ML20206C039
ML20206C039 | |
Person / Time | |
---|---|
Site: | Catawba ![]() |
Issue date: | 04/15/1999 |
From: | DUKE POWER CO. |
To: | |
Shared Package | |
ML20206C037 | List: |
References | |
PROC-990415-01, PROC-990415-1, NUDOCS 9904300165 | |
Download: ML20206C039 (3) | |
Text
.,
'M REACTOR COOLANT SYSTEM 1.31-2 SAFETY VALVES - SHUTDOWN J
COMMITMENT:
A minimum of one pressurizer Code safety valve shall be OPERABLE with a lift setting of 2485 psig + 3%, -2% OR the Reactor Coolant System shall be 2 5 square inches per ITS l
depressurized with a Reactor Coolant System vent of 4
LCO 3.4.12b.
A_PfMCASIMIY_;
MODE 4 when any Reactor Coolant System cold leg temperature is s 285 F.
MODE 5.
REMEDIAL ACTION:
With this COMMITMENT not me.t, immediately suspend all operations involving positive reactivity changes and either 1) place an OPERABLE residual heat removal loop into operation in the shutdown cooling mode, OR 2) verify the Low Temperature Overpressure Protection (LTOP) System OPERABLE per ITS 3.4.12.
c.
I TESTING REQUIREMENTS:
Verify any pressurizer code safety valve being used to meet this COMMITMENT is OPERABLE in accordance with the Inservice Testing Program.
REFERENCES:
1)
Letter from NRC to Gary R. Peterson, Duke, Issuance of Improved Technical Specifications Amendments for Catawba, September 30,1998.
2)
Catawba Safety Evaluation Report, including Supplements 1 through 6.
3)
CNC-1223.03-00-0005," Pressurizer Power Operated Relief Valve Setpoint Verification for Low Temperature Overpressure Protection."
BASES:
The pressurizer Code safety valves do not perform an adequate Low Temperature Overpressure Protection (LTOP) function in the stated modes of APPLICABILITY.
ITS 3.4.12 assures that the PORVs are OPERABLE to perform this LTOP function.
A pressurizer Code safety valve that is removed from its flange or any Reactor l
The lift setting pressure shall correspond to ambient conditions of the valve at nominal operating temperature and pressure.
Chapter 16.5-2 Page 1 of 3 04/15/99 4
9904300165 990419 ~~
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' BAS'ES (con't)
Coolant System vent totaling z 4.5 square inches meets the LTOP option of creating l a Reactor Coolant System vent of 2 5 square inches per ITS LCO 3.4.12b. During 4
cold shutdown and draining of the Reactor Coolant System, there is no adverse effect of opening more than one 4.5 square inch path. Therefore, a minimum of one pressurizer Code safety valve that is removed, or any Reactor Coolant System vent totaling a 4.5 square inches provides an LTOP path that is equivalent and superior to a minimum of one pressurizer Code safety valve that is OPERABLE in response to a mass input or heat input transient. The REMEDIAL ACTION to immediately suspend all operations involving positive reactivity changes is conservative to preclude any reactivity management event. The REMEDIAL ACTION to place an OPERABLE residual heat removal loop into operation in the shutdown cooling mode makes the Residual Heat Removal System suction relief valve available to provide its equivalent LTOP function. Altemately, it is not necessary to place a Residual Heat Removal System back into service as long as the LTOP System is verified OPERABLE per ITS 3.4.12.
The following is excerpted from Section 5.2.2 of Reference 2:
"SRP Section 5.2.2 requires that the overpressure protection system during low temperature operation of the plant shall be designed in accordance with the requirements of BTP RSB 5-2.
O V
The low-temperature overpressure protection is primarily provided by the pressurizer relief valves PORVs. As RCS temperature approaches a specified set point during plant cooldown, an annunciator alerts the operator that plant conditions require low-temperature overpressure protection. A key-lock switch for each train of the PORVs is placed to the low pressure position by the operator'to enable the PORV low pressure set point. Should a pressure excursion occur with the low pressure mode enabled when the plant J
temperature is below the temperature set point, system pressure would be limited to acceptable values, and excess mass would be relieved to the pressurizer relief tank. An annunciator in the control room would alert the operator to system overpressure.
The PORVs and associated block valves are required to have safety-grade emergency power supplies in accordance with item II.G.1 of NUREG-0737.
Section 8.4.12 of this SER provides a discussion of Catawba's compliance with this requirement.
As a backup to the low-temperature overpressure protection system, the residual heat removal system (RHRS) has two suction relief valves with a capacity of 900 gpm each at a set point pressure of 450 psig. The relieving capacity of each valve is adequate to relieve the combined flow of the two centrifugal charging pumps. The RHRS suction relief valves provide j
Chapter 16.5-2 Page 2 of 3 04/15/99 l
,y y BA$ES foon't) overpressure protection after the RHRS is put into operation and the RHRS suction isolation valves are open at an RCS pressure of less than 425 psig.
Also, operating procedures require that the operator lock out the cold-leg accumulator isolation valves in the closed position during shutdown."
Based on the above SER discussion, as well as current LTOP design basis calculations, each inlet line to the Residual Heat Removal System is equipped with a pressure relief valve designed to relieve, at a pressure no greater than the Code maximum allowable pressure, the greater combined flow of: a) two centrifugal charging pumps, or b) one charging pump and one safety injection pump. When the Residual Heat Removal System is in operation, the suction relief valves provide additionallow temperature overpressure protection. These suction relief valves exceed the capacity of the pressurizer PORV. Therefore, it has been demonstrated that given any three of four LTOP relief devices (NC32B, NC34A, ND3, ND38), and assuming single failure affecting any one of these devices, the remaining two will provide overpressure protection for either two centrifugal charging pumps, or one l
charging pump and one safety injection pump.
l O
Chapter 16.5-2 Page 3 of 3 04/15/99
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