ML20116E771

Responds to RAI Re GL 95-07, Pressure Locking and Thermal Binding of Safety-Related Power-Operated Gate Valves

ML20116E771
Person / Time
Site:	Mcguire, McGuire
Issue date:	07/31/1996
From:	Mcmeekin T DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-95-07, GL-95-7, TAC-M93482, TAC-M93483, NUDOCS 9608060118
Download: ML20116E771 (21)

Text

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DukeIbwer Company T C Kntav AlcGdre Nuclear Generation Department VicePresident .i 12700 Pegers Ferry kg(MG01A) ' Ia'04)RTS-4300 '!

. HunterscWe, NC28078-8985 (704)875-4M9 fax }

I DUKEPOWER July.31, 1996 U. S. Nuclear Regulatory Commission  !

Document Control Desk l Washington,'D.C. 20555 I

Subject:

McGuire Nuclear Station '

Docket Nos. 369, 370

. Request for Additional Information -

Generic Letter 95-07, " Pressure Locking '

and Thermal Binding of Safety-Related Power-  ;

Operated Gate Valves" i TAC Nos. M93482 and M93483 l On August 17, 1995, the NRC issued Generic Letter (GL) 95- j t

07, ' Pressure' Locking.and Thermal Binding of Safety-Related i Power-Operated Gate Valves" to request that licensees ~take artjona to ensure that safety-related power-operated gate l valves that are susceptible to pressure locking or thermal  ;

binding are capable of performing their safety functions, i Please find attached McGuire's response to the NRC 2 Request f

for Additional Information dated' July 1, 1996 conce ning '

Generic Letter =95-07.

l Very truly y urs, KApf "

T. C. McMeekin, Vice President  !

McGuire Nuclear Station I

i L

l-9608060118 960731 PDR i

, P ADOCK 05000369 '

PDR I f-  ;

a,m an,.cyrm rew I

McGuire Nuclear Station Units 1 And 2 I Request For Additional Information - GL 95-07," Pressure Lcrking & Thermal Binding" MNS Resrumw To NRC Request For Additional Information Concernine Generic Letter 95-07

1. Valves 1(2)ND0033 and 1(2)ND0018 are isolation valves connecting a common bypass line around ND Heat Exchangers A and B respectively. They are required to remain closed during Modes 1-3 when the ECCS is required. They may be opened in Mode 4 for RHR temperature control, in which case they must i close on demand by operator action on the manual control. They have no safety requirement to open and as I such are not subject to failure from pressure locking or thermal binding as defined by GL 95-07.

The RHR cross-tie valves are 1(2)ND0015B and ND0030A. These valves were evaluated for thermal v-induced pressure locking as documented in the 2/13/96 submittal to GL 95-07.

2. Short term operability for l(2)N10183B, Low Head Injection Pump to Hot Leg Isolation, is based on test results which show that double barrier check valves prevent RCS pressure from acting on the gate valves.

Ilowever we have planned to install bonnet pressure equalization provision to the valves during the next refueling outage (1,2EOCil) to satisfy long term bonnet pressure locking concernsfor these valves. It should be mentioned that an additional test performed on 7/11/96 indicated no pressure on the downstream side of 2N101838. His test in addition to the test performed on 11/11/95, indicate that the hot leg check

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valves are holding tight and not allowing pressurization of the downstream face of 2N10183B. l l

The Duke Power Safety Analysis Group has shown that a single medium head safety injection pump (NI System) recirculating to the hot legs is adequate for boron precipitation removal (see attachment 2). ND j recirculation to the hot legs is therefore not required from a safety analysis perspective. However, the licensing basis has not been changed, therefore the function for this valve to open will be maintained as described.

l l

As requested, the calculations regarding actuator thrust capability for 1(2)NIOl33B are as follow: 1 System Conditions:

l bonnet pressure = 100 psig (maximum expected conditions) l upstream pressure = 120 psig ,

downstream pressure = 0 psig I bonnet heatup = 0 F Ernsme Lockine Force:

The open force required due to pressure locking conditions (Fit) was calculated using the Westinghouse j Owners Group Preslok Model as shown in attachment 1, with the inputs and result as follows:

0 (wedge angle) = 5* j Vr (valve factor,1N10183B) = 1.289 (close Vr from GL 89-10 program)

Vr (valve factor,2N10183B) = 0.534 (from highest 8/3/93 DP test in closed direction) I The disc dimensional information was obtained by measurement and is listed in the Preslok calculation in attachment 1.

%ese valves are made of stainless steel, as identified on the manufacturers drawing. He material properties are:

E = 27.6.0 x 10' psi v = 0.3 For iNIOl83B, F,t= 11,796.5 lbf For 2N10183B, F,1 = 5,223.3 lbf Page1

..~ . . . - - -

I e McGuire Nucle:r Station, Units 1 And 2 Request For Addition 11 Inform 1 tion - GL 95-07," Pressure Locking & Thermal Binding" l Total Unwedcine Force:

1N10183B:

I From 8/31/94 VOTES testing, Static Unwedging Force (FsTAnC) = 49.460.0 lbf +/- 52.0 % instrument error FsTAnc = 49,460.0 lbf(1.52) = 75,179.2 lbf l Fe, = Fn. + PnAne = 11,796.5 Ibf + 75,179.2 lbf = 86,975.7 lbf l l

2NIO183B:

From 8/1/93 VOTES testing, Static Unwedging Force (FsTAnc) = 25,051.0 lbf +/- 52.0 % instrument error 1

Fsyruc = 25,051.0 lbf(l.52) = 38,077.52 lbf l l Fm,,.. = F,, a + PsTAne = 5,223.3 lbf + 38,077.52 lbi .: 43,300.82 lbf l Available Thrust:

1N10183B:

The valve is torque switch bypassed and limit switch controlled in the open direction.

stem factor (S) = 0.0214 (in open direction based on a stem COF = 0.15) undervoltage factor (V) = 0.915 Note: A maximum value of 0.90 will be usedfor this calculation I

stall torque (TsTAu) = 3,900.00 ft-lbf  :

Serial #: A1472E/2 torque at undervoltage (Tuv) = (TsTru.)(V)'= (3900.00 ft-Ibf)(0.90)2 = 3,159.00 ft-lbf l Fama. = (Tuv )/S = (3,159.00 ft-lbf)/0.0214 = 147,616.82 lbf l I 2N10183B:

'Ihe valve is torque switch bypassed and limit switch controlled in the open direction.

i stem factor (S) = 0.0264 (in open direction based on a stem COF = 0.15) l undervoltage factor (V) = 0.906 Note: A maximum value of 0.90 will be usedfor this calculation. l l stall torque (TsTAM.) = 1,800.00 ft-lbf l

l Serial #: B5483X l torque at undervoltage (Tuv) = (TsTAu.)(V)2 = (1800.00 ft-lbf)(0.90)2 = 1,458.00 ft-lbf j l Fou y = (Tuv )/S = (1,458.00 ft-lbf)/0.0264 = 55,227.27 lbf l 7

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1 . -: l

- McGuire Nuclear Station, Units 1 And 2 Request For Additional Informction - GL 95-07," Pressure Locking & Thermal Binding" l Available Thrust Marcin:

i l 1N10183H:

l l @R7.maiiuiistS14,9M.11tirmmwegIWWMM i 2Et0183B:

$$5A%$$MW?MNY k l 1

3. These vtUves were evaluated as part of the 2/13/96 response to GL 95-07. He original list of safety-related power opezated gate valves included many more valves than the 84 mentioned in that submittal. i During the review period, prior to 2/13/96 submittal, the scope was narrowed to 84 valves. Rese 84 valves l

were deter:nined to have a safety function to open, or required to be in the open position to fulfill a safety !

function in any Mode and were closed under conditions for which they must remain operable. This criteria was specified in attachment 2 of the 2/13/96 submittal. The Pressurizer PORV Block Valves were determined not to meet this criteria based on the above discussion and thus determined not to have an active to open f unction. The evaluation for the 2/!3/96 submittal is presented below.

Tech. Spec. 3/4.4.4 requires the Pressu'izer PORV Block Valves (l(2)NC0031,0033,0035) to be open l during Modes 1 3. The Block Valves tre required to close to isolate a stuck open PORV. Credit is taken  !

for one PORV to be able to open to m:tigate the consequences of a Steam Generator Tube Rupture (SGTR),

l which means that at least one isolation valve must be open in this condition. Two PORVs  !

(l(2)NC0032,0034) are also required for LTOP relief below 300" F with lift settings less than or equal to 400 psig per Tech. Spec. 3/4.4.9.3 which requires two isolation valves to be open at this pressure and  ;

temperature range.

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l nrce conditions exist within the Tech. Specs. where the Block Valves may be closed for an extended '

period of time during plant operation.

1. One is when a Block Valve is declared inoperable. This may occur with the Block Valve in the closed position. With the Block Valve inoperable, the Tech. Specs. require that the PORV switch be placed in the 'CLOSE* position.

2. Another condition is when a PORV is declared inoperable due to excessive leakage. In this case, the associated Block Valve must be closed but power maintained to the Block Valve.

3. The third condition would be with the PORV(s) inoperable due to conditions other than excessive leakage.

If all three PORVs or Block Valves were to be inoperable, the Tech. Specs. require that at least one of the valves be restored to operable status within one hour or the plant must be taken to Mode 4. Postulating a SGTR during the one hour allowed for restoration is not credible. Also, the Emergency Procedure (EP) for the SGTR event requires verifying open or opening at least one Block Valve. This step is conducted early in I the EP prior to initiating the primary system cooldown. Therefore, there will always be at least one Block l Valve open in Modes 1-3 or else the plant will be shut down.

Should the situation arise where all three Bhick Valves were inoperable and closed and the plant was being l

taken to Mode 4, the LTOP requirements for the PORVs would not be required until the plant reached 300*

F, in Mode 4. Although the LTOP requirements exist, the licensing basis for MNS is to attain Mode 3.

l Ilowever, to meet LTOP requirements, adequate time would exist to take alternate actions including i establishing reliance on RHR Suction Relief Valve 1,2ND0003 (as stated in Tech Spec 3.4.9.3, license '

amendments No 166 and 148 for Units 1 and 2 respectively) or the plant could be held above LTOP conditions until sufficient LTOP valve requirements are achieved.

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- McGuire Nuclear Station, Units I And 2 Request For Addition 11 Information - GL 95-07, " Pressure Locking & Thermal Binding" Al'though these valves are not presently classified as " active to open", they were evaluated for this response as shown below:

Gate Desien: Flex Wedge (3")

Manufacturer: Borg-Warner Dermal Bindine Evaluaticn: In accordance with the Duke Power Company thermal binding screening criteria, these valve applications are potentially susceptible to thermal binding since the maximum temperature of the valves will be greater than 200* F above which valve operation could initiate thermal binding in flex wedge gate valves. The potential for thermal binding of these valves is minimized for the following reasons: (1) The valve body's are covered with insulation which would result in the valve body and wedge cooling at very similar rates, (2) the body and wedge are made of austenitic stainless steels which would expand and contract at similar rates,(3) the actuators are of the Rotork NAX type which includes an actuator spring pack to minimize stem growth concerns. He actuators are setup such that the valves are torque seated in the close direction at a value less than the full stall capability of the actuators.

Actuator setup, in addition to the other mentioned items, would help to reduce the chance of occurrence of thermal binding. ~

Pressure Lockine Evaluation: In accordance with the Duke Power Company pressure locking screening criteria, these valve applications are potentially susceptible to pressure locking since they are of the flex wedge design. Although unlikely, for conservatism,it is assumed for calculation purposes that a pressure of 2560 psig (maximum RCS pressure based on pressurizer safety setpoint + tolerance) is trapped in the bonnet with 0 psig upstream and 0 psig downstream. Here is no temperature increase after closure of these valves. Therefore, thermally induced pressure locking is not a concern. The required thrust due to pressure forces was calculated using the Comed pressure locking calculation model, assuming RCS pressure trapped in the bonnet. The results of the analysis are shown below.

Thrust (Ibf) INC0031B INC0033A INC0035B 2NC0031B 2NC0033A 2NC0035B Available 18,289 18,481 15,347 18,417 17,138 19,504 Required 13,021 13,507 8,776 12,192 11,305 11,057 Margin 40.46 % 36.82 % 74.88 % 51.06 % 51.60 % 76.39 %

Therefore, pressure locking is judged not to be a problem with these valves.

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4. Of the known instances where valves have been modified to prevent the occurrence of pressure locking, 2N10121 A,2NIO152B, IN10184A, IN10185B,2N10184A and 2NI0185B, a 10CFR50.59 evaluation has been completed to address any adverse impact on plant safety.

Minor modification MGMM-8272 (VN-8272A) was implemented to drill a 1/4" hole in the downstream side of the 2N10121 A valve wedge. He valve originally had a hole in the upstream side. This modification re-oriented the hole to the downstream (high pressure) side. The 50.59 evaluation concluded that placing the hole on the downstream side would improve the normal valve isolation reliability when compared to l drilling a hole in the upstream side. Additionally, since the RCS is at a higher pressure than the NI System (the upstream side), NI pump runs during normal operation would not introduce a reactivity management issue due to NI System inventory being injected in the RCS.

Minor modification MGMM-8272 was implemented to drill a 1/4" hole in the downstream side of' the l

l 2NIO152B valve wedge. Through inspection, the valve was found to contain no hole in the upstream '

! wedge, even though the design drawing indicated that the valve did have a hole. This modification placed a

! hole on the downstream (high pressure) side. The 50.59 cvaluation indicated that a potential for the Ni System to leak to the RCS during NI pump operation existed, if the RCS is at a lower pressure. The evaluation concluded that leakage into the RCS would not be a concern for shutdown or accident conditions. Additionally, potential diverted ECCS flow during cold leg recirculation will be minimized by j the seating forces of the motor operator establishing an acceptable pressure boundary on the upstream side l J

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l McGuire Nuclear Station, Units i And 2 I Request For Additional Information - GL 95-07 " Pressure Lccking & Bermal Binding" of.the wedge. If required to be closed for containment isolation, a more reliable isolation would be achieved with containment pressure in addition to seating forces acting to seat the upstream wedge.

Minor modifications MGMM-7270 and 7161 were implemented to add bonnet vent bypass lines to IN10184B,185A and 2N1018411,185A; respectively. De 50.59 evaluations indicated that no accident different than any evaluated in the SAR was created trj these modifications and that neither the containment isolation function nor the ability to isolate ND flow from the containment sump is degraded.

Only a limited number of procedural changes have been implemented to address pressure locking. No procedural changes have been implemented to address thermal binding concerns. Procedure changes and the modification itself receive a 10CFR50.59 evaluation. In addition, all procedure changes are reviewed and operator updates are issued accordingly.

As a corrective action to PIP 0-M95 1852, potential pressure locking of 1(2)NS0001 B and NS0018A, several procedures were updated. The controlling procedure for low head injection pump (ND system) quarterly testing was revised to monitor ND system pressure at the conclusion of pump operation. If pressure was greater than the allowed maximum, pressure would be bleed and the affected valves would be stroked (1,2NS0001B and NS0018A). Additionally, the ND system operating procedure's enclosure for ~

alignment of the ND system for standby readiness for power operation was revised to include an evaluation of ND operation. If the ND system has been operated in RHR mode or system pressure has exceeded allowed maximum, the affected valves would be stoked (1,2NS0001B and NS0018A).

Training for plant personnel for modifications has been addressed through the Operations modification review process. As required by the modification process, each modification is reviewed by qualified l operations personnel to assess the impact of the modification on Operations personnel / procedures. If new training were to be identified, generally a reading package containing pertinent information would be issued. Additionally, an SRO in the Work Control Center signs all modification work orders where Operations control is required. This process insures Operations personnel are informed of all work. To date no specific training regarding these pressure locking modifications has been conducted for operations personnel, due to the non-complex nature of these modifications. In summary, the Operations review l process in conjunction with input from Engineering would ensure that appropriate training is initiated.

In the case of 1(2)NI0184B,185A; a depiction of the bonnet vent bypass line has been added to the Dow ,

diagrams to clearly indicate that the valves are unique and that a bonnet vent provision exists for the valves l i in question. Graphic depiction's of the bypass lines on the Dow diagrams provides assurance, in addition to )

l the Operations modification review process, of operations awareness of the special conDguration of these l valves.

I NSD 301 requires review of a comprehensive technical issues checklist during the early stages of development of engineering modifications which are not form, fit, or function one-to-one replacements.

The technical issues checklist has been recently revised to include a review for the potential effects of pressure locking and thermal binding. This is an additional measure to ensure that the pressure locking and thermal binding issues are addressed in the modification process.

Additional items - Chances From the 2/13/96180 Day Hesponse

5. The evaluations for 1(2)N10009A,10B documented in the 2/13/96 response to GL 95-07 have been re-evaluated since that submittal. The Susceptibility Summary Evaluation table in the 2/13/96 response indicates that these valves have bonnet relief design features. This is incorrect, the operability basis for pressure locking should be Systems Evaluation. An updated evaluation for these valves is as follows: '

Valve Annlication: High head injection pump discharge to cold leg isolation Safety Function: These valves are normally closed and are required to open to provide Dow from the high head injection (NV System) pumps during the cold leg injection phase of ECCS operation. In the event one of these valves is incapable of opening, then that train of the NV System is inoperable.

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l McGuire Nuclear Station, Units 1 And 2 Request For Additional Informition - GL 95-07," Pressure Locking & Hermal Binding" Gate desien: Flex Wedge l Manufacturer: Walworth-Greensburg I Hermal Bipdine Evaluation: In accordance with the Duke Power company thermal binding screening criteria, these valve applications are not susceptible to thermal binding since the maximum temperature of the valves will be less than the maximum ambient temperature of 133" F, which is less than the threshold temperature of 200* F below which valve operation could not initiate thermal binding in flex wedge gate

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valves.

)

Pressure Lockine Evaluation: In accordance with the Duke Power Company pressure locking screening criteria, these valve applications are potentially susceptible to pressure locking since they are of the flex wedge design. As documented in PIP 2-M96-1066 and indicated on MCM-1205.00-0011-001, these valves do not contain a bonnet vent. Rese valves are designed to open with NV pump discharge pressure acting against one side of the wedge. Since NV pressure is higher than RCS pressure, the GL 89-10 differential pressure case setup bounds the GL 95-07 concern for pressure locking. Herefore, these valves are not subject to hydraulically induced pressure locking concerns.

Rese valves are subject to no temperature conditions while closed that are greater than the possible normal ambient conditions. Here is a significant amount of piping forming a dead leg between the warmer cold leg injection / recirculation piping. Rus, the valves would not be expected to heat up significantly prior to their required operation. Therefore, these valves are not subject to any thermally induced pressure locking effects.

6. Since submittal of the 2/13/96 response to GL 95-07, IN10121 A has been assumed for analysis purposes not to contain a bonnet relief design feature (hole in wedge) as a basis for pressure locking operability.

2NIO121 A and 2NI0152B were inspected intemally during the 2EOCIO refueling outage. 2N10121 A was I modified by moving the hole in the wedge from the upstream side to the downstream wedge face. A hole was placed in the downstream wedge face of 2N10152B after inspection showed no hole present in the upstream face. An updated evaluation of 1(2)N10121 A,152B is listed below.

Valve Application: Medium head injection pumps to hot leg isolations Safety Function: Rese valves are required to open provide flow from the medium head injection (NI  ;

System) pumps to the hot legs during hot leg recirculation phase of ECCS operation. In the event one of  ;

these valves is incapable of opening, then that train of the NI System is inoperable. )

Gate Desien: Flex Wedge i

Manufacturer: Walworth-Greensburg '

Thermal Hindine Evaluation: In accordance with the Duke Power Company thermal binding screening criteria, these valve applications are not susceptible to thermal binding since the maximum temperature of the valves will be less than the maximum ambient temperature of 120* F, which is less than the threshold temperature of 200* F below which valve operation could not initiate thermal binding in flex wedge gate valves.

Pressure Lockinc Evaluation: In accordance with the Duke Power Company pressure locking screening criteria, these valve applications are potentially susceptible to pressure locking since they are of the flex wedge design. As discussed in PIP 2-M96-1066, MGMM-8272 installed a small equalization port in 2N10121 A and 2NIO152B in the downstream side of the valve wedges to act as a vent, should the bonnets ,

become pressurized. Herefore; 2N10121 A,152B are not subject to pressure locking. IN10121 A,152B have been assumed not to contain a bonnet relief design fmture (hole in the wedge), as was evaluated in PIP

?-M95-1066 and PIP l-M95-2066, respectively.

When IN10121 A,152B are required to open, upon initiation of hot leg recirculation, the bonnet pressure could be a maximum of 1550 psig. The 1550 psig could result from medium head injection (NI Systeni) pump discharge head. This pressure could be applied by the NI pumps in injection and cold leg I

recirculation Modes of ECCS operation. Check valve leakage (IN10123,126,127,134 for INIO12l A and i

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1

. McGuire Nuclear Station, Units 1 And 2 Request For Additional information - GL 95-07," Pressure Lczking & Thermal Binding" 1N10156,157,159,160 for IN10152B) from the RCS could potentially pressurize the downstream side of IN10121 A imd IN!0152B. Ilowever, pressure transmission through the downstream check valves was shown to not be a concern based on testing performed on 4/24/96 for IN10121 A and 11/14/95 and 1/22/96 <

for IN10152B. The upstream pressure could be as low as 150 psig (ND pump discharge head) and the downstream pressure could be as low as O psig.

IN10121 A,152B are subject to no temperature conditions while closed that are greater than the possible i normal ambient conditions. There is a significant amount of piping forming a dead leg between the warmer cold leg injection / recirculation piping. Rus, the valves would not be expected to heat up significantly prior to their required operation. Therefore, IN10121 A,152B are not subject to any thermally induced pressure locking conditions. He required thrust due to pressure forces was calculated using the Comed pressure locking calculation model, assuming NI pump discharge head trapped in the bonnet. The results of the analysis are shown below with margin.

Thrust (Ibf) iNIO121 A 1N10152B Available 19,699.48 18,253.52 Required 19,349.08 15.137.45 Margin 1.81 % 20.59 %

l Corrective Action: In the 2/13/96 response to GL 95-07 a commitment was made to inspect IN10152B '

during the next refueling outage (1EOCl1) and install a bonnet vent if one does not already exist. Reliance l on check valves to preclude pressure locking is for short term operability considerations only. Herefore, PIP 0-M96-1066 contains a corrective action to open and inspect INIO121 A during the next refueling outage (IEOCl1) and install a bonnet vent if one does not exist to satisfy the long term pressure locking l concern for these valves.

7. The Susceptibility Evaluation Summary table in the 2/13/96 response to GL 95-07 lists the pressure l

locking basis for operability for 1(2)ND0058A and 1(2)NI0136B as being analysis, which is incorrect. The l l correct basis for operability should be Systems Evaluation.  !

( 8. The corrective action for 2NS0029A on page 12 of the 2/13/96 response to GL 95-07 incorrectly lists l 2NS0029A as 2NS0029B.

1 i

9. In general, the margin numbers supplied in the 2/13/96 response to GL 95-07 have changed since the original submittal as part of refinement of the supporting calculation. However, all valves evaluated still show acceptable positive margin for short-term operability. It should be mentioned that the most severe drop in margin occurred for valves 1(2)NV0221 A,222B. The new results of the required thrusts due to pressure locking forces are shown below with margin.

l Thrust (Ibf) INV022i A INV0222B 2NV0221 A 2NV0222B  ;

Available 7,887.73 10,599.27 10,030.06 11,172.39 Required 6,808.86 9,392.76 9,060.94 10,703.96 Margin 15.85 % 12.85 % 10.70 % 4.38 %

l Corrective Actions: The method of calculation used to determine margin for these valves is acceptable for l short-term operability considerations only. Currently, modifications to install bonnet pressure equalization provisions to the 1(2)NV0221 A,222B are planned for the next refueling outage (1,2EOCl1). As an l alternative to modification, Engineering is evaluating a procedural revision to alleviate the pressure locking

' concerni Either the modifications or procedure change will be made to satisfy the long term pressure locking concern for these valves.

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• Attachment I i ,

Program PRESLOK, Version 1 l -

Revision 0 December 22,1995 INI Ol83B This Mathcad Program is designed to calculate the estimated opening force under pressure locking scenarios for flex-wedge gate valves using a calculational methodology that accounts for wcdge stiffness icsisting pressure locking forces. This l

program was prepared by the Westinghouse Owner's Group based upon the calculational methods developed by Commonwealth Edison.

While this information is presented in good faith and believed to be accurato, the Westinghouse Owner's Group does not guarantee satisfactory results from reliance upon such information. Nothing contained herein is to be construed as a warranty, express or implied, regarding the performance, merchantability, fitness or any other matter with respect to the product, nor as a recommendation to use any product or process in conflict with any patent. The Westinghouse Owner's Group reserves the right, without notico, to alter or improve the methods described herein.

This section of the program reads the thirteen items of input data from the plinput1.dat file, i := 0.12 input; := READ (plinputl)

P bonnet := input o' Psi y := input 8 P up := input3 psi E := input9 psi I)down := input 2' Psi D stem := inputto'I" t := input3 in F po := input 3lbf a := input4 in VF := input l2 b := input5 'I" Hub length := input6 'in 0 := input7 deg i

i l

IWI.3!1)K. W r i, in t u 'ca r, c ,c t)n ~

% t an n:' m.

• rU l' + iM\

Program PRESLOK, Version 1 IfNUTS:

Bonnet Pressuro P bonnet = 200 psi Upstream Pressure P up = 120 psi Downstream Pressure P down = 0 psi Disk Thickness t = 2.27 in (taken at centerline of the hub vertically)

Seat Radius a = 4.89 in (corresponding to mean seat diameter)

Hub Radius (taken at plane of symmetry, b = 2.025 in perpendicular to the hub, radius of circle of equivalent area for non-circular hubs)

Scat Anglo 0 = 5 deg Poisson's Ratio (disk material at temperaturo) v = 0.3 7

Modulus of Elasticity (disk material at temperature) E = 2.76 10 psi Static Pullout Force F po = 0 lbf (measured value from diagnostic test)

Closo Valvo Factor VF = 1.29 Stem Diameter D stem = 2.375 in Hub Longth Hub length = 1.37 in (from inside face of disk to inside face of disk)  ;

l i

)

i

\ l'RUll)K.be1. Ra O I:!22M5 H m ni art)nnurs<vonn .Nw, b: s ? M1 l'm *' i ! \ l I

i i .

( 4 e Program PRESLOK, Version 1 1

PRESSORE FORCE CALCULATIONS l Coefficient of friction betwoon disk and scat: I cos(0) l

!-  := VF- p = 1.155 l 1 + VF sin (0) l Average DP across disks:

P up + P down DPavg := P bonnet - DPavg = 140. psi 1 l 2 Disk Stiffness Constants

'l u

. D :=

E-(t)3 7  ;

'2 D = 2.956 10 lbf in .1 12 1- v '

E G := G = 1.062 107 . psi 2-(1 + v) l Geometry Factors:

1 I b\ I f i

C -

1- 1 1 + 2 in a\ \ C 2 = 0.1315 2 := 4 (aj ( (bjj, 1

b 'Ib\ .l a Ibi C ' -

+I ' I" +' -

-1 3 ;" 4 a (aj (aj- C 3 = 0.0212 (b

I l32.

b C '

l'+ V + (I - v) 8 ;= 2 C 8 = 0.71 ..

(aj i

1 b 1+v li a 1-V I i

C 9 :=a- In + -

1 - b)2 . C 9 = 0.2973 2 (bj 4 (a) .;

a fa\* I a\ la\

L ' ' -

+1 'I" l+ '-I L 3=0 3=4a (a) taj (a) i  !

i 2

a 1+v l l-v l

. L9 :=a- In a\l+ . a3 L9=0 1  ;

2 (aj :4 (aj i-I

/*RESlf)K. Wr I. Rev. A IT2Mi 16strn ehuwe t>wr:cri Gnnp TC9wi F;57 AM I',wr 31:18

. r Program PRESLOK, Version 1  !

Geometr'y Factors: (continued) '

l Ii # I I\ l '

L g g := 64 I

1+4 b) i -5b(aj - 4 b\

' (aj 2r -

b In a\ 1 L g g = 0.0035 ga) gaj (bj.

4 l 1 1-V llb lbg2 f ,)l -

! L '

I-

• I- - ' - - -

1 < (1 + v) In L 17 = 0.1155 t 17 = ~4 4 (aj , (aj (bj.

i  ;

Moment 2 C9

-DPavg a 2 2 l M tb:=

a-b -L 37 M tb = -857.8 lbf l Cg 2ab DPavg 2 2  ;

i Q b ;= a-b Q b = 684.8 -

lbf  :

2b in Deflection due to pressure and bending:

2 3 4 a a DPavg a 5 y bg := M rb'D C 2+O b C 3- II D >

Deflection due to pressure and shear stress:

1 I bg2.

/ai

'K sa := -0.3- 2In -1+ - '

K sa = -0.2804 l

\bj (aj  ;

! 2 ,

i K sa DPavg a 5 I y sq :=

tG- sq = ON I E l l

! l Deflection due to hub stretch:

2 2 P force := x-(a - b ) DPavg i

P fo7ce Hub length l Y stretch

• g.b. '

(2 E) y stretch = 1.6787 10'5 in Total Doflection due to pressure forces:

-5

! Y q := Y bq + Y sq - Y stretch Y q = -9.9261 10 in

/*RI.Sil)K. % r.1. R , o l ~'t2M6 H c nneinwr clasics % Gnviv T ~'5tv6 8:57.A AI l'aer 41 f 5

s.

Program PRESLOK, Vorsion 1 p Ddflection due to seat contact force and shear stress (per Ibfhn.):

la\ l 1.2i In a\ a ysw;*' Y sw = -2.147 10

~7 tG libf)

Deflecti5n due to seat contact force and bonding (por Ibflin.):

l a3\ ~ (C 2) Ia C9 \ (gy ~ gg ybw 1 -L 9 -

1 -

C 3 +L 3 Y bw = -3.241 10 , -

l

\D) {Cg; \b ) \bj flbf)

\ i nj ]

Deflection due to hub compression: '

[2 x a 11ub length I 8 in cmpt= 4 0 N Ycmpr

• g, 2 2E j Ilbf\

l Total deflection due to seat contact force (per Ibflin.): .

-7 in Y w := Y bw + Y sw + Y cmpr Y w = -5.98 10 ,

! ( in j l Seat Contact Force for which doflection is equal to previously calculated deflection from pressure forces:

l yq l F 3 := 2 x a- F s = 5100 lbf I Y W UNSEATING FORCES l l Fy.,is includod in rnoasured static pullout Force j x 2 F piston P JD ste m bonnet F piston -,886 Ibf t 2 l F

vert := x a sin (0)-(2 P bonnetup--P P down) F vert = 1833.2 lbf I F preslock - 2 Fs-( c s(0) - sin (0)) F preslock = 10849.3 lbf F total := -F piston + F vert + F preslock + F pg F pg = 0 lbf l

F total = 11796.5 lbf I

l i

l'Rf.M1)K. h r. I, Ro . O l'./2]M  % rtm:lvaar t},oin 3 Gnmp 2C5NO 8:5~' A A1 lbruc 5 <-l5

1 l

Program PRESLOK, Version 1 Revision 0 l December 22.1995 {

l 2N10183B rhis Mathcad Piogram is designed to calculate the estimatea opening force under )

pressure locking scenarios for flex-wedge gate valves using a calculational  !

rnethodology that accounts for wedge stiffness resisting precsure locking forces. This program was prepared by the Westinghouse Owner's Group based upon the calculational methods developed by Commonwealth Edison.

While this information is presented in good faith and believed to be accurate, the Westinghouse Owner's Group does not guarantee satisfactory results from reliance

{

upon such information. Nothing contained herein is to be construed as a warranty, {

express or implied, regarding the performance, merchantability, fitness or any other matter with respect to the product, nor as a recommendation to use any product or process in conflict with any patent. The Westinghouse Owner's Group reserves the right, without notico, to alter or improve the methods described horcin. -

l This section of the program roads the thirteen items of input data from the plinput1.dat file.

i := 0.12 inputi := READ (plinputl)

P bonnet ;= I"P"l o' Psi y := input 8 P up := input3 psi E := input9 psi l

P down := input2 psi D stem := input)0'I" t := input3 in F pg := input 3lbf a := input4 in VF := input 12 b := input5 'I" Hub length := input 6 'i" 0 := inputydeg 1

(

l iwou>m uc i. va. i' m c,a oc ,:v w u;> m u w c. . i 1 <

i

Program PRESLOK, Version 1 t .

INPUTS:

l Bonnet Pressure P bonnet = 200 psi l Upstream Prossuro P up = 120 psi Downstream Pressuro P down = 0 psi Disk Thickness t = 2.27 in (taken at centerline of the hub vertically)

Seat Radius a = 4.89 in (corresponding to mean seat diameter) i Hub Radius (taken at plano of symmetry, b = 2.025 in i perpendicular to the hub, radius of circle I of equivalent area for non-circular hubs) i Seat Angle 0 = 5 deg Poisson's Ratio (disk material at temperature) y=0.3 i

7 Modulus of Elasticity (disk material at temperature) E = 2.76 10 psi Static Pullc>ut Force F po = 0 lbf (measured value from diagnostic test)

Cl n.,e Valve Factor VF = 0.534 l

Stem Diameter D stem = 2.375 in Hub Length Hub length = 1.37 in (from inside f ace of disk to inside f ace of disk) l l

l iwoun:. u r. i. u,x o anm weseiz.ni o.mrunn twn 8 ss et nw w?

I

i .

. - . 1

. Program PRESLOK, Version 1 <

PRESSURE FORCE CALCULATIONS  !

i Coefficient'of friction betwoon disk anti seat: I cos(0) '

z  := VF- = 0.508 '

1 + VF sin ( 0 ) _  ;

Averago DP across disks:

P up + P down '

DPavg := P bonnet - DPavg = 140 psi  ;

2 ,

Disk Stiffness Constants D :=

E-(t)3 7 2\ D = 2.95610 lbf in 1 I

12-(1 - V ) i E- 7 G := G = 1.062 10 psi 2-(1 + v)

Geometry Factors:

i 2

1 f C -

1- lb3 71 + 2 in ,3 3 C9 = 0.1315 2 := 4

\a) \ \b))_

l\ f

~a\+' lb) - 1 b b C ~~ '

+1 'I" 3"4a (aj (aj C 3 = 0.0212 (b) l 2' l 1

C -

1 + v t (1 - v) . b\ C 8 = 0.71 8 := 2 _\aj 2.

l C 9 :=a-b 1+v 2

In aI +

b 1-V 4

1-bl C 9 = 0.2973

\j (a -

a la\ l a\ la\

L +I +

'I" ' - I L3=0

~

3 ;" 4 a

\a) \aj \a) l a 1+v l 1-V lag 2' L9 := a- In ai + -

1- -

l L9=0 2 \a) 4 \a) l i

(-

I'k13ff)X. Vcr. I, Rn <> l'.L'22?DS.

\\ rsitneitousc On nrr's Group ??.'5:vri 8:3X AM Pa,:< .11f

.?

i l - 4

. Program PRESLOK, Version 1 Goometry Factors: (continued) 1 l I I I\b f

! L 3; := -1 -

1 + 4 bh - 5 b\ - 4 b\ -

2+ -

In a\ L g 3 = 0.0035 64 (aj (aj (aj (aj (bj,

1. 2 1 1-V Ilb I3 b f L -

1- -

1- - , - 1 + ( 1 + v) In ,3 - L g7 = 0.1155 l7 := 4 4 (aj (aj (bj.

Moment 2 C9 / 2

-DPavg a , -

2\

h1 tb = M tb = -857.8 lbf C8 2 a b (a - b ) - L 17 DPavg / 2 2\

Q b:=

2b

-(a - b ) Q b = 684.8.lbf -

in Deflection duo to pressure and bending:

2 3 4 a a DPavg a ~5 y bq := M tb D C 2+Q b C 3- L ii y bq = -4.3516 10 in D D Deficction duo to pressure and shear stress:

I f K sa :" - 0.3- 2In a\ - 1 + , b\ K sa = -0.2804 (b) (aj 2

K sa DPavg a 5

y sq tG 89 Deflection due to hub stretch:

2 2 P force := n-(a - b ) DPavg P

force liub length Y stretch " ,

-5 n b- (2 E) y stretch = 1.6787 10 in y Total Deflection due to pressure forces:

-5 Yq Y bq + Y sq - Y stretch y q = -9.9261 10 in l

l-l

\ 1 RLSil)K. Vrr. I, Rn 0 12/22nd n orm; hrause t)n tu > % < n o:q> LT9,wi +38 .\ A1 Pue,4r!5 l

r  ;

,- e

, . Program PRESLOK, Version 1 l

l Doflectio'n due to seat contact force and chear stress (por Ibf/in.):

fah Ia \

1.2 l In a (a) (b) ~7 in y s w := - y 3, = -2.147 10 -

tG llbf\ 1 1 7

\ In j Deflection due to seat contact force and bonding (por Ibflin.):

I g3\ ~ fC 2) Ia C9\ fa\ ~7 : in

~

~L - -

C 3 +L3 ybw "-(Dj 9 Y bw = -3.241 10 (C8) ( b / (b) libf\

l Deflection due to hub compression:

I2xa Hub length I ~8 in Ycmpr;*~

2 2E cmPr = -5.919 10 j

( in j .

Total deflection due to seat contact force (per Ibf/in.): ,

l

-7 In I Y w :" Y bw + Y sw + Y cmpr Y w = -5.98 10 t Scat Contact Forco for which deflection is equal to previously calculated deflection from pressure forces:

1' Yq l F s := 2 x a- F s = 5100 lbf -

i yw

l. l t

UNSEATING FORCES l F ,9 is included in measured static pullout Force l

x 2 l F P piston " j D ste m bonnet F piston = 886 lbf i

2 F

vert := x a sin (0)-(2 P bonnetup- -P P down) F vert = 1833.2 lbf i

F preslock := 2 Fs -( cos(0) - sin (0)) F preslock = 4276.1 lbf l

F total := -F piston + F vert + F preslock + F pg F pg = 0 lbf

, Ftotal = .5223.3 lbf i i i

i l'Nl0 $A)N. \1 r. l. RCV. O I N2}f)5 Wr vlin stlew t G A Iy O Gitsup 2 NWi b ?h A At l 'u n li of ?

, Attachment 2,!

. 1

-)

!a  !

(

l

\

August 24.1992 i l

l l

l C. W. Boyd. Mechanical / Nuclear Engineering Manager Catawba NuclearStation l Attention: S. L. Williams l

Subject:

McGuire NuclearStation l Catawba NuclearStation l

l Background Information on Hot Leg Recirculation for the ND DBD MC-1552.00. CN-1552.00 {

Attached is the final draft of the discussion of hot leg recirculation for the Catawba ND Design Basis Specification. 'Ihe information presented is equally applicable to McGuire. If you have any questions please call me at 382 7565.

4.

H. Jackson Lee, Jr., Senior Engineer Nuclear Engineering Group Nuclear Services Division HJL/ .

l cc: J. W. Byrd. Jr. (MNS)

W. H. Barron (CNS)

D. M. McGinnis (MNS)

S. R. Frye (CNS)

D. A. Baxter(MNS) l l

l i

s 9

t 4

A

l'j 10 CFR 50.46(b)(4) and (5) require that the core geomeuy and the ECCS be such that the core is amenable to long term cooling. If a LOCA is large enough that the coolant level cannot l accumulate above a cenain level, as in the case of a double-ended guillotine rupture of the main coolant loop piping, coolant injected into the same side of the NC system as the break will not be l

effective for core cooling via sensible heat removat ne Dow injected into the cold legs will keep the reactor vessel downcomer full of liquid. After core reflood is completed the core will be covered by a two-phase mixture. Boiling in the core will onven some of the reactor vessel j liquid into steam. He static head ofliquid in the downcomer will force additional liquid into the i core to replace that which is boiled. Any liquid in excess of this core boiloff requirement will exit through the break. For example. if there is a large cold leg LOCA any excess liquid injected into intact cold legs will not flow through the core but will simply enter the downcomer and exit through the bmken cold leg. Likewise, for a large hot leg LOCA any excess liquid injected into intact hot legs will not flow through the core but will simply enter the upper plenum and exit through the broken hot leg. If water is only injected fmm a single direction relative to the core, i.e. only into the cold legs or only into the hot legs, this situation can result in a volume of relatively stagnant borated water sunounding the core. Since no water is forced through the ciore, that stagnant volume is kept heated to the saturation temperature. and the water boils, leaving the boric acid behind. If this process contmues the boric acid concentration in the core region could exceed the solubility limit resulting in the deposition of solid boric acid on the fuel rods and +

other core s' ructures.

I To prevera the precipitation described above the ECCS systems are realigned to inject water into both the hot and cold legs. If the break is on a cold leg. the flow from the NI and possibly the ND. pumps is injected into the hot legs and must flow through the core to exit through the break.

Likewise, if the break is on a hot leg, the flow from the NV pumps continues to inject into the cold legs and must flow through the core to exit through the break. The flow ofliquid through the core reduces the boric acid concentration in the core region. Both flow directions are used because the location of the break (hot leg vs. cold leg) might not be able to be reliably detennined.

If the LOCA is small enough that the NC system level can refill to an elevation that allows liquid from the core to reach the break, the transfer to a hot leg recirculation alignment is not necessary.

His criterion is obviously met for breaks in which NC system subcooling is restored. For larger breaks, the exact elevation to which the system must refill to make a hot leg recirculation alignment unnecessary has not been explicitly calculated. A decision would be made prior to the procedural hot leg recirculation initiation time. Flow through the 44 unplugged reactor vessel upper head cooling nozzles, an area of 65 in2 at the elevation of the reactor vessel flange, would probably allow sufficient core liquid outflow to preclude continued boric acid buildup.

Even ifit were concluded that the hot leg recirculation alignment was necessary, consideration of existing conditions detennines the specific valve manipulations that would be made. First, as stated below, only a limited amount of hot leg injection flow is necessary to both remove decay heat at the switchover time and dilute the core region boron concentration. If at least this much flow can be provided by the available NI pump (s) when aligned for hot leg recirculation. a direct ND hot leg injection flow path need not be aligned. Funher, the FS AR Section 6.2.1.1.3.1 peak l containment pressure transient analysis takes credit. as shown in Table 6-17. for a cenain amount of ND auxiliary containment spray flow. Simultaneous alignment of an ND pump for direct hot l

, leg injection and auxiliary containment spray is unlikely, because of the relative resistances of the two flow paths. to result in significant auxiliary containment spray. Therefore. an ND pump which is the sole means of providing auxiliary containment spray should not be aligned te direct

i hot leg injection unless it can be verified that there exists an equivalent amount of normal containment spray heat removal capacity beyond that already credited in peak containment pressure transient analysis.

1 The mechanism for preventing boron precipitation with the hot leg recirculation alignment is that the excess flow, i.e., the flow above the decay heat removal requirement, is assumed to be at the core region boron concentration and removes at least a boron mass equal to that which is carried into the core region by safety injection flow. Calculation DPC-1552.08-00-0064 documents the

, flow required to remove decay heat at the time of the emergency alignment to hot leg recirculation. The additional flow required for boron dilution is not explicitly calculated but is approximately 10 gpm much less than the decay heat removal flow requirement. A single NI pump, at the time of hot leg recirculation alignment in the emergency procedures, is predicted to be able to supply much more than the minimum amount of core cooling and boron dilution flow required. 'Iherefore, the ND pump need not be realigned for direct hot leg injection for the accidents evaluated in the FSAR.

1

! 1