Regulatory Guide 1.151: Difference between revisions

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{{Adams
{{Adams
| number = ML092330219
| number = ML020360111
| issue date = 07/31/2010
| issue date = 07/31/1983
| title = Instrument Sensing Lines
| title = (Task IC 126-5) Instrument Sensing Lines
| author name =  
| author name =  
| author affiliation = NRC/RES
| author affiliation = NRC/RES
Line 9: Line 9:
| docket =  
| docket =  
| license number =  
| license number =  
| contact person = O'Donnell, Edward, RES/RGB
| contact person =  
| case reference number = DG-1178
| case reference number = FOIA/PA-2002-0095
| document report number = RG-1.151, Rev 1
| document report number = Reg Guide 1.151
| package number = ML092330215
| document type = Regulatory Guide
| document type = Regulatory Guide
| page count = 8
| page count = 4
}}
}}
{{#Wiki_filter:The NRC issues regulatory guides to describe and make available to the public methods that the NRC staff considers acceptable for use in implementing specific parts of the agency's regulations, techniques that the staff uses in evaluating specific problems or postulated accidents, and data that the staff needs in reviewing applications for permits and licenses. Regulatory guides are not substitutes for regulations, and compliance with them is not required. Methods and solutions that differ from those set forth in regulatory guides will be deemed acceptable if they provide a basis for the findings required for the issuance or continuance of a permit or license by the Commission.
{{#Wiki_filter:U.S. NUCLEAR REGULATORY COMMISSION
REGULATORY GUIDE
OFFICE OF NUCLEAR REGULATORY RESEARCH
REGULATORY GUIDE 1.151 (Task IC 126-5)
INSTRUMENT SENSING LINES


This guide was issued after consideration of comments received from the public.
==A. INTRODUCTION==
Section 50.34, "Contents of Applications; Technical Information," of 10 CFR Part 50, "Domestic Licensing of Production and Utilization Facilities," requires, in part, that design criteria be established for structures, systems, and components important to safety that will provide reasonable assurance that the facility can be operated without undue risk to the health and safety of the public.


Regulatory guides are issued in 10 broad divisions:  1, Power Reactors; 2, Research and Test Reactors; 3, Fuels and Materials Facilities; 4, Environmental and Siting; 5, Materials and Plant Protection; 6, Products; 7, Transportation; 8, Occupational Hea lth; 9, Antitrust and Financial Review; and 10, General.
Criterion 1, "Quality Standards and Records," of Appen dix A, "General Design Criteria for Nuclear Power Plants,"
to 10 CFR Part 50 requires, in part, that structures, systems, and components be erected (installed) to quality standards commensurate with the importance of the safety functions to be performed.


Electronic copies of this guide and other recently issued guides are available through the NRC's public Web site under the Regulatory Guides document collection of the NRC's Electronic Reading Room at http://www.nrc.gov/reading-rm/doc-collections/ and through the NRC's Agencywide Documents Access and Management System (ADAMS) at http://www.nrc.gov/reading-rm/adams.html, under Accession No. ML092330219.  The regulatory analysis may be found in ADAMS under Accession No. ML102040145.
Criterion 13, "Instrumentation and Control," of Appendix A to 10 CFR Part 50 requires, in"
part, that instrumentation be provided to ensure adequate safety. Criterion 24, "Separation of Protection and Control Systems," of Appendix A to 10 CFR Part 50 and Section
4.7.3, "Single Random Failure," of IEEE Std 279-1971 require, in part, that the interconnection of the protection and control systems be limited so as to ensure that safety is not significantly impaired.


U.S. NUCLEAR REGULATORY COMMISSIONJuly 2010      Revision 1REGULATORY GUIDE OFFICE OF NUCLEAR REGULATORY RESEARCH
This regulatory guide describes a method acceptable to the NRC staff for complying with the Commission's regu lations with regard to the design and installation of safety related instrument sensing lines in nuclear power plants.
  REGULATORY GUIDE 1.151 (Draft was issued as DG-1178, dated December 2008) INSTRUMENT SENSING LINES


==A. INTRODUCTION==
The term "safety-related"  
This guide describes a method that the staff of the U.S. Nuclear Regulatory Commission (NRC) considers acceptable for use in complying with the agency's regulations with respect to the design and installation of safety-related instrument sensing lines in nuclear power plants.  To meet these objectives, the sensing lines must serve a safety-related function to prevent the release of reactor coolant as a part of the reactor coolant pressure boundary and to provide adequate connections to the reactor coolant system for measuring process variables (e.g., pressure, level, and flow).  The term "safety-related" refers to those structures, systems, and components necessary to ensure (1) the integrity of the reactor coolant pressure boundary, (2) the capability to shut down the reactor and maintain it in a safe-shutdown condition, or (3) the capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposures comparable to the guideline exposures in Title 10, of the Code of Federal Regulations , Part 100, "Reactor Site Criteria" (10 CFR Part 100) (Ref. 1).  
refers to those structures, systeqms, and components necessary to ensure (1) the integsty of the reactor coolant pressure boundary, (2) the capability to shut down the reactor and maintain it in a safe shutdown condition, or (3) the capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposures comparable to the guideline exposures of 10 CFR Part 100.
 
The Advisory Committee on Reactor Safeguards has been consulted concerning this guide and has concurred in the regulatory position.
 
USNRC REGULATORY GUIDES
Regulatory Guides are issued to describe and make available to the public methods acceptable to the NRC staff of implementing specific parts of the Commission's regulations, to delineate tech niques used by the staff in evaluating specific problems or postu lated accidents, or to provide guidance to applicants. Regulatory Guides are not substitutes for regulations, and compliance with them is not required. Methods and solutions different from those set out In the guides will be acceptable if they provide a basis for the findings requisite to the Issuance or continuance of a permit or license by the Commission.


The regulatory framework that the NRC has established for nuclear power plants consists of a number of regulations and supporting guidelines, include, but are not limited to, General Design Criterion (GDC) 1, "Quality Standards and Records"; GDC 13, "Instrumentation and Control"; GDC 24, "Separation of Protection and Control Systems"; and GDC 55, "Reactor Coolant Pressure Boundary Penetrating Containment," as set forth in Appendix A, "General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50, "Domestic Licensing of Production and Utilization Facilities" (Ref. 2).  The provisions of 10 CFR Part 50 require that design criteria be established for structures, systems, and components important to safety to provide reasonable assurance that the facility can be operated without undue risk to public health and safety. GDC 1 requires that structures, systems, and components important to safety be designed and installed to quality standards commensurate with the safety Rev. 1 of RG 1.151, Page 2 importance of the functions to be performed.  GDC 13 requires that instrumentation be provided to monitor variables and systems to ensure adequate safety.  GDC 24 requires, in part, that the interconnection of the protection and control systems be limited so as to ensure that safety is not significantly impaired.  GDC 55 requires, in part, that each line that is part of the reactor coolant pressure boundary and that penetrates the primary reactor containment be provided with containment isolation valves, unless it can be demonstrated that the containment isolation provisions for a specific class of lines (such as instrument lines) are acceptable on some other defined basis.  Regulatory Guide 1.53, "Application of the Single-Failure Criterion to Safety Systems" (Ref. 3), provides guidance on acceptable methods for satisfying the Commission's regulations with respect to the separation and independence of the electrical power, instrumentation, and control portions of nuclear power plant safety systems.
This guide was Issued after consideration of comments received from the public. Comments and suggestions for improvements in these guides are encouraged at all times, and guides will be revised, as appropriate, to accommodate comments and to reflect new informa tion or experience.


This regulatory guide contains information collection requirements covered by 10 CFR Part 50 that the Office of Management and Budget (OMB) approved under OMB control number 3150-0011.  The NRC may neither conduct nor sponsor, and a person is not required to respond to, an information collection request or requirement unless the requesting document displays a currently valid OMB control number.
Any guidance in this document related to information activities has been cleared under OMB Clearange No. 3150
0011.


==B. DISCUSSION==
==B. DISCUSSION==
Committee SP67.02 of the Instrument Society of America (ISA) prepared American Nuclear Standards Institute (ANSI)/ISA-67.02.01-1999, "Nuclear Safety-Related Instrument-Sensing Line Piping and Tubing Standard for Use in Nuclear Power Plants" (Ref. 4), and ISA approved the standard on November 15, 1999.  ANSI/ISA-67.02.01-1999 provides design, physical protection, and installation requirements for safety-related instrument sensing lines, and for sampling lines previously covered by ANSI/ISA-S67.10-1994, "Sample-Line Piping and Tubing Standards for Use in Nuclear Power Plants" (Ref. 5).  ANSI/ISA-67.02.01-1999 establishes the applicable code requirements and code boundaries for the design and installation of instrument sensing lines interconnecting safety-related piping and vessels with both safety-related and nonsafety-related instrumentation.
ISA-$67.02, "Nuclear-Safety-Related Instrument Sens ing Line Piping and Tubing Standards for Use in Nuclear Power Plants,"* was prepared by Committee SP67-02 of the Instrument Society of America (ISA). It was approved, by the ISA Nuclear Power Plant Standards Committee on October 19, 1978, and subsequently by the ISA Standards and Practices Board in June 1980. The standard provides design, physical protection, and installation requirements for instrument sensing line piping and tubing for nuclear power plant applications. It establishes the applicable ASME code requirements and boundaries for the design and installation of instrument sensing lines that interconnect safety-related piping and' vessels with safety-related instru mentation and non-safety-related instrumentation.
 
==C. REGULATORY POSITION==
The requirements of ISA-$67.02,  
"Nuclear-Safety Related Instrument Sensing Line Piping and Tubing Stan dards for Use in Nuclear Power Plants," 1980, provide a basis acceptable to the NRC staff for the design and installation of safety-related instrument sensing lines in nuclear power plants subject to the following:
1. The requirements for instrument sensing lines in Section 4.1 of ISA-$67.02 should be supplemented with the following:
A single instrument sensing line should not be used to perform both a safety-related function and a non safety-related function unless it can be shown that:
Copies are available from the Instrument Society of America,
67 Alexander Drive P.O. Box 12277, Research Triangle Park, North Carolina 27701.
 
Comments should be sent to the Secretary of the Commission.
 
U.S. Nuclear Regulatory Commission, Washington, D.C. 20555, Attention: Docketing and Service Branch.
 
The guides are Issued In the following ten broad divisions:
 
===1. Power Reactors ===
 
===6. Products ===
2. Research and Test Reactors


The Power Generation Committee of the Institute of Electrical and Electronics Engineers (IEEE) Power Engineering Society developed ANSI/IEEE Standard (Std) 622-1987, "Recommended Practice for the Design and Installation of Electric Heat Tracing Systems for Nuclear Power Generating Stations" (Ref. 6), and the IEEE Standards Board approved it on December 11, 1986. ANSI approved it on November 23, 1987. The standard provides recommended practices for designing and installing electric heat tracing on systems in nuclear power generating stations to prevent them from freezing in cold weather and to prevent certain concentrations of chemicals, such as boric acid solutions, from crystallizing or solidifying within an instrument piping system. The recommendations include identification of requirements, heater design considerations, power systems design considerations, temperature control considerations, alarm considerations, finished drawings and documents, installation of materials, startup testing, temperature tests, and maintenance of electric pipe heating systems.
===7. Transportation ===
3. Fuels and Materials Facilities S. Occupational Health
4. Environmental and Siting
9. Antitrust and Financial Review
5. Materials and Plant Protection 10. General Copies of issued guides may be purchased at the current Government Printing Office price. A subscription service for future guides in spe cific divisions is available through the Government Printing Office.


Operational events have occurred in which evolved gases in instrument sensing lines have affected measured water levels in operating nuclear power plants.  The NRC issued Information Notice 92-54, "Level Instrumentation Inaccuracies Caused by Rapid Depressurization," dated July 24, 1992 (Ref. 7), to alert licensees to potential inaccuracies in water-level indication during and after rapid depressurization events.  NRC Information Notice 93-27, "Level Instrumentation Inaccuracies Observed during Normal Plant Depressurization," dated April 8, 1993 (Ref. 8), alerts licensees to potential inaccuracies in reactor vessel level indication during normal reactor depressurization.  In addition to potential inaccuracies in reactor vessel level indication during normal and rapid reactor Rev. 1 of RG 1.151, Page 3 depressurizations, operational events have occurred in which flashing within reactor water level reference legs affected reactor water level measurements in operating nuclear power plants.
Information on the subscription service and current GPO prices may be obtained by writing the U.S. Nuclear Regulatory Commission.


Inaccuracies in level instrumentation could affect the performance of safety functions in pressurized-water reactor (PWR) and boiling-water reactor (BWR) plants.  NRC Information Notice 95-20, "Failure in Rosemount Pressure Transmitters Due to Hydrogen Permeation into the Sensor Cell,"
Washington, D.C. 20555. Attention: Publications Sales Manager.
dated March 22, 1995 (Ref. 9), presents evidence of the presence of dissolved gas in a PWR instrument line. For BWRs, a potential problem is that dissolved gases can evolve in the reference leg for level measurements in the reactor vessels as the solubility of the gases decreases during depressurization. Such gases can be trapped in the instrument sensing line and affect differential pressure measurements, particularly level measurements.  Such events have been reported in licensee event reports with significant level measurement errors. Since level instrumentation plays an important role in plant safety and is required for both normal and accident conditions, NRC Bulletin 93-03, "Resolution of Issues Related to Reactor Vessel Water Level Instrumentation in BWRs," dated May 28, 1993 (Ref. 10), recommended that each utility implement corrective actions to ensure that the level instrumentation design is of high functional reliability for long-term operation.  In response to the bulletin, the majority of BWR licensees decided to install a reference leg backfill system to supply a continuous flow of water from the control rod drive hydraulic system through the reference legs to preclude migration of dissolved noncondensable gases into the legs.  However, NRC Information Notice 93-89, "Potential Problems with BWR Level Instrumentation Backfill Modifications," dated November 26, 1993 (Ref. 11), reported on several potential design problems with the retrofitted backfill system by which a single failure in the backfill system would lead to a severe transient on multiple level sensing channels.  Consequently, the design measures that respond to trapped gas in the reference leg should ensure that the features and systems that mitigate or preclude evolved gases do not themselves introduce additional single-failure mechanisms in the protection system.  The following regulatory provisions support taking additional measures to address the potential for evolved gases in instrument sensing lines: 


* GDC 13 states, "Instrumentation shall be provided to monitor variables and systems over their anticipated ranges for normal operation, for anticipated operational occurrences, and for accident conditions as appropriate to assure adequate safety."
ni July 1983


* GDC 21 states, "The protection system shall be designed for high functional reliability and inservice testability commensurate with the safety function to be performed."
a. The failure of the common sensing line would not simultaneously (1) cause an action in a non-safety related system that results in a plant condition requiring protective action and (2) also prevent proper action of a protection system channel designed to protect against the condition; or b. If the failure of the common sensing line can cause an action in a non-safety-related system that results in a plant condition requiring protective action and can also prevent proper action of a protection system channel designed to protect against the condition, the remaining redundant protection channels are capable of providing the protective action even when degraded by a second random failure. The rupture of a second instru ment sensing line need not be considered as a second random failure.


* GDC 22 states, "The protection system shall be designed to assure that the effects of natural phenomena, and of normal operating, maintenance, testing, and postulated accident conditions on redundant channels do not result in loss of the protection function."
Provisions should be included so that this requirement can still be met if a channel is bypassed or removed from service for test or maintenance purposes. Acceptable provisions include reducing the required coincidence, defeating the signals taken from the same sensing line in non-safety-related systems, or initiating a protective action from the bypassed channel.


* 10 CFR 50.55a(h) requires that reactor protection systems satisfy the criteria of IEEE Std 603-1991, "IEEE Standard Criteria for Safety Systems for Nuclear Power Generation Stations" (including a correction sheet, dated January 30, 1995) (Ref. 12), or of IEEE Std 279-1971, "Criteria for Protection Systems for Nuclear Power Generating Stations" (Ref. 13).  Section 5.5, "System Integrity," of IEEE Std 603-1991 states, "The safety systems shall be designed to accomplish their safety functions under the full range of applicable conditions enumerated in the design basis."  Section 4.20 of IEEE Std 279-1971 states, "The protection system shall be designed to provide the operator with accurate, complete, and timely information pertinent to its own status and to generating station safety."
2. The mechanical design requirements in Tables I and 2 and Figures 1, 2, 3, 4, 7, and 8 of ISA-S67.02 for instru ment' sensing lines connected to ASME Class 1 and 2 process piping and vessels should be supplemented with the following:
Additionally, the staff notes the following concerns that support these measures:
a. Instrument sensing lines that are connected to ASME Class 1 or 2 process piping or vessels should not be less than ASME Class 2 Seismic Category I
from their connections to the process piping or vessel to and including the accessible isolation valve.


Rev. 1 of RG 1.151, Page 4
l*. Instrument sensing lines that are connected to
* Level-sensing instrumentation may not accurately monitor reactor vessel water levels under normal cooldown or accident conditions.
'*ASME Class I or 2 process piping or vessels and that are used to actuate or monitor safety-related systems should not be less than ASME Class 2 Seismic Category I from their connections to the process piping or vessel to the sensing instrumenta tion.


* Instrumentation may not be reliable during and following normal and rapid depressurization.
3. The mechanical design requirements in Tables I and 2 and Figures 5, 6, and 9 of ISA-$67.02 for instrument sensing lines connected to ASME Class 3 process piping and vessels should be supplemented with the following:
Instrument sensing lines that are connected to ASME
Class 3 process piping and vessels and that are used to actuate or monitor safety-related systems should not be less than ASME Class 3 Seismic Category I from their connection to the process piping or vessel to the sensing instrumentation.


* Degassing may cause a loss of the reactor vessel water-level indication function during and following normal depressurization and rapid depressurization.
4. Freezing temperatures should be added to the environ mental and installation conditions listed in Section 5.2.1(5)
of ISA-S67.02 that sensing lines should be able to with stand and continue to perform their function.


==C. REGULATORY POSITION==
5. The special considerations in Section 5.2.2 of ISA-$67.02 that should be addressed in the design and installation of instrument sensing lines should be supple mented with the following:  
ANSI/ISA-67.02.01-1999 provides an approach that the NRC staff considers acceptable for satisfying the agency's regulatory requirements with respect to designing and installing safety-related instrument sensing lines in nuclear power plants.  This regulatory guide endorses ANSI/ISA-67.02.01-1999, with the following exceptions and clarifications:  
a. Instrument sensing lines that can be exposed to freezing temperatures and that contain or can be expected to contain a condensable mixture or fluid that can freeze should be provided an environmental control system (heatingand venti lation or heat tracing) to protect the lines from freezing during extremely cold weather.
1. The endorsement of ANSI/ISA-67.02.01-1999 is limited to instrument sensing lines and does not include Section 6, "Sample-Line Fabrication, Routing, Installation, and Protection."  The original ANSI/ISA-S67.02 covered only sensing lines, while ANSI/ISA-S67.10 addressed sampling lines.  ANSI/ISA-67.02.01-1999 combines the two.  This regulatory guide addresses only the instrument sensing line guidance.  The term "instrument sensing line" used in this guidance applies to valves, fittings, manifolds, tubing, and piping used to connect instruments to main piping, other instruments, apparatus, or measuring equipment.
 
b. The environment associated with those instrument sensing lines in a. that are safety related should be monitored and alarmed so that appropriate correc tive action can be taken to prevent loss of or damage to the lines from freezing in the event of loss of the environmental control system.


2. ANSI/ISA-67.02.01-1999 does not address containment isolation requirements for water-filled sensing lines that penetrate the containment boundary. The requirements of GDC 55 regarding penetrations of the containment by lines forming the reactor coolant pressure boundary must be observed.  For each sensing line that penetrates primary reactor containment, root valve and accessible isolation valves should be provided, unless it can be demonstrated that the containment isolation provisions for sensing lines are acceptable on some other defined basis in accordance with GDC 55.  The root valve and accessible isolation valve may be the same valve, if the arrangement meets all other requirements for isolation and accessibility.
c. The environmental control system recommended in a., and for which b. applies, should be electri cally independent of the monitoring and alarm system so that a single failure in either system, including their power sources, does not affect the capability of the other system.


3. IEEE Std 622-1987 provide a basis acceptable to the NRC staff for designing and installing electric heat tracing systems in nuclear power generating stations.
d. The environmental control and monitoring systems of a. and b. should be designed to stan dards commensurate with their importance to safety and with administrative controls that are implemented to address events or conditions that could render the systems inoperable.


4. In addition to guidance provided by ANSI/ISA-67.02.01-1999, provisions should be made to (a) determine the potential impacts of noncondensable gases in sensing lines during or following depressurization and the potential impacts of flashing in reference leg and (b) mitigate such potential impacts, as long as the associated measurements are required for monitoring the plant or for operating the safety system. This position is based on GDC 13, GDC 21, GDC 22, and 10 CFR 50.55a(h).  
6. The Summer 1981 Addenda to Section III of the ASME Boiler and Pressure Vessel Code deleted Paragraphs NB-3676, NC-3676, and ND-3676 in their entirety. Refer ences to these paragraphs in Section 4.2.1, Section 6.2, and Section 7 of ISA-$67.02 should be disregarded.


==D. IMPLEMENTATION==
==D. IMPLEMENTATION==
The purpose of this section is to provide information to applicants and licensees regarding the NRC's plans for using this regulatory guide. The NRC does not intend or approve any imposition or backfit in connection with its issuance.
The purpose of this section is to provide information to applicants and licensees regarding the NRC staff's plans for using this regulatory guide.
 
Except in those cases in which an applicant or licensee proposes an acceptable alternative method for complying with specified portions of the Commission's regulations, the method described in this guide will be used by the NRC  
staff in its evaluation of the design and installation of safety-related instrument sensing lines for all construction permit applications issued after September 1,1983. Licensees or other applicants may use this guide in discussions with the staff as justification for the adequacy of sensing line design and installation or for modifications to sensing line design and installation. However, the staff does not intend to recommend the systematic application of every aspect of this guide to plants currently operating or under review.
 
1.151-2
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)
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VALUE/IMPACT STATEMENT
 
===1. BACKGROUND ===
The licensee of a nuclear power plant is required by the Commission's regulations to provide principal design criteria for those structures, systems, and components that provide reasonable assurance that the facility can be operated without undue risk to the health and safety of the public. General guidance for the design and installation of instrument sensing lines is given in Regulatory Guide 1.26,
"Quality Group Classifications and Standards for Water-,
Steam-, and Radioactive-Waste-Containing Components of Nuclear Power Plants." The Instrument Society of America (ISA) has developed more definitive guidance on instru ment sensing lines in ISA-S67.02, "Nuclear-Safety-Related Instrument Sensing Line Piping and Tubing Standards for Use in Nuclear Power Plants."
The action endorses this additional guidance, with appropriate supplementary material, in a regulatory guide.
 
2. VALUE/IMPACT ASSESSMENT
2.1 General The guidance for design and installation of instrument sensing lines in ISA-S67.02 is endorsed by this regulatory guide.
 
2.1.1 Value The action should result in more effective design and installation of instrument sensing lines, thus providing more assurance that the sensing lines will perform their safety function under all service conditions. It establishes the NRC
position on a national consensus standard and therefore reduces uncertainty as to what the staff considers accept able in, the area of sensing line design and installation.
 
the line meets provisions equivalent to the provisions of Sections 4.7.3 and 4.7.4 of IEEE Std 279-1971.


In some cases, applicants or licensees may propose an alternative or use a previously established acceptable alternative method for complying with specified portions of the NRC's regulations.
2.2.1 Value Any design in which a single failure could cause an event and at the same time prevent mitigating action should be avoided or additional redundancy should br provided.


Rev. 1 of RG 1.151, Page 5 Otherwise, the methods described in this guide will be used in evaluating compliance with the applicable regulations for license applications, license amendment applications, design certifications, and amendment requests.
2.2.2 Impact The avoidance of common-mode failures is a general design objective and consequently there should be no impact.


Rev. 1 of RG 1.151, Page 6 GLOSSARY  backfill-In the context of instrument sensing lines, backfill refers to a specific measure to supply a flow of reactor coolant into sensing lines to prevent the collection of trapped gas.  In resolving the occurrence of false level readings, this modification came to be known as the "backfill modification."  (See Ref. 9.)
2.3 Mechanical Design Regulatory Positions 2 and 3 were included to modify the guidance to make it consistent with the guidance of Regulatory Guide 1.26.
evolved gas-Gas released from reactor coolant caused by a chemical reaction or a change in the solubility of the coolant.


instrument sensing line-A group of valves, fittings, manifolds, tubing, and piping used to connect instruments to main piping, other instruments, apparatus, or measuring equipment.
2.3.1 Value The regulations require that components of the reactor coolant pressure boundary be designed and erected in accordance with the requirements of ASME Class 1. After reviewing a number of applications for construction permits and operating licenses and after discussions with repre sentatives of professional societies and industry, the NRC
staff developed the classifications and guidance given in Regulatory Guide 1.26, thus providing the assurance that structures, systems, and components were designed and erected (installed) to quality standards commensurate with the importance of the safety functions to be performed.


trapped gas-Gas confined to a region of piping by buoyancy force. Trapped gas in a sensing line gives a false reading of the pressure in the sensing line.
2.3.2 Impact There should be no impact since no new requirements
2.1.2 Impact are imposed.


Rev. 1 of RG 1.151, Page 7 REFERENCES
Most of the impact on industry has already occurred during development, review, and approval of the consensus standard.
1  1. 10 CFR Part 100, "Reactor Site Criteria," U.S. Nuclear Regulatory Commission, Washington, DC.


2. 10 CFR Part 50, "Domestic Licensing of Production and Utilization Facilities," U.S. Nuclear Regulatory Commission, Washington, DC.
Additional impact associated with the NRC
endorsement of the standard should be minimal.


3. Regulatory Guide 1.53, "Application of the Single-Failure Criterion to Safety Systems," U.S. Nuclear Regulatory Commission, Washington, DC.
2.2 Common Sensing Lines Regulatory Position 1 was included to ensure that a single sensing line would not be used to perform a non safety-related function and a safety-related function if the failure of the sensing line could cause a transient and at the same time prevent the mitigation of that transient unless
2.4 Environmental Conditions Regulatory Position 4 was included to add freezing temperatures to the list of environmental conditions to be considered in the design of instrument sensing lines.


4. ANSI/ISA-67.02.01-1999, "Nuclear Safety-Related Instrument-Sensing Line Piping and Tubing Standard for Use in Nuclear Power Plants," American National Standards Institute/Instrument Society of America, Research Triangle Park, NC, 1999.
2.4.1 Value Instrument sensing lines should remain functional under all environmental conditions. In the past, there have been many occurrences of frozen instrument lines because
1.151-3


2  5. ANSI/ISA-S67.10-1994, "Sample Line Piping and Tubing Standards for Use in Nuclear Power Plants," American National Standards Institute/Instrument Society of America, Research Triangle Park, NC, 1994.
extremely cold temperature was not given adequate consid eration in the design. Consequently, special attention must be given to prevent such occurrences.


6. ANSI/IEEE Std 622-1987, "Recommended Practice for the Design and Installation of Electric Heat Tracing Systems for Nuclear Power Generating Stations," Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1987.
2.4.2 Impact There is no impact since this is not a new requirement.


7. NRC Information Notice No. 92-54, "Level Instrumentation Inaccuracies Caused by Rapid Depressurization," U.S. Nuclear Regulatory Commission, Washington, DC, July 24, 1992.
IE Bulletin 79-24, "Frozen Lines," was issued requesting all licensees and construction permit holders to ensure that freezing temperatures are taken into the design considera tions for instrument sensing lines.


8. NRC Information Notice No. 93-27, "Level Instrumentation Inaccuracies Observed During Normal Plant Depressurization," U.S. Nuclear Regulatory Commission, Washington, DC, April 8, 1993.  9. NRC Information Notice No. 95-20, "Failures in Rosemount Pressure Transmitters Due to Hydrogen Permeation into the Sensor Cell," U.S. Nuclear Regulatory Commission, Washington, DC, March 22, 1995.
2.5 Environmental Control and Monitoring Regulatory Position 5 was included to provide guidance in the design and installation of instrument sensing lines to account for extremely cold weather conditions.


10. Bulletin 93-03, "Resolution of Issues Related to Reactor Vessel Water Level Instrumentation in BWRs," U.S. Nuclear Regulatory Commission, Washington, DC, May 28, 1993.
2.5.1 Value The guidance provided is consistent with a technical position of the Instrumentation and Control Systems Branch (NRR) that was developed after it became evident that frozen instrument lines had become a problem. It ensures that the concerns of IE Bulletin 79-24, "Frozen Lines," were adequately addressed.


11. Information Notice 93-89, "Potential Problems with BWR Level Instrumentation Backfill Modifications," U.S. Nuclear Regulatory Commission, Washington, DC, November 26, 1993.
2.5.2 Impact There should be no impact since no new requirements are imposed.


12. IEEE Std 603-1991, "Standard Criteria for Safety Systems for Nuclear Power Generating Stations," Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1991 (and the correction sheet, dated January 30, 1995).
===3. CONCLUSION ===
3                                               
A regulatory guide endorsing ISA-S67.02 has been devel oped to provide guidance for the design and installation of instrument sensing lines.
1 Publicly available NRC published documents are available electronically through the Electronic Reading room on the NRC's public Web site at: http://www.nrc.gov/reading-rm/doc-collections/. The documents can also be viewed on-line or printed for a fee in the NRC's Public Document Room (PDR) at 11555 Rockville Pike, Rockville, MD; the mailing address is USNRC PDR, Washington, DC 20555; telephone 301-415-4737 or (800) 397-4209; fax (301) 415-3548; and e-mail PDR.Resource@nrc.gov.    2 Copies of American National Standards (ANS) may be purchased from the American National Standards Institute (ANSI), 1819 L Street, NW., 6th floor, Washington, DC 20036 [phone: (202) 293-8020)].  Purchase information is available through the ASCE Web site at http://webstore.ansi.org/ansidocstore/
. 
Rev. 1 of RG 1.151, Page 8
13. IEEE Std 279-1971, "Criteria for Protection Systems for Nuclear Power Generating Stations," Institute of Electrical and Electronics Engineers, Piscataway, NJ, 1971.


3 Copies of Institute of Electrical and Electronics Engineers (IEEE) standards may be purchased from the IEEE Standards Association, 445 Hoes Lane, Piscataway, NJ 08855-1331; telephone (800) 678 4333.  Purchase information is available through the IEEE Standards Association Web site at http://www.ieee.org
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Latest revision as of 01:12, 17 January 2025

(Task IC 126-5) Instrument Sensing Lines
ML020360111
Person / Time
Issue date: 07/31/1983
From:
Office of Nuclear Regulatory Research
To:
References
FOIA/PA-2002-0095 Reg Guide 1.151
Download: ML020360111 (4)
v • d • e


U.S. NUCLEAR REGULATORY COMMISSION

REGULATORY GUIDE

OFFICE OF NUCLEAR REGULATORY RESEARCH

REGULATORY GUIDE 1.151 (Task IC 126-5)

INSTRUMENT SENSING LINES

A. INTRODUCTION

Section 50.34, "Contents of Applications; Technical Information," of 10 CFR Part 50, "Domestic Licensing of Production and Utilization Facilities," requires, in part, that design criteria be established for structures, systems, and components important to safety that will provide reasonable assurance that the facility can be operated without undue risk to the health and safety of the public.

Criterion 1, "Quality Standards and Records," of Appen dix A, "General Design Criteria for Nuclear Power Plants,"

to 10 CFR Part 50 requires, in part, that structures, systems, and components be erected (installed) to quality standards commensurate with the importance of the safety functions to be performed.

Criterion 13, "Instrumentation and Control," of Appendix A to 10 CFR Part 50 requires, in"

part, that instrumentation be provided to ensure adequate safety. Criterion 24, "Separation of Protection and Control Systems," of Appendix A to 10 CFR Part 50 and Section

4.7.3, "Single Random Failure," of IEEE Std 279-1971 require, in part, that the interconnection of the protection and control systems be limited so as to ensure that safety is not significantly impaired.

This regulatory guide describes a method acceptable to the NRC staff for complying with the Commission's regu lations with regard to the design and installation of safety related instrument sensing lines in nuclear power plants.

The term "safety-related"

refers to those structures, systeqms, and components necessary to ensure (1) the integsty of the reactor coolant pressure boundary, (2) the capability to shut down the reactor and maintain it in a safe shutdown condition, or (3) the capability to prevent or mitigate the consequences of accidents that could result in potential offsite exposures comparable to the guideline exposures of 10 CFR Part 100.

The Advisory Committee on Reactor Safeguards has been consulted concerning this guide and has concurred in the regulatory position.

USNRC REGULATORY GUIDES

Regulatory Guides are issued to describe and make available to the public methods acceptable to the NRC staff of implementing specific parts of the Commission's regulations, to delineate tech niques used by the staff in evaluating specific problems or postu lated accidents, or to provide guidance to applicants. Regulatory Guides are not substitutes for regulations, and compliance with them is not required. Methods and solutions different from those set out In the guides will be acceptable if they provide a basis for the findings requisite to the Issuance or continuance of a permit or license by the Commission.

This guide was Issued after consideration of comments received from the public. Comments and suggestions for improvements in these guides are encouraged at all times, and guides will be revised, as appropriate, to accommodate comments and to reflect new informa tion or experience.

Any guidance in this document related to information activities has been cleared under OMB Clearange No. 3150

0011.

B. DISCUSSION

ISA-$67.02, "Nuclear-Safety-Related Instrument Sens ing Line Piping and Tubing Standards for Use in Nuclear Power Plants,"* was prepared by Committee SP67-02 of the Instrument Society of America (ISA). It was approved, by the ISA Nuclear Power Plant Standards Committee on October 19, 1978, and subsequently by the ISA Standards and Practices Board in June 1980. The standard provides design, physical protection, and installation requirements for instrument sensing line piping and tubing for nuclear power plant applications. It establishes the applicable ASME code requirements and boundaries for the design and installation of instrument sensing lines that interconnect safety-related piping and' vessels with safety-related instru mentation and non-safety-related instrumentation.

C. REGULATORY POSITION

The requirements of ISA-$67.02,

"Nuclear-Safety Related Instrument Sensing Line Piping and Tubing Stan dards for Use in Nuclear Power Plants," 1980, provide a basis acceptable to the NRC staff for the design and installation of safety-related instrument sensing lines in nuclear power plants subject to the following:

1. The requirements for instrument sensing lines in Section 4.1 of ISA-$67.02 should be supplemented with the following:

A single instrument sensing line should not be used to perform both a safety-related function and a non safety-related function unless it can be shown that:

Copies are available from the Instrument Society of America,

67 Alexander Drive P.O. Box 12277, Research Triangle Park, North Carolina 27701.

Comments should be sent to the Secretary of the Commission.

U.S. Nuclear Regulatory Commission, Washington, D.C. 20555, Attention: Docketing and Service Branch.

The guides are Issued In the following ten broad divisions:

1. Power Reactors

6. Products

2. Research and Test Reactors

7. Transportation

3. Fuels and Materials Facilities S. Occupational Health

4. Environmental and Siting

9. Antitrust and Financial Review

5. Materials and Plant Protection 10. General Copies of issued guides may be purchased at the current Government Printing Office price. A subscription service for future guides in spe cific divisions is available through the Government Printing Office.

Information on the subscription service and current GPO prices may be obtained by writing the U.S. Nuclear Regulatory Commission.

Washington, D.C. 20555. Attention: Publications Sales Manager.

ni July 1983

a. The failure of the common sensing line would not simultaneously (1) cause an action in a non-safety related system that results in a plant condition requiring protective action and (2) also prevent proper action of a protection system channel designed to protect against the condition; or b. If the failure of the common sensing line can cause an action in a non-safety-related system that results in a plant condition requiring protective action and can also prevent proper action of a protection system channel designed to protect against the condition, the remaining redundant protection channels are capable of providing the protective action even when degraded by a second random failure. The rupture of a second instru ment sensing line need not be considered as a second random failure.

Provisions should be included so that this requirement can still be met if a channel is bypassed or removed from service for test or maintenance purposes. Acceptable provisions include reducing the required coincidence, defeating the signals taken from the same sensing line in non-safety-related systems, or initiating a protective action from the bypassed channel.

2. The mechanical design requirements in Tables I and 2 and Figures 1, 2, 3, 4, 7, and 8 of ISA-S67.02 for instru ment' sensing lines connected to ASME Class 1 and 2 process piping and vessels should be supplemented with the following:

a. Instrument sensing lines that are connected to ASME Class 1 or 2 process piping or vessels should not be less than ASME Class 2 Seismic Category I

from their connections to the process piping or vessel to and including the accessible isolation valve.

l*. Instrument sensing lines that are connected to

'*ASME Class I or 2 process piping or vessels and that are used to actuate or monitor safety-related systems should not be less than ASME Class 2 Seismic Category I from their connections to the process piping or vessel to the sensing instrumenta tion.

3. The mechanical design requirements in Tables I and 2 and Figures 5, 6, and 9 of ISA-$67.02 for instrument sensing lines connected to ASME Class 3 process piping and vessels should be supplemented with the following:

Instrument sensing lines that are connected to ASME

Class 3 process piping and vessels and that are used to actuate or monitor safety-related systems should not be less than ASME Class 3 Seismic Category I from their connection to the process piping or vessel to the sensing instrumentation.

4. Freezing temperatures should be added to the environ mental and installation conditions listed in Section 5.2.1(5)

of ISA-S67.02 that sensing lines should be able to with stand and continue to perform their function.

5. The special considerations in Section 5.2.2 of ISA-$67.02 that should be addressed in the design and installation of instrument sensing lines should be supple mented with the following:

a. Instrument sensing lines that can be exposed to freezing temperatures and that contain or can be expected to contain a condensable mixture or fluid that can freeze should be provided an environmental control system (heatingand venti lation or heat tracing) to protect the lines from freezing during extremely cold weather.

b. The environment associated with those instrument sensing lines in a. that are safety related should be monitored and alarmed so that appropriate correc tive action can be taken to prevent loss of or damage to the lines from freezing in the event of loss of the environmental control system.

c. The environmental control system recommended in a., and for which b. applies, should be electri cally independent of the monitoring and alarm system so that a single failure in either system, including their power sources, does not affect the capability of the other system.

d. The environmental control and monitoring systems of a. and b. should be designed to stan dards commensurate with their importance to safety and with administrative controls that are implemented to address events or conditions that could render the systems inoperable.

6. The Summer 1981 Addenda to Section III of the ASME Boiler and Pressure Vessel Code deleted Paragraphs NB-3676, NC-3676, and ND-3676 in their entirety. Refer ences to these paragraphs in Section 4.2.1, Section 6.2, and Section 7 of ISA-$67.02 should be disregarded.

D. IMPLEMENTATION

The purpose of this section is to provide information to applicants and licensees regarding the NRC staff's plans for using this regulatory guide.

Except in those cases in which an applicant or licensee proposes an acceptable alternative method for complying with specified portions of the Commission's regulations, the method described in this guide will be used by the NRC

staff in its evaluation of the design and installation of safety-related instrument sensing lines for all construction permit applications issued after September 1,1983. Licensees or other applicants may use this guide in discussions with the staff as justification for the adequacy of sensing line design and installation or for modifications to sensing line design and installation. However, the staff does not intend to recommend the systematic application of every aspect of this guide to plants currently operating or under review.

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VALUE/IMPACT STATEMENT

1. BACKGROUND

The licensee of a nuclear power plant is required by the Commission's regulations to provide principal design criteria for those structures, systems, and components that provide reasonable assurance that the facility can be operated without undue risk to the health and safety of the public. General guidance for the design and installation of instrument sensing lines is given in Regulatory Guide 1.26,

"Quality Group Classifications and Standards for Water-,

Steam-, and Radioactive-Waste-Containing Components of Nuclear Power Plants." The Instrument Society of America (ISA) has developed more definitive guidance on instru ment sensing lines in ISA-S67.02, "Nuclear-Safety-Related Instrument Sensing Line Piping and Tubing Standards for Use in Nuclear Power Plants."

The action endorses this additional guidance, with appropriate supplementary material, in a regulatory guide.

2. VALUE/IMPACT ASSESSMENT

2.1 General The guidance for design and installation of instrument sensing lines in ISA-S67.02 is endorsed by this regulatory guide.

2.1.1 Value The action should result in more effective design and installation of instrument sensing lines, thus providing more assurance that the sensing lines will perform their safety function under all service conditions. It establishes the NRC

position on a national consensus standard and therefore reduces uncertainty as to what the staff considers accept able in, the area of sensing line design and installation.

the line meets provisions equivalent to the provisions of Sections 4.7.3 and 4.7.4 of IEEE Std 279-1971.

2.2.1 Value Any design in which a single failure could cause an event and at the same time prevent mitigating action should be avoided or additional redundancy should br provided.

2.2.2 Impact The avoidance of common-mode failures is a general design objective and consequently there should be no impact.

2.3 Mechanical Design Regulatory Positions 2 and 3 were included to modify the guidance to make it consistent with the guidance of Regulatory Guide 1.26.

2.3.1 Value The regulations require that components of the reactor coolant pressure boundary be designed and erected in accordance with the requirements of ASME Class 1. After reviewing a number of applications for construction permits and operating licenses and after discussions with repre sentatives of professional societies and industry, the NRC

staff developed the classifications and guidance given in Regulatory Guide 1.26, thus providing the assurance that structures, systems, and components were designed and erected (installed) to quality standards commensurate with the importance of the safety functions to be performed.

2.3.2 Impact There should be no impact since no new requirements

2.1.2 Impact are imposed.

Most of the impact on industry has already occurred during development, review, and approval of the consensus standard.

Additional impact associated with the NRC

endorsement of the standard should be minimal.

2.2 Common Sensing Lines Regulatory Position 1 was included to ensure that a single sensing line would not be used to perform a non safety-related function and a safety-related function if the failure of the sensing line could cause a transient and at the same time prevent the mitigation of that transient unless

2.4 Environmental Conditions Regulatory Position 4 was included to add freezing temperatures to the list of environmental conditions to be considered in the design of instrument sensing lines.

2.4.1 Value Instrument sensing lines should remain functional under all environmental conditions. In the past, there have been many occurrences of frozen instrument lines because

1.151-3

extremely cold temperature was not given adequate consid eration in the design. Consequently, special attention must be given to prevent such occurrences.

2.4.2 Impact There is no impact since this is not a new requirement.

IE Bulletin 79-24, "Frozen Lines," was issued requesting all licensees and construction permit holders to ensure that freezing temperatures are taken into the design considera tions for instrument sensing lines.

2.5 Environmental Control and Monitoring Regulatory Position 5 was included to provide guidance in the design and installation of instrument sensing lines to account for extremely cold weather conditions.

2.5.1 Value The guidance provided is consistent with a technical position of the Instrumentation and Control Systems Branch (NRR) that was developed after it became evident that frozen instrument lines had become a problem. It ensures that the concerns of IE Bulletin 79-24, "Frozen Lines," were adequately addressed.

2.5.2 Impact There should be no impact since no new requirements are imposed.

3. CONCLUSION

A regulatory guide endorsing ISA-S67.02 has been devel oped to provide guidance for the design and installation of instrument sensing lines.

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