ML20028D950

Forwards Response to Instrumentation & Control Sys Branch Questions & Discussion on Design of Auxiliary Shutdown Complex

ML20028D950
Person / Time
Site:	Catawba
Issue date:	01/18/1983
From:	Tucker H DUKE POWER CO.
To:	Adensam E, Harold Denton Office of Nuclear Reactor Regulation
References
NUDOCS 8301200112
Download: ML20028D950 (8)

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e Duxe Powna GOMPANY P.O. nox 33180 CI(AltLOTTE. N.C. 28242 II AL II. TUGkEH Tzternown mecaramen (704) 373-453

.mm. e- ="= January 18, 1983 Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Comission Washington, D. C. 20555 Attention: Ms. E. G. Ader; sam, Chief Licensing Branch No. 4 Re: Catawba Nuclear Station Docket Nos. 50-413 and 50-414

Dear Mr. Denton:

Mr. T. M. Novak's letter of January 7, 1983 transmitted five concerns and positions related to the NRC Instrumentation and Control Systems Branch (ICSB) review of Catawba. Attachment 1 provides a response to each of these items.

Also attached is a discussion of the Catawba Auxiliary Shutdown complex as requested by ICSB during a November 16 and 17 meeting in Bethesda.

Very truly yours, eWh / _

Hal B. Tucker ROS/php Attachment cc: Mr. James P. O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303 Mr. P. K. Van Doorn NRC Resident Inspector Catawba Nuclear Station Mr. Robert Guild, Esq.

Attorney-at-Law P. O. Box 12097 Charleston, South Carolina 29412 Palmetto Alliance 21355 Devine Street Mp' Columbia, South Carolina 29205 B301200112 030118 PDR ADOCK 05000413 A PDR

Mr. Harold R. Denton, Director January 18, 1983 Page 2 2

l cc: Mr. Jesse L. Riley Carolina Environmental Study Group 854 Henley Place Charlotte, North Carolina 28207

. Mr. Henry A. Presler, Chairman Charlotte-Mecklenburg Environmental Coalition

. 943 Henley Place

! Charlotte, North Carolina 28207 1

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ATTACHMENT 1 INSTRUMENIATION AND CONIRUL LICLNSING POSITIONS FOR CATAWBA

1. CONCERN: ICSB has previously expressed concern over the operation of the valves used to terminate upper head injection (SER 7.6.2.3). Hydraulic accumulators are used to effect automatic, fast closure of these valves.

Manual closure is only provided using a hydraulic oil pump to close one valve at a time. The hydraulic oil pump is not safety grade and valve closure by this means is a slow process (1.5 minutes per valve).

POSITION: The staff's position is that a safety grade manual closure should be provided for the upper head injection isolation valves to permit the opera-tor to terminate this safety function. Since automatic closure has been provided for these valves as a control on an ESF system, the staff position is that safety grade manual closure should also be provided in accordance with paragraph 4.17 of IEEE-STD-279.

RESPONSE: Safety grade maqual closure capability will be provided for the upper head injection isol4 tion valves to permit the operator to terminate this safety function.

2. CONCERN: ICSB has previously expressed concern that level indication is only provided for the upper head injection accumulator surge tank and not for the accumulator itself (SER 7.6.2.4).

POSITION: The staff's position is that indication, with a range from the bottom of the accumulator to the normal level in the surge tank, should be provided for the upper head injection accumulator. The staff believes this should be provided in accordance with paragraph 4.20 of IEEE-STD-279 and table 2 for type D variables of Regulatory Guide 1.97.

RESPONSE: The UHI surge tank is designed to accomodate changes in the volume of the water accumulator due to temperature changes and to allow for some leakage in or out of the system. It maintains the accumulator and piping up to the UHI rupture disc water solid. The two existing level instruments (NILT5700,NILT5710) are used, by the operator to maintain the required water level in the surge tank. These instruments are of suitable range to perform their intended function.

The UHI system is designed as a passive water injection system for a large break LOCA. For this event a redundant, single failure proof system provides isolation to assure no nitrogen is injected into the reactor vessel head. Since this is a fast moving event and timing is critical, automatic isolation is provided.

For some ever.'s (e.g. steam generator tube rupture) the staff postulated that operator isolation by safety grade means was desirable in order to control reactor coolant pressure rapidly. These control means are being added but the use of these controls would be based on reactor coolant pressure not accumulator l evel . Thus the existing instrumentation is judged adequate and no changes are planned.

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3. CONCLRN: ICSil has previously distu. sed with the applicant that testing of the manual reactor trip channel does not allow independent verification of the operability of the ', hunt trip mil and the undervoltage coil because operation of a manual trip switch results in a simultaneous trip action by both coils (SER 7.2.2.1). The applicant has stated that he opposes testing of the shunt trip coils.

POSITION: The staff's position is that the diverse features of the reactor trip breakers (shunt and undervoltage coils) provide an additional degree of reliability for assuring the ability to trip the reactor. Therefore, surveillance procedures should independently verify the operability of these diverse features. Tests to confirm the operability of the shunt trip coils should be conducted on a refueling outage interval .

RESPONSE: Duke Power endorses the Westinghouse position on testing of the reactor trip breakers. (Ref. E. P. Rabe's October 18, 1982 letter to T. P.

Speis). This issue applies to all Westinghouse plants and Duke Power requests that it be reviewed and resolved as a generic item.

4. CONCERN: ICSB has previously expressed concern over.the testability of the circuitry which isolates main feedwater lines on high doghouse level (SER 7.3.2.9). The logic for this isolation is one-out-of-one for each train.

The applicant has indicated that this circuitry can only be tested during periods of shutdown.

POSITION: The staff's position is that doghouse level switches used for the main feedwater isolation should be testable during power operation in accordance with paragraph 4.9 of IEEE STD. 279 (10 CFR 50.55a(h)). The design should be modified such that a functional test of the level switches can be performed during plant operation without initiating main feedwater isolation.

RESPONSE: The doghouse level switches and associated circuitry are tested preoperationally and at refueling shutdowns. The switches are simple, rugged, highly reliable devices. They employ no electronics or complex logic processing which would merit frequent testing. They will be tested at refueling shutdowns and the results of those tests should validate the test interWal selected. If results of these tests indicate the need for more frequent testing, Duke would make any necessary modifications at that time to permit online test capability of the sensors.

The doghouse level switches are provided for protection from a very unlikely flooding event. They serve 20 reactor protection or ECCS function. This subject was discussed at length in our September 7-9, 1982 ICSB meeting in Charlotte and agreement was reached that this item was closed.

5. CONCERN: One of ICSB's previous concerns identified the Staff's position that instrumentation performing safety functions should be provided with alarms and indicators commensurate with the importance to safety function and should be testable without interferring with normal plant operations (SER 7.5.2.5).

Our concern contained a list of features which should be provided for such instrumentation channels. The applicant was requested to review all instrument channels which perform safety functions and list areas where Catawba does not meet our position. The applicant stated, in a November 23, 1982 letter, that the adequacy of instrumentation would be determined as part of the Catawba Control Room Design Review. Since the applicant did not fully respond to our previous

concern, the staff performed an audit review of Catawba instrumentation which performe, sa rnty function'., Ar, a rs".ul t o f i hl', rev i ew, 1 C",11 h.1, identified that the containment pressure transmitters used for the Con-tainment Pressure Control System do not have indicators to facilitate surveillance checks.

POSITION: The staff's position is that indicators should be provided for the above pressure transmitters to be used for periodic surveillance checks.

The staff believes that this is in accordance with paragraph 4.9 of IEEE STD. 279 (10 CFR50.55a(h) as the only practical method to perform daily channel checks of the transmitters during reactor operation.

RESPONSE: Indicators will be provided for the Containment Pressure Control System pressure transmitters.

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ATTACHMENT 2

, The Auxiliary Shutdown Complex (ASC) for Catawba Nuclear Station was designed in accordance with General Design Criteria 19 and is descrlinsi in Section 7.4.7 of the FSAR.

The ASC was designed to bring the plant safely to a hot shutdown in the event the control room must be evacuated. A design basis of the Catawba ASC was also to provide the capability to bring the unit to a hot shut-down condition with a fire in the control room. The design provides for these capabilities even with a loss of offsite power. Cold shutdown can subsequently be reached through the use of suitable procedures.

A Standby Shutdown Facility (SSF) is also being provided at Catawba which provides additional depth to facilitate remote shutdown. This facility is complete with its own power sources (diesel generators, batteries, etc.)

controls and instrumentation. The instrumentation provided consists of completely separate loops which are in addition to the control room instru-mentation and instrumentation provided for the ASC. This facility will be further described in the Catawba Fire Plan.

The design intent for the ASC was to provide the capability for an orderly, well controlled shutdown similar to that normally achieved from the control room. Hence, many normal shutdown means are employed instead of proceeding directly to the use of ECCS shutdown methods.

However, the staff asked Duke in a November 16th and 17th,1982 ICSB meeting in Bethesda to provide a review of the Catawba ASC design to the Faust Rosa - August 5,1982 guidance document which was provided to ICSB reviewers. This guidance interpretation centers on provision of redundant, safety grade, seismic, single failure proof shutdown means. Hence the scope of this response primarily addresses that capability and not the more normal shutdown capabilities already discussed with the staff.

General Design Criteria 19 does not address any requirements for the remote shutdown system to be redundant, safety grade, single failure proof, or seismic. Additionally the 10CFR50 Appendix R requirements do not support this staff interpretation. A seismic event will not cause the need for a control room evacuation. ' The probability of a seismic event occurring during a control room evacuation is extremely smc11 and should not merit inclusion as a regulatory requirement.

Functions needed to achieve and maintain hot shutdown of a unit are as follows:

- Reactor Heat Removal A. Steam Generator Feedwater B. Main Steam Release

- Maintain Proper Reactor Coolant Inventory A. Ma keup B. Letdown mm e- + a

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l Steam Generator Feedwater is furnished by the Auxiliary feedwater (CA)

' system. This syston is redundant and ,alety ejrade includinej Llie l>rovi, lori .

for a seismically qualified source of water. The necessary controls for

alignment and actuation are provided by the ASC.

Release of main steam is normally accomplished via the main steam power operated relief valves which can be controlled from the ASC. In the event of a failure such as loss of control air the valves can be locally manually i controll ed.

1 Reactor coolant system makeup is provided by a portion of the Chemical and

Volume Control (NV) system. This portion of the NV system is safety grade and partially redundant. Operation of all' devices necessary for reactor coolant system makeup can be accomplished from the ASC. A single failure in the non-redundant section of the system can be mitigated by manually positioning valves.

l - Reactor coolant system letdown is normally accomplished by a portion of t t the NV system which has redundant flow paths with safety-grade controls at the ASC. However, inside containment fail-closed pneumatic valves in these flow paths could preclude letdown of reactor coolant in this manner.

Alternately, the pressurizer power operated relief and block valves or the j pressurizer. safety relief valves could be utilized for letdown. .The power ,

operated relief and block valves provide redundant flow paths, and have ,

safety grade controls at the ASC. However, the power operated relief valves are also fail-closed pneumatic valves. The safety relief valves are always available to let down reactor coolant in the event of failures of the other l letdown means.

l Reactor coolant pump seal integrity is maintained by continuing seal injection or thermal barrier cooling.

4 Seal injection to the RCPs is furnished by a portion of the NV system which is safety grade and partially redundant. A single failure in the non-redundant portion of the seal injection supply line can be mitigated by the manual positioning of valves. The seal injection return line contains normally open motor. operated valves and fail open pneumatic valves located inside containment which could terminate return flow due to a failure.

Cooling to the RCP thermal barriers is accomplished by a portion of the Component Cooling (KC) system whicn is safety grade and partially redundant.

Failure of normally open motor operated valves located in containment could result in the loss of thermal . barrier cooling.

In addition to the two methods described above, the Standby Shutdown Facility Standby Makeup Water Pump is available to provide seal injection to the RCPs.

A further description of this system will be provided in the Fire and Security Plan submittals.

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e Other f.upport aye.Lem anti r.y'.Le m* nes;e".*. 2ry to prome tl to a e o lil *.hu t ilown

. are the Nuclear Service Water (RN), Component Cooling (KC) and Residual llcat Removal (ND) r.ystems. The neces .ary lortions of each of tin '.e system, is safety grade and redundant with the appropriate controls provided by the ASC with one exception in the ND system. The HD suction lines from the reactor coolant system both employ A and B train series isolation valves.

However, a single failure in these valves can be mitigated by the use of permanently installed local motor starters which can be connected to the valves to provide an alternate source of power.

Loss of offsite power will not negate the shutdown capability of the ASC.

A loss of offsite power following a transfer to the ASC will not result in subsequent overloading of the essential busses or the diesel generators.

The parameters displayed in order to achieve and verify a safe shutdown condition are as follows:

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Pressurizer Pressure Pressurizer Level Reactor Coolant Temperature

- Steam Generator Level Component Cooling Essential Header Flow Nuclear Service Water Essential Header Flow

- Charging Header Flow In the Catawba ASC design additional instrumentation loops were provided for the above functions which are totally separate and in no way dependent on equipment located in the control room. This instrumentation is control grade and non seismic.

The auxiliary shutdown panels are seismically qualified to preclude un-desirable interaction with ESF components or circuits during non ASC events (i.e. LOCA).

A design basis of the ASC is to provide the capability for bringing the plant to hot shutdown following a fire in the control complex. As such all control would be isolated from the control room to prevent spurious operation. In some cases, valves that do'not require subsequent ASC control are positioned automatically on transfer to insure proper position for ASC operation.

Normally these valves are not repositioned but are given a signal to remain in their normal position. Examples of valves that are repositioned on trans-fer are the RN switchover valves from Lake Wylie to the SNSWP.

Keys required for access into the ASC are provided in the shift supervisor's office which is located outside the control complex.

The 10CFR50 Appendix R requirements will be addressed in the Catawba Fire Pl a n . This submittal will describe the Standby Shutdown Facility which provides redundant shutdown capability to the control room and/or the ASC for fire or security events.

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