-Basis.for Protection Against Natural Phenomena." The power diversity of the AFW system as described above, provides suitable redundancy.of comoo-nents and features to assure'the' system will be available for decay heat removal assuming offsite, or onsite power is not available, as required by General Design Criterion 34 " Residual Heat Removal."

The arf system consists of two 100 percent pumps. In Amendment 8 the applicant 'at our' request provided a failure analysis-to show how the system design meets our requirements regarding a high energy pipe break.

in the AFW system coincident with a single ~ active failure. During normal operation when the AFW pumos are not operating, the system is pressurized between the steam generators and the. upstream check valves (two. in series), with normally~ closed isolation valves _ acting as a backup to the check valves. A break in this portion of the AR4 piping could result in turbine trio and loss of offsite power, and an AFW start signal.

5%ce both AFW pumos are nomally lined up in parallel, both AFW pumps could lose water through the pipe break and AFW flow to the unaffected' steam generator could be reduced. The' AFW ' system is therefore provided with automatic interlocks m,

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Q g.1 (F0GGisystem - Feed Only Good Generator) to sense the faulted steam' genera-tor.and' isolate.it from the AFW system, such that the remaining AFW pump 2

will feed.only the intact-steam generator. -The FOGG system is powered from redundant: Class lE busses 'and'need not meet 'our power diversity reouirements because.we do 'not postulate a ' complete-loss of-AC.or DC power following a

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pipe break. The design features described above meet ou-criteria regarding

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high energy line break in the AFW system coincident with single. failure during nomal operation when the AFW pumps are secured. During periods when the AFW system is in operation such as startup and shutdown, the motor driven pump supplies both steam generators, and the entire AFW system -is pressurized.

~

Operation of the turbine driven. pump during normal operation is orecluded by:-

plant Technical Specifications so that a pipe break in the steam header tc the turbine,' downstream'of the isolation valves need'not be oostulated. During these. periods, a pipe break could occur in the discharge piping of.the operating AFW pump, and a coincident single active failure of the turbine -

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. driven.pumo could result in no-AFW flow. Since the tuttine generator is not on the line during this period, no electrical transients will-occur as a

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. result of the break, and therefore loss of offsite power need not be assumed.

Two check valves :in ' series prevent blowdown of either steam generator due 4

i to this ' event. -We. agree..with the~ results of the applicant's failure mode

analysis and concluoe that the AFW system design meets our Branch' Technical Position APCSB 3-1

" Protection Against Postulated Piping Failures in Fluid '

.Sys. tem Components Outside Containment" regarding high energy line break in the' AFW system coincident with single active failure.

4 Dufing our review weLalso requested the apolicant to demonstrate a single

activel failure ~ could n.otL prevent feeding the 'unaffec' 2a steam generator s

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.following a mainsteam or feedwater line break.

It was our concern that

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an electricalcfailure that caused the motor operated level control valve s

to the unaffected steam-generator, to close would result in no )M94 flow to that generator.

In Amendment' 14. -the applicant provided revised control system drawings for the level control valve to show redundant contacts and circuitry in.theLcontroller to show-that no single electri-cal fault could cause the motor operated valve to close. This design.has been. reviewed and accepted as evaluated-in Section 8.3 of this report.

With these design features the AFW system meets the requirements of our-Branch Technical' Position ASB_3-1 regarding high energy line break in

- the. main steam or feedwater system. coincident with single active failure in the AFW-system.

The AFW system design meets the requirements of General Design Criterion-4 " Environmental-and Missile Design Basis" regarding protection against missiles', pipe whip'and jet impingement since each train is located in

- seoarate compartments of the auxiliary building. Protection against high energy line breaks is evaluatec in section'J.6 of this report.

- As a result of the new Branch Technical Position RSB S-1 " Design Require-ments of the Residual Heat Removal System", the. Staff is currently review-l ing the overall Midland clant' design with rescect to. bringing the plant to

a. safe-cold snutdown with ~ and without offsite cower using only. safety grade-ecuinhent and assuming any single failure. Refer to Section 5.4 of this SER.for an evaiaution of tnis'ascect of the Midland design.

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As -'a' result of our review as discussed'above we have determined that.

~the AP4 system meets-the guidelines -of Regulatory Guide l.26 and--

.~1 29 the reauirements of General Design Criteria 2, 4, and 34 and the

-: requirements of Branch Technical: Positions-3-1 and 10-1. We, therefore, conclude-that-the AFW system is acceptable.-

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