ML17228A280
| ML17228A280 | |
| Person / Time | |
|---|---|
| Site: | Saint Lucie  |
| Issue date: | 08/20/1993 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Shared Package | |
| ML17228A278 | List: |
| References | |
| REF-GTECI-070, REF-GTECI-094, REF-GTECI-NI, TASK-070, TASK-094, TASK-70, TASK-94, TASK-OR GL-90-06, GL-90-6, NUDOCS 9309080208 | |
| Download: ML17228A280 (4) | |
Text
~p,a RE00
+o
~o Cy
~
~
~+0
~o~
++*++
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, O.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION
RESPONSE
TO GENERIC LETTER 90-06 FLORIDA POWER AND LIGHT COMPANY ST.
LUGIE UNITS 1
AND 2 DOCKET NOS.
50-335 AND 50-389
- 1. 0 INTRODUCTION Generic Letter (GL) 90-06, "Power Operated Relief Valves and Block Valve reliability and Additional Low Temperature Overpressure Protection for Light Water Reactors" delineated the Nuclear Regulatory Commission (NRC) staff positions relating to Generic Issue (GI) 70, "Power Operated Relief Valve and Block Valve Reliability" and GI 94, "Additional Low-Temperature Overpressure Protection for Light Water Reactors."
On the basis of its technical studies of the GI, the staff recommended licensee actions to resolve GIs 70 and 94.
By letters dated December 29,
- 1990, December 6,
- 1991, Hay 11, 1992, and October 9, 1992, Florida Power and Light Company (FPL or the licensee) submitted its responses to GL 90-06.
The licensee submittals described the existing hardware and associated operating procedures, and proposed actions to comply with the GL 90-06.
The staff's evaluation of the licensee's responses are presented and discussed below.
2.0 EVALUATION
- 2. 1 GI-70 "Power 0 crated Relief Valve and Block Valve Reliabilit "
On the basis of NUREG-1316 "Evaluation of Power-Operated Relief Valve and Block Valve Reliability in PWR Nuclear Power Plants,"
GL 90-06 recommended actions and technical specification changes which are necessary to resolve GI-70 safety concerns.
The recommended actions involved included Power-Operated Relief Valves (PORVs) and Block Valves within the scope of an operational quality assurance program that is in compliance with the 10 CFR Part 50, Appendix B, in-service testing of the PORVs and Block Valves, and modification of the technical specifications (TS).
The quality assurance program involves three elements:
(1) operational quality assurance; (2) maintenance and refurbishment; and (3) replacement and spare parts.
The licensee has verified that the PORVs and associated Block Valves are classified as the American Society of Mechanical Engineers (ASHE)
Code Class 1'valves and are included in its quality assurance program for maintenance and procurement activities.
Thus, the licensee has complied with all of the elements of the quality assurance recommendations of the GL 90-06.
9309080208 9308201
'j PDR ADOCK 05000335, P
PD~R
The in-service testing recommendation also consists of three elements:
(1) including the PORVs and Block Valves within the scope of the ASHE Code Section XI, Subsection IWV, "Inservice Testing of Valves in Nuclear Power Plants,"
program; (2)
PORV stroke-testing only in Nodes 3 or 4, (hot standby or hot shutdown, respectively);
and (3) including the Block Valves in the Hotor Operated Valve (MOV) test program discussed in GL 89-10, "Safety-Related Hotor Operated Valve Testing and Surveillance."
The licensee has taken exception to the stroke-testing requirement in Hodes 3 or 4, on the basis that:
(1) the amount of steam in the space between the block valve and the PORV is not enough for PORV testing and, therefore, stroke testing would require opening block valves which is equivalent to a small break loss-of-coolant accident (LOCA); (2) the St.
Lucie PORVs are pilot-operated valves (as opposed to electromagnetic relief valves assumed in the GL 90-06);
(3) using reactor pressure as the motive power for testing at lower temperatures and pressures would provide reasonable assurance that the valves function properly at higher pressures; (4) the PORVs are not part of the accident management strategy for the reactor coolant system (RCS) depressurization; (5) the Emergency Operating Procedures (EOPs) are based on Combustion Engineering (CE)
Emergency Procedure Guidelines, CEN-152 Revision 3; (6) emergency RCS depressurization is accomplished using pressurizer sprays with safety grade equipment; and (7) these methods are part of the St. Lucie licensing bases.
GL 90-06 states that the required actions represent a new staff position and they are a cost-justified backfit.
- However, GL 90-06 refers to plants which use the PORVs to perform a number of safety-related functions.
In older
- plants, PORVs and the associated block valves were not safety-grade equipment.
At St. Lucie, all of the GL 90-06 safety-related functions involved in GL 90-06 are accomplished without the PORVs using safety-grade equipment.
The EOPs do not involve PORVs in accident management.
In response to staff questions, the licensee provided information on July 21, 1993 (which is an enclosure to the memorandum from J. Norris to File dated August 3, 1993) to show that St.
Lucie essentially employs the same means for depressurization as other CE plants which do not have PORVs.
Therefore, we find that the intent of GL 90-06 does not cover St. Lucie; thus, the exception from PORV testing in Hodes 3
or 4 is acceptable.
GL 90-06 recommends modification of the TS to minimize the potential for an accident by reducing reactor operation time with inoperable PORVs and block valves.
The licensee does not propose to implement the recommended TS changes because neither the PORVs no} the block valves are credited with the mitigation of any accident conditions.
The staff finds that the intent of GL 90-06 does not cover the St. Lucie plant, which uses other safety-grade equipment to accomplish the functions described in the GL and, therefore, the licensee's position to not implement the recommended changes to the TS is acceptable.
2.2 GI-94 "Additional Low Tem erature Over ressure Protection for Li ht Water Reactors" GL 90-06 showed that low temperature overpressure protection (LTOP) system unavailability is the dominant contributor to risk from low-temperature overpressure transients.
To improve availability of LTOP protection devices when the potential for an overpressure event is the highest, and especially water solid operation, the staff recommended TS changes and administrative restrictions to the LTOP system.
The licensee stated that it "will submit a
change to the LTOP Technical Specifications similar to the GL recommendations for St. Lucie Unit I, within one year of receipt of the staff acceptance of the proposed plans for implementation of the GL recommendations."
The licensee has estimated core damage frequency (CDF) due to an LTOP event to be approximately 3 E-7/reactor year which is less than the 3.24 E-6/reactor year limit accepted by the staff in the LTOP generic regulatory analysis.
In view of the favorable overpressurization record of the St. Lucie plants (never experienced an overpressurization event),
and the extremely low estimated CDF due to LTOP, the staff, finds the proposed implementation schedule for the GL technical specification to be acceptable.
The existing St. Lucie, Unit 2, TS are similar to the GL-recommended TS.
The differences between the plant-specific TS and the GL-recommended
.TS are only administrative and arise from the fact that St. Lucie, Unit 2, has more than two depressurization devices available, i.e.,
two PORVs and two shutdown cooling relief valves, and the action statement (d) in the GL relating to verification of the vent path is equivalently addressed in the surveillance requirements of the St. Lucie, Unit 2, TS.
The staff finds that the existing St. Lucie, Unit 2, TS fulfillthe intent of GL 90-06 and, therefore, are acceptable.
3.0
SUMMARY
AND CONCLUSIONS The staff has reviewed the information submitted by FPL, in response to GL 90-06 regarding the St. Lucie plant.
For the reasons stated
- above, the staff finds that the FPL response is in compliance with the intent of Generic Letter 90-06; therefore, the staff finds it acceptable.
Principal Contributor:
L. Lois Date: August 20, 1993
0 0
I t.