ML18347A188

Proposed Technical Specifications Changes Relating to Overpressure Protection System

ML18347A188
Person / Time
Site:	Palisades
Issue date:	01/03/1978
From:	Hoffman D Consumers Power Co
To:	Schwencer A Office of Nuclear Reactor Regulation
References
Download: ML18347A188 (18)

Text

consumers Power company*

General Offices: 212 West Michigan Avenue, Jackson, Michigan .49201

• Area Code 517 788-0550 January 3, 1978 Director of Nuclear Reactor Regulation Att: Mr Albert Schwencer, Chief Operating Reactors Branch No 1 US Nuclear Regulatory Commission Washington, DC 20555 DOCKET.50-255 - LICENSE DPR PALISADES PLANT - OVERPRESSURE PROTECTION SYSTEM Attached are proposed.Technical Specifications changes relating to the Palisades Plant overpressure protection system. The purpose of these proposed changes are to meet requirements established by the NRC staff in their l_etter of July 18, 1977 which documented the review of plant specific reports concerning low-temperature reactor vessel overpressure p~otection systems.

The Palisades Plant specific analysis was submitted on June 24, 1977 and supple-mented on November 28, 1977. Attachments 1 and 2 of this letter provide an update of the Palisades Plant "overpressure protection subsystem" and responses to the July 18, 1977 staff "positions."

~~(/?~mcuJ David P Hoffman Assistant Nuclear Licensing Administrator CC:. JGKeppler, USNRC

CONSUMERS POWER *COMPANY Docket 50-255 Request for Change to the Technical Specifications License DPR-20 For the reasons hereinafter set forth, it is requested that the Technical Speci-fications contained in Provisional Operating License DPR-20, Docket 50-255, issued to Consumers Power Company on October 16, 1972 for the Palisades Plant be changed as described in Section I below:

I. Changes A. Add the following paragraph:

"3.1.1.i. During the cooldown of the primary coolant system, the

.cold leg temperature shall not be decreased below 225°F until the overpressure protection system is enabled for operation at the low set point of 400 psia. The over-pressure protection system shall remain in the armed condition whenever the PCS co~d leg temperature is below 225°F and the primary coolant system is not otherwise protected from overpressurization."

B. Add the following paragraph:

"3.1.1.h. During cooldown, at least one PCP must be in operation until there are equilibrium conditions (That 2_ Tcold + 2°F) in the PCS and the PCS is 180°F or less."

C. To the end of BASIS section of 3.1.1, add:

"The Palisades Plant overpressurization analysis(5) had identified design bases transients that must be protected against to assure that 10 CFR 50, Appendix G limits are not exceeded. Current control is accomplished by utilizing an overpressure protection system during particular PCS conditions.

(5),Palisades Plant Overpressurization Analysis,' Energy Incorporated, June, 1977."

D. Add the following paragraph:

"3. 3. 3 Whenever the pressurizer pressure is below 1, 400 psia., and the PCS is not otherwise protected from overpressurization, the control system fuses in their fuse holders for the HPSI pumps (P66A, P66B and P66C) are to be removed from- the circuit."

E. Add to. Table 4.1. 3:

"TABLE 4 .1. 3 Surveillance Channel Description Function Frequency Surveillance Method

15. PCS Overpres- A. Test R A. Introduce simulate signal sure Protec- levels sufficient for system tion System operations. Observe sole-noid actuation ..

B. Calibrate R B.

(1) Temper- (1) Apply known resistances ature for temperature devices.

(2) Pressure (2) Apply known pressures."

II. Discussion The above Technical Specifications changes are being proposed to complete requirements identified by the staff in their review of the plant specific reports concerning low-temperature reactor vessel overpressure protection systems.

III. Conclusion Based on the foregoing, both the Palisades Plant Review Committee and the Safety and Audit Review Board have reviewed these proposed Technical Specifi-cations changes and recommend their approval.

CONSUMERS POWER COMPANY C R Bilby, Production & Transmission Sworn and subscribed to before me this 3rd day of January 1978. /.': ,,-'.' .,, .

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y Public Jackson County, ichigari My commission expires July 9, 1979.

ATTACHMENT 1 PALISADES PLANT PRIMARY COOLANT SYSTEM OVER~RESSURIZATION SUBSYSTEM DESCRIPTION PREPARED BY ENERGY INCORPORATED NOVEMBER 1977 FOR CONSUMERS POWER COMPANY

PALISADES PLANT PRIMARY COOLANT SYSTEM OVERPRESSURIZATION PROTECTION SUBSYSTEM

• Purpose The Primary Coolant System Overpressurization Subsystem is designed to provide automatic pressure relief of the primary coolant system whenever the conditions of low temperature (250°F or lower) and high pressure (400 psia or higher) exist concurrently.

General Two redundant and separate overpressurization protection channels are provided. A channel includes a power operated pressure relief valve (PORV), a temperature loop, a pressure loop, a control switch and indicator lights. The channels are identified as channel 11 A11 and channel 11 8 11

• Figure 1. is a logic diagram for channel 11 A11

• Pressure relief for the primary coolant system is ac.complished by the automatic opening of power operated relief valves (PORV) PRV-10428 and/or PRV-10438. The automatic opening will occur when the primary system temperature is less than 250°F and the pressure is equal to (or greater than) 400 psia.

Two redundant and separate pressure and temperature control loops will be utilized.

Each control loop will be powered from a separate power source. Channel

.separation will be provided either by distance or physical barriers separating wire and equip.ment.

Three annunciators are provided and are labeled:

KEY SIHTCH HS-Ol05A I

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ANNUNCIATOR i--en- PORV OPEN T::. 250F l PSX-0105A-l (PR~r6~

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PTR-Oll 5A LOOP - AND I - ACTUATED

- . ACTUATED P.?_ 400 PSIA RED PT-Ol05A PSX-0105/\-2 IflDICATOR LOOP LIGHT ACTUATED FIGURE -1

(1) 11 NO PCS PROTECTIOW (2) "PCS PRESSURE 375 PSIA" (3) 11 PORV OPEN" The first annunciator will advise the operator to arm the system (if it has not already been done) when the primary coolant system (PCS) decreases to a temperature of 300°F as the syst~m is cooled down from an operating -1 I

I condition. Figure 2 is a logic diagram for the 11 No PCS Protection" annunciator.

The second annunciator advises the operator of an approaching high pressure condition whenever the PCS is in a water solid condition.

The third annunciator advises the operator that the pressure has increased to 400 psia and the PORV's have been opened.

A key lock switch is provided for arming each channel. Indicator lights on the control' panel light to inform the operator that (1) the isolation valves are open, (2) the overpressurization system is armed and (3) the overpressurization system has been activited.

Figure 3 shows the arrangement of controls and indicator lights.

Detailed Description Figures 4a and 4b show the schematic diagrams for actuation of pressure relief channel "A". Pressure relief channel 11 8 11 will be identical. The operation of channel 11 A11 is described in detail below (refer to Figures 4a and 4b).

To provide PCS pressure relief, both the isolation valve M0-1042A and PORV PRV-10428 must be open. M0-1042A is opened by using the existing control switches located on control panel section C-02. When M0-1042A T< 300F PTTf--0 l l 5f\

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is open, contact POS...,L closes actuating relay POSX-0105A-l. One contact of POSX-0105A-l actuates a position indication light on panel C-02. The other contact of POSX-Ol05A-l is in the channel 11 A11 11 Armed 11 circuit.

The Over Pressure Protection System channel 11 A11 is in an 11 Armed 11 condition if key lock switch HS-Ol05A is closed and the POSX-Ol05A-l armed contact is closed (the POSX-0105A-l armed contact will close when M0-1042A is open). When channe 1 11 N' is 11 A.rmed 11 , a white 1 i ght on pane 1 C-12 wi 11 be illuminated and automatic opening of PRV-10428 will result upon low-low primary coolant temperature (250°:F) arid high-high pressure (400 psia).

During system shutdown the pressure and temperature will be decreased.

When the temperature in loop lA decreases to 250°F (as sensed by TS-0115),

the LOW PCS TEMP-A contact opens and provides an annunciation unless both pressure relief channels A and 8 are armed. If both channels A and 8 are armed, contacts POSX-OlOSA-2 and POSX-01058-2 will be closed and the annunciator is not received.

When the PCS temperature is at 250°F or below the LOW PCS TEMP-A contact (TS-0115) is closed, and if the PCS pressure rises to 375 psia (as sensed by PT-OlOSA), a high pressure contact (PS-Ol05A) will close actuating relay PSX-Ol05A-3 and an annunciator, alerting the operator of approaching high PCS pressure, will be received. If the pressure continues to rise and reaches a value of 400 psia, the high-high pressure contact will close actuating relays PSX-OlOSA-1 and PSX-OlOSA-2. A ~ontact of PSX-OlOSA-1 closes to actuate SV-10428 which operates PRV-10428. A 11 second contact of PSX-lOlSA-1 closes to actuate the annunciator PORV

. ) OPEN 11

• A contact of PSX-OlOSA-2 closes to actuate a red light on panel C-12.

This light will remain illuminated until it is reset by operator initiation of PB/0105A.

Equipment Two new pressure transmitters (Rosemount Model 1151) will be installed for the pressure control loop. Radiation levels have been established for the installed locations which are below the rated capabilities of the transmitters.

Existing temperature control loops will be utilized. Rochester Instrument System Model ET-215 solid state electronic alarm modules will be installed to provide the contact closures required for actuation of the overpressuriiation system relays.

The relays to be used are Allen-Bradley series 700 AC control relays.

ATTACHMENT 2 The July 18, 1977 NRC letter contained the eight staff positions. Consumers Power has addressed these items previously in the submittal of the Palisades Plant specific report and supplements. To consolidate our position, the following responses are provided:

1. 6T Across Steam Generator: A number of licensees are assuming a maximum 6T across the steam generator in their analyses of energy addition transients.

However, the licensees are not specifying how they will limit the 6T nor how they will monitor the 6T.

Staff Position: Certain energy addition scenarios may be eliminated by admin-istrative methods. The methods for maintaining less than a specified 6T across the steam generator shoul~ be clearly spelled out as well as the means of monitoring this maximum 6T.

Response

The worst case PCS overpressure event as revealed by the specific plant analy-sis is the start of a primary coolant pump with a 6T of 70°F. This 6T of 70°F is the temperature differential that could exist between the steam generator in total and the rest of the primary system after the primary coolant pumps have been shut down and shutdown cooling has reduced the rest of the primary system to 120°F.

The plant operating procedures dictate that the last primary coolant pump shall not be shut down until the PCS has reached a temperature of 160°F to 180°F. Since the secondary side of the steam generator is vented to the condenser and its physical construction is designed expressly to transfer heat across the primary to secondary interface, the wate'T on both sides of the unit will assume the same temperature. Furthermore, an analysis, by energy*incorporated concerning the residual heat in the steam generator for extremely conservative conditions, shows the temperature of the water on the primary side will rise only 2°F after the PCP has been shut down three hours.

Therefore, present temperature monitoring instrumentation is adequate to determine the temperature of the steam generator when the last primary coolant pump is shut down and the physical characteristics of the unit will ensure that its temperature does not increase with time. The temperature differ-ential that must be considered is then that which exists in the PCS when the last primary coolant pump is shut down and that which exists when shutdown cooling is secured. Worse Case is 180°F - 120°F = 60°F. The specific plant analysis considered a 6T = 70°F and determined that ~ PORV was capable of mitigating this event. Th~s analysis leads us to the conclusion that tempera-ture monitoring of secondary side of the steam generator is of no value and will not be implemented. Proposed Technical Specification 3.1.1.h. supports our conclusions.

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2. Isolation Valve Alarm: The upstream isolation valve from the PORVs must be open for the overpressure protection system to properly function. Some means should be provided to insure proper alignment of the isolation valve during overpressure protect~on system operation.

Staff Position: The position of the upstream isolation valve should be wired into the overpressure pro~ection alarm so that the alarm will not clear unless the system is enabled and the isolation valve is open.

Response

The overpressure protection system is designed to ensure that the isolation valves M0-1042A and M0-1043A must be open to allow the arming of.the system.

If, in fact, they are not opened, the "armed" indicating light will not illumi-nate when the keylock switch is turned to the "on" position and the annunciator window "no PCS *protection" will alarm when the PCS temperature decreases below 300°F.

3. PORV Train Separability: A number of licensees have designed systems with one set point switch and one hi/low reset switch for both PORVs.

Staff Position: In order to assure redundancy of the PORVs, each should have an independent keylock enable/disable switch and a hi/low reset switch or similar arrangement. Additionally, the PORVs should be connected to separate vital buses or power supplies.

Response

The overpressure protection system has two independent and redundant channels "A" and "B," each with its own keylock arming switch and alarm reset push button. Also, each channel derives its power from separate vital power buses.

Channel "A" is connected through fuses to bus Y30 breaker #7 and channel "B" is connected through fuses. to bus Y to breaker #7.

4. Circuit Diagrams: Licensees have not been submitting detailed circuit dia-grams with their plant specific reports.

Staff Position: Licensees should submit a detailed diagram of the overpres-sure protection circuitry with their plant specific reports for review by NRC.

Response

Detailed diagrams, schematics, and system operating description are included in the report "Palisades Plant Primary Coolant System Overpressurization Sub-system Description" and the construction package. This information is an attachment to this letter.

5. PORV Valve Cycling: Cycling of PORVs has not been addressed in the Combustion Engineering generic or plant specific reports.

Staff Position:. The results of your transient .pressure analysis should be extended beyond the first pressure cycle. The capabilities of the PORVs with regard to pressure cycling should be .discussed in detail. If the valves do not cycle, the consequences of pressure undershoot and its effect on reactor coolant pumps should be discussed.

Response

The PCS overpressure protection system is designed to open the PORVs, PRV-1042B and PRV-1043B, whenever the PCS temperature is less than 250°F and the pressure exceeds 400 psia. Further, the valves will close when the PCS pressure de-creases to 400 psia. This circuit configuration will produce valve cycling with a cycle time of 31 seconds and will result in approximately 20 valve opening-closing cycles before credit can be taken for operator action at the.

10-minute mark. This cycle time can be increased to 80 seconds or approxi-mately 7 cycles if the circuit dead band is increased to allow the PCS pressure to sag to 200 psia. A PCS pressure of 200 psia is considered the lowest pres-sure level that can be tolerated before appreciable primary coolant pump seal degradation will be experienced.

Considered opinion is that 20 valve cycles will not be any more damaging to the valve than 7 cycles, simply because if damage to the valve occurs it will take place in the first few cycles of operation. Any foreign material in the system in the vicinity of the valve will pass over its seat in the initial operation of the valve. The valve testing program should reveal the degrada-tion effects, if any, that cycling will have on the valve.

6. IEEE 279 and Seismic Criteria: IEEE 279 and Seismic Criteria should be con-sidered in the design of the overpressure protection system. Deviations from these standards should be clearly described and detailed justification should be provided.

Response

The PCS overpressure protection system design in regard to IEEE 279 and Seismic Criteria has been clearly addressed.in the plant specific analysis. This sys-tem has been designed to comply with the requirements of the original plant design under which it was licensed to operate. There is no single failure of a component or system or single event that has been identified in our analysis as capable of both causing an overpressure event and defeating the protection afforded against such events.

7. Testability: The program for testing the PORVs for low pressure protection system operability is not addressed in the plant specific reports.

Staff Position: The control circuitry from pressure sensor to valve solenoid should be tested prior to each heatup or cooldown. The PORVs should be stroked during each refueling. Deviations from this criterion should be justified.

Response

The location of the valve and its solenoid in addition to its physical con-struction/operation makes testing the PCS overpressure protection system during operation.prior to cooldown not possible. The electrical portion of the sys-tem will be tested and calibrated during each refueling outage. And since the valve itself is pilot-operated, it cannot be stroked without a pressure differ-ential existing across it. Therefore, the valve testing and frequency will be in compliance with the applicable requirements of ASME Code Section XI, Sub-section IWV, and addressed in the Palisades Plant Inservice Inspection Program.

8. Technical Specifications: The overpressure protection system is not being designed to mitigate the consequences of certain scenarios. This may be accept-able if the scenario is made extremely improbable by appropriate administrative measures. However, these administrative procedures have not been discussed in the reports reviewed thus far.

Staff Position: If a scenario is to be administratively eliminated or miti-gated, the actions required to change the scenario should be placed in the Technical Specifications. A draft of the Technical Specifications should be provided with the plant specific report or soon after it is submitted. Some items which should probably be included in the Technical Specifications are:

a. Enabling/disabling the Overpressure Protective System.

b. Maintaining maximum ~T across the steam generator.

c. Disabling pumps, accumulators, heaters.

d. Testing PORV and control circuitry.

e. Testing ECCS with head off.

Response

Proposed Technical Specifications changes are attached which address the staff position.