ML20198N603
| ML20198N603 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 12/22/1997 |
| From: | NRC (Affiliation Not Assigned) |
| To: | |
| Shared Package | |
| ML20198N601 | List: |
| References | |
| NUDOCS 9801210138 | |
| Download: ML20198N603 (4) | |
Text
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k UNITED STATES p,
1 NUCLEAR REGULATORY COMMISSION wasumeron, o.c. mess.emi
\\*sese RAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION i
1 CONCERNING TECHNICAL SPECIFICATION CHANGES REGARDING 1
i LOW TEMPERATURE QVERPRESSURE PROTECIlON i
FLORIDA POWER CORPORATION CRYSTAL RIVER UNIT 3
, DOCKET NO. 50 302 j
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1.0 INTRODUCTION
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Currently, Crystal River Unit 3 (CR3) is implementing Low Temperature Overpressure Protection (LTOP) features by administrative controls. By letter dated February 4,1997, the Nuclear Regulatory Commission (NRC) staff requested that the licensee submit a proposed 1
Technical Specification (TS) to replace the administrative controls currently used to implement LTOP features. By letter dated July 18,1997, the licensee proposed a new TS 3.4.11,
- Low Temperature Overpressure Protection (LTOP) System," with its associated bases. By letter dated September 12,1997, FPC supplemented Ns submittal by removing actions F.1.1 and l
F.1.2 of proposed TS 3.4.11. These actions were removed to make the TS consistent with the Babcock and Wilcox (B&W) Standard TS, NUREG-1430, Revision 1. By letter dated l
October 25,1997, FPC further modified its original request to include instrument uncertainty in the TS limits for the power operated relief valve, LTOP enable temperature, and the pressurtzer level. Neither of these changes affect the NRC's original proposed no significant hazards consideratlon or expand the scope of the original Feders/ Register notice. The proposed TS 3.4.11 will ensure that LTOP is provided for CR3 up to 15 effective full power years (EFPY) of reactor operation.
2.0 BACKGROUND
i The LTOP system mitigates overpressure transients at low temperatures so that the integrity of the reactor coolant pressure boundary is not compromised by violating the pressure and temperature (P/T) hmits of the American Society of Mechanical Engineers (ASME) Code Section XI, Division 1, Code Case N-514 (NRC has approved the Code Case N-514 to be apphed at CR3). CR3's LTOP system uses the combination of a pressurizer power operated relief valve (PORV) and the steam volume in the pressurizer (by limiting the pressurizer water level) or a reactor coolart system (RCS) vent with the reactor depressurized to accomplish this function. The system is manually enabled by operators and uses a single setpont as the lift i
pressure for the PORV. The design basis of CR3's LTOP system considers both mass-addition i
and heat addition transients. The mass-addition analyses account for the irQection from one makeup pump to RCS with the control valve failed to the fully open position. The heat-addition analyses accounts for heat input from the secondary sides of the once through steam E EkO S M 302 D
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i 2-I generators (OTSGs) into the RCS upon starting a single roedor coolant pump (RCP). The l
heat addition transient analysis assumes the OTSGs are fills,d to 95 percent with 420'F l
feedwater with the inkiel RCS temperature of 150'F. The results of this heat-addition trarmient j
show that this event is self limiting below the P/T limits. Also, it has been demonstrated that the mass-addition transient is the limiting case with resped to LTOP design. In general, a plant j
i with the B&W design is normally operated with a gas (nitrogen or steam) blanket in the j
pressurtzer and the relative small sire, and honoe heat capacity, of the OTSGs, is not l
l susceptible to heat addition transients (see NRC staff assessment dated July 3,1979).
The CR3 proposed LTOP enable temperature and actuation setpoint were established using a l
plant specific methodology in combination with ASME Code Case N 514, " Low Temperature jl Overpressure Protection." NRC letter dated July 3,1997, which granted CR3 en exemption from the requirements of 10 CFR 50.60, " Acceptance Criteria for Fracture Prevention Measures
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for Light Water Nuclear Power Reactors for Normal Operation," has approved the use of the methodology in ASME Code Case N-514 et CR3.
f 3.0 EVALUATION l
The proposed Limiting Conditions for Operation (LCO) in TS 3.4.11 requires that an LTOP l
l System shall be operable with a maximum of one makeup pump capable of injecting into the RCS, the high pressure injection (HPI) deactivated, the core flood tanks (CFTs) isolated, and j
the following: (a) Pressurtzer level s 135 inches and an operable PORV with a lift setpoint of i
s 457 poig; or (b) The RCS depressurtred and RCS vent of a 0.75 square inches. This TS is 1
applicable when RCS temperature is s 259'F. Consistent with this LCO, the licensen proposed i
a modification to TS 3.5.3, "ECCS [ emergency core cooling system} Shutdown", which Indicates that HPl may be deactivated in accordance with LCO 3.4.11. We find the modified TS 3.5.3 occeptable. The staff evaluation of the LTOP setpcints is presented below:
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3.1 LTOP Enable Tamparature i
The LTOP enable temperature is the temperature below which the LTOP system is required to l
t be operable. The licensee proposed to establish an LTOP enable temperature methodology to:
(1) account for instrument uncertainties associated with the instrumentation used to enable the LTOP system and, (2) implement the ASME Code Case methodology of using an enable RCS i
liquid temperature corresponding to the reactor vessel %-t metal temperature of RT. + 50'F or 200'F, whichever is greater. Therefore, the licensee proposed to calculate the enable temperature as RT
+ 50'F + F
__ in this calculation, RT refers to tim highest adjusted reference temperature for wold or base metal in the beltline region at a distance one-fourth of the vessel section thickness from the vessel inside surface, as determined by Regulatory Guide 1.99, Revision 2; and FE _ _ refers to instrument error. The licensee has calculated the i
temperature difference between the reactor coolant and the metal at %-t distance after heatup ins been suspended for more than 90 minutes. The value of this dalta-T is insignificant (less than 1*F). The TS Bases B3.4.11 reflects that the RCS hostup holding period of at least 90 minutes after the enable temperature has been exceeded and prior to exiting the LTOP LCO allows the M4 location to stabilire, in addition, the licensee has stated that a step will be included in the plant heatup procedure to require an RCS heatup holding period of at least 90 F
minutes after the enable temperature has been exceeded and prior to exiting the LTOP LCO.
Therefore, the effect of this temperature difference is minimal in the LTOP design.
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i 3-l Based on the above described methodology, the licensee proposed an LTOP enable temperature of 25g'F in its TS 3.4.11. The staff finds that this proposed LTOP enable temperature is conservative with respect to the minimum LTOP enable temperature allowed by
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ASME Code Case N 514 ard therefore, is acceptable.
l 3.2 LTOPActuationBatpolni
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LTOP systems are usually designed to mitigate overpressure transients at low temperatures to prevent violating 10 CFR Part 50, Appendix G P/T limits. ASME Code Case N-514 allows the i
LTOP system be designed to limit the peak prsssure at the controlling location to 110 percent of i
10 CFR Part 50 Appendix G P/T limits. Additionally, since overpressure events most likely occur during isothermal conditions in the RCS, the NRC has accepted the use of the steady-l state Appendix G limits for the design of LTOP systems. The LTOP actuation setpoint is the pressure at which the PORVs will lift, when the LTOP system is enabled, to limit the peak RCS pressure during a pressurization trarisient.
CR3's LTOP methodology for determining the PORV actuation setpoint is consistent with the ASME Code Case N 514 which permits the actuation setpoint to be determined in a manner j
which protects 110 percent of the Appendix G P/T limits instead of the actuallimits. Since the staff has already approved the use of Code Case N 514 at CR3, it is acceptable for CR3 to use t
this methodology for calculating the PORV actuation setpoint.
The licensee proposed a PORV actuation setpoint of s 457 poig which was calculated in i
accordance with the proposed methodology. The licensee's evaluation and analyses related to i
the LTOP system were submitted with letters dated July 18,1997, September 5,1997, and October 25,1997. The proposed TS value of the PORV actuation setpoint of less or equal to 457 psig has been adjusted with location correction and instrument uncertainties.
The licensee has performed an analysis for the limitmg mass addition transients. The analysis assumed an inadvertent water injection from one makeup pump through a failed control valve in its fully open position with two RCPs operating. This analysis showed that at 10 minutes, the peak pressure would remain well below the P/T limit of 548 poig at 85'F. Additionally licensee i
evaluations demonstrated that should operators fail to take manual ections to mitigste the pressurization transient, a singit 'ORV with the proposed setpoint of s 457 psig can mitigate the event and protect the P/T lin, of 548 psig at 85'F. System pressure overshoot, that is, an incrosse of RCS pressure after it reaches the PORV setpoint value, does not occur at CR3 due to the rapid action of the PORV and relatively slow rates of pressure increase due to the steam space maintained in the pressurizer.
The licensee proposed PORV actuation setpoint of s 457 psig is selected to assure the l
7 maximum RCS pressure of 464 psig with instrumentation uncertainties considered. Based on the above discussion, we find the proposed PORV setpoint acceptable.
1 3.3 Pressurizar Water Level 4
s The licensee proposed a maximum pressurizer water level of 136 inches in TS 3,4.11. This TS
- value is derived from an analytical value of 180 inches which could provide 10 minutes for operator action to terminate the event during the limiting mass-addition transient with the PORV l
Inoperable. There are diversified alarms wh6ch could provide operators with early indications of L a mass-addition transient.- Operating procedures are available at CR3 for timely termination of L
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the event within 10 minutes. The results of the licensee's er,elysis demonstrated that the transient pook RCS pressures during this event are below the LTOP allowable pressure limits within the temperature range of LTOP. The proposed TS value of the maximum pressurtzer i
water level of 135 inches has been a@usted for instrument uncertainties. We find this maximum pressuriser poter level acceptable.
3.4 RCS Vent Siza With the RCS depressurized, the results of the licensee's analysis shows that a vent size of 0.75 square inches is capable of mitigating the transient resulting from full opening of the i
makeup control valve while the makeup pump is providing RCS makeup. The capability of a j
vont th's size is prester than the flow resulting from this limiting mass addition transient. We find thk W 9.e acceptable.
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4.0 STATE CONSULTATION
i Based upon written noiNm of the proposed amendment, the Florida State official had no f
comments.
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5.0 ENVIRONMENTAL CONSIDERATION
S The amendment changes requirements with respect to installation or use of a facility l
component located within the restricted area as defined in 10 CFR Part 20 or are administrative. The NRC staff has determined that the amendments involve no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration and there has been no public comment on such finding (62 FR 43369). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(g) and (10). Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issua,ce of the amendment.
6.0 CONCLUSION
The NRC staff has reviewed the licensee's proposed TS 3.4.11 for the LTOP system's enable i
temperature and actuation setpoint. The NRC staff finds these Fic-;-:::d TS values consistent with BTP RSB 5-2, Generic Letter 88-11,'NRC Position on Radiation Embrittlement of Reactor Vessel Materials and its impact on Plant Operations," and ASME Code Case N 514 which was approved for use at CR3 in a July 3,1997 letter. The NRC staff has also reviewed the licensee's analyses related to the proposed a noble temperature of 25g'F and actuation setpoint of s 457 poig. The NRC staff finds that the licensee's analyses were performed in a manner consistent with the approved methodology and that the results of the analyses conservatively demonstrated that the reactor P/T limits will be met with these setpoints and. therefore, finds the proposed TS 3.4.11 with its associated beses regarding LTOP acceptable.
1 Principal Contributor: C.Y. Liang Date: Decad=r 22, 1997
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