ML20207M148

Forwards Design Rept for Reactor Coolant Inventory Tracking Sys to Be Installed During Cycle 8 Refueling Outage.Related Info Encl

ML20207M148
Person / Time
Site:	Rancho Seco
Issue date:	10/07/1988
From:	Croley B SACRAMENTO MUNICIPAL UTILITY DISTRICT
To:	Knighton G NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
AGM-NTS-88-258, NUDOCS 8810180132
Download: ML20207M148 (11)

Text

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gSMUD SACRAMENTO MUNICIPAL UTILITY DISTRICT O 6201 S Street, Po. Box 15830, Sacramento CA 958521830,(916) 452 3211 AN ELECTRIC SYSTEM SERVING THE HEART OF CAllFORNIA AGM/NTS88-258 October 7, 1988 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Wcsh.ington, DC 20555 Docket No. 50-312 T'ancho Seco Nuclear Generating Station Licorise No. DPR-54 REr.CTOR VESSEL LEVEL

• NSTRUMENTATION SYSTEM Attention: George Knighton Attachment I is a design report for the Reactor Coolant Inventory Tracking System (RCITS) which will be insthlled during the Cycle 8 refueling outage. The District preposed Inadequate Core Cooling instrumentation to satisfy the NRC Order For Modification of Licenso for Rancho Seco Nuclear Generating Station on April 15 ,- 1983, and supplied additional information requested by the NRC on June 28, 1984. A preliminary design for RCITS was provided by letter dated December 30, 1985 (Attachment II). Por District commitment in a letter dated September 30, 1985, the balance of the RCITS will be installed during the Cycle 8 outago.

The basic design of the system has not changed sinco the descrip-tion of the proposed RCITS was transmitted to the Commission on December 30, 1985. The RCITS Design Basis Report is in prepara-tion; therefore, specific information regarding components may change as a result of final review and approval. ,

I 8810180132 881007 PDR P ADOCK 050003)2 ppy

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RANCHO SECO NUCLEAR GENERATING STATION O 14440 Ten Cities Road, Herald, CA 95638 9709: (209) 333 2935 m

George Knighton AGM/NTS88-258 Members of your staff with questions requiring additional infor-mation or clarification may contact Mr. Steve Crunk at (209) 333-2935, extension 4913.

Sincerely,

, Bob G. Croley Assistant Genera Manager Nuclear Technica Services Attachments cc w/atch: J. B. Martin, NRC, Walnut Creek A. D'Angelo, NRC, Aancho Seco i

. . l George Knighton AGM/NTS88-258 bc:

w/atch w/o atch 2 'l General Manager HS 41

_ __ X Chief Executive Officer, Nuclear HS 209

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__ AGH, Plant Support Services MS 259 -

__. AGH, Nuclear Technical Services MS 206

__ AGH, Nuclear Power Production MS 254  :

l_ Director, Nuclear Quality MS 271

__. J. , Manager, Nuclear Training MS 296

___ __X _ Manager Licensing MS 298 i l_ _ _ . , Manager, Nuclear Engineering MS 208-6  !

__ Manager, Cost Control Services MS 208-10

__ Manager, Maintenance MS 254

__ Manager, Operations MS 255

__ Hanager, Envir. Hon. & Emer. Prep. MS 292A ,

_ ,_ Manager, Rad. Protection MS 244

,__. Manager, Nuclear Chemistry MS 250

___ __ Manager, Plant Performance MS 258

__ Hanager Safety & Risk Hgmt. MS 40

._._, Plant Support Eng. Manager HS 208-5

_ _ . HSRC Secretary (R. Colombo) HS 256 c _. X Public Information MS 204

_ Surveillance Coordinator MS 278

l. IIRG HS 298

l. NAC (4) HS 204

_ T. Baxter  :

_ F. Burke (8&W) ,

3 D. Seavers (ANI)  !

._ _ LER Files MS 298  !

3. Licensing Correspondence Tracking MS 286 ,

L PRC Secretary (R. Colombo) MS 256 l l_ RIC File 1A.200 MS 224 .

_ Special Report Files MS 298  !

. _ Tech. Spec./PA Files MS 298

_ NOV/N00 Files MS 286 l

_ _ Licensing Verification MS 286 l l_ Elizabeth Gebur HS 298 3 Jerry Delezenski HS 298 I

___ BHOG T.S. Committee (8) 1_ Paul 80sakcwski, Proj. Mgr. (RCITS) MS 270 e um_

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Attachment I Reactor Coolant Inventory Tracking System Design Report a

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. s Attachment I Page 1 of 3 I. Systed Purpose The Reactor Coolant Inventory Tracking System (RCITS) provides a reliable and unambiguous indication of reactor coolant inventory trending with the reactor coolant pumps (RCPs) either running or tripped. The system meets the intent of NUREG-0737, Item II.F.2, "Instrumentation for Detection of Inadequate Core Cooling" and the requirements for a Reg. Guide 1.97 Category 1 variable (ex-cept for RCP motor current).

II. System Description The RCITS measures three parameters for reactor coolant inventory trending:

l o Differential pres ~e (DP) across the vertical run of the t hot legs (tot leg avel) - QA Class I; o DP across the upper region of the reactor vessel (RV level)

- QA Class I; and o RCP motor current - QA Class II.

Hot Lea Level Measurement The hot leg level measurement instrumentation was installed dur-ing the Cycle 7 outage and the unscheduled outage commencing '

December 26, 19R5.

Reactor Vessel Level Measurement The RV level measurement indicates reactor coolant inventory trends when the RCPs are not operating. The RV level measurement ranges from the top of the RV head to the center of the cold leg.

The design requires the removal of the central control rod drive nechanism (CRDM) to penetrate the RV head for the top RV pressure tap. An existing tMp on the Loop A cold leg for level transmit-ter LT-21046 will la modified and used as the lower pressure tap.

The central CRDM and associated control rods will be replaced by a standpipe assembly. The assembly will have flanged connections on each and and will be bolted to the CRDM housing flange. Two manual shut-off valves will be installed in the standpipe assem-

bly to provide isolation capability. In addition, a manual valve

, for venting the assembly during filling of the Reactor Coolant System will also be installed. A small piping subassembly will be included to which instrument lines will be attached. Supports to meet seismic and ASME code requirements will be installed as necessary.

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Attachment I Page 2 of 3 The standpipe assembly will be ASME Class 1 from the face of the CRDM housing flange through the second rc(.ucer, and will be manu-factured from 304 stainless steel. The rest of the assembly (in-cluding the piping subassembly) will be ASME III, Class 2. The supports for tha standpipe and subassembly will mee'c the require-ments of ASME Section III, Subsection NF. The standpipe will be insulated to prevent excessive heat loss to surrounding CRDMs.

Two DP transmitters (one per channel) will be used to provide re-dundancy. Each will be powered independently by QA Class I instrumentation power. The transmitters will be located inside containment and will be qualified to withstand the normal, abnor-mal, and post accident conditions in accordance with the environ-mental qualifications program. They will be installed in insula-ted enclosures to protect them from temperature transients during a design basis event and to improve their performance. The DP transmitters will withstand the pressure conditions imposed on the diaphragm of the transmitters when the RCPs are running and will be fully recoverable when the RCPs are stopped.

The design includes density compensation for level measurements due to temperature effects on process liquid density. The QA Class I incore temperature (T-incore) will be used in temperature compensation. Density compensation on the reference legs (ver-tical runs) is not required because the reference legs (instru-ment lines) will be insulated with 2-inch thick insulation to maintain the temperature of the reference legs relatively con-stant. The maximum temperature rise of the reference legs has been calculated to be approximately 8 F0 above normal containment atmospheric temperature when subjected to the temperature tran-rients during a design basis event. The sencing lines will be installed to seismic Class I requirements.

The output of the transmitters will be connected to the QA Class I Anatec multiplexer system for level trending indications on the QA Class I Safety Parameter Display System (SPDS) and QA Class II Interim Data Acquisition and Display System (IDADS). Isolation for IDADS is provided for in the multiplexers. IDADS has trend recording capability.

A sketch of the RV level measurement system is shown in Figure 1.

A proposed Inadequate Core cooling display is shown in Figure 2.

RCP Motor Current RCP motor current monitors (QA ClLas II) provide trending indica-tion of the voids in the RCS with the RCPs running. The RCP motor current signal is used to infer the average density of liquid (or two-phase liquid / vapor) which passes through the pump.

Coolant tenperatare at the inlet is used to infer the density of each individual phase of the fluid as it passes through the pump,

Attachment I Page 3 of 3 ,

RCP motor current measurement uses Class II current transducers (one for each RCP) which provide an analog signal proportional to RCP motor current. The curront transducers will be connected to existing Class II current transformers and installed in the same compartment as existing 6.9kV switchgear supplying power to the RCPs.

The current transducer output signals will be fed into a Class II i Anatec multiplexer located in the same switchgear room as the transducers. The signals will be processed by IDADS to present on-demand percent void indications for the RCPs. IDADS also has on-demand trending and recording capability. Void fraction indi-cation will be available on IDADS whenever the RCPs are running.

i A sketch of the RCP motor current measurement system is shown in i Figure 3.

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i Attachment II District Letter of December 30, 1985 1

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RJR 85-578 Cocamber 30, 1985 l

l OIRECTOR CF NUCLEAR REACTOR REGULATICN ATTN HUCH L ThCP.PSCN JR j i

OIVISION OF LICENSING  !

U S NUCLEAR REGULATCRY CCf1MISSICN '

WASHINGTCN OC 20555 j I

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RANCHO SECO NUCLEAR GENERATING STATION UNIT NO. 1 . .

NUREG 0737 ITEM II.F.2 INADEQUATE CORE C00LLW (ICC)

.h Sy letter dated. April 15, 1983, the District proposed ICC instrumentation to  !

satisfy your Order For Modification of License for Rancho Seco Nuclear Cenerating Station, dated December 10, 1982. On June 28, 1984, the District i responded to your Request for Additional Information, dated t,ugust 24, 1983.

In these submittals, the District identified a heated junction thermocouple .,

system (hJTCS) as the preferred method for reactor vessel coolant inventory .;

trending. A differential pressure (CP) system was identified as an option.

Due to the recent availability of qualified higher accuracy transmitters and procurement difficulties with the HJTCS, the District has reevaluated the options and decided to pursue the DP system.

The attachment to this letter provides a design description for the precosed reactor coolant inventory tracking sy: tem (RITS). This information supersedes the reactor vessel level measurement lystes description provided by the District's April 15, 1983 and June 28, 1984 submittals. The previous descriptions of the balance of the ICC instrumentation, including hot leg level, are still valid.

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RJR-85-573 December 30, 1985 Hugh L. Thompson. Jr. -2 The District remains committed to install the balance of the RITS '

instrumentation during the Cycle 8 refueling outage, as reiterated in our letter of September 30, 1985.

4 If you have any questions concerning the above, please contact Robert Little at (916) 732-6021. ,

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d R. J. Rt RIGUE j ASSISTANT GENERAL MANAGER, I

NUCLEAR Attachment bc: 0. K. K. Lowe R. J. Rodriguez I f

i R. P. Cubre' L. R. Xeilman '

R. A. Dieterich V. C. Lewis (2)

R. W. Colombo (2) t J G. A. Coward L. G. Schwieger (2) G. C. Andognini (MS 39) i i Syd Miner (NRC, Bethesda) J. Eckhardt (NRC, Ranch)

P. G. Delezenski Fourth Floor Files L l

Eng. Files-Plaza 50 Licensing Files (MS 32)

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AtQ3chment REACTOR CCCLANT INVENTORY TRENOUJG SYSTEM l The reactor coolant inventory tracking system (RITS) is designed The RITS to will provide unambiguous indication of reactor coolant inventory trending.with the reactor coolan provide inventory trending indicationThe system is being designed to meet the intent of either running or tripped.

NUREG 0737, Item II.F.2.

'he RITS measures three parameters for reactor coolant invesory trending determination:

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differential pressure (DP) across the vertical run of the hot legs (hot leg level);

e CP across the upper region reactor vessel (RV level); and

. RCP motor ocwer.

Hot Leo level Measurement The hot leg level portion of the RITS is described in tha Oistrict's .

submittals of April 15, 1H3 and June 28, 1984.

RV Level deasurement The RV level measurement providis an indication of reactor coolant inventory k, trending when the RCPs are not operating, The RV level measurement ranges from the top of the reactor vesse to the center of the cold leg. ,.

control drive mechanism to provide a penetration in the RV head for location 6 of the top RV pressure tap. The existing tap on the Loop A cold leg i

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l (discharge of RCP P-2108) will be used as a lower pressure tap. .

j existing cold leg tap provides the following benefits: l

. elimination of sirgle failure concerns relative to use of the tap on decay i I

heat drop line common with the hot leg CP transmitters; ard i ,

• lower personnel exposure over installing a new hot leg tap. i l

Two OP transmitters (one per channel) will be used to provide redurdancy.

Each transmitter will be powered independently by Class 1 instrumentation power. The DP transmitters will be located inside containment and will bo qualified to withstand the normal, abnormel, and post accident conditions,ThG OP in accordance with the District's environmental qualification program.  !

i transmitters will be qualified to withstand the overpressure conditions l l

imcosed on the diapt.ragm of the transmitters when the RCPs are running andThe  !

) will be fully recoverable when the RCPs are stopped.

installed in an insulated enclosure to protect them from temcerature l transients during design basis events and to improve treir perforstnce.

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The design includes density corcensation for level measurements due to temperature ef fects on process liquid density. Consity comconsation on *.he esference legs (vertical runs) is not required because the sensing lines will  !

be insulated with 1" thick insulation to maintain the temperature of the reference legs relatively constant. The maximum tempe'rature'rf'se of tne reference legs is anticipated to be 10*F above normal containment at.nospheric temcorature (120*F) when subjected to the temperature transients during a design basis event.

The output of the transmitters will ba connected to the Class 1 sultiplexer system for the level irdications on the safety parameter display systea (SPOS) and the interim data acquisition and display system (ICA03) CRTs. Isolation .

For ICA05 is provided in the multiplexers. IDAOS is the primary display system for ICC and has trend recording capability showing the level-time history of representative RV level readings.

Primary (IDADS) and backup (SPOS) display channels are electrically ,

independent. IDA05 is gewered from battery backed Class 2 power source and '

SPOS will be powered from a Class 1 power source. ,SPOS mod!fications will be implemented per the t.iving Schedule ard in accordance with Reg. Cuide 1.97 and CRCR recommendations.

A skatch of the RV level portion of the RITS is'shown in Figure 1.

9CP Motor Power .

RCP motor power and pump inlet temperature measurements will be used by the i*G RITS to trend the reactor coolant void fraction when one, or more, of the RC'2s  ?

is operating.

RCP power measurement requires the use of 3-phase Watt-transducers (Class 2),

one for each RCP, to provide an analog signal proportional to RCP actor .

power. Watt-transducers will use existing Class 2 current and potential

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transformer signals and will be self pcared. The transducers will be high quality commercial grade components and will be installed in the same ,

environment as the existing 6.9kV switchgear supplying power to RCPs.

The output from the transducers will be fed into Class 2 sultiplexers located in the same switchgear roca. The Watt-transducers' signals will be processed in IDADS (Primary display) to provide percent void indication for each puma via CRT on demand. !0A05 also has trend capability and recording capability on demand. Since IDADS is powered from a battery backed Class 2 peser source and the RCP actors are powered from a Clas: 2 power source, the percent void indication will be available on IDAOS CRT whenever the RCPs are running.

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