ML20151H334

Forwards Revised Position Accepting Use of Exit Core Thermocouples as Alternative to Use of Hot Leg Temp Resistance Temp Detectors.Use of Thermocouples Will Comply w/10CFR50,App R

ML20151H334
Person / Time
Site:	Byron
Issue date:	03/18/1983
From:	Rubenstein L Office of Nuclear Reactor Regulation
To:	Mattson R Office of Nuclear Reactor Regulation
Shared Package
ML20151H337	List: ML20151H334 ML20151H398
References
NUDOCS 8304150458
Download: ML20151H334 (4)

Text

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UNITED STATE;(

NUCLEAR REGULATORYtOMMISSION

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MAR i s 1983 f{ o

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MEMORANDDM'FDR: Roger J. Mattson, Director W

Division of Systems Integration b FROM:

L. S. Rubenstein, Assistant Director for Core and h

Plant Systems., Division of Systems Integration k i

SUBJECT:

REVISION TO STATEMENT OF STAFF POSITION REGA RANGE FLUX, REACTOR COOLANT TEMPERATURE, AND STEAM A

GENERATOR PRESSURE INDICATION TO NEET APPENDIX By memorandum dated January 7,1983, we' documented the need for' sou flux, reactor coolant temperature, and steam generator at an alternate location (remote to the control room). pressure indication That document was licensees to obtain compliance with Appendix R. requested by DL

• Since that time, those utilities which obtained copies of our January 7,1983 memorandum, provided feedback with respect to plant specific c~orisiderations, among ture RTD's. them, the use of exit core thermocouples (ECTs) versus hot leg tempera-In addition, we have consulted with various personnel at the Chattanooga Reactor Training Center regarding the staff pos,itio_n... As a alternative to the use of hot leg temperature RTDs. result of these Enclosed is the revised staff position regarding the acceptability of ECTs.

Other changes are principally editorial in nature.

W-l f.0 Dhm Y l L. S. Rube Ltein Assistant Director l for Core and Plant Systems

' Division of Systems Integration -

Enclosure:

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Enclosure Staff Position Section III.L.1 of Appendix R to 1,0 CFR 50 yequires that alternative shutdown capability shall be able to achieve and maintain subcritical reactivity conditions in the reactor.Section III.L.2 of Appendix R to 10 CFR 50 requires provision for direct readings of the process variables necessary to perform and control the reactor shutdown function.

sourte range Among the process variables which are to be monitored are: These flux, reactor coolant temperature, and steam generator pressure.

three have been controversial so we have set forth our basis for concluding that they are necessary in order to meet Section III.L of Appendix R.

Source Range Flux Monitoring of core flux provides a direct indicati6n of the reactor shutdown condition. The monitoring.of other process

• variables would provide an inferred answer only. With regard to the fission process, changes in neutron flux provides the quickest means of assessing reactor criticality condi tions. Dilution events caused by the postulated spurious operation of valves could result in power excursion which would not be readily detected

( by interpreting the changes in other process variables (.such as reactorPer coolant temperature or pressure). '

for boron concentration is considered inadequate for determining "real-time" boron requirements. Additionally, should the operators fail to detect a loss of negative reactivity in a timely manner, the capability to prevent ,

a criticality is indeterminate since components needed for such actions may Thus, the provision for post fire source range be unavailable due to fire.

flux monitoring is necessary to meet Section III.L.2 of Appendix R.

Rsactor Coolant Temperatures .

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The reactor coolant temperatures, in conjunction with tNe reactor coolant

' system (RCS) pressure, a,re essential parameters necessar) for-plani Th'e coold and control and, hence, conformance with Section III.L.2 of Appendix R.

plant control el.ements which rely on accurate reactor cool Concerns.

In the natural circulation mode of operation, the (1) Natural Circulation:

hot leg temperature, cold leg temperature and the difference between the hot leg and cold leg temperatures, (TH - Tc), provide indication by which In order to verify natural circulation conditions can be determined.

l that natural circulation has been established, normal plant It has procedures been require the operator to use cold leg temperature Tc.

suggested that the saturation temperature correspondingThe to the staffsecondary side steam generator pressure Tsat, will approximate TC .

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aElinoEledges that suc 'a condition can exist if natural circulation is Cooldown is usually occurring; however, the converse cannot be assumed.

- achieved by the operator contrnlling the steam generater pressure and auxiliary feedwater flow to the steam generators. Due to the inherent lag in response between the secondary and primary side, T,. cannot be inferred from T .

Natural circulation is normally detePsined by

- T.sgservin tnat T are constant or decreasing, knowing T andbymobtohing(Tu-T c. Sinc $andTnonnak control room procedures require the use of Tr in conYirsing natural circulation, emergency procedures should not deviate from this practice. Thus the provision for post fire cold leg temperature. Te wide range indication is necessary for meeting

~ Section III.L.2 of Appendix R. .

(2) Upper Vessel Voiding: (Deleted) - . ,

.Subcooling: The bulk fluid temperature TH provides a reliable indication (3) of the degree of RCS subcooling when used in conjunction with the RCS pressure. Tu is also used as a means of verifyi.ng natural circulation.

It has been Nuggested that exit core thermocouples (ECTs) provide temperature indications equivalent to T . ECT readings provide local temperature conditions above the core, $nd can give representative equivalent T H provided the individual ECTs are judiciously selected, since ECT readings are dependent not only upon radial positioning, but l-also local flow rates past the ECTs. Thus, the provision for wide range ECTs is an acceptable alternate to wide range TuloopeRTDs for meeting Section III.L.2 of Appendix R provided that the licensee demonstrates that their selection of ECTs will result in averaged -

temperature readings representative of Ty. Also, the licensees should demonstrate that under-condition.s where ,the, reacto,r vessel upper head.. . .. -

void is expanding thus, bringing higher.. temperature.. fluid .into the nutist----

plenum and hot legs, the~ ECTs give a conservative indication of outlet plenum temperature. in con-(4) Pressurized Thermal Shock and Appendix G' Considerations: T -

~ junction with the RCS pressure, provides a direct indicatiob,of the plant condition relative to the plant's pressure / temperature limits as it pertains.to the Pressurized / Thermal Shock considerations and the i

low temperature overpressure protection as outlined in Appendix G of .

10 CFR 50. Due to the collective effect of the stedm generator conw ditions (i.e., feedwater flow and steam generator pressure) on the primary. coolant temperatures, and the inherent lag beteen the secondary and primary' sides conditions especially during transient conditions, T may not be accurately inferred from the secondary side steam chnditions.

Steam' Generator Pressure During non-power modes of operation, " control" is effected principally by adjusting secondary system parameters (the parameter usually specified by

' procedures is pressure) to compensate 'for variances in primary system e

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.. performance. Maintenance of level in the steam generators may not be sufficient in itself to control the heat removal rate and thereby maintain a " hot standby" or " hot shutdown" mode, or translate from " hot shutdown" mode to " cold shutdown" mode. Improper pressure control may cause an imbalance in heateramoval whi.ch .could result in excessive depressurization, the result of which could be generation of an undesired bubble in the primary system (e.g., upper head for all PWRs or candy cane for B&W designs) or rapid,cooldown and potential for violation of vessel pressure / temperature limits. For the monitoring of secondary system heat removal, two secondary system parameters should be known: level (inventory), and pressure. Thus, provisions for post fire steam generator pressure and level monitoring are -

.. necessary. .for meeting Section III.L.2 of Appendix R. ,

Instrumentation GuidelinesSection III.L.6 requires that, " Shutdown systems installed to ensure post-fire shutdown capability need not be designed to meet seismic Category I criteria, single; failure criteria ' or other design basis accident criteria, except where,for required for. other reasons', e.g., because of. interface with or impact on existing safety systems, or because of adve'rie? valve actions due to fire damage." Thus the monitors for the above listed para-

-- meters need not be " safety grade" in order to meet the requirements of Appendix R. 2.

Section III.G.3 requires that, " Alternate or dedicated shutdown capability '

and its associated circuits, independent of cables, systems or components i

in the area, room or zone under consideration, shall be provided." For a postulated fire, an electrically independent monitoring capability for the

' above listed parameters should be provided outside the control room.

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Based on the above, the revised list cf instrumentation needed for PWRs is:

i l a) pressurizer, pressure and., level, b) reactor coolant' hot leg temperature or exit core thermocouples,

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. cold leg temperature, c) steam generator pressure and level (wide range); ; 1 .- ..

d) source range flux monitor, e) diagnostic instrumentation for shutdown' systems, and f) level indication for all tanks used (e.g., CST).

The instrumentation needed for BWRs is unchanged.

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TA SCHEDULED WBS PROJECT NUMBER COMPLETION STATUS 16.10.001 File Merging and Data Entry Enhancemen ts 83-24 12-28-83 We are on schedule wi th the Analysis 16.12.001 for Technology Transfer Division ph ase. In the process of establishing routines to readily identify the names I. Merge the Reader Service Card file in the RSC file to the names in the (RPC/RSC) and the NASA Tech Brief Tech Brief Malling List.

Malling List flie (RPC/TTD) into a single file (RPC/TU).

2. Implement changes to the data entry program for the new combined file RPC/TU similar to those detailed in Facility report " Improved Data Entry for Technology Transfer Division."

Februa ry 19. 1982.

, 16.11.001 UTS-400 Enhancements 83-11 COMPLETED All design and development work on these 3 enhancements has been completed.

L, This task will provide the design and o developpent of sof tware modifications for both RECON and UTS-400 to enhance the previously designed STACKING.

STORING. QUERY ALTER / CREATE and SELECT FORMAT FOUR commands.

16.13.001 AI AA Data Ent ry Support 81-2 UNKNOWN This system is production status. The use of the system is being delayed pending a This task will provide programming meeting wi th AI AA pe rsonnel.

support for entry of AIAA data into the IAA file through N0lPS. This support will include any effort incident to the procurement of the necessary equipment for AIAA.

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