ML17308A207
| ML17308A207 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 03/25/1986 |
| From: | NRC |
| To: | |
| Shared Package | |
| ML17216A460 | List: |
| References | |
| NUDOCS 8603280260 | |
| Download: ML17308A207 (4) | |
Text
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UNITEDSTATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555 EVALUATION OF FIRE PROTECTION SPRINKLER SYSTEMS ST.
LUCIE PLANT, UNIT NO.
2 TIA 83-64, REGION II Introduction During an inspection conducted by Region II at the St.
Lucie Plant, Unit No.
2 in 1983, it was observed that in certain plant locations, the existing ceiling-level sprinkler systems appeared to be obstructed by cable trays, HVAC ducts and other equipment.
Region II issued a Notice of Violation and Notice of Deviation dated October 19, 1983 regarding this finding.
The licensee, in letters dated November 18 and 19, 1983, challenged the validity of this deviation.
During a subsequent plant inspection by Region II and NRR representatives, it was agreed that, as one possible approach to resolving this issue, the licensee would request a formal interpretation from the National Fire Protection Association (NFPA) Standard No.
13 Committee.
By letter dated March 14, 1984, the licensee committed to request a code interpretation and also provided design information which purports to demonstrate that the existing sprinkler system design "...meets the intent..."
of NFPA 13.
The licensee was subsequently informed by the NFPA that it would be unable to provide such an interpretation.
By memorandum dated February 28,
- 1986, Region II requested that NRR review the licensee's March 14, 1984 justification and evaluate the adequacy of the sprinkler design system.
Discussion In their March 14, 1984 letter, the licensee stated that the obstructions will not degrade sprinkler system effectiveness and are mitigated by the design of the sprinkler systems.
Where, in general, a sprinkler dischar ge density of O. 1 to 0.2 gallons per minute/square foot is needed for effective fire control, the licensee has demonstrated by hydraulic calculation that a flow of 0.3 gpm/sq. ft. can be achieved by the sprinkler system in the areas of concern.
The licensee also stated that the existing sprinkler system design was found acceptable by a consulting group of fire protection specialists.
Evaluation In Section
- 7. E. 3.(c) of the St.
Lucie 2 FSAR, Appendix 9. 5. a., the licensee stated that the provisions of NFPA Standard No.
13 were followed in the design of the automatic sprinkler sytems.
Section 4-4 of this standard establishes that sprinkler heads should be installed under features of construction (such as decks and ducts) that would represent a significant obstruction to the discharge of water from the sprinkler system.
NFPA 13 does not specifically mention cable trays, light fixtures and other features typical of a nuclear power plant.
However, this standard establishes that where atypical conditions exist, the "authority having jurisdiction" is the final arbiter concerning the adequacy of any design.
The NRC represents the authority having jurisdiction when questions arise pertaining to the adequacy of fire protection features of a nuclear power plant.
Based on two inspections conducted at the plant by Region II, it was concluded that in certain areas of the plant "...moderate to severe obstructions hinder proper water discharge..."
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i The staff review confirms that flows in excess of the generally accepted minimum could be achieved in the areas of concern.
However, this added water density that may be available from each sprinkler head would not provide sufficient mitigation for the obstructions because there is no reasonable assurance that water would be discharged onto the fire, due to aggregate of ductwork, cable trays, light fixtures and other features that ex>st below the individual sprinkler heads.
In considering the relevant factors associated with this issue, the staff concludes that the critical determinant is the vulnerability of redundant shutdown systems that may be present in any fire area.
Where redundant shutdown systems are located in a single fire area, the successful functioning of the sprinkler system is necessary to assure that one division remains free of damage so that safe shutdown can be achieved and maintained in accordance with Appendix R criteria'as contained in the Standard Review Plan.
Therefore, in such areas, the sprinkler system obstructions should be mitigated by the addition of new sprinkler heads, the location of existing sprinklers below the obstruction, and/or removal of the obstruction.
In those locations where only one shutdown division exists, degraded performance of the sprinkler system will not prevent the plant from shutting down because a redundant train is located in a separate fire area enclosed by fire-rated construction.
Therefore, modifications to compensate for sprinkler obstructions will not significantly enhance fire safety. 'his position is consistent with the resolution of an identical issue at the Matts Bar Nuclear Plant.
Principal Contributor:
D. Kubicki Date:
Harch 25, 1986
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