istog industry issues interactive session gregg joss (ginna station vice chair istog) ron lippy...

ISTOG INDUSTRY ISSUES

Interactive SessionGregg Joss (Ginna Station Vice Chair ISTOG)Ron Lippy (True North Consulting ISTOG Facilitator)

Topic 1—Check Valve Categorization

Topic 1: When is a Check Valve a Category A/C Valve and when is it a Category C Valve?


ISTC-1300 Valve CategoriesValves in ISTC scope shall be categorized as:

Category ACategory BCategory CCategory D

When more than one distinguishing category characteristic is applicable, all requirements of each of the individual categories are applicable, although duplication or repetition of common testing requirements is not necessary.


Definitions: (From OM Code ISTC-1300)

Category C—Valves that are self-actuating in response to some

system characteristic, such as pressure(relief valves) or flow direction (check valves) for fulfillment of the required function(s), as specified in ISTA-1100.


Category A—Valves for which seat leakage is limited to a specific maximum amount in the closed position for fulfillment of their required function(s), as specified in ISTA-1100.

If a check valve has the characteristics of both Cat C and Cat A, it is considered Cat A/C.


Licensee should consider Whether the flow requirements for connected systems can

be achieved with the maximum possible leakage thru the CV

Effect of reduced system flows as a result of leakage thru the CV on other systems/components

Consequences of loss of water on system inventory Effect of backflow thru the CV on piping/components (i.e.

temperature and thermal stresses The radiological exposure to plant personnel and the

public.


Per the NUREG 1482, R1, section 4.1 “if any of the above considerations indicate that Category C testing may not be adequate, licensees should assign the check valve to Category A/C and should comply with the associated leak testing requirements.”


NRC Workshop Summary (July 1997), 2.1.3A valve which has a specific leakage limit assigned for the close direction is leak tested per Category A requirements. If a system has a leakage limit (e.g., for required inventory), but the individual valve(s) have no specific leakage assigned (as in off-site dose analysis), are the system valves required to be Category A in the IST program? If no, why are containment isolation valves required to be Category A, since the leakage limit is for the whole system (i.e., the containment)?


The staff recently evaluated this issue (Reference letter dated August 20, 1996 from NRC to Arkansas Nuclear One, Docket 50-313 and 368, “Safety Injection System Recirculating Valve Leak Test Requirements, Arkansas Nuclear One, Units 1 and 2”), and has determined that if a licensee has determined that a total system leakage limit, rather than a valve specific leakage limit is appropriate, Category A does not apply and reverse flow closure verification meets the inservice testing requirements for valve seating.


Containment Isolation valves have a total system limit (i.e., 0.60 La per 10 CFR 50, Appendix J), therefore these valves would not have to be classified Category A, unless Option B of Appendix J was utilized or the licensee requires each valve’s leakage to be limited to a specific amount (See interpretation XI-81-01). Option B requires that a performance criterion be established for Type C tests. The staff in GL 89-04, Position 10, however states that all containment isolation valves that are included in the Appendix J program should be included in the IST program a Category A or A/C valves.

Additional staff guidance may be required?????


Clear that the regulatory position is NOT “fixed” as of today. We need to “help” the NRC establish clear definitions of the Categories by using the Code Committee to “clarify” the positions for Categorization.

Example:– Category A and A/C valves are valves for which

maximum leakage has been established based on guidance for the “operability” of the check valve.

– Category C valves are valves for which maximum leakage has NOT been established based on guidance for the “operability” of the check valve.


The concern exists as to what constitutes a Cat AC valve.

Need to discuss “gross leakage” and “specified leakage”

There has recently been some regulatory questions as to when a check valve is considered Cat AC and when it is ONLY a Cat C check valve.


In other words, if the leakage of the valve is a requirement for determining “operability” of the valve versus “operability” of the system.

Just some thoughts….. How about some of yours????

Topic 2—General Check Valve Issues:

When is a check valve Active? (ISTA-2000) OM Code, Subsection ISTC-1300 Valve

Categories– Category C: Valves that are self-actuating in

response to some system characteristics, such as flow direction for fulfillment of the required function(s).


Active Valve (ISTA-2000): Valve(s) that are required to change obturator position to accomplish a specific function in shutting down a reactor to the safe shutdown condition, maintaining the safety shutdown condition, or mitigating the consequences of an accident.


When is a check valve Passive? Passive Valve: Valves that maintain

obturator position and are not required to change obturator position to accomplish the required function(s) in shutting down a reactor to the safe shutdown condition, maintaining the safe shutdown condition, or mitigating the consequences of an accident.


When is a check valve Passive? NUREG 1482, R1, section 4.1

– A check valve would ONLY be considered Passive:

Flow was blocked to the CV (flange, manual valve, etc.,)

The obturator was POSITIVELY held in place (Stop-Check Valve)


Check Valves—Cat C Require testing dependent upon safety

function:– Exercise full stroke Open– Exercise full stroke Close– Exercise normal flow Bi-

directional (if applicable)– Leakage testing (if applicable)– PIT (if applicable)


NUREG 1482, R1, section 4.1 “The NRC staff considers check valves,

and other automatic valves designed to close without operator action after an accident and for which flow is not blocked as “active” valves that would be classified as such in the IST program. Similar criteria could be applied to the opening function of a check valve.”


Bi-directional testing of CVs?– OM Code ISTC-3522

Category C CVs shall be exercised as follows:

During Operation at Power


Exercised or examined in such a manner that verifies obturator travel.

ISTC-5221(1)—CVs that have a safety function in both open and close directions shall be exercised by initiating flow and observing that the obturator has traveled to either the full open position or to the position required to perform its intended function and verify that on cessation or reversal of flow the obturator has traveled to the seat.


ISTC-5221(2)—CVs that have a safety function in only the open direction shall be exercised by initiating flow and observing that the obturator has traveled either the full open position or to the position required to perform its intended functions, and verify closure.


ISTC-5221(3)—CVs that have safety function in only the close direction shall be exercised by initiating flow and observing that the obturator has traveled at least the partially open position and verify that on cessation or reversal of flow the obturator has traveled to the seat.

Observations shall be made by observing a direct indicator (e.g. position-indicating device) or by other positive means (e.g. changes in system pressure, flow rate, level, temperature, seat leakage testing, or NIT.


NIT for CVs Acoustics Magnetics Radiography Ultrasonics


CV Disassembly and InspectionGrouping Documented in IST Program Technically Justified Consider as a minimum

– Valve Mfg.– Design– Service– Size– Materials of construction– Orientation


Maintenance and Modification history Potential Flow Instabilities Required degree of disassembly Need for tolerances or critical dimension checks During disassembly Full stroke motion of the

obturator verified Full stroke motion of the obturator re-verified

immediately prior to completing reassembly


At least one valve from each group DI each RFO

All valves in group DI once every 8 years After Reassembly Partial Stroke (if

practicable) and leak test (if applicable), before return to service.


CVs that have their obturator disturbed before full stroke motion is verified shall be examined to determine if a condition exists that could prevent full opening or reclosure of the obturator (e.g. spring loaded lift cvs or cvs with the obturator supported from the bonnet)


Condition Monitoring Rules (OM Code ISTC-5222, Appendix II)

Improve Valve Performance (High Failure Rate, cannot be exercised under NOP/NOT or shutdown—i.e. DI, exhibit unusual abnormal or unexpected behavior during exercising or operation, or the owner elects to monitor for improved valve performance)


Optimize Testing/Examination/PM activities in order to maintain the continued acceptable performance of a select group of CVs (Had performance improved under CMP, cannot be exercised or are not readily exercised during NOP/NOT or shutdown, can only be DI or owner elects to optimize all of the associated activities of the valve group in a consolidated program.


Permits “cherry picking” of valves If CMP is discontinued then the

requirements of ISTC-5221 shall apply. CMP Program Attributes: Groupings

– Determined by Owner– Technically Justified– Based on:


The intended purpose of the CMP (e.g. improve performance or optimize testing/examination/PM activities

Analysis of test results and maintenance history Design characteristics, application and service

condition Owner must assess the significance to plant

safety as a result of extended intervals Consider DI grouping details


Analysis Owner performs an analysis of the test and maintenance history

of a valve or group of valves in order to establish the basis for specifying IST, exam, PM activities. Must include:

Common failure or maintenance patterns Analyze patterns to determine their significance and to identify

potential failure mechanisms Determine if certain PM activities would mitigate the failure or

maintenance patterns Determine if periodic disassembly and exam activities would be

effective in monitoring for these failure mechanisms Determine if changes in the valve grouping are required


CM Activities Valve obturator movement during applicable test or exam

activities shall be sufficient to determine the bidirectional functionality of the moving parts

A full stroke open exercise or a open test to the position required to perform its intended function is not required

Performance Improvement Activities If sufficient info is not currently available to complete the analysis

required in CMP:, or if the analysis is inconclusive—then the following activities shall be performed at sufficient intervals over an interim period of the next 5 years or two roes whichever is less to determine the cause of the failure or the maintenance patters


Identify interim tests (e.g. NIT) to assess the performance of the valve or the group of valves.

Identify interim exams to evaluate potential degradation mechanisms

Identify other types of analysis that will be performed to assess CV condition

Identify which of these activities will be performed on each valve in the group

Identify the interval of each activity Identify attributes that will be trended. Trending and

evaluation of existing data must be used as the bases to reduce or extend the time interval between tests or exams


Complete or revise the CMP test plans to document the CV program performance improvement activities and their associated frequencies


Perform these activities at their associated intervals until: Sufficient info is obtained to permit an adequate evaluation

of the specific application or Until the end of the interim period

After performance , review those attributes that were selected for trending along with the results of each activity to determine if any changes to the CMP are required. If significant changes to the CMP area required the program shall be revised prior to the performance of the next activity and the applicable requirements of Grouping analysis and CMP activities shall be repeated.


Optimization of CM Activities If sufficient info is available to asses the performance

adequancy of the CV or the group then: Identify applicable PM activities including their associated

intervals that are required to maintain the continued acceptable performance of the cv or group of cv.

Identify the applicable exams activities and associated interval s that will be use d to periodically assess the condition of each cv or group of cvs


Optimization of CM Activities Identify the applicable test activities and intervals Identify the applicable interval of each activity, interval

extensions shall be limited to one fuel cycle per extension. Intervals shall not exceed the maximum intervals show below . All valves in a group sampling plan must be tested or examined again before the interval can be extended again or until the maximum interval would be exceeded. The requirements of ISTA-3120 do not apply (Traditional IST intervals (10 years).


Identify attributes that will be trended. Trending and evaluation of existing data must be used to reduce or extend the time interval between tests or examinations.

Revise the test plans to document the optimized CMP activities and the associated intervals of each activity

Perform the following activities at their associated intervals


After performance of the activities review the results to determine if any changes to the optimized CMP are required

If changes required must revise CMP prior to performance of the next activity

Changes to IST intervals must consider plant safety and be supported by trending and evaluating both generic an plant-specific performance data to ensure that the component is capable of performing tits intended functions over the entire interval.


Group Size Maximum Interval

Note 1, years

>/= 4 16

3 12

2 12

1 10


Note 1: The maximum interval was determined by how many interval extensions could be obtained based on an 18-month or 24-month fuel cycle. All of the valves had to be tested or examined within the maximum interval to be considered a valid extension.


Corrective Maintenance If corrective maintenance is performed on

a cv the analysis used to formulate the basis of the CMP activities for that cv and the assoc valve group shall be reviewed to determine if any changes are required.


Documentation Include List of valves in the CMP List of valves in each valve group Dates valves were added/deleted to CMP

and reason for inclusion/deletion


Documentation Analysis forming basis for CMP Identified failure or maintenance history pattern

for each valve CMP activities including the trended attributes

Methods of CV Testing/Examination, basis for associated intervals for each valve and valve group.


Methods of CV Testing/Examination Exercise with flow/dp NIT Leakage testing (Appendix J) DI PM activities

Topic 3 IST Pump Testing (in particular CPT)

Group APumps which are operated routinely during operation, shutdown or startup.

– Component Cooling Water Pumps– Service Water Pumps– Auxiliary Feedwater Pumps’– Shutdown Cooling Water Pumps


Group A

Testing– Frequency - Quarterly– Reference Value - +/- 20% of Design Flow or as close as practicable– Vibration Measurements Required– Hold time required (2 minutes after stabilization)– Instruments– No change from previous OM Code


Group BPumps which are NOT routinely operated except for testing.– Turbine Driven Auxiliary Feedwater Pumps– High Pressure Safety Injection Pumps– Containment Spray Pumps


Group B

Testing– Frequency - Quarterly– Reference Value - +/- 20% of Design Flow or as close as

practicable– No vibration Measurements Required– No hold time required – Instruments– No change from previous OM Code


CPT Testing

– Frequency - Biennially– Reference Value - +/- 20% of Design Flow – Vibration Measurements Required– Hold time required – Instruments

Flow- +/- 2% of either FS or of reading Dp/pressure - +/- 0.5% FS or reading


Reference Values are established ONLY when the pump is know to be

Operating acceptably—ISTB-3300(c) NUREG 1482, R1, section 5.2.1—

Licensees shall only establish reference values when the pump is known to be operating acceptably

istog industry issues interactive session gregg joss (ginna station vice chair istog) ron lippy...

Documents

check valve categorizationistc

check valve categorizationper

category ac valve

category c valve

valve categoriesvalves

valve seating

valve specific leakage

system valves