ML20249C450
| ML20249C450 | |
| Person / Time | |
|---|---|
| Site: | Prairie Island  |
| Issue date: | 06/22/1998 |
| From: | Richard Anderson NORTHERN STATES POWER CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9806300008 | |
| Download: ML20249C450 (18) | |
Text
..
Northern states Power Company 414 Nicoller Mall Minneapolis, MN 55401 Telephone 612-330-5500 l
June 22,1998 l
10 CFR Pad 50 Section 50.90 U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50-282 License Nos. DPR-42 50-306 DPR-60 l
Supplement 13 to License Amendment Request Dated January 29,1997 Amendment of Cooling Water System Emergency Intake Design Bases This letter is submitted to supplement the subject license amendment request pursuant to discussions with the NRC Staff. This license amendment request was submitted to address an unreviewed safety question relating to the Cooling Water System emergency intake line flow capacity. The original submittal dated January 29,1997 provided Updated Safety Analysis Report (USAR) pages marked up to
(
incorporate proposed changes to the licensing basis for the Prairie Island Operating I
Licenses. As the result of subsequent evaluations and ongoing discussions with the NRC Staff, the licensing basis changes and resultant USAR page changes have been modified.
O provides the marked up USAR pages incorporating the license basis changes which resolve the Cooling Water System unreviewed safety question.
. contains the revised USAR pages. These pages supercede, in their entirety, the USAR pages submitted with the original license amendment request.
These USAR changes will be incorporated into the USAR at the next USAR update, but no later than June 1,1999 as required by License Condition 3 assuming the 9806300008 980622 PDR ADOCK 05000282 P
-_.-._-_-.-A
USNRC 6/22/98 Page 2 of 3 NORTHERN STATES POWER COMPANY analyses submitted to date with these changes satisfy the requirements of License Condition 2.
included in.the USAR revisions proposed in this supplement are changes to the
. definition of Class l* Design Classification for structures, system and components
- (SSCs). Design classification specifically deals with the analysis, design, and/or l
testing to assure that SSCs are capable of performing their intended function under l
a set of operating and/or accident conditions defined by the acceptance criteria for l
that classification. The expanded definition for Class l* provided in the proposed USAR revision expresses more precisely the original intent of distinguishing safety related (Design Class l) SSCs from those that are not safety related but whose
failure" could adversely affect the intended functions of the safety related SSCs. By definition, Class l' items were and are treated as non-safety related in their design, l
l fabrication, and installation. However, they are differentiated from other non-safety related SSCs (Design Class 11, lil*, and 111) in that, in addition, they have to demonstrate their capability to resist Design Basis Earthquake (DBE) dynamic loading.
l This demonstration is fulfilled by analyzing or testing the SSC at the time of the i
original design, or subsequently to upgrade a lower classification SSC to Class l*
l designation to the DBE dynamic loading. The inherent characteristics of the original j
or upgraded Class l* SSC will not have changed provided the SSC is capable of -
resisting the DBE loading. In the Prairie Island licensing basis, only two classes of SSCs are required to be able to resist the dynamic loading of a DBE. They are Class I and Class l*. Thus, the expanded definition of Class 1* provides a basis for j
preserving the original definition and more accurately encompasses the original
' intent for this classification. The intake Canal embankment fits into the definition of Class l* since it has been seismically analyzed and continues to provide enough cooling water in the canal for the safeguards cooling water pumps to fulfill their intended safety function following a DBE.
l A revised Safety Evaluation, Significant Hazards Determination and Environmental
[
Assessment have not been submitted since these evaluations, as presented in the original January 29,1997 submittal and Supplement 5 dated March 11,1997, continue to bound the proposed license amendment as supplemented by this letter.
USNRC l
=
~
6/22/98 Pcg3 3 of 3 NORTHERN STATES POWER COMPANY If you have any questions related to this supplement to the subject license amendment request, please contact myself or Dale Vincent at G12-388-1121.
j:!
g[
v Roger O. Anderson
- Director,
. Nuclear Energy Engineering Attachments:
Affidavit, Marked up USAR pages, Revised USAR pages Cocies Regional Administrator - 111, NRC NRR Project Manager, NRC l
Senior Resident Inspector, NRC State of Minnesota Attn: Kris Sanda J E Silberg l
l 1
l l
c
1 UNITED STATES NUCLEAR REGULATORY COMMISSION NORTHERN STATES POWER COMPANY PRAIRIE ISLAND NUCLEAR GENERATING PLANT DOCKET Nos. 50-282 50-306 i
REQUEST FOR AMENDMENT TO OPERATING LICENSES DPR-42 & DPR-60 LICENSE AMENDMENT REQUEST DATED January 29,1997 Amendment of Coolina Water System Emeraency intake Desian Bases Northem States Power Company, a Minnesota corporation, bv this letter dated June 22,1998, with its attachments provides supplemental information in support of the subject license amendment request dated January 29,1997. Attachment 1 provides USAR pages marked up showing licensing basis changes to the Operating License. Attachment 2 contains the revised USAR pages.
This letter and its attachments contain no restricted or other defense information.
NORTHERN STATES POWER COMPANY Yj!Aw By i:
n R'ogerjD."Ahderson Director Nuclear Energy Engineering On this 22 day of d 4/KJL before me a notary public in and for said County, personally appeared, Roger O. Anderson, Director, Nuclear Energy Engineering, and being first duly sworn acknowledged that he is authorized to execute this document on behalf of Northern States Power Company, that he knows the contents thereof, and that to the best of his knowledge, information, and belief the statements made in it are true and that it is not inter-posed for delay.
~
((
tii 1
CYNTHIA V.JAK0880N Notary Puldie-Minnesote l
Hennepin County y Commission Expires Jan 31. 2000 {
j
o s
ATTACHMENT 1 SUPPLEMENT 13 to LICENSE AMENDMENT REQUEST DATED January 29,1997 Amendment of Cooling Water System Emergency Intake Design Bases Updated Safety Analysis Report Marked Up Pages (underlined material to be added, strikethrough material to be removed)
USAR 10.4-6 USAR 10.4-7 USAR 10.4-8 USAR 10.4-9 USAR 12.2-1 USAR Table 12.2-1 Page 10 of 12 1'
l I
t
's PRAIRIEISLAND UPDATED SAFETY AHALYSIS REPORT usAn sects n to Rsvlalon 16 Page 10.4-6 10.4.1.2.'1 Auxiliary Building and Containment Chilled Water System A common non-safety related chilled water system was added for both units 1 and 2. The system provides chilled water during normal plant operation for the containment atmosphere recirculation coolers and the control rod drive mechanism shroud cooling coils, as well as for the new and existing unit coolers located within the auxiliary building. The chilled water system was integrated with the cooling water system. The combined system provides chilled water during normal plant operation but upon loss of power or safety signal actuation, the system will return to its original design integrity and configuration by isolating the chilled water system from the cooling water equipment.
10.4.1.2.2 Emergency Cooling Water Intakt The Emergency Cooling Water intake provides water to maintain safe shutdown for both unite for reacter chutdown coc!!ng after a Design Operationa! Basis Earthquake., accuring that *he Circulating Water 'ntake Cana! ic b!ccked and Lock and Dam No. 3 downctream of the p! art is destrcycd, This intake is a 36-in. pipe buried approximately 40 feet below the Circulating Water intake Canal water level in nonliquefiable soil, connecting the screenwell to a submerged intake crib in a branch channel of the Mississippi River. This Emergency Cooling Water intake is a Class I structure as is the Approach canal which supplies its intake crib from the main channel of the Mississippi. The intake crib is designed to exclude trash, and means are provided for back flushing. This emergency intake supplies a bay in the screenwell which has Class I traveling screens and which provides suction for the Class I cooling water pumps. The emergency cooling water atake ! ne has been dec!gned to de"ver nc !ccc than 18,000 gpm "?h a crib submergence of no more thar A.5 feet g
cauced by +he fa!!ure of Lock and Dam No. 3. Specific hydrau!!c ena!ycie hac chowa that 8
Mth the expected !cwcct river !cve!, the 36" intake !'ne chou!d be capab!e of do!!ver!ng at
! cast 22,500 gpm, and with Lock and Dam No. 3 intact, cou!d de!!ver at !cact 30,000 gpm The doc!gr criteria for C! ace ! ctructurec and equipmert are deceribed in Sectier 12.
To maintain both units in safe shutdown. the safeguards cooling water oumos must orovide sufficient flow to remove heat from the recuired comoonents. The sucolv to the safeguards oumos' suction must be greater than or eoual to that demand in the event of a design basis seismic event. non-seismic aualified comoonents cannot be relied uoon to maintain safe shutdown. The effect on the coolina water system is that only the
~
safeguards oumos are available. off-site oower islost. and the instrument air system is not available. Since many control valves fail to the ooen oosition uoon loss of air or control cower. the flow demand in the coolina water system increases. With two safeauards l
. cooling water oumos ooerating. the cooling water system demand will exceed the sucoly caoacity of the emeraenev intake line (EILL i
- At the onset of the seismic event. the emeraencv intake line and the intake canal both
~
sucolv the suction of the safeguards pumos. The design basis seismic event assumes that Lock & Dam No. 3 is destroyed bv the seismic event. Failure of Lock & Dam No. 3 causes l
the upstream and downstream cools fo eaualize. Over time the uostream oool level is costulated to decrease to 666"-6'. the normallevel of the downstream oool. This orovides 4.5 feet of submergence above the emergencv intake line. Original design calculations
PRAIRIEISLAND UPDATED SAFETY ANALYSIS REPORT USAR Secti:m 10 Rsvbion 16 Page 10.4-7 oredict a minimum sucolv caoacitv of 18000 gom. However. orecoerational testina. when extrapolated for minimum submergence. demonstrated that oniv 15.000 com is actually available.
Uoon occurrence of the design basis seismic event. the coolina water system flow demand
~
is acoroximatelv 29.750 gom (Reference A). This is with the two diesel driven safeauards cooling water cumes coerating. since this creates the highest demand on the suction sucoly. There is an additional 2000 com demand from the diesel fire oumo. Initiallv. the sucolv to the safeauards coolina water oumos is from both the intake canal and the emergencv intake line. The stability of the intake canal banks has been evaluated (References B & C). The evaluations demonstrate that the intake canal will succort the safeguards function of the cooling water system. The volume in the intake canal orovides acoroximatelv 4.8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> for a flow demand of 31750 gom (Reference D).
Assuming no make uo from the river to the :ntake canal. the volume in the intake canal is
_decleted in acorcximately 4.8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. After this time. the emergencv intake line will be the sole sucolv of water to the cooling water cumos. It is necessarv for the coerators to reduce the cooling water system flow demand to a value within the caoacity of the emergency intake line. Procedural guidance directs the coerator which coolina water system loads to secure to reduce demand. Instrumentation orovides the coerator with cooling water header flow and oressure. The crocedure ensures comoonents needed to maintain safe shutdown are available.
An evaluation was cerformed (Reference El comoaring the minimum water volume of the intake Canal reauired for coerator action to the minimum water volume of the intake Canal availab!e oost-DBE. In terms of cercentage of total Intake Canal volume. 26.9% is the minimum reauired volume for coerator action. The minimum water volume available in the intake Canal after a design basis earthauake is 99.5% for the desian basis case and 94.1% for the bounding analysis. This demonstrates a significant coerating marain.
The caoacity of the Ell must succort the minimum eauioment reauired for safe shutdown.
As stated above. it is assumed the eauioment that is not aualified to seismic criteria does not tunction. Therefore. off-site oower is lost and the instrument air system is not available. The following is the minimum eauioment for safe shutdown and the design flow LalfL 1 - Unit 1 Emergencv Diesel Generator 900 com 1
2 - Auxiliarv Feedwater Pumos (1 cer unit) 440 aom 2 - Comoonent Cooling Heat Exchangers (1 cer unit) 3600 gom 1 - Control Room Chiller 320 gom 2 - Containment Fan Coil Units (1 cer unit) 900 gom Iotal 6160 gom Taken bv itself. this would be the minimum reauired flow caoacity of the EIL. However.
l cooling water system loads that are not isolated from the control room must also be considered as cooling water system demand. Also. a costulated crack in each non-safety related cooling water oice off of the main header will increase the cooling water system l
I' l
PRAIRIE ISLAND UPDATED SAFETY ANALYSIS REPORT usAn Szcts::n to Rsvlalon 16 Page 10.4-8 demand.' The cracks are oostulated to be a result of the seismic event. The size is determined using the moderate energv line break methodoloav. that is. a circular ooenina of area eaual to that of rectanale one-half oice diameter in lenoth and one half oice wall ~
thickness in width. (Reference F). The desian flow information. the non-isolated loads and I
the leakaae due to cracks in non-safety relat'ed oices have been evaluated usina a
~
thermal-hvdraulic comouter model. Th'e outout of'the model calculates that this configuration would result in a cooling water system flow demand of 10.643 gom (Reference G). This then is the minimum reauired flow caoacity of the EIL. Note that through ooerator action. this flow rate can be redistributed within the coolina water system.
based on the soecific event.
References I
(A) ENG-ME-302. rev 0 (B) Sucolement 9. dated June 30.1998. including attachments (C) Letter dated March 23.1998. incluaina attachments (D) ENG-ME-347. rev 0
/E5 ENG-ME-355. rev 0 l
(F) Service Water System Self Assessment. auestion AO-3. dated October 30.1995 (G) ENG-ME-310. rev 0 l
l The basic design intent for the emergency pipe was to provide enough flexibility in the system to withstand earthquakes. This was accomplished by introducing four flexonics expansion joints, two near the screenhouse and the other two in the pipe riser at the intake crib. The articulation provided by the joints is expected to act in a fashion similar to paired flexible joints in steam lines.
In order for the emergency intake pipe to behave elastically, as intended, the portion of the l
pipe embedded in the screenhouse was wrapped with rodoform to alleviate localized stresses due to the settlement of the soil. Special backfill material was placed around the pipe to prevent liquefaction !!quification of the' soil which would result in flotation of the pipe.
All natural material has been replaced by nonliquifiable backfill materials up to the liquefaction levelin accordance with the recommendations of Dames & Moore.
.he design of the 36" emergency intake pipe and the approach canal are based upon
. recommendations by earthquake consultants J. A. Blume & Associates and Dames &
Moore. Professor H. Bolton Seed of the University of California at Berkeley, in his letter dated June 3,1970 to Mr. Garrison Kost of John A. Blume & Associates in San Francisco, stipulates the following minimum criteria to ensure inswe that the emergency service water intake pipe at Prairie island would not be disrupted by displacements due to soil liquefaction:
a.
"The slope of any liquefiable material should not exceed about 1 degree,
- b. The pipe line should be supported or protected against settlement or uplift due to liquefaction of the underlying soils.
PRAIRIE ISLAND UPDATED SAFETY ANALYSIS REPORT USAR Szcuon 10 Revision 16 Page 10.4-9 The pipe should be located at least 25 times the height of any bank beyond the c.
toe of the bank in order to protect it from lateral forces due to movement of liquefied soil."
l l
Professor Seed then proceeds to make the following specific recommendations: It will be possible to design:
a.
"A section near the plant where the pipe would be placed in non-liquefiable soils.
b.
A section to be stabilized against liquefaction by densification and in which the pipe would be brought up to a higher elevation, and I
A section designed in accordance with the criteria listed above so that the pipe c.
would not be disrupted even if the underlying and adjacent soil should liquefy."
The RS&E design of the 36" emergencv intake oice and the aooroach canal applies to40 2!! cf 'he three critoria cut"ned above and ut#izes the
- ret and third of Dr Socdc cpecific l
recommendatienc. The cpecific recommendatienc "/cre app"cd !a the fc!!c"'ing maraer the followina criteria:
Near the screenhouse, where the pipe line is above the liquefiable horizon, we have l
removed all liquefiable material around the pipe and replaced it by non liquefiable material.
The east-west run of the emergency intake pipe has been placed below the horizon of the liquefiable soil. Trench backfill materials are non-liquefiable up to the horizon of liquefaction.
i At the intake, where the pipe line rises vertically through potentially liquefiable strata, we i
have provided secure anchorage of the intake crib by piling into the non-liquefiable strata.
In order to protect the riser pipe itself, we have designed a considerable degree of flexibility into the riser by installing two Flexonics joints which are capable of swivelling 6 in any direction.
In accordance with the explanation and criteria set forth by Dr. Seed, lateral rnovements of j
liquefied soil layers are not expected in the intake area, nor do we expect a covering of the I
intake itself, because the intake crib is located in a 575 ft, wide intake canal which has been sized by applying the 25 to 1 slough angle cited by Dr. Seed. The bottom of the canal has been kept flat.
The bed of the branch channel of the Mississippi River in which the emergency intake crib is located has been backfilled to Elevation SED 560 in order to minimize any potential gradients which might cause a flow of liquefied materials. The slough angle of 25 to 1 has again been observed at the underwater bank which rises from Elevation SSD 560 to Elevation SSMi SSA.S.
1 L___.__
PRAIRIE ISLAND UPDATED SAFETYANALYSIs REPORT USAR Stction 12 Revision 14 Page 12.2-1 12.2 PLANT PRINCIPAL STRUCTURES AND EQUIPMENT 12.2.1 Design Basis 12.2.1.1 Classification of Structures and Comoonents All structures (including the Reactor Building), systems (including instruments and controls), and components are classified as Class I,11 or til according to their function and importance in relation to the safe operation of the reactor, with emphasis on the degree of integrity required to protect the public. These are listed in Table 12.2-1.
The Turbine Building, Administration Building, Auxiliary Building and Shield Building structures are constructed as a contiguous complex. In general, these structures are identified as either Class I or Class lil by placing emphasis on the predominant use of the structure in its relation to the safe operation of the reactor, in some instances there may be more than one classification applicable within a building or structure. This situation will be treated as a mixed classification.
The definition of the Nuclear Safety Desigr Classifications is given in the following paragraphs:
a.
Class l Those structures and components including instruments and controls whose failure might cause or increase the severity of a loss-of-coolant accident or result in an uncontrolled release of substantial 1 amounts of radioactivity, and those structures and components vital to safe shutdown and isolation of the
- reactor, b.
Class 1*
Some items in Table 12.2-1 are designated as Class l* indicating that these items have been oriainallv desianed or have been subseauentiv analvzed or a
tested to Class I. Desian Basis sarthauake loadin'g (dvnamici oniv. and that these items are treated as Class lll items in all other resoects.Some iteme in Tab!e 12.2 1 are dec!gnated 2: C! arc !* Mdicating that these item: have bcon dec!gned to C! ace !, Design Bac!: Eadhquake !cading (dynamic) en!y, end-tht thece iteme are treated 2: C!aec !" 'teme in 2!! cther recpectc.
1 c.
Class 11 0
3 8
Those structures and components which are important to reactor o
'A substantial amount of radioactivity is defined as that amount of radioactive material which would produce radiation levels at the site boundary in excess of 1.0% of 10CFR100 limits.
PRAIRIEISLAND UPDATED SAFETYANALYSIS REPORT usAR stetton 12 Revizien 14 TABLE 12.2-1 CLASSIFICATION OF STRUCTURES, SYSTEMS AND COMPONENTS (Page 10 of 12) 11em Class Classification of Systems and Comoonents (Continued)
Turbine Plant Turbine, Generator, Foundation, Exciter. Oil ill Purification, Turbine Gland Seal System, Reheaters and Moisture Separators, Generator Cooling Water System, Hydrogen and CO Systems 2
Cooling Water Svstem Up to Class l System Isolation Valves l
All that is not Class l Ill i
Circulating Water Svstem Emergency Cooling Water Intake 1
l Approach Canal I
Circulating Water Pumping Equipment 111 Intake Canal 1*44 Circulating Water Pump Discharge Piping Ill Condenser Discharge Piping ill intake and Discharge Equipment til Cooling Towers and Pumping Equipment lli i
i
ATTACHMENT 2 t
SUPPLEMENT 13 to LICENSE AMENDMENT REQUEST DATED January 29,1997 Amendment of Cooling Water System Emergency intake Design Bases Updated Safety Analysis Report Revised Pages USAR 10.4-6 USAR 10.4-7 USAR 10.4-8 USAR 10.4-9 USAR 12.2-1 USAR Table 12.2-1 Page 10 of 12 l
l l
l
_ _____ __ ______-_-________________ _ _ A
PRAIRIE ISLAND UPDATED SAFETY ANALYSIS REPORT USAR Sects:n to Revision 16 Page 10.4-6 10.4.1.2.1 Auxiliary Building and Containment Chilled Water Svstem A common non-safety related chilled water system was added for both units 1 and 2. The system provides chilled water during normal plant operation for the contaironent atmosphere recirculation coolers and the control rod drive mechanism shroud cooling coils, as well as for the new and existing unit coolers located within the auxiliary building. The chilled water system was integrated with the cooling water system. The combined system provides chilled water during normal plant operation but upon loss of power or safety signal actuation, the system will return to its original design integrity and configuration by isolating i
the chilled water system from the cooling water equipment.
i 10.4.1.2.2 Emergency Cooling Water Intake The Emergency Cooling Water Intake provides water to maintain safe shutdown for both units after a Design Basis Earthquake. This intake is a 36-in pipe buried approximately 40 feet below the Circulating Water intake Canal water level in nonliquefiable soil, connecting the screenwell to a submerged intake crib in a branch channel of the Mississipp! River. This Emergency Cooling Water Intake is a Class I structure as is the Approach canal which supplies its intake crib from the main channel of the Mississippi.
The intake crib is designed to exclude trash, and means are provided for back flushing.
This emergency intake supplies a bay in the screenwell which has Class I traveling screens and which provides suction for the Class I cooling water pumps.
I To maintain both units in safe shutdown, the safeguards cooling water pumps must provide sufficient flow to remove heat from the required components. The supply to the 1
safeguards pumps' suction must be greater than or equal to that demand. In the event of a design basis seismic event, non seismic qualified components cannot be relied upon to maintain safe shutdown. The effect on the cooling water system is that only the safeguards pumps are available, off-site power is lost, and the instrument air system is not available. Since many control valves fail to the open position upon loss of air or control power, the flow demand in the cooling water system increases. With two safeguards cooling water pumps operating, the cooling water system demand will exceed the supply L
capacity of the emergency intake line (EIL).
At the onset of the seismic event, the emergency intake line and the intake canal both supply the suction of the safeguards pumps. The design basis seismic event assumes that Lock & Dam No. 3 is destroyed by the seismic event. Failure of Lock & Dam No. 3 causes the upstream and downstream pools to equalize. Over time the upstream pool level is postulated to decrease to 666"-6', the normallevel of the downstream pool. This provides 4.5 feet of submergence above the emergency intake line. Original design calculations predict a minimum supply capacity of 18000 gpm. However, preoperational testino, when extrapolated for minimum submergence, demonstrated that only 15,000 gpm is actually available.
Upon occurrence of the design basis seismic event, the cooling water system flow demand is approximately 29,750 gpm (Reference A). This is with the two diesel driven safeguards cooling water pumps operating, since this creates the highest demand on the suction
PRAIRIE ISLAND UPDATED SAFETY ANALYSIS REPORT USAR section to l
Revision 16 l
Page 10.4-7 supply. There is an additional 2000 gpm demand from the diesel fire pump. Initially, the supply to the safeguards cooling water pumps is from both the intake canal and the i
emergency intake line. The stability of the intake canal banks has been evaluated l
(References B & C). The evaluations demonstrate that the intake canal will support the safeguards function of the cooling water system. The volume in the intake canal provides approximately 4.8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> for a flow demand of 31750 gpm (Reference D).
Assuming no make up from the river to the intake canal, the volume in the intake canal is depleted in approximately 4.8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />. After this time, the emergency intake line will be the sole supply of water to tne cooling water pumps. It is necessary for the operators to reduce the cooling water system flow demand to a value within the capacity of the emergency intake line. Procedural guidance directs the operator which cooling water system loads to secure to reduce demand. Instrumentation provides the operator with cooling water header flow and pressure. The procedure ensures components needed to maintain safe shutdown are available, An evaluation was performed (Reference E) comparing the minimum water volume of the intake Canal required for operator action to the minimum water volume of the intake Canal available post-DBE. In terms of percentage of total Intake Canal volume,26.9% is the minimum required volume for operator action. The minimum water volume available in the Intake Canal after a design basis earthquake is 99.5% for the design basis case and l
94.1% for the bounding analysis. This demonstrates a significant operating margin.
The capacity of the EIL must support the minimum equipment required for safe shutdown.
' As stated above, it is assumed the equipment that is not qualified to seismic criteria does not function. Therefore, off-site power is lost and the instrument air system is not available. The following is the minimum equipment for safe shutdown and the design flow rate.
l 1 - Unit 1 Emergency Diesel Generator 900 gpm l
2 - Auxiliary Feedwater Pumps (1 per unit) 440 gpm 2 - Component Cooling Heat Exchangers (1 per unit) 3600 gpm 1 - Control Room Chiller 320 gpm l
2 - Containment Fan Coil Units (1 cer unit) 900 aom l
Total 6160 gpm l
Taken by itself, this would be the minimum required flow capacity of the EIL. However, l
cooling water system loads that are not isolated from the control room must also be l
considered as cooling water system demand. Also, a postulated crack in each non-safety l
related cooling water pipe off of the main header will increase the cooling water system demand. The cracks are postulated to be a result of the seismic event. The size is l
determined using the moderate energy line break methodology, that is, a circular opening i
of area equal to that of rectangle one-half pipe diameter in length and one half pipe wall l
thickness in width. (Reference F). The design flow information, the non-isolated loads and the leakage due to cracks in non-safety related pipes have been evaluated using a thermal-hydraulic computer model. The output of the model. calculates that this configuration would result in a cooling water system flow demand of 10,643 gpm
PRAIRIE ISLAND UPDATED SAFETY ANALYSIS REPORT USAR Szctian to l
Revision 16 l
Page 10.4-8 (Refere'nce G). This then is the minimum required flow capacity of the EIL. Note that through operator action, this flow rate can be redistributed within the cooling water system, based on the specific event.
References
-(A) ENG-ME-302, rev 0 (B) Supplement 9, dated June 30,1998, including attachments (C) Letter dated March 23,1998, including attachments (D) ENG-ME-347, rev 0 (E) ENG-ME-355, rev 0 (F) Service Water System Self Assessment, question AQ-3, dated October 30,1995 (G) ENG-ME-310, rev 0 l
The basic design intent for the emergency pipe was to provide enough flexibility in the system to withstand earthquakes. This was accomplished by introducing four flexonics expansion joints, two near the screenhouse and the other two in the pipe riser at the intake crib. The articulation provided by the joints is expected to act in a fashion similar to paired flexible joints in steam lines.
In order for the emergency intake pipe to behave elastically, as intended, the portion of the pipe embedded in the screenhouse was wrapped with rodoform to alleviate localized stresses due to the settlement of the soil. Special backfill material was placed around the 1
l pipe to prevent liquefaction of the soil which would result in flotation of the pipe. All natural material has been replaced by nonliquifiable backfill materials up to the liquefaction level in accordance with the recommendations of Dames & Moore.
The design of the 36" emergency intake pipe and the approach canal are based upon recommendations by earthquake consultants J. A. Blume & Associates and Dames &
l Moore. Professor H. Bolton Seed of the University of California at Berkeley,in his letter dated June 3,1970 to Mr. Garrison Kost of John A. Blume & Associates in San Francisco, stipulates the following minimum criteria to ensure that the emergency service water intake pipe at Prairie Island would not be disrupted by displacements due to soil liquefaction:
a.
"The slope of any liquefiable material should not exceed about 1 degree.
b.
The pipe line should be supported or protected against settlement or uplift due l
to liquefaction of the underlying soils.
l
- c. The pipe should be located at least 25 times the height of any bank beyond the toe of the bank in order to protect it from lateral forces due to movement of liquefied soil."
Professor Seed then proceeds to make the following specific recommendations: It will be possible to design:
a.
"A section near the plant where the pipe would be placed in non-liquefiable j
soils.
A
PRAIRIE ISLAND UPDATED SAFETY ANALYSIS REPORT USAn Section 10 Revision 16 Page 10.4-9
- b. A section to be stabilized against liquefaction by densification and in which the pipe would be brought up to a higher elevation, and.
I
- c. A section designed in accordance with the criteria listed above so that the pipe would not be disrupted even if the underlying and adjacent soil should liquefy."
The design of the 36" emergency intake pipe and the approach canal applies to the following criteria:
Near the screenhouse, where the pipe line is above the liquefiable horizon, we have removed all liquefiable material around the pipe and replaced it by non-liquefiable material.
The east-west run of the emergency intake pipe has been placed below the horizon of the liquefiable soil. Trench backfill materials are non-liquefiable up to the horizon of liquefaction.
I At the intake, where the pipe line rises vertically through potentially liquefiable strata, we have provided secure anchorage of the intake crib by piling into the non-liquefiable strata.
In order to protect the riser pipe itself, we have designed a considerable degree of flexibility irito the riser by installing two Flexonics joints which are capable of swivelling 6 in any direction.
I In accordance wi';h the explanation and criteria set forth by Dr. Seed, lateral movements of liquefied soil layers are not expected in the intake area, nor do we expect a covering of the intake itself, because the intake crib is located in a 575 ft, wide intake canal which has been sized by applying the 25 to 1 slough angle cited by Dr. Seed. The bottom of the canal has been kept flat.
The bed of the branch channel of the Mississippi River in which the emergency intake crib is located has been backfilled to Elevation 660 in order to minimize any potential gradients I
which might cause a flow of liquefied materials. The slough angle of 25 to 1 has again been observed at the underwater bank which rices from Elevation 660 to Elevation 664.5.
The non-compacted, non-liquefiable backfill has been designed and specified according to recommendations by John Blume Associates, according to which the sieve analysis is:
70% passing 0.742 in. screen opening 36% - 50% passing #4 screen, 10% passing #10 screen.
The material used for the non-liquefiable backfill closely approximates that recommendation.
10.4.1.3 Performance Analysis The cooling water system is designed to prevent a component fai!ure from curtailing normal station operation. The system has been designed and equipment furnished to
PRAIRIE ISLAND UPDATED SAFETY ANALYSIS REPORT USAR Section 12 Revision 14 Page 12.2-1 12.2 PLANT PRINCIPAL STRUCTURES AND EQUIPMENT l
12.2.1 Design Basis 12.2.1.1 Classification of Structures and Components All structures (including the Reactor Building), systems (including instruments and controls), and components are classified as Class I,11 or ill according to their function and importance in relation to the safe operation of the reactor, with emphasis on the degree of integrity required to protect the public. These are listed in Table 12.2-1.
i The Turbine Building, Administration Building, Auxiliary Building and Shield Building structures are constructed as a contiguous complex. In general, these structures are identified as either Class I or Class !!I by placing emphasis on the predominant use of the structure in its relation to the safe operation of the reactor.
In some instances there may be more than one classification applicable within a building or structure. This situation will be treated as a mixed classification.
The definition of the Nuclear Safety Design Classifications is given in the following paragraphs:
- a. ClassI.
Those structures and compoilents including instruments and controls whose failure might cause or increase the severity of a loss-of-coolant accident or result in an uncontrolled release of substantial 1 amounts of radioactivity, and those structures and components vital to safe shutdown and isolation of the reactor.
b.
Class 1*
l Some items in Table 12.2-1 are designated as Class l* indicating that these items have been originally designed or have been subsequently analyzed or tested to Class I, Design Basis Earthquake loading (dynamic) only, and that L
these items are treated as Class lll items in all other respects.
c.
Class ll Those structures and components which are important to reactor 1
1A substantial amount of radioactivity is defined as that amount of radioactive material which would produce radiation levels at the site boundary in excess of 1.0% of 10CFR100 lirnits.
PRAIRIE ISLAND UPDATED SAFETY ANALYSIS REPORT usAR secti::n 12 Raviilon 14 TABLE 12.2-1 CLASSIFICATION OF STRUCTURES, SYSTEMS AND COMPONENTS (Page 10 of 12) llam GaSa Classification of Systems and Comoonents (Continued)
Turbine Plant Turbine, Generator, Foundation, Exciter, Oil Ill Purification, Turbine Gland Seal Systam, Reheaters and 1%isture Separators, Generator Cooling Water Systein, Hydrogen and CO Systems 2
Coolina Water Svstem Up to Class i System isolation Valves I
All that is not Class I til Circulating Water Svstem j
Emergency Cooling Water Intake i
Approach Canal l
J Circulating Water Pumping Equipment lli Intake Canal 1*
Circulating Water Pump Discharge Piping 111 Condenser Discharge Piping Ill Intake and Discharge Equipment lll l
Cooling Towers and Pumping Equipment lil e
._