ML20236D294
| ML20236D294 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 10/28/1987 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML20236D293 | List: |
| References | |
| NUDOCS 8710280126 | |
| Download: ML20236D294 (4) | |
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-.-..---A ENCLOSURE SAFETY'EVALVATION REPORT.~
-PROPOSED CHANGE 5 TO FIRE SUPPRESSION SYSTEMS V0GTLE UNIT.2
1.0 INTRODUCTION
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' By letter dated July 7,1987, the' applicant proposed' three changes..to the TVogtle Unit 2 fireLsuppression system.
The three proposed changes are:
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-(1)' revise ~ sprinkler hanger design based on the results of seismic testing for qualification. purposes rather than analytical means as done previously,
.(2). revise, the criteria' fo'rLolacement of in-tray sprinkler
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, protection to include them only in the cable spreading rooms, and (3) revise'the fire suppression flushing procedures, which provides
'an alternate to flushing of the sprinkler system piping, The applicant's position'is-that the proposed changes will not compromise the ability of the fire protection systems to perfonn their intended function during a-fire.
2.0 EVALUATION
'2.1 Revised Sprinkler Hanger Design Fire protection guidance furnished by. the staff does not require a licensee to
. postulate a fire and. earthquake simultaneously. However, in man suppression systems are classified as seismic two-over-one (2/1)y areas, fire systems.
This means that their integrity during and after a seismic event should be ensured so as not to jeopardize the integrity of adjacent equipment and structure, which may be. essential for safe shutdown of the plant. Automatic sprinkler 4 ystems installed in creas containing safety-related equipment or components, therefore, must be-designed and installed so that they will not
. fail during an earthquake and damage the safety-related equipment or components. The. automatic sprinkler systems of Unit I were designed and installed to. meet strict support stiffness and piping deflection criteria.
However, the " Standard for the Installation of Sprinkler Systems," NFPA-13, published by the~ National Fire Protection Association, permits use of more
~ flexible supports, including sway bracing, for sprinkler systems which may be subject to seismically-induced vibratory loadin A recent experimental effort perfonned by ANC0 Engineers, Inc. (ANCO)gs.for Bechtel Western Power Corporation (BWPC) successfully demonstrated that the rod-suspended sprinkler systems at the South Texas Project were capable of withstanding simulated seismic events in excess of predicted design criteria without collapse.
In order to verify the adequacy of the more flexible sprinkler hanger design proposed for Unit 2, the applicant contracted with ANC0 to test three segments of actual Unit I sprinkler systems.
The three test assemblies chosen were 8710280126 071026
.PDR ADOCK 05000425 p.
. representative of actual installed systems, and each consisted of approximately 40 feet of feed main with several branch lines and a simulated deluge valve connection.
Supports and sway braces for each test assembly were designed and installed using NFPA-13 recommendations. All supports incorporated standard off-the-shelf hardware, including swivel connections to act as pins at the top of the supports.
The assemblies were tested on the ANC0 R-4 Shake Table.
Each was subjected to dynamic loadings equivalent to five operating basis earthquakes (OBE), after several scaling earthquakes to include the effects of fatigue, and one safe shutdown earthquake (SSEl.
Each test assembly was-hydrostatically tested before and after the first OBE test to demonstrate functionality.
- Finally, each of the test assemblies was subjected to dynamic loadings equivalent to 1.2 x SSE and 1.4 x SSE to demonstrate survivability and establish a design margin. Test results indicated that the fragility limits of the test assemblies exceeded the capacity of the shake table and far exceeded the seismic design criteria of the site. The staff finds the above test procedure and test results to be acceptable.
The staff also agrees with the applicant's proposed FSAR changes related to the above. The proposed changes are contained in Inserts B, C, E, and F to Attach-ment 4 of the applicant's letter dated July 7, 1987.
Findings Based on the above evaluation, the staff finds that these tests demonstrated that automatic sprinkler fire suppression systems designed and installed in accordance.with NFPA-13, using rod type hangers and sway bracing, will be able to withstand the design seismic loadings and, therefore, are acceptable.
2.2 Revised Placement of In-Tray Sprinkler Protection Only in Cable Spreading FSAR Section 9.5.1.2.1.4 addresses fire suppression design criteria for cable trays containing safe shutdown cables and specifies in-tray directional spray nozzles above each tray.
On the basis of additional staff guidance, and as a result of more refined methods of evaluating cable tray fire hazards and protection required (including test results from industry and NRC-sponsored research programs), the applicant realized that the protection provided for Unit I safe shutdown cables was un-necessarily conservative. Therefore, the applicant has proposed alternative design criteria for protection of cable trays throughout Unit 2.
The applicant proposes that design of automatic sprinkler protection for cable trays in Unit 2
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be based upon the following criteria:
j (1) The area coverage boundaries for suppression systems will be j
in accordance with that identified on fire area drawings (FSAR Figures 9A-1 through 9A-46).
(2)
In the cable spreading rooms, in-tray directional spray nozzles will be provided. Area protection at the ceiling will provide coverage for the first three safety-related trays in a vertical stack, and in-tray protection will be provided for the remaining safety-related trays starting with the fourth tray in the stack and ending with the last tray in the stack (typical Unit i design).
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(3). ' ForL electrical cable chases-and tunnels, sprinklers will be provided at the ceiling designed to. discharge 0.3 gom per square foot over the.
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most remote 3000' square feet or. area within the cutoff. fire boundaries, whichever is less.
.. (4 ) Foraother areas containing three safety-related cable trays or. less in a: vertical stack, sprinklers will be provided at the ceiling
~ design to discharge 0.21 gpm pers square ; foot ~over the most remote i
1500 square : feet or. area within the cutoff fire. boundary, whichever
_ is:less (typical. Unit'l design).
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-(5) For other areas containing.more than three s~afety-related cable trays'in.a vertical stack.. sprinklers will be provided at the
. ceiling designed.to discharge 0.3 gpm per square. foot over the -
most remote 3000 square. feet or area within the cutoff fire boundaries, whichever is less.
Except'for cable spreading rooms, cable tray installations generally are con--
sidered to'have low to moderate fuel loads (80,000 Btu /sq.ft. of floor area.
being equivalent to a 1-hour fire). Based upon the low to moderate fuel loading in the cable. trays throughout the plant, and an increased water densit/
l discharge design criteHa for' ceiling sprinklers in Unit 2 compared'to the i
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lower water density discharge design criteria used for ceiling sprinklers in
' Unit.1, the staff agrees with 'the applicant that in-tray sprinkler protection does not have to be provided in areas other than the cable spreading room.
q The staff also agrees with the FSAR changes proposed by.the applicant as they relate to these changes'in automatic sprinkler protection. The proposed FSAR changes accepted by the staff are shown as Insert A to Attachment 4 of the 1
, applicant's-letter of July 7, 1987.
Findings Based on the above evaluation, the staff finds that the proposed changes in
~ design criteria.for sprinkler protection for cable trays containing safe shutdown cables meets the guidelines of CMEB BTP-9.5-1 (NUREG-0800), Section C.S.e is consistent with protection designs that have been accepted at other nuclear power plants, will provide adequate fire suppression protection for safe shutdown cables and is, therefore, acceptable.
2.3 ' Fire Suppression System Flushing Section 1-11.1.1 of NFPA-13 " Standard for the Installation of Sprinkler
. Systems," reads as follows:
"1-11.1.1-Underground mains and lead-in connections to system i
risers shall be flushed before connestion is made to sprinkler piping in order to remove foreign materials which may have entered the underground piping during the course of the installation.
For all systems, the flushing operation shall be continued until water is clear."
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The purpose of this flushing is to assure that foreign materials that may have entered the underground piping during construction do not enter the j
sprinkler system piping.
The applicant performed the flushing operations of the underground mains and lead-in connections at Unit 1 while they were connected to the sprinkler systems.
This deviation from the provisions of NFPA-13 resulted in an open item being added in SSER 2 that was later closed in SSER 4.
For Unit 2, the applicant is proposing a different method of assuring that the underground mains and lead-in piping to fire suppression systems are properly flushed, and.that foreign material does not enter the. suppression system piping.
The proposal for Unit.2 provides for the use of test blanks, as follows:
(1) A test blank will be installed between the system isolation valve and preaction sprinkler valve prior to system installation.
(2) The test blanks will be vi.sible when installed and controlled through the use of drawings, procedures, and inspections.-
(3) Test blanks will be removed after header piping is verified clean.
i By telephone conference call on September 2, 1987, the staff was assured by applicant representatives that the test blanks will be so installed as to pennit flushing of all portions of the underground main and system lead-in piping utilizing flushing flow rates in'accordance with Section 1-11.1.2 of NFPA-13 Based upon that information, the staff agrees with the applicant's proposed approach to use test blanks to prevent introduction of fcreign materials into sprinkler system piping during flushing operations of the underground mains and lead-in piping to the sprinkler systems.
The staff also agrees with the FSAR changes proposed by the applicant as contained in Attachment 4 of its letter of July 7,1987, and applicable'to j
flushing of underground mains and system lead-in piping.
The applicable proposed changes are contained in Insert D to FSAR Table 9,5.1-9 (sheet 2 of 16).
Findings I
Based on the above evaluation, the staff finds that the proposed changes in proceoures for flushing under i
will satisfy CMEB BTP 9.5-1 (ground mains and lead-in piping to system usersNUREG-NFPA-24. " Standard for the installation of Private Fire Service Mains and Their Appurtenances," Section 8-8 and are, therefore, acceptable.
3.0 CONCLUSION
On the basis of the above evaluation, the staff concludes that the fire suppres-
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sion system changes proposed by the applicant for Vogtle Unit 2 in its letter dated July 7, 1987, are acceptable to satisfy specific provisions of Standard Review Plan 9.5.1 (NUREG-0800).