Issue Date: 04/30/10 - 1 - 62710 

 NRC INSPECTION MANUAL IRIB

INSPECTION PROCEDURE 62710 

POWER-OPERATED GATE VALVE 

PRESSURE LOCKING AND THERMAL BINDING 

PROGRAM APPLICABILITY: 2515 

62710-01 INSPECTION OBJECTIVES 

The objective of this procedure is to provide guidance to inspectors to independently 

assess licensee conclusions regarding extent of condition of issues, when selected, as a 

part of supplemental inspections using IP 95002, AInspection for One Degraded 

Cornerstone or Any Three White Inputs in a Strategic Performance Area.@ The inspection 

procedure may also be used when power-operated gate valve pressure-locking and 

thermal-binding issues are applicable to each input contributing to a degraded cornerstone 

(2 white or 1 yellow) or to address extent of condition for any white input to the Strategic 

Performance Area that results in implementation of IP 95002. 

62710-02 INSPECTION REQUIREMENTS 

The scope of the inspection using this procedure should be specifically focused on an 

independent extent of condition review and oversight of licensee self-assessment 

consistent with the objectives of IP 95002. 

The inspection plan should include one or more of the specific requirements listed below 

that are appropriate to perform an independent extent of condition review and oversight of 

licensee self-assessment necessary to assess the capability of power-operated gate valves 

in safety-related systems to operate under pressure-locking and thermal-binding conditions 

(or avoid such conditions) during normal, accident and abnormal conditions. The 

inspection may involve an in-depth review of calculations, analyses, diagnostic test results, 

modifications, and operating procedures used to ensure that proper operation of poweroperated gate valves is not prevented by pressure-locking and thermal-binding conditions. 

Select a sample of risk-significant power-operated gate valves from more than one system. 

The sample size should be appropriate for the scope of the inspection. Considerations for 

the review of the licensee's scope of its Generic Letter 95-07,@Pressure Locking and 

Thermal Binding of Safety-Related Power-Operated Gate Valves,@ program are provided in 

the Attachment 1 to this inspection procedure. Attachment 2 provides a generic list of 

valves that are normally included in the scope of GL 95-07. Changes that have been made 

to GL 95-07 programs and modifications involving the installation of power-operated gate 

valves susceptible to pressure locking or thermal binding should be considered during the 
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selection of the sample of power-operated gate valves for inspection review. These 

changes may involve revised design basis, plant modifications, power uprate, revised 

calculations, valves added to or removed from the program, revised safety valve setpoints, 

or the incorporation of new industry guidance into the program. Power-operated gate valve 

performance should be considered during valve selection. For example, review of trend 

reports, nonconformance reports, Licensee Event Reports, maintenance history or other 

plant documents may reveal that a valve was subjected to pressure-locking or thermalbinding conditions. 

02.01 Program Scope. Review power-operated gate valve program scope to ensure that 

the appropriate safety-related valves are included and modifications to systems or valves 

that could have altered the susceptibility of a power-operated gate valve to pressure locking 

or thermal binding. 

02.02 Design Bases Conditions. Review design documents used to determine poweroperated gate valve functional requirements during normal, accident and abnormal 

conditions, and susceptibility to pressure locking or thermal binding. 

02.03 Pressure-Locking and Thermal Binding Calculations. Review calculations used to 

demonstrate that power-operated gate valves are capable of operating if susceptible to 

pressure-locking and thermal binding conditions. 

02.04 Testing. Review diagnostic test results used to support pressure-locking and 

thermal-binding assumptions in design calculations or other engineering documents. 

02.05 Pressure Locking Corrective Actions. Review pressure-locking corrective actions 

including modifications that were implemented to eliminate the potential susceptibility of 

valves to pressure lock, or to provide for the capability of the valve to operate under such 

conditions, and operating procedures that contain special instructions for valves susceptible 

to pressure locking. 

02.06 Thermal Binding Corrective Actions. Review thermal-binding corrective actions 

including modifications that were implemented to eliminate the potential susceptibility of 

valves to thermally bind, or to provide for the capability of the valve to operate under such 

conditions, and operating procedures that contain special instructions for valves susceptible 

to thermal binding. 

02.07 Trending. Review trend reports, failure analysis, corrective actions, 

nonconformance reports, or other plant documents that may reveal pressure-locking or 

thermal-binding conditions. 
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02.08 PI&R Inspection Reports. Review past PI&R inspection reports on this subject. 

Determine if there were any significant problems identified with pressure locking or thermal 

binding of valves. 

62710-03 INSPECTION GUIDANCE 

General Guidance

In response to the identification of plant-specific power-operated gate valve pressure 

locking and thermal binding issues, the NRC staff may determine that an inspection of the 

licensee=s GL 95-07 program is appropriate using IP 62710. In planning the inspection 

under this procedure, the assigned regional inspector should review the identified poweroperated gate valve pressure locking and thermal binding performance issues. The 

inspector should then prepare an inspection plan incorporating one or more of the specific 

inspection requirements outlined in Section 62710-02 that the inspector considers 

necessary to perform an independent extent of condition review and oversight of the 

licensee self-assessment with respect to the pressure locking and thermal binding issues 

identified at the plant. Based on the extent of the selected inspection requirements, the 

inspector should estimate the resources necessary to perform the inspection as discussed 

in Section 62710-04. 

This inspection procedure is intended to assess the adequacy of calculations, analyses, 

test results, operating procedures and modification packages that are used to ensure that 

power-operated gate valves are not prevented from performing their safety function by 

pressure locking and thermal binding. 

Pressure locking and thermal binding represent potential common-cause failure 

mechanisms that can render redundant safety systems incapable of performing their safety 

functions. Pressure locking occurs in flexible-wedge and double-disk gate valves when 

fluid becomes pressurized inside the valve bonnet and the actuator is not capable of 

overcoming the additional thrust requirements resulting from the differential pressure 

created across both valve disks by the pressurized fluid in the valve bonnet. Thermal 

binding is generally associated with solid-wedge and flexible-wedge gate valves that are 

closed while the system is hot and then allowed to cool before an attempt is made to open 

the valve. 

On August 17, 1995, the NRC issued Generic Letter (GL) 95-07 to request that licensees 

take certain actions to ensure that safety-related power-operated gate valves that are 

susceptible to pressure locking or thermal binding are capable of performing their safety 

functions within the current licensing bases of the facility. The NRC staff reviewed the 

licensees= actions in response to GL 95-07 in a safety evaluation (SE) for each unit. Each 

SE describes the actions taken by the licensee to ensure that power-operated gate valves 

operate during pressure-locking and thermal-binding conditions that were reviewed and 

accepted by the NRC staff when closing GL 95-07. This safety evaluation should be 

reviewed by the inspector prior to the inspection. 
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GL 89-10, ASafety-Related Motor-Operated Valve Testing and Surveillance,@ requested 

that nuclear power plant licensees and construction permit holders ensure the capability of 

motor operated valves (MOVs) in safety-related systems to perform their intended functions 

by reviewing MOV design bases, verifying MOV switch settings initially and periodically, 

testing valves under design-basis conditions where practicable, improving evaluations of 

MOV failures and necessary corrective action, and trending MOV problems. GL 96-05, 

APeriodic Verification of Design-Basis Capability of Safety-Related Power-Operated 

Valves,@ requested each nuclear power plant licensee to establish a program, or to ensure 

the effectiveness of its current program, to verify on a periodic basis that safety-related 

MOVs continue to be capable of performing their safety functions within the current 

licensing bases of the facility. In most instances, risk insights were used to develop MOV 

diagnostic test schedules developed in response to GL 89-10 and GL 96-05. 

The vast majority of gate valves identified as susceptible to pressure locking and thermal 

binding were MOVs. Therefore, the MOV risk insights developed in response to GL 89-10 

and GL 96-05 should be considered during the selection of sample valves to be inspected. 

Valves may be risk ranked with respect to their relative importance to core-damage 

frequency and other considerations added by an expert panel. The MOV selection should 

include valves ranked as high risk if possible. The NRC staff is describing its review of 

licensees= actions in response to GL 96-05 in an SE for each unit. Each SE notes the MOV 

risk-ranking methodology that was accepted by the NRC staff when closing GL 96-05. 

Several licensees did not use risk insights to rank their valves in the development of their 

GL 89-10 or GL 96-05 programs. Generic MOV risk insights for boiling water reactors 

(BWRs) may be obtained from BWR Owners Group Report NEDC-32264A (Revision 2). 

Generic MOV risk insights for Westinghouse plants may be obtained from Westinghouse 

Owners Group (WOG) Report V-EC-1658 (Revision 1). These risk ranking approaches 

were reviewed and accepted by the NRC staff in SEs dated February 27, 1997 (BWR), and 

April 14, 1998 (WOG). 

The WOG MOV risk-ranking approach can also be used to provide insights for ranking 

MOVs in Combustion Engineering and Babcock & Wilcox design plants based on their 

safety significance, except that the generic list of high risk valves in WOG Report V-EC1658 only apply to Westinghouse design plants. 

Specific Guidance

03.01 Program Scope. The criteria for determining the scope of power-operated valves 

for GL 95-07 are consistent with the staff's acceptance of the scope of MOVs associated 

with GL 89-10. Considerations for the review of the licensee's scope of its GL 95-07 

program are provided in the Attachment 1 to this inspection procedure. Attachment 2 

provides a generic list of valves that are normally included in the scope of GL 95-07. Since 

the completion of SEs for GL 95-07, some licensees may have modified the scope of their 

power-operated gate valve pressure-locking and thermal-binding programs. Where a 

licensee has modified the scope of its program, the inspector should determine whether the 

licensee has adequately justified the removal of any power-operated valves from its 

program. Further, the inspector should be alert for modifications to systems or valves that 
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could have altered the susceptibility of a power-operated gate valve to pressure locking or 

thermal binding. 

03.02 Design Bases Conditions. The inspector should review the appropriate design 

documents and operating and surveillance procedures and verify that the licensee has 

considered (1) all credible leak paths into valve bonnets; (2) external and internal conditions 

that may exist or change during normal, surveillance or operating conditions that may 

cause the temperature of the valve to increase; (3) the potential for gate valves to pressure 

lock or thermally bind during surveillance testing or other special tests; and (4) the potential 

for valves to be closed while the system operating fluid is at a relatively high temperature, 

the valve is allowed to cool, and then required to open. For example, the fluid may enter 

the valve bonnet (1) during normal open and close valve cycling; (2) when pump discharge 

pressurizes a valve bonnet and the pressure becomes trapped in the bonnet after the pump 

is secured; (3) if the gate valve is in a line connected to a high-pressure system and 

isolated only by check valves (which may transmit pressure even when passing leaktightness criteria); and (4) during a hydrostatic test of adjacent piping. 

A valve bonnet that contains steam or gas is susceptible to hydraulic-induced pressure 

locking. However, thermally induced pressure locking is mitigated during conditions where 

the bonnet is filled with steam or gas. The licensee should address the heat transfer to the 

valve from the adjacent piping and atmosphere that can occur during accident conditions. 

For example, conditions that can cause the temperature of the valve bonnet to increase 

include heat from pump motors, steam driven turbines, and high temperature fluid in 

adjacent piping. Normal ambient temperature changes are not required to be considered. 

In some cases, reliance on entrapped gas to limit bonnet pressure was accepted in GL 95-

07 when detailed justification was provided by the licensee. 

03.03 Pressure-Locking and Thermal Binding Calculations Some licensees used 

pressure-locking and thermal-binding methodologies to demonstrate that valves are 

capable of operating under pressure-locking and thermal-binding conditions. Calculations 

used to demonstrate that selected valves are capable of operating during pressure-locking 

or thermal-binding conditions should be reviewed. Motor sizing calculations must consider 

degraded voltage and elevated ambient temperature conditions. For example, the 

inspector should ensure that the lowest motor terminal voltage commensurate with the 

design-basis conditions has been factored into the calculation. Proper actuator pullout 

efficiency and application factor must be used. The weak link capability of the MOV should 

also be evaluated to ensure that the valve or actuator is not damaged if required to operate 

during pressure-locking or thermal-binding conditions. In Technical Update 98-01 and its 

Supplement 1, Limitorque Corporation provided updated guidance for predicting the torque 

output of its ac-powered motor actuators. In its letter dated July 17, 1998, forwarding 

Technical Update 98-01, Limitorque indicates that a future technical update will be issued 

to address the application of dc-powered valves. 

The inspector should verify that thermal induced pressure locking calculations assume a 

reasonable temperature/pressure rate increase. NUREG-1275, AOperating Experience 

Feedback Report-Pressure Locking and Thermal Binding of Gate Valves,@ states that the 

rate of pressure rise can be as high as 100 psi per 1 F temperature increase in a solid 

filled bonnet for system temperature above 450 F. For lower system temperature 
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(approximately 100 F), the rate noted in NUREG-1275 is reduced to 33 psi per 1 F 

temperature rise. Testing sponsored by the NRC that was conducted by the Idaho National 

Engineering and Environmental Laboratory (INEEL) suggested that a pressure rise of 50 

psi per 1 F temperature increase was applicable. The results of this testing are 

documented in NUREG/CR-6611, AResults of Pressure Locking and Thermal Binding Tests 

of Gate Valves.@ These thermal induced pressurization rates were accepted by the NRC 

staff in the SEs closing GL 95-07. 

Adequate bases must exist for stem factors, valve factors, and other assumed parameters, 

as applicable, that are used in calculations. The inspector should verify that the valve and 

stem factors used in calculations are consistent with GL 89-10 program values. The 

following is a list of the pressure-locking methodologies most often used by licensees in 

their GL 95-07 submittals to demonstrate that valves are capable of operating under 

pressure-locking conditions. 

a. A pressure-locking methodology developed by Commonwealth Edison Company 

(ComEd) was used for flexible wedge gate valves. The margins along with 

diagnostic equipment accuracy and methodology limitations are defined in a letter 

from ComEd to the NRC dated May 29, 1998. The use of the ComEd pressure 

locking methodology is acceptable provided these margins, diagnostic equipment 

accuracy requirements and methodology limitations are incorporated into the 

pressure-locking calculations as specified in the applicable GL 95-07 SE. The NRR 

Mechanical and Civil Engineering Branch (EMEB) developed a computer program 

to assist inspectors in assessing the capability of flexible gate valves to open during 

pressure-locking conditions using the ComEd thrust prediction pressure-locking 

methodology. Contact EMEB or the regional motor operated valve inspector for 

further information regarding use of the computer program. 

b. A modified industry gate valve thrust equation was used to predict the thrust 

required to open flexible wedge gate valves during pressure locking conditions. 

Pressure locking tests sponsored by the NRC were conducted by the INEEL on a 

flexible wedge gate valve. The results of this testing are documented in 

NUREG/CR-6611. Test data demonstrated that the modified industry gate valve 

calculation conservatively estimated the thrust required to open a pressure-locked 

flexible wedge gate valve. 

c. A modified industry gate valve thrust equation was used to predict the thrust 

required to open double disk gate valves during pressure-locking conditions. 

Pressure-locking tests sponsored by the NRC were conducted by INEEL on a 

double disk gate valve. The results of this testing are documented in NUREG/CR6611. Test data demonstrated that the modified industry gate valve calculation 

underestimated the thrust required to open a pressure-locked double disk gate 

valve; however, the results of the calculation properly trended with actual test 

results. Sizing the power actuator to satisfy the modified industry gate valve thrust 

equation provides reasonable assurance that flexible wedge gate valves 

susceptible to pressure locking are capable of performing their intended safetyrelated function provided that the margin between predicted pressure-locking thrust 

and actuator capability is equal to or exceeds approximately 40 percent. The 
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licensee should provide additional justification if it proposes a margin less than 

approximately 40 percent. 

This is not a complete list of pressure-locking methodologies used by licensees to 

demonstrate that valves are capable of operating during pressure-locking conditions. 

Some licensees developed a site-specific pressure locking or thermal binding thrust 

prediction methodology to demonstrate that valves are capable of opening under pressurelocking or thermal-binding conditions. The conditions and limitations associated with the 

use of the individual methodology are discussed in the site-specific GL 95-07 SE. In 

instances where a licensee developed and used a site-specific methodology (methodology 

was not described in section 03.03a, b or c in this inspection procedure), the inspector 

should review the test data used to ensure that the methodology accurately predicts the 

thrust required for the valve to open during pressure-locking or thermal-binding conditions. 

The inspector should (1) verify test equipment is setup and calibrated in accordance with 

vendor recommendations; (2) verify qualification of test personnel; (3) determine test 

equipment inaccuracies and test data accuracy; and (4) verify that the methodology 

accurately predicts the thrust (torque) required to open the pressure-locked or thermallybound valve. 

Following the initial verification of valve capability under design-basis conditions, the valve 

settings will need to be re-verified if the valve is replaced (which would constitute the need 

for a complete demonstration of design-basis capability), modified, or overhauled to the 

extent that the licensee considers that the existing test results are not representative of the 

valve in its modified configuration. Because of the interrelationship of various operating 

parameters, the performance of the valve can be affected by routine maintenance work, 

such as valve packing adjustments. 

03.04 Testing. The inspector should review the diagnostic test results used to support 

pressure-locking and thermal-binding assumptions in design calculations or other 

engineering documents. The assumptions include valve factors and stem factors for MOVs 

which were established under the GL 89-10 program and periodically verified under the GL 

96-05 program. Diagnostic testing to support MOV pressure-locking and thermal-binding 

assumptions should be consistent with the diagnostic testing methods justified under the 

GL 89-10 and GL 96-05 programs. 

03.05 Pressure Locking Corrective Actions. The inspector should review the corrective 

actions performed in response to GL 95-07 for the sampled valves. The following are 

examples of corrective actions to prevent or overcome pressure locking accepted in GL 

95-07 SEs. 

a. Procedures

1. Procedures were modified to cycle valves following evolutions that could 

potentially create a pressure-locking condition. 

2. Procedures were revised to minimize the time that pumps could be operated 

at minimum flow conditions if temperature of the system increased due to 

operation of the pumps at minimum flow. 
Issue Date: 04/30/10 - 8 - 62710 

3. The bonnet of the valve was aligned to the reactor side piping on valves 

equipped with a body drain. 

4. The position of the valve was changed from closed to open or procedures 

were revised to not require that the valve be opened during pressure-locking 

conditions. 

5. The containment sump suction piping was filled with water or maintained in a 

dry-lay condition to prevent the temperature of the valves from increasing 

during accident conditions. 

6. Procedures were revised to prevent one train from being inadvertently 

pressurized when testing the other train. 

7. The suction of one train of residual heat removal was aligned to the refueling 

water storage tank when the other train of residual heat removal was aligned 

for shutdown cooling. 

b. Modifications

1. Actuator control logic was changed to utilize the limit switch to minimize travel 

of the disk into the seat. Procedures were revised to periodically review 

diagnostic test data to ensure that disk travel was minimized. 

2. Valves were modified to eliminate the potential for pressure locking by drilling 

a hole in the high pressure side of the valve disk or installation of a bonnet 

pressure equalization line. 

3. Valves were replaced with valves not susceptible to pressure locking. 

4. Valve bonnets were equipped with a relief valve or blowout plug to limit the 

pressure in the bonnet and a pressure locking analytical method used to 

calculate the thrust (torque) required to open the valve during pressurelocking conditions below the relief valve or blowout plug setpoint. 

5. Valve bonnets were equipped with an accumulator to limit the pressure in the 

bonnet and a pressure locking analytical method used to calculate the thrust 

(torque) required to open the valve during pressure-locking conditions below 

the maximum accumulator pressure. 

6. A bonnet vent with a manual valve was installed and procedures were 

revised to cycle the bonnet vent valve prior to opening the valve during 

pressure-locking conditions. 

7. The actuator was modified or replaced with a larger actuator to increase 

thrust (torque) output to meet thrust prediction pressure-locking methodology 

requirements. 
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8. Insulation was installed on the valve body and bonnet to minimize the heat 

transfer to the bonnet during conditions when the ambient temperature could 

increase during a design basis accident. 

9. Valve bodies were equipped with a 3-way check valve system to limit the 

pressure in the bonnet. The 3-way check valve usually has 3 connections to 

the valve body: upstream and downstream of the valve seats and the third 

connection between the upstream and downstream valve seats. The 3-way 

check valve system aligns the bonnet area of lower pressure to provide a 

pressure vent path, be it either upstream or downstream side of the valve. 

c. Analyses/Calculations

1. Some licensees relied on pump discharge pressure to equalize pressure 

in the bonnet of a valve that is susceptible to pressure locking. As a 

result, the MOV may operate at locked rotor. The NRC staff accepted 

operation of actuators for approximately 1 second at locked-rotor 

conditions because testing performed by INEEL (NUREG/CR-6478) 

demonstrates that the capability of the actuator does not degrade over this 

short time period. 

2. The ComEd pressure-locking thrust prediction methodology was used to 

demonstrate that flexible wedge gate valves would operate during 

pressure-locking conditions. 

3. A modified industry gate valve thrust equation was used to demonstrate 

that double disk gate valves would operate during pressure-locking 

conditions. 

4. A modified industry gate valve thrust equation was used to demonstrate 

that flexible wedge gate valves would operate during pressure-locking 

conditions. 

5. In cases where 12 or more hours elapse between pressurizing the valve 

bonnet and opening the valve, leakage was credited to vent the valve 

bonnet provided that the temperature of the valve did not increase over 

the 12-hour period. In one case, valve leakage was credited to vent the 

bonnet of each of the unit=s reactor coolant system hot leg injection valves. 

 There were six hot leg injection valves and six redundant hot leg flow 

paths in each unit and one hot leg injection valve was required to be 

opened 5.5 hours or more after a loss of coolant accident. The basis for 

accepting this analysis was that the probability of a loss of coolant 

accident combined with the failure of all six hot leg injection valves to open 

due to pressure locking is exceedingly low. The results of valve seat 

leakage test performed by several licensees and INEEL (NUREG/CR6611) demonstrate that valve leakage is probable when pressure-locking 
Issue Date: 04/30/10 - 10 - 62710 

conditions exist; however, the specific leakage rates that were obtained 

during the tests were inconclusive. 

6. Heat transfer calculations were used to demonstrate that the temperature 

of valves would not increase during accident conditions. Normal ambient 

temperature changes were not required to be considered. 

03.06 Thermal Binding Corrective Actions. The inspector should review the corrective 

actions performed in response to GL 95-07 for the sampled valves. The following are 

examples of accepted corrective actions to prevent or overcome thermal binding. 

a. Procedures

1. Technical Specifications were changed to require that valves be declared 

inoperable and the appropriate Technical Specification action statement 

entered whenever the valves are closed while the system is hot and then 

allowed to cool before an attempt is made to open the valves. 

2. Procedures were modified to cycle valves following evolutions that could 

potentially create a thermal-binding condition. 

3. Procedures were revised to shut the valve prior to increasing the 

temperature of the valve. 

b. Modifications

1. Valves were replaced with valves not susceptible to thermal binding. 

2. Valves equipped with spring-compensating actuators, position seated, 

and/or set up with minimal unwedging thrust to reduce the potential for 

thermal binding. 

c. Analyses/Calculations

1. When evaluating whether flexible and solid-wedge gate valves were 

susceptible to thermal binding, licensees assumed that thermal binding 

would not occur below specific temperature thresholds. These 

assumptions were based on industry experience. 

2. Several thermal-binding methodologies were developed and used to 

demonstrate that valves were capable of operating during thermal-binding 

conditions. Test data that quantified the magnitude of the thermal binding 

effect were used to validate the thermal-binding methodology. 

3. Diagnostic testing performed during thermal-binding conditions 

demonstrated that a valve was not susceptible to thermal binding at 

current settings. 

4. Operational history was used to demonstrate that valves were not 

susceptible to thermal binding. 
Issue Date: 04/30/10 - 11 - 62710 

03.07 Trending. The inspector should review the adequacy of the licensee's analyses of 

power-operated gate failures that may be attributed to pressure locking or thermal binding. 

The inspector should review recent failures and the resulting corrective action. The 

licensee=s failure analysis should include the results and history of each as-found 

deteriorated condition, malfunction, test, inspection, analysis, repair, or alteration. 

03.08 PI&R Inspection Reports. No specific guidance. 

62710-04 RESOURCES 

This inspection procedure provides guidance that could be used to assess the entire GL 

95-07 program. However, since the scope of the inspection is focused on an independent 

extent of condition review and oversight of licensee self-assessment and may be limited to 

specific inspection requirements identified in Section 62710-02, it is estimated that it may 

take an inspector a minimum of 4 hours to accomplish. If the nature of the problems 

prompting the inspection are extensive requiring a more broad review, then it may take up 

to 30 hours to accomplish the inspection. 

Other factors that affect the amount of time required to complete the inspection are the 

knowledge and experience of the inspector(s) and the number of safety-related poweroperated gate valves in each unit. It is recommended that inspector(s) knowledgeable of 

GL 89-10, GL 95-07, and GL 96-05 recommendations and power-operated gate valve 

mechanical and electrical characteristics perform the inspection. The majority of poweroperated gate valves that were identified to be susceptible pressure locking and thermal 

binding in GL 95-07 submittals were MOVs. Some early-vintage units may have fewer 

safety-related power-operated gate valves than later-vintage units. The number of safetyrelated power-operated gate valves should be considered when determining the amount of 

time needed to accomplish the inspection. 

62710-05 REFERENCES 

GL 89-10, ASafety-Related Motor-Operated Valve Testing and Surveillance@

GL 96-05, APeriodic Verification of Design-Basis Capability of Safety-Related MotorOperated Valves@

GL 95-07, APressure Locking and Thermal Binding of Safety-Related Power-Operated 

Gate Valves@

BWR Owners Group (BWROG) Report NEDC-32264A (Revision 2), AApplication of 

Probabilistic Safety Assessment to Generic Letter 89-10 Implementation@ 

Westinghouse Owners Group (WOG) Report V-EC-1658 (Revision 1), ARisk Ranking 

Approach for Motor-Operated Valves in Response to Generic Letter 96-05@
Issue Date: 04/30/10 - 12 - 62710 

NUREG-1275 “Operating Experience Feedback Report – Pressure Locking and 

 Thermal Binding Gate Valves.” 

NUREG/CR-6611 “Results of Pressure Locking and Thermal Binding Tests of Gate 

 Valves.” 

NUREG/CR-6478 “Motor-Operated Valve Actuator Motor and Gearbox Testing” 

END 

Attachments: 

1. Considerations in Reviewing Licensee Scope of Generic Letter 95-07 Programs. 

2. Generic List of Valves Susceptible to Pressure Locking and Thermal Binding.

3. Revision History for IP 62710 
Issue Date: 04/30/10 Att1-1 62710 

Attachment 1 – Considerations in Reviewing Licensee Scope of GL 95-07 Program

1. The scope of the program extends to safety-related power-operated valves as 

defined in the NRC regulations. In GL 95-07, the staff requests licensees to 

determine the design basis for the operation of each safety-related power-operated 

valve including the maximum pressure and temperature conditions expected during 

normal operations and abnormal events, to the extent that these valve operations 

and events are included in the existing approved design basis. 

2. Safety-related power-operated valves that are always in their safety position, or 

would have no affect on the operation of the safety train if placed in the non-safety 

position, can be removed from the GL 95-07 program. 

3. Section 3.1.2 of NUREG-1482, "Guidelines for Inservice Testing at Nuclear Power 

Plants," issued by GL 89-04 (Supplement 1), "Guidance on Developing Acceptable 

Inservice Testing Programs," dated April 4, 1995, discusses the capability of plant 

components and surveillance testing. In this regard, safety-related power-operated 

valves that are placed in a position that prevents the safety-related system (or train) 

from performing its safety function must be capable of returning to their safety 

position, or the system (or train) must be declared inoperable and the appropriate 

plant technical specifications followed. 

4. In the second footnote in GL 89-10, the staff states that design-basis events are 

defined as conditions of normal operation, including anticipated operational 

occurrences, design-basis accidents, external events, and natural phenomena for 

which the plant must be designed to ensure the function delineated as "safetyrelated" can be performed. The staff further states in the footnote that the design 

bases for each plant are those documented in pertinent licensee submittals, such 

as the final safety analysis report. In Bulletin 85-03, the staff requested Boiling 

Water Reactor (BWR) plants to ensure that valves in the Reactor Core Isolation 

Cooling system can perform their safety function. 

5. Supplements 4 and 7 to GL 89-10 removed the recommendation that licensees of 

BWR and pressurized water reactor nuclear plants, respectively, consider 

inadvertent mispositioning of valves as part of their GL 89-10 programs. 

6. The residual heat removal pump hot-leg injection valve(s) was (were) not in the 

scope of GL 95-07 if the final safety analysis report (FSAR) accident analysis did 

not credit the residual heat removal pumps for providing hot-leg injection. The 

pressurizer power-operated relief valve block valve was not in the scope of GL 95-

07 if technical specifications allowed the unit to operate indefinitely with the 

pressurizer power-operated relief block valve shut and deenergized. Emergency 

core cooling system valves for modes other than criticality and recovery from an 

inadvertent reactor trip were not in the scope of GL 95-07 if technical specifications 

required that the emergency core cooling systems be operable for the criticality and 

recovery from an inadvertent reactor trip. 

7. Licensees may rely on analysis results for each design-basis event and each 

system's required capability to satisfy event acceptance limits provided in the FSAR 
Issue Date: 04/30/10 Att1-2 62710 

where the licensee can demonstrate that the information in the updated FSAR is 

consistent with the licensing basis of the facility. 

8. Licensees are required to meet the single failure criterion in the NRC regulations. 

Other criteria may also apply at the same time (e.g., loss of offsite power). Further, 

safety systems are required to meet the redundancy provisions of Appendix A to 10 

CFR Part 50. The consideration of the single failure criterion as applied to 

anticipated operational transients should be consistent with the staff's licensing 

review for the individual facility. 

9. The safe shutdown licensing basis for each facility is defined in licensing 

documents. Valves that are operated during conditions below the safe shutdown 

licensing basis are not required to be in the scope of the GL 95-07 program 

provided that the licensee does not have any other commitments that the MOV 

must operate during certain conditions. For example, if the safe shutdown licensing 

basis is Hot Shutdown, valves that are operated during conditions below Hot 

Shutdown are not required to be in the scope of the program. 

END 
Issue Date: 04/30/10 Att2-1 62710 

Attachment 2 – Generic List of Valves Susceptible to Pressure Locking and Thermal 

Binding 

BABCOCK & WILCOX-DESIGN PLANTS

Valve Susceptible to Pressure Locking

Decay Heat Cooler Discharge to Makeup Suction 

Decay Heat Drop Line Isolation 

Decay Heat Injection 

Decay Heat Supply to High Pressure Injection (HPI) Pump Suction 

Emergency Feedwater (EFW) Header Cross Connect 

EFW Pump Discharge 

EFW Pump Service Water Suction 

EFW Turbine Steam Admission 

HPI Pump Discharge Cross Connect 

Low Pressure Injection (LPI) Header Isolation to HPI 

LPI/Decay Heat Loop Isolation 

LPI Isolation 

LPI Reactor Building Isolation 

LPI Return from Reactor Coolant System (RCS) 

Post Loss of Coolant Accident Boron Dilution to the Emergency Sump 

Pressurizer Electromatic Relief Valve Isolation 

Pressurizer Power-Operated Relief Valve (PORV) Block 

RCS Return from Letdown Line 

Reactor Building Cooling Unit Inlet Isolation 

Sodium Hydroxide Tank Suction 

Spent Fuel Pool to RCS Makeup Pump Suction Block 

 

Valves Susceptible to Thermal Binding

 

EFW Pump Injection 

EFW Turbine Steam Inlet 

LPI Injection 

Pressurizer Electromatic Relief Valve Isolation 

Pressurizer Sample Isolation 

Pressurizer Vent Stop 

Pressurizer PORV Block 

Reactor Building Sump Isolation 

Safety Injection Pump Suction 
Issue Date: 04/30/10 Att2-2 62710 

COMBUSTION ENGINEERING-DESIGN PLANTS

Valves Susceptible to Pressure Locking

Auxiliary Feed Water (AFW) Pump Discharge 

AFW Pump Turbine Steam Supply 

Boric Acid Gravity Feed Isolation 

Boric Acid Makeup (BAMU) Pump to Charging Pump Suction Control Valve 

BAMU Tank Gravity Feed to Charging Pump 

BAMU Tank to Charging Pump Suction Header Control Valve 

Containment Spray Header Isolation 

Containment Spray Shutdown Cooling Heat Exchanger Bypass 

Containment Sump Header Isolation 

High Pressure Safety Injection Long Term Loop Recirculation 

Low Temperature Overpressure Relief Isolation 

Pressurizer Emergency Core Cooling Vent 

Pressurizer Power-Operated Relief Valve (PORV) Block 

Refueling Water Storage Tank to Charging Pump Suction 

Safety Injection Pump Recirculation to Refueling Water Storage Tank 

Service Water to Emergency Feedwater Pump Isolation 

Shutdown Cooling Cross Tie 

Shutdown Cooling Heat Exchanger Inlet 

Shutdown Cooling Heat Exchanger Outlet 

Shutdown Cooling Hot Leg Suction 

Shutdown Cooling to Low Pressure Safety Injection Pump Suction 

Valves Susceptible to Thermal Binding

Boric Acid Pump to Charging Pump Suction 

Boric Acid Storage Tank Outlet Isolation 

Charging Pump Suction Header and Boric Acid Supply 

Emergency Feedwater Injection 

Emergency Feedwater Turbine Steam Inlet 

High Pressure Safety Injection/Charging Cross Tie 

Pressurizer PORV Block 

Shutdown Cooling Heat Exchanger Isolation 

Shutdown Cooling Hot Leg Suction 

WESTINGHOUSE-DESIGN PLANTS

Valves Susceptible to Pressure Locking

Alternate Charging Isolation 

Auxiliary Feedwater Pump Discharge to Steam Generators 

Boric Acid Tank Gravity Boration 

Boron Injection Tank Inlet 

Boron Injection Tank Outlet 

Component Cooling Water from Residual Heat Removal (RHR) Heat Exchangers 
Issue Date: 04/30/10 Att2-3 62710 

Containment Spray Pump Discharge 

Containment Sump to RHR Pump Suction 

Diesel Generator Lube Oil Filter Bypass 

High Head Safety Injection (SI) Pump to Cold Leg 

Low Head SI Pump Suction 

Main Steam to Turbine Driven Auxiliary Feedwater Pump 

Normal Charging Isolation 

Pressurizer Power Operated Relief Valve (PORV) Block 

Quench Spray Pump Discharge 

Reactor Building Cooling Unit Outlet Isolation 

Refueling Water Storage Tank (RWST) to Charging Pump Suction 

RHR Cross-Tie Isolation 

RHR Heat Exchanger Outlet 

RHR Heat Exchanger Outlet to Containment Spray Header 

RHR Pump Suction from the RWST 

RHR to Hot Leg Injection 

RHR to Reactor Vessel Deluge 

RHR to SI/Charging Suction 

Recirculation Spray System (RSS) to RHR Cross Connect 

RSS Cooling Pump Discharge Isolation 

RSS Pump Discharge Isolation 

RSS to SI 

SI Pump Hot Leg Isolation 

SI Pump Discharge Isolation 

SI to Charging System 

Service Water Supply to Standby Auxiliary Feedwater Pumps 

Steam Generator Pressure Relief Isolation 

Sodium Hydroxide to Reactor Building Spray Pump Suction 

Volume Control Tank (VCT) Outlet 

VCT Outlet 

Valves Susceptible to Thermal Binding

Low Head SI Cold Leg Isolation 

Pressurizer PORV Block 

Reactor Coolant System to RHR Pump Suction 

RHR Minimum Flow Control 

Steam Generator PORV Block 

GENERAL ELECTRIC-DESIGN PLANTS

Valves Susceptible to Pressure Locking

Containment Spray Isolation 

Core Spray Injection 

Drywell Spray 

Essential Low Pressure Coolant Injection Inverter Room Cooler Inlet 

High Pressure Coolant Injection (HPCI) Isolation 
Issue Date: 04/30/10 Att2-4 62710 

HPCI Turbine Steam Admission 

High Pressure Core Spray (HPCS) Pump Minimum Flow 

HPCS Pump Suction from Suppression Pool 

Isolation Condenser Condensate Return 

Low Head Safety Injection (SI) Cold Leg Isolation 

Low Pressure Core Spray Pump Minimum Flow Bypass Isolation 

Main Steam Drain Isolation 

Main Steam Isolation Valve Leakage Control 

Reactor Core Isolation Cooling (RCIC) Injection 

RCIC Pump Suppression Pool Suction 

RCIC Steam Exhaust to Suppression Pool 

RCIC Steam Supply Isolation 

Reactor Water Clean Up Isolation 

Residual Heat Removal (RHR) Containment Spray Shutoff 

RHR Heat Exchanger Inlet 

RHR Heat Exchanger Outlet 

RHR Loop Isolation 

RHR Low Pressure Coolant Injection 

RHR Pump Minimum Flow 

RHR Pump Suction from Suppression Pool 

RHR Pump Torus Suction 

RHR Test Return to Suppression Pool 

RHR Torus Cooling/Spray Block 

Service Water (SW) from RHR Heat Exchanger 

SW/RHR Containment Flooding Cross Tie 

SW Return Isolation from Diesel Generator Cooler 

SW to Control Room Chiller Isolation 

SW to Spent Fuel Cooling Heat Exchanger Isolation 

Shutdown Cooling Hot Leg Suction 

Valves Susceptible to Thermal Binding

HPCI Injection 

HPCI Turbine Steam Admission 

Isolation Condenser Condensate Return Isolation 

RCIC Injection 

RHR Heat Exchanger Inlet and Outlet 

RHR Minimum Flow Bypass 

END 
Attachment 3 – Revision History for IP 62710 

Issue Date: 04/30/10 Att 3-1 

Commitment Tracking Number 

Issue Date Description of Change Training 

Needed 

Training CompletioDate 

N/A 04/30/10 

CN 10-013 

Researched commitments for 4 years and found none. IP 62710 has been revised to address feedback form 62710-1482 a missed possible modification to or valve design of gate valves that can be used to address pressure-locking concerns. 

NO N/A