United States Nuclear Regulatory Commission - Protecting People and the Environment

Fire Protection Rule (45 FR 76602, November 19, 1980) (Generic Letter 81-12)



                                UNITED STATES
                        NUCLEAR REGULATORY COMMISSION
                           WASHINGTON, D.C.  20555

                              February 20, 1981

TO ALL POWER REACTOR LICENSES WITH PLANTS
LICENSED PRIOR TO JANUARY 1, 1979 

SUBJECT:  FIRE PROTECTION RULE (45 FR 76602, NOVEMBER 19, 1980) - 
               Generic Letter 81-12 

Paragraph 50.48(b) of 10 CFR Part 50, which became effective on February 17,
1981, requires all nuclear plants licensed to operate prior to January 1, 
1979 to meet the requirements of Section III.G, III.J and III.O of Appendix 
R to 10 CFR Part 50 regardless of any previous approvals by the Nuclear 
Regulatory Commission (NRC) for alternative design features for those items. 
This would require each licensee to reassess all those areas of the plant 
"... where cables or equipment, including associated non-safety circuits, 
that could prevent operation or cause maloperation due to hot shorts, open 
circuits or shorts to ground or (sic) redundant trains of systems necessary 
to achieve and maintain hot shutdown conditions are located within the same 
fire area outside of primary containment ..."* to determine whether the 
requirements of Section III.G.2 of Appendix R are satisfied.  If not, the 
licensee must provide alternative shutdown capability in conformance with 
Section III.G.3 or request an exemption if there is some justifiable basis. 

Paragraph 50.48(c)(5) requires that any modifications that the licensee 
plans in order to meet the requirements of Section III.G.3 of Appendix R 
must be reviewed and approved by the NRC.  This paragraph also requires that 
the plans, schedules and design descriptions of such modifications must be 
submitted by March 19, 1981.  To expedite our review process and reduce the 
number of requests for additional information with regard to this review, we
are enclosing two documents which specify the information that we will 
require to complete our reviews of alternative safe shutdown capability. 
Enclosure 1 is "Staff Position Safe Shutdown Capability".  This document was
originally sent to you in late 1979.  Section 8 specifies the information 
required, you need only reference that previous submittal.  Enclosure 2 
indicates the additional information needed to ensure that associated 
circuits for alternative safe shutdown equipment is included in your 
reassessment and in our review.  If you made no modifications that were 
required to provide alternative safe shutdown capability and if your 
reassessment concludes that alternative safe shutdown capability in 
accordance with the provisions of Section III.G.3 is not necessary, you do 
not have to provide the information requested by these Enclosures. 

*    Quoted from Section III.G.2 of Appendix R to 10 CFR Part 50.  Note that
     the "or" preceding "redundant trains" is a typographical error and 
     should read "of redundant trains". 
.

                                    - 2 -

Finally, we request that as part of your submittal of plans and schedules 
for meeting the provisions of Paragraphs (c)(2), (c)(3) and (c)(4) of 10 CFR
50.48 as required by Paragraph 50.48(c)(5), you include the results of your 
reassessment of the design features at your plant for meeting the 
requirements of Sections III.G, III.J and III.O of Appendix R to 10 CFR Part
50. 

This detailed information need not accompany the design description that 
must be submitted by March 19, 1981.  However, we request that it be 
submitted as soon as possible, but no later than May 19, 1981. 

This request for information was approved by GAO under a blanket clearance 
number R0071 which expires September 30, 1981.  Comments on burden and 
duplication may be directed to the U. S. General Accounting Office, 
Regulatory Reports Review, Room 5106, 441 G Street, N. W., Washington, D. C.
20548. 

                              Sincerely, 



                              Darrell G. Eisenhut, Director 
                              Division of Licensing 
                              Office of Nuclear Reactor Regulation 

Enclosures:
1.   Staff Position
2.   Request for Additional
          Information
.

                                                               Enclosure 1 

                              STAFF POSITION 
                         SAFE SHUTDOWN CAPABILITY 

Staff Concern 

During the staff's evaluation of fire protection programs at operating 
plants, one or more specific plant areas may be identified in which the 
staff does not have adequate assurance that a postulated fire will not 
damage both redundant divisions of shutdown systems. This lack of assurance 
in safe shutdown capability has resulted form one or both of the following 
situations: 

*    Case A:   The licensee has not adequately identified the systems and 
               components required for safe shutdown and their location in 
               specific fire areas. 

*    Case B:   The licensee has not demonstrated that the fire protection 
               for specific plant areas will prevent damage to both 
               redundant divisions of safe shutdown components identified in 
               these areas. 

For Case A, the staff has required that an adequate safe shutdown analysis 
be performed.  This evaluation includes the identification of the systems 
required for safe shutdown and the location of the system components in the 
plant.  Where it is determined by this evaluation that safe shutdown 
components of both redundant divisions are located in the same fire area, 
the licensee is required to demonstrate that a postulated fire will not 
damage both divisions or provide alternate shutdown capability as in Case B.

For Case B, the staff may have required that an alternative shutdown 
capability be provided with is independent of the area of concern or the 
licensee may have proposed such a capability in lieu of certain additional 
fire protection modifications in the area.  The specific modifications 
associated with the area of concern along with other systems and equipment 
already independent of the area form the alternate shutdown capability.  For
each plant, the modifications needed and the combinations of systems which 
provide the shutdown functions may be unique for each critical area; 
however, the shutdown functions provided should maintain plant parameters 
within the bounds of the limiting safety consequences deemed acceptable for 
the design basis event. 

Staff Position 

Safe shutdown capability should be demonstrated (Case A) or alternative 
shutdown capability provided (Case B) in accordance with the guidelines 
provided below: 

1.   Design Basis Event 

     The design basis event for considering the need for alternative 
     shutdown is a postulated fire in a specific fire area containing 
     redundant safe shutdown cables/equipment in close proximity where it 
     has been determined that fire protection means cannot assure that safe 
     shutdown capability will be preserved.  Two cases should be considered: 
     (1) offsite power is available; and (2) offsite power is not available. 
.

                                    - 2 -

2.   Limiting Safety Consequences and Required Shutdown Functions 

     2.1  No fission product boundary integrity shall be affected: 

          a.   No fuel clad damage; 
          b.   No rupture of any primary coolant boundary; 
          c.   No rupture of the containment boundary. 

     2.2  The reactor coolant system process variables shall be within those
          predicted for a loss of normal ac power. 

     2.3  The alternative shutdown capability shall be able to achieve and 
          maintain subcritical conditions in the rector, maintain reactor 
          coolant inventory, achieve and maintain hot standby* conditions 
          (hot shutdown* for a BWR) for an extended period of time, achieve 
          cold shutdown* conditions within 72 hours and maintain cold 
          shutdown conditions thereafter. 

*    As defined in the Standard Technical Specifications. 

3.   Performance Goals 

     3.1  The reactivity control function shall be capable of achieving and 
          maintaining cold shutdown reactivity conditions. 

     3.2  The reactor coolant makeup function shall be capable of 
          maintaining the reactor coolant level above the top of the core 
          for BWR's and in the pressurizer for PWR's. 

     3.3  The reactor heat removal function shall be capable of achieving 
          and maintaining decay heat removal. 

     3.4  The process monitoring function shall be capable of providing 
          direct readings of the process variables necessary to perform and 
          control the above functions. 

     3.5  The supporting function shall be capable of providing the process 
          cooling, lubrication, etc. necessary to permit the operation of 
          the equipment used for safe shutdown by the systems identified in 
          3.1 - 3.4. 

     3.6. The equipment and systems used to achieve and maintain hot standby
          conditions (hot shutdown for a BWR) should be (1) free of fire 
          damage; (2) capable of maintaining such conditions for an extended
          time period longer than 72 hours if the equipment required to 
          achieve and maintain cold shutdown is not available due to fire 
          damage; and (3) capable of being powered by an onsite emergency 
          power system. 

     3.7  The equipment and systems used to achieve and maintain cold 
          shutdown conditions should be either free of fire damage or the 
          fire damage to such systems should be limited such that repairs 
          can be made and cold shutdown conditions achieved within 72 hours. 
          Equipment and systems used prior to 72 hours after the fir should 
          be capable of being powered by an onsite emergency power system; 
          those used after 72 hours may be powered by 
.

                                    - 3 -

          offsite power. 

     3.8  These systems need not be designed to (1) seismic category I 
          criteria; (2) single failure criteria; or (3) cope with other 
          plant accidents such as pipe breaks or stuck valves (Appendix A 
          BTP 9.5-1), except those portions of these systems which interface 
          with or impact existing safety systems. 

4.   PWR Equipment Generally Necessary For Hot Standby 

     (1)  Reactivity Control 

          Reactor trip capability (scram).  Boration capability e.g., 
          charging pump, makeup pump or high pressure injection pump taking 
          suction from concentrated borated water supplies, and letdown 
          system if required. 

     (2)  Reactor Coolant Makeup 

          Reactor coolant makeup capability, e.g., charging pumps or the 
          high pressure injection pumps.  Power operated relief valves may 
          be required to reduce pressure to allow use of the high pressure 
          injection pumps. 

     (3)  Reactor Coolant System Pressure Control 

          Reactor pressure control capability, e.g., charging pumps or 
          pressurizer heaters and use of the letdown systems if required. 

     (4)  Decay Heat Removal 

          Decay heat removal capability, e.g., power operated relief valves 
          (steam generator) or safety relief valves for heat removal with a 
          water supply and emergency or auxiliary feedwater pumps for makeup
          to the steam generator.  Service water or other pumps may be 
          required to provide water for auxiliary feed pump suction if the 
          condensate storage tank capacity is not adequate for 72 hours. 

     (5)  Process Monitoring Instrumentation 

          Process monitoring capability e.g., pressurizer pressure and 
          level, steam generator level. 

     (6)  Support 

          The equipment required to support operation of the above described
          shutdown equipment e.g., component cooling water service water, 
          etc. and onsite power sources (AC, DC) with their associated 
          electrical distribution system. 
.

                                    - 4 -

5.   PWR Equipment Generally Necessary For Cold Shutdown* 

     (1)  Reactor Cooling System Pressure Reduction to Residual Heat Removal
          System (RHR) Capability 

          Reactor coolant system pressure reduction by cooldown using steam 
          generator power operated relief valves or atmospheric dump valves.

     (2)  Decay Heat Removal 

          Decay heat removal capability e.g., residual heat removal system, 
          component cooling water system and service water system to removal
          heat and maintain cold shutdown. 

     (3)  Support 

          Support capability e.g., onsite power sources (AC & DC) or offsite
          after 72 hours and the associated electrical distribution system 
          to supply the above equipment. 

*    Equipment necessary in addition to that already provided to maintain 
     hot standby. 

6.   BWR Equipment Generally Necessary For Hot Shutdown 

     (1)  Reactivity Control 

          Reactor trip capability (scram). 

     (2)  Reactor Coolant Makeup 

          Reactor coolant inventory makeup capability e.g., reactor core 
          isolation cooling system (RCIC) or the high pressure coolant 
          injection system (HPCI). 

     (3)  Reactor Pressure Control and Decay Heat Removal 

          Depressurization system valves or safety relief valves for dump to
          the suppression pool.  The residual heat removal system in steam 
          condensing mode, and service water system may also be used for 
          heat removal to the ultimate heat sink. 

     (4)  Suppression Pool Cooling 

          Residual heat removal system (in suppression pool cooling mode) 
          service water system to maintain hot shutdown. 

     (5)  Process Monitoring 

          Process monitoring capability eg., reactor vessel level and 
          pressure and suppression pool temperature. 
.

                                    - 5 -

     (6)  Support 

          Support capability e.g., onsite power source (AC & DC) and their 
          associated distribution systems to provide for the shutdown 
          equipment. 

7.   BWR Equipment Generally Necessary For Cold Shutdown* 

     At this point the equipment necessary for hot shutdown has reduced the 
     primary system pressure and temperature to where the RHR system may be 
     placed in service in RHR cooling mode. 

     (1)  Decay Heat Removal 

          Residual heat removal system in the RHR cooling mode, service 
          water system. 

     (2)  Support 

          Onsite sources (AC & DC) or offsite after 72 ours and their 
          associated distribution systems to provide for shutdown equipment.

*    Equipment provided in addition to that for achieving hot shutdown. 

8.   Information Required For Staff Review 

     (a)  Description of the systems or portions thereof used to provide the
          shutdown capability and modifications required to achieve the 
          alternate shutdown capability if required. 

     (b)  System design by drawings which show normal and alternate shutdown
          control and power circuits, location of components, and that 
          wiring which is in the area and the wiring which is out of the 
          area that required the alternate system. 

     (c)  Demonstrate that changes to safety systems will not degrade safety
          systems.  (e.g., new isolation switches and controls witches 
          should meet design criteria and standards in FSAR for electrical 
          equipment in the system that the switch is to be installed; 
          cabinets that the switches are to be mounted in should also meet 
          the same criteria (FSAR) as other safety related cabinets and 
          panels; to avoid inadvertent isolation from the control room, the 
          isolation switches should be keylocked, or alarmed in the control 
          room if the "local" or "isolated" position; periodic checks should 
          be made to verify switch is in the proper position for normal 
          operation; and a single transfer switch or other new device should 
          not be a source for a single failure to cause loss of redundant 
          safety systems). 

     (d)  Demonstrate that wiring, including power sources for the control 
          circuit and equipment operation sor the alternate shutdown method,
          is independent of equipment wiring in the area to be avoided. 
.

                                    - 6 -

     (e)  Demonstrate that alternate shutdown power sources, including all 
          breakers, have isolation devices on control circuits that are 
          routed through the area to be avoided, even if the breaker is to 
          be operated manually. 

     (f)  Demonstrate that licensee procedure(s) have been developed which 
          describe the tasks to be performed to effect the shutdown method. 
          A summary of these procedures should be submitted. 

     (g)  Demonstrate that spare fuses are available for control circuits 
          where these fuses may be required in supplying power to control 
          circuits used for the shutdown method and may be blown by the 
          effects of a cable spreading room fire.  The spare fuses should be
          located convenient to the existing fuses.  The shutdown procedure 
          should inform the operator to check these fuses. 

     (h)  Demonstrate that the manpower required to perform the shutdown 
          functions using the procedures of (f) as well as to provide fire 
          brigade members to fight the fire is available as required by the 
          fire brigade technical specifications. 

     (i)  Demonstrate that adequate acceptance tests are performed.  These 
          should verify that:  equipment operates from the local control 
          station when the transfer or isolation switch is placed in the 
          "local" position and that the equipment cannot be operated from 
          the control room; and that equipment operates from the control 
          room but cannot be operated at the local control station when the 
          transfer or isolation switch is in the "remote" position. 

     (j)  Technical Specifications of the surveillance requirements and 
          limiting conditions for operation for that equipment not already 
          covered by existing Tech. Specs.  For example, if new isolation 
          and control switches are added to a service water system, the 
          existing Tech. Spec. surveillance requirements on the service 
          water system should add a statement similar to the following: 

          "Every third pump test should also verify that the pump starts 
          from the alternate shutdown station after moving all service water 
          system isolation switches to the local control position." 

     (k)  Demonstrate that the systems available are adequate to perform the
          necessary shutdown functions.  The functions required should be 
          based on previous analyses, if possible (e.,g., in the FSAR), such
          as a loss of normal a.c. power or shutdown on a Group I isolation 
          (BRW).  The equipment required for the alternate capability should
          be the same or equivalent to that relied on the above analysis. 
.

                                    - 7 -

     (1)  Demonstrate that repair procedures for cold shutdown systems are 
          developed and material for repairs is maintained on site. 
.

                                                               Enclosure 2 

                    REQUEST FOR ADDITIONAL INFORMATION 

1.   Section III. G of Appendix R to 10 CFR Part 50 requires cabling for or 
     associated with redundate safe shutdown systems necessary to achieve 
     and maintain hot shutdown conditions be separated by fire barriers 
     having a three-hour fire rating or equivalent protection (see Section 
     III.G.2 of Appendix R).  Therefore, if option III.G.3 is chosen for the 
     protection of shutdown capability cabling required for or associated 
     with the alternative method of hot shutdown for each fire area, must be 
     physically separated by the equivalent of a three-hour rated fire 
     barrier from the fire area. 

     In evaluating alternative shutdown methods, associated circuits are 
     circuits that could prevent operation or cause maloperation of the 
     alternative train which is used to achieve and maintain hot shutdown 
     condition due to fire induced hot shorts, open circuits or shorts to 
     ground. 

     Safety related and non-safety related cables that are associated with 
     the equipment and cables of the alternative, or dedicated method of 
     shutdown are those that have a separation from the fire area less than 
     that required by Section III.G.2 of Appendix R to 10 CFR 50 and have 
     either (1) a common power source with the alternative shutdown 
     equipment and the power source is not electrically protected from the 
     post-fire shutdown circuit of concern by coordinated circuit breakers, 
     fuses or similar devices, (2) a connection to circuits of equipment 
     whose spurious operation will adversely affect the shutdown capability, 
     e.g., RHR/RCS Isolation Valves, or (3) a common enclosure, e.g., 
     raceway, panel, junction box, with alternative shutdown cables and are 
     not electrically protected from the post-fire shutdown circuits of 
     concern by circuit breakers, fuses or similar devices. 

     For each fire area where an alterative or dedicated shutdown method, in
     accordance with Section III.G.3 of Appendix R to 10 CFR Part 50, is 
     provided by proposed modifications, the following information is 
     required to demonstrate that associated circuits will not prevent 
     operation or cause maloperation of the alternative or dedicated 
     shutdown method: 

     A.   Provide a table that lists all equipment including instrumentation
          and support system equipment that are required by the alternative 
          or dedicated method of achieving and maintaining hot shutdown. 

     B.   For each alternative shutdown equipment listed in 1.A above, 
          provide a table that lists the essential cables (instrumentation, 
          control and power) that are located in the fire area. 

     C.   Provide a table that lists safety related and non-safety related 
          cables associated with the equipment and cables constituting the 
          alternative or dedicated method of shutdown that are located in 
          the fire area. 

     D.   Show that fire-induced failures of the cables listed in B and C 
          above will not prevent operation or cause maloperation of the 
          alternative or dedicated shutdown method. 

     E.   For each cable listed in 1.B above, provide detailed electrical 
          schematic drawings that show how each cable is isolated from the 
          fire area. 
.

                                    - 2 -

2.   The residual heat removal system is generally a low pressure system 
     that interfaces with the high pressure primary coolant system.  To 
     preclude a LOCA through this interface, we require compliance with the 
     recommendations of Branch Technical Position RSB 5-1.  Thus, this 
     interface most likely consists of two redundant and independent motor 
     operated valves.  These two motor operated valves and their associated 
     cable may be subject to a single fire hazard.  It is our concern that 
     this single fire could cause the two valves to open resulting in a 
     fire-initiated LOCA through the subject high-low pressure system 
     interface. To assure that this interface and other high-low pressure 
     interfaces are adequately protected from the effects of a single fire, 
     we require the following information: 

     A.   Identify each high-low pressure interface that uses redundant 
          electrically controlled devices (such as two series motor operated
          valves) to isolate or preclude rupture of any primary coolant 
          boundary. 

     B.   Identify the device's essential cabling (power and control) and 
          describe the cable routing (by fire area) from source to 
          termination. 

     C.   Identify each location where the identified cables are separated 
          by less than a wall having a three-hour fire rating from cables 
          for the redundant device. 

     D.   For the areas identified in item 2.C above (if any), provide the 
          bases and justification as to the acceptability of the existing 
          design or any proposed modifications. 
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