ML20049J391
| ML20049J391 | |
| Person / Time | |
|---|---|
| Issue date: | 06/30/1981 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML20049J390 | List: |
| References | |
| TASK-MS-901-4, TASK-RE REGGD-01.XXX, REGGD-1.XXX, NUDOCS 8203180054 | |
| Download: ML20049J391 (10) | |
Text
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Draft 1 1
June 1981 3
REGULATORY GUIDE SC 901-4 4
IDENTIFICATION OF VALVES FOR INCLUSION 5
IN INSERVICE TESTING PROGRAMS
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6 A.
INTRODUCTION 7
Paragraph 50.55a(g) of 10 CFR Part 50 "D o estic Licensing of Production 8
and Utilization Facilities" requires that certain valves be designed and pro-9 vided with access to enable the performance of inservice testing to assess 10 operational readiness in accordance with the requirements of ASME Boiler and 11 Pressure Vessel Code Section XI.
Paragraph 50.55a(g) further requires that
'd ASME Section III Code Class 1, 2, and S valves meet the requirements of sub-13 sequent Code editions and addenda of Section XI to the extent practical within 14 the limitations of design, geometry and materials of construction.
15 General design criterion 32 " Inspection of Reactor Coolant Pressure Bound-16 ary" of Appendix A, " General Design Criteria for Nuclear Power Plants," to 10 CFR 17 Part 50 requires, in part, that components that are part of the reactor coolant 18 pressure boundary be designed to permit periodic inspection and testing of impor-19 tant areas and features to assess their structural and leaktight integrity.
20 Criteria 37, 40, 43, and 46 require that specified systems be designed to 21 permit appropriate periodic pressure and functional testing to ensure (1) the 22 structural and leaktight integrity of its components and (2) the operability 23 and performance of active components of the system.
24 If the licensee determines that conformance with certain Code requirements 25 is impractical or if conformance to the code would cause unreasonable hardship 26 without compensating increase in safety, paragraph 50.55a(g) requires the 27 licensee to notify the Commission and submit information to support this deter-28 mination.
Following the evaluation of this information the Commission may 29 grant relief.
30 This regulatory guide provides guidance on the staff's practice in identify-31 ing valves for inclusion in the licensee's inservice testing program and the 32 information needed by the staff for its review of the program and on the infor-33 mation needed to evaluate requests for relief from any of the Code provisions.
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1 B.
DISCUSSION 2
In the summer 1973 addenda, the ASME Boiler and Pressure Vessel Code Sec-3 tion XI first published the requirements for inservice testing of valves. The 4
scope of the testing program and the owner's responsibility to submit a listing 5
of valves to be tested are given in Article IW 1000 of the code.
To bring 6
the scope of testing programs in agreement with the NRC staff's requirements, 7
the Winter 1977 edition of the Code limited the scope of the testing program 8
to valves that are required to perform a specific function in shutting down 9
the reactor to a hot or cold shutdown condition or to mitigate the conse-10 quences of an an accident.
Previously the Code was less specific and merely 11 referred to operational readiness of certain code cless 1, 2, and 3 valves.
12 Some licensees have interpreted the code and K 50.55a of the regulations to 13 require testing of all code class 1, 2, and 3 valves and no others. After 14 reviewing a number of inservice testing programs the staff has developed 15 guidelines for the implementation of the inservice testing requirements and 16 informed licensees as to which valves are to be included in the program.
This 17 guide is intended to document these requirements.
18 1.
Valves to be' Considered for Inclusion in the Testing Program 19 The NRC staff recognizes that, since many of the plants were built prior 20 to the issuance of Section XI, fundamental differences will exist between the 21 submittals of the various plant.
In reviewing the various licensee testing l
22 programs, the staff has been limiting the scope to valves that are required to:
23 (1) Mitigate the consequences of en accident, 24 (2) Shut down the reactor to the cold shutdown condition, or 25 (3) Maintain the reactor in a safe shutdown condition.
26 Typically, these valves would be classified by the licensee in the safety 27 analysis report as ASME Section III code class 1, 2, and 3 for plants granted 28 construction permits after January 1,1971.
For plants with construction permits 29 issued prior to that date, however, the systems performing functions that are 30 important to safety could be classified as non-code. Moreover, some systems 31 that may be needed to keep the reactor in a safe shutdown condition following 32 a loss-of-coolant accident may also be classified as non-code, or as Quality 33 Group D in Regulatory Guide 1.26.
These systems, as viewed by the staff, are i
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important to safety and are subject to the testing provisions of ASME Section XI 2
within the limitations of design, geometry, and materials of construction.
3 Examples of systems that the staff has considered for inclusion in an 4
inservice testing program are listed in Appendix A to this guide. This appen-5 dixinconjunctionwiththelicensee'ssafetyanalysisre$ortcanbeusedas 6
the basis for developing a comprehensive inservice t'esting program for valves.
7 2.
Reactor Coolant Pressure Isolation q
8 There are locations in existing light water reactors where high pressure
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reactor coolant is isolated from a system having a lower operating or design j
10 pressure.
Generally, two or more normally closed valves are required to iso-11 late high-and low pressure systems.
A postulated f ailure of these valves 12 would result in a LOCA, and in some configurations'," the LOCA may be outside 13 the containment.
An event leading to the latter in PWR's was found to be a 14 significant contributor to postulated core melt accidents. Where~it can be 15 identified that such valves perform both a pressure isolation function and a 16 containment isolation function, although not necessarily at coincident times, 17 the staff has determined that these valves must be testedjto verify both opera-18 tional readiness in accordance with ASME Section.\\I and leaktight integrity 7in 19 accordance with Appendix J to 10 CFR Part 50 and ASME Section XI (IWV-3420).
20 Valves whose only function is to perform pressure isolation between high-and 21 low pressure systen.s and which are not part of the containment boundary have 22 been required to show operational readiness and leak tightness in accordance 23 with ASME Section XI.
In the case where check valves are used to perform the
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24 function of prassure isolation, as is generally the case in the low-head safety 25 injection system, intermediate-head safety injection system, and high press ~ure 26 safety injection system, it must be ascertained that the valve discs.are actually 27 in place and capable of seating to confirm,the pressure protection offered by 28 these valves as well as their capability to deliver full injection flows.
29 3.
Containment Isolation Valves 30 Where systems are required to penetrate the contai'imeat boundary and either 31 communicate with the primary reactor coolant system or the containment atmosphere, 32 Regulatory Guide 1.141 recommends and the staff has been requiring that such l
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systems be provided with sufficient redundancy to ensure leak tight containment
~2' isolation.
Those valves that are required to perform only a containment isola-3 tion function under,any postulated accident condition and are not required for 4
primary reactor coolant system isolation may meet the requirements stipulated
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5 in Appendix J to 10 CFR Part 50 and need not be further leak tested to Sec-6 tion XI. >However, fin such cases it would be desirable to perform type C tests 7
asdefined'inAppeiidix.Jandindividuallyleaktesteachvalve. Total inte-8 grated containment leakage measurements do not necessarily reflect the potential 9
for incipient failure for each valve or provide assurance that each valve will 10 perform itr isolation,functioli during an accident. These valves could be impor-11 tant in limlting radi$ tion release to the environment and the staff has required 12 them to be tested for leaktight integrity and operability and they therefore
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13 should be included in the inservice testing program.
14 4.
ASME Section X Convenience Valves 15 Although IWV-1300 of the 1974 Edition and IWV 1200 of the 1977 Edition of 16 Section XI of the ASME Boiler and Pressure Vessel Code excludes valves used 17 for operating convenience and maintenance from testing requirements, it has
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18 been the NRC staff's position that any such valve that is in the normal or 19 alternativefiowpathofcoolingwaterforengineeredsafetysystemsmaybe 20 included in the valve testing program.
For those plants which must comply with 21 the 1975 Addenda to ASME XI, valves that are normally locked open or closed 22 should be categorized E in the program and their positions verified during 23 inservice testing.
This recommendation has also been applied to engineered 24 safety sys'tems that are designed to remove decay heat from the reactor care 25 followii16 a Ioss-of-coolant accident.
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26 5.
Conditions Under Which Valves Should Be Excluded from Tests 27
-There are vsives that when exercised under certain conditions could put 28 theplantinanunsafA/ condition.
In almost all such cases, some failure in a l
29 redundant' system or a' failure in'the valve itself has occurred.
For example, 30 there a're vabes whose failure to close during cycling tests would result in a 31 loss of contajnment integrity. This is the case in which the redundant valve r
32 has failed open a'ad exercising the remaining valve during plant operation would 33 breach the containment. Also, there are valves whose failure in a non-34 conservative position duH ag cycling tests would cause a loss of system func-35 tion.
Inc16ded in this c'ategory would be nonredundant valves such as a single 4
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1 discharge line from the refueling water tank or accumulator discharge lines.
2 Other valves may fall into this category under certain system configurations 3
or operating modes.
For example, when one train of a redundant system such as 4
the emergency core cooling system (ECCS) is inoperative, the valves in the 5
remaining system become nonredunds.nt, and their failure or their isolation to 6
perform the required tests would render the entire ECCS system inoperative.
7 In certain pressure isolation cases, e.g., the isolation valves of the 8
residual heat removal / shutdown cooling systems and certain ECCS valves, if one 9
or more of the check valves on the high pressure side has failed, exercising 10 the valve on the low pressure side could subject the low pressure system to 11 pressures above their design pressures. The staff's position has been that 12 routine exercising of this valve should not be performed unless a reliable 13 method exists to detect leakages past the check valves (i.e., pressure indi-14 cation monitored in the control room).
If practical, exercising of this valve 15 should be performed at the next cold shutdown.
16 6.
Exceptions to Section XI Testing Intervals 17 The ASME Code recognizes the need for flexibility in the required valve 18 testing frequency.
For example, IW 3410 of the Code permits valves that can-19 not be exercised every three months to the position required to fulfill their 20 function to be partly stroked during normal operation of the reactor and fully 21 stroked at cold shJtdown.
It may not be practical to de-inert a Containment 22 to test or inspect the movement of a valve at the stated valve test period or 23 to measure stroking times.
24 The practice of the staff has been to not require reactor down time for 25 the express purposes of routine valve testing.
A balanced judgement between 26 the hardships and compensating increase in the level of safety must be j
27 explicitly justified if, for example an extended shutdown period is required l
28 to test all the valves at the prescribed code interval. On the other hand, it 29 is necessary to avoid the situation in which tests are postponed to the re-30 fueling outage merely to avoid the inconvenience of testing systems at the 31 temperature / pressure conditions that prevail during plant operation. This 32 situction is covered in paragraph 50.55a(g)(6)(i), which requires that the 33 staff evaluate the determination that Code requirements are impractical in 34 specific cases.
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1 7.
Relief from Code Requirements 2
The concern for the NRC staff in the review of an inservice testing program 3
is that insufficient information is provided for justifying relief from Sec-4 tion XI requirements.
In the past many requests for relief have not provided 5
adequate technical information for the staff to review.
Detailed technical 6
information is necessary so that the staff can evaluate the request for relief 7
on the basis of the burden imposed on the licensee in complying with the code 8
and the compensating increase in safety.
The information would include items 9
such as accessibility, radiation level, estimated man-rems for work involved, 10 or the capability to withstand valve leakage without impacting on the ability 11 to mitigate consequences of an accident or achieve cold shutdown condition.
12 If all necessary information is provided with the program submittal subsequent 13 requests by the staff for additional information will be reduced or eliminated, 14 and the review of such programs can be expedited.
15 C.
REGULATORY POSITION 16 1.
Valves that are needed for safe plant shutdown, required to main-17 tain the plant in a safe shutdown condition, or required to mitigate the conse-18 quences of an accident'are considered by the staff as important to safety and 19 should be included in a comprehensive inservice testing program regardless of 20 whether they were constructed to the requirements of ASME Section III or some 21 other voluntary standard. Typical systems that fall into this category are l
22 presented in Appendix A to this guide.
23 2.
Valves that perform a pressure isolation function between high-and 24 low pressure systems should be classified as Category A or AC if they are 25 leak-tested to ascertain that the pressure protection offered by these valves 26 is adequate for system safety. Active valves 1 in this group should be exer-27 cised in accordance with ASME Section XI (IWV-3400).
l 28 3.
Valves that perform a containment isolatin function only are subject 29 to the provisions of Appendix J to 10 CFR Part 50 and need not meet Section XI 30 leak-test requirements.
31 32
' Active valves are defined in ASME Section XI, Subarticle IWV-2100.
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1 4.
Certain valves that are used for operating convenience and maintenance 2
have been excluded from testing by ASME Section XI.
If these valves are in a 3
system important to safety and in a normal or alternative flow path of engi-4 neered safety feature systems, they should be incluh d in the inservice test 5
program only if they are locked open or closed (1975 Addenda to ASME Sec-6 tion XI).
7 5.
If the exercise of a valve as required by Section XI could result in 8
an unsafe plant condition under certain conditions of plant operation, that 9
valve should be tested at some other condition of the plant.
10 6.
The testing of valves should be performed at a frequency as near to 11 the Code-required intervals as practical with due consideration to plant safety.
12 7.
Requests for relief from Code requirements or from frequency of 13 testing should be accompanied by sufficient detailed information for the NRC 14 staff to fully evaluate the impact on plant safety of granting such relief.
15 Information in support of requests for relief from the requirements of 16 the ASME Code,Section XI, should include, as a minimum, the following details:
17 a.
Identity of Component 18 (1) Name and number as given in the FSAR 19 (2) Function of component within the system and its coordinate 20 location in P&I diagram 21 (3) ASME Section III Code Class 22 (4) Specific ASME Section XI valve category (see IWV 2000) 23 b.
Identification of the applicable ASME Code Editions and Addenda and 24 those specific requirements from which relief is requested.
25 c.
Information to justify a determination that testing is impractical 26 or unnecessary (i.e., the basis for requesting relief).
27 d.
An alternative inservice testing proposal if not in accordance with l
28 Section XI (at cold shutdown and refueling in that order).
Explain why the 29 proposed inservice testing will provide an acceptable level of quality and 30 safety and not endanger the public health and safety.
31 e.
The schedule for implementing the alternative procedures 32 f.
The alternative testing frequency, if the Code-required shortest test 33 frequency is not applied in testing any valve assembly. The reasons for not 34 doing so should be provided and supported by test results and a trend analysis.
35 The trend analysis should be presented in tabular or plotted form for easy and 36 consistent interpretation.
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D.
IMPLEMENTATION 2
This draft regulatory guide has been released to encourage public partici-3 pation in its development.
Except in those cases in which an applicant proposes 4
an acceptable alternative method for complying with specified portions of the 5
Commission's regulations, the method to be described in the active guide re-6 flecting public comments will be used in evaluating the applicant's inservice 7
testing program.
8 In addition, the NRC staff intends to implement this guide for all plants.
9 For operating plants the licensee should submit an IST Program in accordance 10 with this guide six months prior to the start of the next 120-month interval 11 beginning three months after issuance of the active guide.
12 For plants under construction, the IST Program for the initial 120-month 13 interval r.hould be submitted with the Operating License Application beginning 14 three months after the issuance of the active guide.
15 For plants under canstruction with an Operating License Application, 16 including the initial IST Program submitted prior to the issuance of this guide, 17 a new or revised initial IST Program should be submitted within three months 18 after issuance of the active guide.
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1 APPENDIX A 2
The valves in the following systems and components in systems important to 3
safety should be considered for inclusion in a comprehensive inservice testing 4
program. The list is not intended to be all inclusive; key components in 5
instrumentation and auxiliary systems that are required to directly support 6
plant shutdown or safety system function should also be considered.
7 1.
Pressurized Water Reactors 8
1.1 Reactor Coolant System (RCS) and any proposed flow path for 9
establishing natural circulation 10
- 1. 2 Portons of Main Steam System
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- 1. 3 High Pressure Injection System (HPCI) 12 1.4 Low Pressure Injection System (LPCI) 13 1.5 Accumulator Systems 14 1.6 Containment Spray System 15
- 1. 7 Primary and secondary System Safety and Relief Valves, and 16 Atmospheric Relief Valves 17 1.8 Portions of Main Feeawater System 18 1.9 Auxiliary Feedwater Systems 19 1.10 Residual Heat Removal System (Shutdown Cooling) 20 1.11 Component Cooling Water Systems 21 1.12 Service Water Systems 22 1.13 Containment Isolation Valves Required to change position on a 23 containment isolation signal 24 1.14 Chemical Volume and Control System l
25 1.15 Emergency diesel engine fuel oil storage and transfer system 26 1.16 Ventilation Systems that perform a safety function t
27 1.17 Instrument Air Systems that are required to support safety 28 system functions 29 2.
Boiling Water Reactors l
30 2.1 Reactor Coolant Recirculation System (RCS) l 31
- 2. 2 Portions of Main Steam Supply 32 2.3 High Pressure Injection System (HPCI) 33 2.4 Low Pressure Injection System (LPCI) 34 2.5 Residual Heat Remo/a1 System (Steam Condensing, Shutdown Cool-35 ing, Suppression Pool Cooling) 9
1 2.6 Low Pressure Ccre Spray System 2
2.7 Safety, Relief and Safety / Relief Valves of RCS and secondary 3
systems 4
2.8 Reactor Core Isolation Cooling System 5
2.9 Containment Cooling System (Spray) 6 2.10 Containment Isolation Valves Required to Change Position on a 7
Containment Isolation Signal 8
2.11 Standby Liquid Control System 9
2.12 Automatic Depressurization System 10 2.13 Control Rod Drive Hydraulic System 11 2.14 Active Valves in Service and Backup Water and/or Closed Cooling 12 Water and/or Firewater and/or Well Water Systems.
13 2.15 Emergency diesel engine fuel oil storage and transfer system 14 2.16 Portions of Main Feedwater System.
15 2.17 Instrument Air Systems that are required to support safety system 16 functions 17 Note: The terminology for various systems such as Accumulator Systems and 18 others may vary depending upon the distinctive preference of the 19 individual nuclear steam system supplier.
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