Fire Protection Rule (45 FR 76602, November 19, 1980) (Generic Letter 81-12)
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".
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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
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.
Darrell G. Eisenhut, Director
Division of Licensing
Office of Nuclear Reactor Regulation
1. Staff Position
2. Request for Additional
SAFE SHUTDOWN CAPABILITY
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
* 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
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.
Safe shutdown capability should be demonstrated (Case A) or alternative
shutdown capability provided (Case B) in accordance with the guidelines
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.
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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
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
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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
(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.
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.
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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.
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
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.
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Support capability e.g., onsite power source (AC & DC) and their
associated distribution systems to provide for the shutdown
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
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
(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.
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(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.
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(1) Demonstrate that repair procedures for cold shutdown systems are
developed and material for repairs is maintained on site.
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
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
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
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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
B. Identify the device's essential cabling (power and control) and
describe the cable routing (by fire area) from source to
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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