ML19317D221

Proposed Tech Spec 2.3 Deleting Loss of One Pump Trip Setpoint,Outdated Info & Setpoints Associated W/Single Loop Operation

ML19317D221
Person / Time
Site:	Oconee
Issue date:	02/16/1978
From:	DUKE POWER CO.
To:
Shared Package
ML19317D220	List: ML19317D219 ML19317D221
References
NUDOCS 7911190609
Download: ML19317D221 (7)

Text

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L 2.3 LIMITING SAFETY SYSTEM SETTINGS, PROTECTIVE INSTRUMENTATION

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' Applicability Applies to instruments monitoring reactor power, reactor power imbalance, reactor coolant system pressure, reactor coolant outlet temperature, flow, number of pumps in operation, and high reactor building pressure.

Objective To provide automatic protective action to prevent any combination of process variables from exceeding a safety limit.

Specification The reactor protective system trip setting limits and the permissible bypasses for the instrument channels shall be as stated in Table 2.3.lA-Unit 1 and 2.3-13-Unit 2 2.3-1C-Unit 3 Figure 2.3-2A-Unit 1 2.3-2B-Unit 2 2.3-2C-Unit 3 The pump monitors shall produce a reactor trip for the following conditions:

a. Loss of one pump during four-pump operation of Unit 1 (only) if power level is greater than 80% of rated power.

b. Loss of two pumps and reactor power level is greater than 55% of rated power.

c. Loss of two pumps in one reactor coolant loop and reactor power level is greater than 0.0% of rated power.

d. Loss of one or two pumps during two-pu=p operation.

Bases The reactor protective system consists of four instrument channels to monitor each of several selected plant conditions which will cause a reactor trip if any one of these conditions deviates from a pre-selected operating range to the degree that a safety limit may be reached.

The trip setting limits for protective system instru=entation are listed in Table 2.3-1A-Unit 1. The safety analysis has been based upon these protective 2.3-13-Unit 2 2.3-lC-Unit 3 system instrumentation trip setpoints plus calibration and instrumentation errors.

Nuclear Overpower A reactor trip at high power level (neutron flux) is provided to prevent damage to the fuel cladding from reactivity excursions too rapid to be detected by pressure and temperature measurements.

2.3-1 ,993g190 g

During nor=al plant op'^7 tion with all racccor coolant 'mps operating, roector trip is initiewed wh;n th] raccter powar laval rasches 105.5% of ratad powar. Adding to this tha possible variation in trip setpoints dua t,o calibration and instrument errors, the maximum actual power at which a trip would be actuated could be 112%, which is more conservative than the value used in the safety analysis. (4)

Overpower Trip Based on Flow and Imbalance The power level trip set point produced by the reactor coolant system flow is based on a power-to-flow ratio which has been established to acco=modate the most severe thermal transient considered in the design, the loss-of-coolant flow accident from high power. Analysis has demonstrated that the specified power-to-flow ratio is adequate to prevent a DN3R of less than 1.3 should a low flow condition exist due to any electrical malfunction.

The power level trip set point produced by the power-to-flow ratio provides both high power level and low flow protection in the event the reactor power level increases or the reactor coolant flow rate decreases. The power level trip set point produced by the power-to-flow ratio provides overpower DN3 pro-tection for all modes of pump operation. For every flow rate there is a =axi-

=um per=issible power level, and for every power level there is a =ini=um permissible low flow rate. Typical power level and low flow rate combinations for the pump situtations of Table 2.3-1A are as follows:

1. Trip would occur when four reactor coolant pu=ps are operating if power is 105.5% and reac:or flow rate is 100%, or flow rate is 94.8% and power level is 100%.

2. Trip would occur when three reactor coolant pu=ps are operating if power is 78.8% and reactor flow rate is 74.7% or flow rate is 71.1% and power level is 75%.

3. Trip would occur when one reactor coolant pump is operating in each loop l

(total of two pu=ps operating) if the power is 51.7% and reactor flow rate is 49.0T. or flow rate is 46.4% and the power level is 49%.

The flux-to-flow ratios account for the maximum calibration and instrument errors and the maxi =rm variation from the average value of the RC flow signal in such a manner that the reactor protective system receives a conservative indication of the RC flow.

For safety calculations the maxi =um calibration and instrumen:a: ion errors for the power level trip were used.

The power-i= balance boundaries are established in order to prevent reactor thermal limits from being exceeded. These thermal limits are either power peaking kw/ft li=1:s or DNER li=its. The reac:or pcuer i= balance (pever in l

l the top half of core =inus power in the bottom half of core) reduces the power i

level trip produced by the power-to-flow ratio such that the boundaries of Figure 2. 3-2A - Uni: I are produced. The power-to-flow ratio reduces the pcwer 2.3 Unit 2 2.3-2C - Uni: 3 2.3-2 i

Icv 21 trip cnd cssoc sd raccter power /rscctor power .mb31cnca bounderires by 1.055% fer it flow rcduction.

d Pump Monttors The pump monitors prevent the minimum core DNBR from decreasing below 1.3 by tripping the reactor due to the loss of reactor coolant pump (s). The circuitry monitoring pump operational status provides redundant trip protection for DNB by tripping the reactor on a signal diverse from that of the power-to-flow ratio. The pump monitors also restrict the power level for the number of pumps in operation. The reactor trip upon loss of one pump during 4-pump operation above 80% FP is specified for Unit 1 in order to provide a minimum of 11.2%

DNBR margin in the flux / flow trip setpoint to accommodate the possible reduc- -

tion in thermal margin due to rod bowing. For units 2 and 3, loss of one pump trip is not required because of thermal credits from excess RC flow.

Reactor Coolant System Pressure During a startup accident from low power or a slow rod withdrawal from high power, the system high pressure set point is reached before the nuclear over-power trip set point. The trip setting limit shown in Figure 2.3-1A - Unit 1 2.3-1B - Unit 2 2 3-IC - Unit 3 for high reactor coolant system pressure (2355 psig) has been established to maintain the system pressure below the safety limit (2750 psig) for any design transient. (1)

The low pressure (1800) psig and variable low pressure (11.14 T wt -4706) trip (1800) psig (11.14T -4706)

(1800) psig (ll.14T"I -4706) setpointsshowninFigure2.3-1AhavebeenestablishedtomainkafntheDNS 2.3-1B 2.3-lC ratio greater than or equal to 1 3 for those design accidents that result in a pressure reduction. (2,3)

Due to the calibration and instrumentation errors the safety analysis used a variable low reactor coolant system pressure trip value of (11.14 T -4746)

(11.14 T"* -4746) ut (11.14 T out -4746)

Coolant Outlet Temperature The high reactor coolant outlet temperature trip setting limit (619 F) shown in Figure 2.3-1A has been established to prevent excessive core coolant 2.3-1B 2 3-lC temperatures in the operating range. Due to calibration and instrumentation errors, the safety analysis used a trip set point of 620 F.

Reactor Building Pressu e The high reactor building pressure trip setting limit (4 psig) provides positive assurance that a reactor trip will occur in the unlikely event of a loss-of-coolant accident, even in the absence of a low reactor coolant system pressure trip.

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m, -3 J J Shutdown Byptss In order to provide for control rod drive tests, zero power physics testkg, and startup procedures, there is provision for bypassing certain segments

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the reactor protection system. The reactor protection system segments whicn can be bypassed are shown in Table 2.3-1A. Two conditions are imposed when 2.3-1B .

2.3-IC the bypass is used:

1. By administrative control the nuclear overpower trip set point must be reduced to a value <5.0% of rated power during reactor shutdown.

2. A high reactor coolant system pressure trip setpoint of 1720 psig is automatically imposed.

The purpose of the 1720 psig high pressure trip set point is to prevent normal operation with part of the reactor protectiori system bypassed. This high pressure trip set point is lower than the normal low pressure trip set point so that the reactor must be tripped before the bypass is initiated. The over power trip set point of <5.0% prevents any significant reactor power from being produced when performing the physics tests. Sufficient natural circulation (5) would be available to remove 5.0% of rated power if none of the reactor coolant pumps were operating.

Sinale Loop Operation Single loop operation is permitted only after the reactor has been tripped and is subject to the limitations set forth in Specification 3.LS. The RPS trip setting limits and permissible instrument channels bypasses will be confirmed prior to single loop operation.

l REFERENCES i

! (1) FSAR, Section 14.1.2.2 (2) FSAR, Section 14.1.2.7 (3) FSAR, Section 14.1.2.8 (4) FSAR, Section 14.1.2.3 (5) FSAR, Section 14.1.2.6 l

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Table 2.1-IA lini t I 4

Reart or Prate rtIwe Syntem Trlp Set _t Ing I.im_tt e One Reartor Four Reactor Ihree peartor Conlant Pump Coo l . nee t Pumps Cm lant Pnmpa Operaling In Operatlug Opcrating F.ach IAtop (operat fier, Power (operating Power (Operating Power Shutdown RPS, Segment ifM)? Rate.1) - 757. R.it ed) -49% Rated) By pa_ a n_,

1. Nurlent Power Max. 10p.5 105.5 ,

105.5 5.0(1)

(I Rated)

2. N.orlear Power lieu. Raned 1.055 timen flow I 055 times flov l.055 t imen flow Bypanned on Flow (2) and Imbalance, minug reduction minus reduc t ion minun reduction i (1 R.it e.9) d e.e to t at.a l anc e d ee to inhalance due to inhalance

1. Nuclear Power Man. Sage.1 NA 801 552 Bypenned on rump Monitorn, (2, Rated)

4. High Reartor Coolant 2155 2155 2155 1720 System Pressure, psig. Max.

5. IAtw Reactor Coolant 1800 1R00 1800 Byranned y System Freneure, pala, Min.

'I - 4706)(1) - 4 06)(I) (11.14T - 4706)(I) Bypaened g 6. Variable Im Reactor (ll.14T et (ll.14T mst C<vilant System Prennure pntg, Min.

7. Reactor Cnolant Temp. F., Max. 619 619 619 619

8. Mlph Reactor Building 4 4 4 4 Prennure, pain Max.

_ _ _____ ).

(I) T,,,, la in degreen Fahrenh*It ("F).

(2) Reactor Coolant Syst em Fl..w, I.

(1) Administratively enntroIIed relurtion met only during teartnr shestetown.

(4) Automatically net when na h.'r ner. ment s of the RPS are bypanne.t.

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Table 2.1-lh Unit 2 Reactor Protective Sya_ tem _ Trip Se,ttIng.l.iml M one Reactor Four Reactor Three Reactor Cemlant riemp CeIant Iumpn ConIant rumpg Operaeing in Operating operating Fat h loop (Operating f%wer (Operating rower (Operating Shutdown RPS Segment -1002 R.ated) -751 Rated) -491 Rated) Apae n_

l. Nuclear Power H.en. 105.5 105.5 105.5 5.0

(! Rated)

2. Nuclear Power Han. Ba ge.1 1.055 timen flow l.055 t imen flow 1.055 t imen flow Rypagned ,-

en flow (2) and Imbalance, minus reduction minus reduc t ion minue reduction (I Rated) due to imh.e l a are due to lab.e l anc e due to inhalance Nucient Power Max. Rancd p y ransed

1. NA FA 55%

l

' on rump t%uit t er s , (% Rated)

4. filph Reactor Coolant System 2155 21 % 2155 1720 Freneure, pelg, Han.

5. Iow Reactor Coolant System lH00 1H00 1R00 Rypaeged Frengure, pala, Hin.

(ll.14 7out- 4706)( I Bypeoned

6. Variable lev Beactor Coolant (11.14 Tet - 4706) (31.14 T - 4706) out System Prengure pair., Hin.

7. Reactor Coolant Temp. F., Max. 6l9 619 619 619 ft . High Reactor BullJing 4 4 4 4

, Freenure, pelg, H.ix.

(1) T la in degrees Fahrenheit ("F).

(2) Re. actor Can'ont Synt s tm Flow, I.

(1) Adelnlatratively controlled reduction net only during reactor nhutetuwn.

(4) Aestomatically set when ot her neymerit s of I the RPS ate hyp. egged.

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.t -

9 Tahic 2.1 -1 C Unit i Reactor Protective System Trip Settin6 1.5 mi t,s one Reartnr Four Reactor Three Reactor Conlant Pump Coulant Pumps Coolant Pumpg Operating in Operating Operating Earh loop (Operating Power (Operatina Power (Operating Shutdown Br5 segment _ -Im)2_ Rated! -75% Rated)_ ,-491_ Rated), _Bypase_

I. Nuclear rower M.is. 105.5 105.5 105.5 5.0 (7. Rated)

2. Muclear Power Ham. Raned 1.055 timen finw 3.055 times flow 1.055 timen flow Rypanned on Flow (2) and Inhalance, minun reduction minun reduction minun reduction (1 Rated) due to imbalanc e due to tahalance due to tahalance

1. Nuclear Power Man. Baned NA NA 55% Rypassed on Pump Monitorn, (t Rassd)

4. Illah Reactor Coolant 2355 2355 2355 1720I 'I System Pressure, palm. Ham.

5. Imv Reactor Coolant System 1R00 1800 1R00 Bypassed Freneure, pela, Min.

6. Variable low Reactor Conlant (11.14 T - 4706) (ll.14 T""- 4706)UI (11.14 ""

7 - 4706)III Bypanned System Freneure, pelg, Min.

7. Reactor Coolant Temp. F., 619 619 619 619 Ham.

R. Hiph Reattur Butiding 4 4 4 4 Preneure, pets, Mas. s Q

(1) T,,, la in degrees Fahrenheit ("F).

(2) Reactor Coolant System Flow, 2.

(1) Adelnintratively cont rolled reduct ion ner only during reactor shutdown.

(4) Automatically set when other negmenen of t he RPS are leyranned.

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