ML20055J369
| ML20055J369 | |
| Person / Time | |
|---|---|
| Issue date: | 07/21/1989 |
| From: | Beckjord E NRC OFFICE OF NUCLEAR REGULATORY RESEARCH (RES) |
| To: | Jordan E Committee To Review Generic Requirements |
| Shared Package | |
| ML20055C236 | List: |
| References | |
| TASK-DG1002, TASK-RE NUDOCS 9008020158 | |
| Download: ML20055J369 (11) | |
Text
I, 3
I
/p*Mouq'o UNITED STATES l'
NUCLEAR REGULATORY COMMISSION
>m g
g e
WASHINGTON. D. C. 20bbb i
't, * * " ',$
JUL t 1 1989 i
NEMORANDUM FOR:
Edward L. Jordan Chairman CommitteetoRevIewGenericRequirements FROM:
Eric S. Beckjord, Director Office of Nuclear Regulatory Research
SUBJECT:
CRGR REVIEW - REGULATORY GUIDE DG-1002, ' CRITERIA FOR ELECTRIC ISOLATION DEVICES USED IN SAFETY SYSTEMS FOR NUCLEARPOWERPLANTS*(10BEISSUEDFORPUBLICCOMMENT) i
Background:
Paragraph (h) of Section 50.55(a) of 10CFR Part 50 invokes IEEE Std. 279-1971, which requires that, when it is necessary (or desirable) to transmit a signal from a safety system to a safety system interface and from a safety system to a non-safety system, the signal shall be transmitted i
through an isolation device.
The purpose of an isolation device is to prevent undesirable intrusions from entering the safety system from the non-safety system.
This inc1rdes the effects of. failures, such as short circuits, grounds, open circuits, voltage surges, etc.
l It is, therefore, essential that the isolation devices be designed and tested j
to assure that they can withstand certain anomalier without failure while l
preventing these anomalies from passing through, in a detrimental wa,y, to the safety system.
General requirements for isolation devices used in safety systems are contained in regulations, and the recommendations and guidance in meeting those regulatory requirements are provided la a number of documents.
However, no specific guidance pertaining to isolation devices has been published by NRC.
Discussion:
The proposed Regulatory Guide DG-1002 reflects the current licensing practice.
This proposed regulatory guide will apply to all future nuclear power plants and to operating plants that add or modify a safety system design requiring the use of isolation devices.
Staff Coments The proposed Regulatory Guide DG-1002 was reviewed by the NRR and RES staff without significant coment.
Concurrence on this memorandum was obtained from the Director of NRR, who has determined that the provisions contained in this proposed regulatory guide 4
have been applied uniformly for all licensing evaluations for the past 10 years.
In addition, the Director of rIRR has determined that the issuance of this Regulatory Guide is desirable to document an existing technical position and to continue to maintain its uniform application.
9008020108 690823 FDR REVGP NR6CRGR MEETING 167 FDC
E. Jordan 2
O l 2 1 rppg Office of General Counsel has no legal objection to the issuance of this regulatory guide.
Value and Impact This regulatory guide does not impose new requirements or costs.
bh Eric S. Beckjord, Director Office of Nucleat Regulatory Research
Enclosures:
1.
Reg. Guide DG-1002, April 10, 1989 2.
CRGR Summary i
i j
l April 1989 I
Division 1 Task DG-1002
Contact:
S. K. Aggarwal (301) 492-3829 r
CRITERIA FOR ELECTRIC ISOLATION DEVICES 1
USED IN SAFETY SYSTEMS FOR NUCLEAR POWER PLANTS A.
INTRODUCTION Paragraph (h) of $ 50.55a, " Codes and Standards," of 10 CFR Part 50, "Do-mestic Licensing of Production and Utilization Facilities," invokes IEEE Std 279-1971, which requires, in Paragraph 4.7.2, " Isolation Devices " that trans-mission of signals from protection system equipment be through isolation devices that meet all the requirements of the protection system.
Section 50.49, " Environmental Qualification of Electric Equipment Important to Safety for Nuclear Power Plants," of 10 CFR Part 50 provides specific require-ments pertaining to qualification of certain electric equipment important to safety, which includes safety-related equipment.
Criterion 1. " Quality Standards and Records," of Appendix A, " General Design Criteria for Nuclear Power Plants," to 10 CFR Part 50 requires that structures, i
systems, and components be designed, fabricated, erected (installed), and tested to quality standards commensurate with the importance of the safety function to be performed.
Criterion III, " Design Control," of Appendix B " Quality Assurance Criteria for Nuclear Power Plants and Fuel Reprocessing Plants," to 10 CFR Part 50 re-quires that, where a test program is used to verify the adequacy of a specific feature, it must include suitable qualification testing of a prototype unit under the most adverse design conditions.
This regulatory guide describes a method acceptable to the NRC staff for l
complying with the Commission's regulations with regard to the design, qualifi-cation, and use of electric isolation devices in safety systems of nuclear power plants.
l l
4/10/89 1
RG DG-1002
Any information collection activities mentioned in this regulatory guide are contained as requirements in 10 CFR Part 50 which provides the regulatory basis for this guide.
The information collection requirements in 10 CFR Part 50 have been cleared under OMB Clearance No. 3150-0011.
B.
DISCUSSION The NRC regulations fequire that, when it is necessary or desirable to transmit a signal from a safety system to a safety system interface and from a safety system to a non-safety system, the signal be transmitted through an isolation device whose purpose is to prevent undesirable intrusions from enter-ing the safety system from the non-safety system.
This includes the effects of failures, such as short circuits, open circuits, grounds, and the application
- of the maximum credible ac and de potential to the terminals on the non-safety system side of the isolation device, as well as intrusions, such as voltage surges, that could enter the safety system through the safety system /non-safety system interface and thus adversely affect the safety system.
Since some electric isolation devices themselves contain solid-state com-ponents, it is essential that these devices be designed and tested to assure that they can withstand certain anomalies without failure, while preventing these anomalies from passing through, in a detrimental way, to the safety system.
In other words, if isolation devices fail, their failure must not have an adverse effect on the safety system.
General requirements for isolation devices used in safety systems are con-tained in the regulations, with some recommendations and guidance in meeting those regulatory requirements presently provided in a number of documents, includ-ing Regulatory Guide 1.75, " Physical Independence of Electric Systems"; Regula-tory Guide 1.89, " Environmental Qualification of Certain Electric Equipment Important to Safety for Nuclear Power Plants"; Regulatory Guide 1.97 "Instru-mentation for Light-Water-Cooled Nuclear Power Plants To Assess Plant and En-virons Conditions During and Following an Accident"; Regulatory Guide 1.100,
" Seismic Qualification of Electric and Mechanical Equipment for Nuclear Power Plants"; and Regulatory Guide 1.153, " Criteria for Power, Instrumentation, and Control Portions of Safety Systems." However, the specific provisions pertaining to isolation devices have not been addressed in adequate detail in these-regula-tory guides.
4/10/89 2
RG DG-1002
h One of the qualification tests included in this regulatory guide requires the application of maximum credible fault (MCF) applied in the transverse mode on the non-safety-related side of the isolator.
The MCF must be applied to both sides for safety system to safety system applications.
In most cases, the MCF is a function of the largest voltages and current identified in the cabinets where the isolators are housed.
In some cases, experimentation or analysis or both may be necessary to determine the MCF, Thus, the determin6 tion of the value of MCF is plant-specific and must be carefully evaluated for each application.
C.
REGULATORY POSITION Electric isolation devices intended for use in safety systems of nuclear power plants should be designed, fabricated, and installed to quality stendards commensurate with safety system criteria.
They should also be tested tr, assure that they can meet their specified performance requirements.
The fo1 Nwing should be included as criteria for electric isolation devices.
1.
The use of interrupting devices actuated by fault current are con-sidered to be acceptable isolation devices for interfacing safety-related to non-safety related circuits, with the exception of power distribution circuit breakers and fuses.
2.
For a safety system to a non-safety system interface, qualification testing should include the application of credible failures to the output of the isolation device.
Examples of credible failures include short circuits, open circuits, grounds, and the application of the maximum credible fault (MCF) test.
The MCF is the application of the maximum ac and de voltages and current that could inadvertently be applied to the output terminals and the low voltage power supply excitation terminals of the isolation device in the transverse mode [sig-nal and return), as shown in Figure 1.
The MCF is generally a function of the largest voltages and current identified in the cabinets where the isolators are housed (e.g., 120V at 20 amps).
The minimum voltage applied should not be less than 120 volts ac and 125 voits dc (fully charged battery) from a 20-amp source.
The fault voltages should be applied for a sufficient duration to allow for the measurements to be made and for the effects on the isolation device to occur and then settle down to steady-state values.
During and following the application of the fault, there should be no degradation or perturbation to the input that would have a detrimental effect on the safety system.
06/02/89 3
RG DG-1002 l
3.
For a safety system to a safety system interface, the credible failures outlined in Regulatory Position 2 should be applied as specified to the output terminals.
In addstion, the credible failures outlined in Regulatory Position 2 should be applied to the input terminals as shown in Figure 2.
During and fol-lowing the test, the isolation device shoulo not allow any energy pass-through from the output to the input or from the input to the output that would have a detrimental effect on the safety system opposite from where the fault is applied.
4.
When using relays as isolation devices (coil to contact), qualifica-tion testing should include an oscillatory voltage surge test to assure that postulated voltage surges in the non safety system are effectively blocked from entering, by conduction or leakage, through the isolation device into the safety system.
In such applications, the MCF test is not required.
The surge test in-volves the application of the surge wave shape and characteristics as outlined in the IEEE Std 472-1974/ ANSI C37.90a-1974, " Guide for Surge Withstand Capability (SWC) Tests" to the output terminals, and alternately to the power source termi-nals of the isolation device, as s>.own in Figure 3.
The isolation device should not allow any energy pass-through from the output or the power source to the input that would have a detrimental effect in the intended safety system application.
5.
Attention should be given to the physical arrangement of components in an electric isolation device design to prevent, in the event of failure, shattered parts in the form of missiles, solder splatter, and fire and smoke of failed components from adversely affecting (i.e., bridging the barrier) the safety system to which the device is connected.
Physical separation, barriers, and encapsulation or enclosures should be considered in meeting this provision.
D.
IMPLEMENTATION The purpose of this section is to provide information to applicants and li-censees regarding the NRC staff's plans for using this regulatory guide.
Except in those cases in which the applicant or licensee proposes an accept-able alternative method for complying with specified portions of the Commission's regulations, the methods described herein will be used in the evaluation of the design and qualification of electric isolation devices for the following nuclear 1
power plants:
1 4/10/89 4
RG DG-1002 l
j l
Safety system i Non-sa,ety system t
O, I
c o
iSOLATON u
i DEVICE i
MCF y
p u
I P
1 o'
i ff b ' c i
i l
l MCP t
Figure 1
- MCF test should be applied to the power supply input if the operating voltage is less than the MCF, l
u,e,v.v. tem j
.e,v.v.te.
DMalon I i
DMelon 2 ob g
u n
l t
MW p
i T
u l
P t
I u
O l
'o i
l i
Figure t (MCF is applied to both sides)
MCF = Maximum Credible Fault T = Test equipment (oscilloscope, chart recorder) sensitive enough to detect any perturbation.
t 5
. ~..
l t
l Safety System i Non-safety System I
o, l
c l
e ISOLATION i
u DEVICE t
T p
SWC u
l P
+
t I
u O
l
'O i
i l
I Pleure 3 SWC = Surge Withstand Capabildy voltage T = Test measurement equipment 1
M i
I I
e r
6
1.
Plants for which the construction permit is issued af ter (issue date of guide).
2.
Plants for which the operating licensee application is docketed 6 months or more after (issue date of guide).
3.
Operating plants that add or modify a safety system design' requiring the use of isolation devices after (issue date of guide).
DRAFT VALUE/ IMPACT STATEMENT BACKGROUND 9
General requirements for isolation devices used in safety systems are con-tained in regulations, with some recommendations and guidance in meeting those regulatory requirements presently provided in a number of documents, including Regulatory Guides 1.75, 1.89, 1.97, 1.100 and 1.153.
However, the specific guidance pertaining to isolation devices has not been addressed in any published NRC document.
As a consequence, licensing reviews of isolation devices are being done on a case-by-case basis.
VALUE This guide presents an acceptable method of complying with the Commis-sion's regulations.
This guide should, therefore, enhance the licensing process.
IMPACT This regulatory guide is consistent with current NRC practice-and simply intended to document an existing technical position.
This guide does not require replacement of installed isolation devices in the operating nuclear power plants.
It applies to future nuclear power plants and to only those operating nuclear power plants that add or modify a safety system design requiring the use of j
isolation devices.
Therefore, this regulatory guide will not have any immediate l
cost impact on operating nuclear power plants, i
7/14/89 7
RG DG-1002
o,;
The staff believes that most of the currently available models of isolation l
devices have been tested and will meet the provisions of this regulatory guide.
l However, if a licensee decides to use an unqualified isolation device..the cost l
of testing would not be over $10,000.
j 9
i 6
r i
I I
}
- )
h
- e
' i
-I I
i e
t e
^
r 1
h 7/14/89-8 RG DG-1002-
.m,,.
4
. _. ~ _
l I
i
SUMMARY
OF PROPOSED REGULATORY GUIDE FOR CRGR REVIEW 0FFICE OF NUCLEAR REGULATORY RESEARCH Date: July 21, 1969 RES Task No.:
DG-1002 I
RES Program Manager:
S. K. Aggerwal Telephone: 492-3829 j
Title of Proposed Action j
Proposed Kegulatory Guide, DG-1002, " Criteria for Electric Isolation Devices used in Sattty Systems for Nuclear Power Plants" April 1989.
j Statement of the Proble.n Heretofore, no specific guidance pertaining to isolation devices used in safety-systems has been published by NRC.
General requirements are however, contained in regulations.
Paragraph (h) of Section 50.55(a),of 10CFR Part 50 invokes IEEE Std 279-1971, which requires that, when it is necessary (or desirable) to transmit a signal from a safety system to a safety system i
interface and from a safety system to a non safety system, the signal shall be transmitted through an isolation device.
It is essential that the isolation devices be designed and tested to assure that they can withstand certain anomalies without failure, while preventing these anomalies from passing through, in a detrimental way, to the safety system.
Objective:
The objective is to document an existing technical position. The provisions contained in this proposed regulatory guide have been applied uniformly for all licensing evaluations for the past 10 years.
Consequences:
Currently, licensing reviews of isolation devices are being done on a l
case-by-case basis.
Issuance of this guide will reduce staff efforts during the licensing review process.
Decision Rationale:
The guide should be issued, since it is consistent with current NRC practice and simply intended to document an existing technical position.
implementation:
This guide applies to future nuclear power plants and to those operating i
l nuclear power plants that add or modify a safety system design requiring the use of isolation devices.
This guide does not require replacement of installed isolation devices in the operating nuclear p0wer plants.
ENCLOSURE 2
__