ML20206N341

Safety Evaluation Re Util 860406 Request to Add Resistance Temp Detector as Alternate Means of Measuring RCS Water Temp.Proposed Change Acceptable

ML20206N341
Person / Time
Site:	Crane
Issue date:	06/24/1986
From:	NRC
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Shared Package
ML20206N334	List: ML20206N330 ML20206N341
References
NUDOCS 8607010441
Download: ML20206N341 (7)

Text

0 ATTACHMENT SAFETY EVALUATION Introduction Section 3.4.9.1 of the Appendix A Technical Specifications requires that the temperature of the reactor coolant system (RCS) be maintained between 50 F and 200'F. The purpose of this requirement is to avoid precipitation of the boron used to maintain subcriticality at low temperatures and minimize radioactive releases to the containment atmosphere due to boiling of the unpressurized RCS at high temperatures.

Bulk RCS water temperature is currently measured by approximately 30 operable incore thermocouples. As defueling progresses, disablement w!11 become necessary to minimize the possibility of damage to reactor vessel integrity.

In order to minimize stress to the instrument guide tube penetrations due to defueling the licensee proposes to sever each of the incore detector assemblies near the reactor vessel lower head. This will eliminate the RCS bulk water temperature measurements by the incore thermocouples.

In order to retain the capability of measuring the RCS bulk water temperature the licensee has installed three resistance temperature detectors (RTDs) in the Internals Indexing Fixture (IIF).

Discussion The three RTDs are located in the vicinity of the reactor vessel flange in the northeast quadrant. The licensee proposes that the readings from these three RTD's satisfy the surveillance requirement of Table 4.3.7 of the TMI-2 Recovery 8607010441 860624 PDR ADOCK 05000 0

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.o Operations Plan. The revised table would allow any combination of incore thermocouples or in-vessel RTDs resulting in a minimum of two operable temperature detectors to satisfy the surveillance requirement. The in-vessel RTDs would provide the licensee the flexibility and diversity to determine i

i the RCS temperature when the incore thermocouples become inoperable.

Additionally they presently provide the licensee with a second method of verifying reactor vessel coolant temperature.

Prior to installation of the in-vessel RTDs reactor coolant system bulk water i

temperature was measured only by the incore thermocouples. These incore thermocouples have experienced a number of failures in the past. Currently, the licensee uses the average of operational incores as opposed to individual incore readings. The licensee has determined that the locations of the incore junctions are undefinable. The accuracy of individual incores is uncertain, thus they are collectively used to indicate RCS temperature trends.

Hourly readings over a two week period from the three in-vessel RTDs were compared to the incore thermocouple average temperatures for the same period.

Changes in the RCS temperature were simultaneously reflected by both the incore thermocouples and the RTDs.

During the two week period the RCS bulk water temperature changed approximately 3 F. The incore thermocouple average temperature and the average temperature of the 3 RTDs differed by about 6 F during the entire 2 week period. As of June 2, 1986 the average incore thermocouple temperature was 84 F and the average RTD was 78 F.

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l Conclusion i

The three in-vessel RTDs will provide a second method of verifying the reactor vessel bulk water temperature. The staff finds that the agreement between the readings from the incore thermocouples and the in-vessel RTDs is cceptable.

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Since defueling will ultimately result in the elimination of all incore thermocouples an alternative method of measuring RCS bulk water temperature is necessary. The in-vessel RTDs will provide an acceptable method for measurement of bulk water temperature. The inclusien of the three RTDs in Table 4.3-7 of the Recovery Operations Plan will enhance safety by providing additional and alternative surveillance capability of the RCS bulk water. The change will not result in any environmental effects and falls within the scope of activities previously considered in the Programmatic Environmental Impact Statement.

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4 Enclosure i

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FACILITY OPERATING LICENSE NO. DPR-73 DOCKET NO. 50-320 i -

Replace the following pages of the TMI-2 Recovery Operations Plan with the enclosed-pages as indicated:

4.3-10 4.3-10a 3

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TABLE 4.3-7 w.

ESSENTIAL PARAMETERS MONITORING INSTRUMENTATION SURVEILLANCE REQUIREMENTS 5

A 25 MINIMUM R

CHANNEL CHANNEL (13 READ 0UT OPERABLE

. INSTRUMENT CHECK CALIBRATION LOCATION (S)

CHANNELS 7

E 1.

Reactor Building Pressure S

R Control Room 2

. 2.'

Reactor Vessel Water Level S/W(2)

SA Control Room (2) 2(2)

E' 3.

Incore Thermocouples/RCS S

R Control Room or 2(3)

Z Temperature Detectors Cable Room 3

N 4.

Reactor Building Water Level NA SA Control Bldg.

1 Area West

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Borated Water Storage Tank' Level S

R Control Room 1

5.

6.

Steam Generator Level NA NA NA 1/ Generator w

7.

Spent Fuel Storage Pool S/W(2)

SA Control Room (2) 2(2)

"A" Water Level or Fuel Handling Bldg 8.

Fuel Transfer Canal S/W(2)

SA Control Room.(2) 2(2)

(deep end) Water Level or Reactor Bldg (See following page for notes) 9 E

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9 TABLE 4.3-7 (Cont'd)

ESSENTIAL PARAMETERS MONITORING INSTRUMENTATION SURVEILLANCE REQUIREMENTS

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R1 Notes:

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1)

Nuclear detectors and all channel components located inside containment may be excluded from CHANNEL CALIBRATON.

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'2)

One channel consist of a visual indication such as a level stand pipe.

5 Seven day surveillance applies to visual indication only.

Visual indication readout may be in the Reactor Building, or Fuel Handling Building, or by remote television.

3)

Any combination of incore thermocouples, or RC-TI-l'05 points A, B, or.C that results in a minimum

{l of two operable temperature detectors, satisfy this requirement.

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TMI-2 SERVICE LIST i

Dr. Thomas Murl:y Willis"Blaby. Sitt Manager Regional Administrator. Region I U.S. Department of Energy U.S. wclear Regulatory Cossetss'on P.0. Boa 84 631 Park Avenue-Middletown. PA 17057 0311 L

King of Prussia PA 19406 David J. McGoff

(

John F. Wolfe. Esq., Chairman.

Olvision of Three Mile Island Programs Administrative Judge Nf.23 3409 Shepherd St.

U.S. Department of Energy Chevy Chase. Mo. 20015 Washington. 0.C.

20545 Dr. Oscar H. Paris William Lochstet Administrative Judge 104 Davey Laboratory AtomlC Safety and Licensing Pennsylvania State University Board Panel University Park PA 16802, U.S. Nuclear Regulatory Coassission Washington. 0.C.

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• Dr. Frederick H. Shon 812 Market St.

Administrative Judge Harrisburg. PA 17105 Atomic Safety and Licensing Board Pane)

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Assistant Attorney General Bethesda. MD.

20814 505 Esecutive House P.O. Bos 2357 Michael Churchhill. [sq.

Harrisburg. PA 17120 PILCOP 1315 Walnut St., Suite 1632 Dr. Judith H. Johnsrud Philadelphia, PA 19107 Environmental Coalition on Nuclear Power Linda W. Little 433 Orlando Ave.

5000 Hermitage DR.

State Co11ege. PA 16801 Rat,eigh.NC 27612 George F. Trowbridge. Esq.

Marvin I. Lewis

$ haw. Pittman. Potts and 6504 Bradford Terrace Trowbridg.

Philadelphia, PA 19149 1800 M. St.,

h..

Washington, D.C.

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Atomic Safety and Licensing Board Panel Etters.PA 17319 U.S. Nuclear Regulatory Comission Washington D.C.

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$ctretary Department of Justice U.S. Nuclear Regulatory Comission Strawberry Square 14th Flour ATT4: Chief. Docketing & Service Branch Harrisburg. PA 17127 Washington, D.C.

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Mr. Larry HoChendoner

. Board of Supervisors Dauphin County Conselssioner Londonderry Township P.O. Boa 1295 Rr0 #1 Geyers Churce ad.

Harrisburg.*PA 17108 1295 Middleto-n. PA 17057 Fred Rice. Chairperson Robert L. Knupp. [sgaire Dauphin County Board of Consissioners Assistant Solicitor Dauphin County Courthouse Knupp and Andrews Front and Market Streets P.O. Boa P Harrisburg, PA 17101 407 N. Front St.

Harrisburg PA D108 Dauphin County Office of Emergency

" Preparedness John Levin. (squire Court House. Room 7 Pennsylvania PubifC Utilities Com.

Front & Market Streets P.O. Box 3265 Harrisburg PA 17101 Harrisburg PA 17120 U.S. Environmental Protection Agency Region 111 Office ATTN: EIS Coordinator Curtis 6u11 ding (51sth Floor) 6th & Walnut Streets Mr. Edwin cintner Philadelphia. PA 19106 (accutive rice President Thomas M. Gerusky. Director General Pubile Utilities Nuclear Corp.

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