ML20100A894

Proposed Tech Spec Defining Allowable Power Levels for RCS Flow Rates Less than 100% of Thermal Design Flow

ML20100A894
Person / Time
Site:	Summer
Issue date:	11/29/1984
From:	SOUTH CAROLINA ELECTRIC & GAS CO.
To:
Shared Package
ML20100A886	List: ML20100A883 ML20100A894
References
NUDOCS 8412040122
Download: ML20100A894 (6)

Text

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a NOTE: When operating in Region III, the restricted power levels shall be considered to be 100% of Rated Thermal Power (RTF) for Tigure 2.1-1.

Figure 3.2 3 RCS FLOW RATE VERSUS R SUf1MER - UNIT 1 3/4 2-10 8412040122 841129 PDR ADOCK 05000395 P

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Figure 2.11 Reactor Core Safety Limit Three Loops in Operation When operating in Region III of Technical Specificial 3.2.3

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(Figure 3.2-3), the restricted power level must be considered 100% RTP for this figure.

i SUMMER - UNIT 1 2-2

y ATTACHMENT 2 RCS FLOW RATE LESS THAN THERMAL' DESIGN (TD) FLOW Current Technical Specification 3.2.3, Figure 3.2-3 limits operation to less than 5% of Rated _ Thermal Power (RTP)should measured RCS Flow be less than the TD; flow used in the plant safety analyses.

This Technical Specification does not recognize the possibility of a' long term reduction in flow, nor the various trade-offs allowed by the relationships between flow, departure from nucleate boiling (DNB), 'and core power.

i These trade-offs can be used to justify., continued operation at some reduced maximum allowed power if_the measured RCS flow is less than the TD flow.

It is widely recognized that the relationships between core power,_ flow, and DNB are f

h Flow 14 (Eq. 1)

=

2) DNB 1%

A dPower 1%

(Eq. 2)

=

d DNB 1.8%

Thus the relationship between Power and Flow ist c) Power 1%

(Eq. 3)

=

dFlow 1.8%

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- ATTACEMENT 2 (cont' d)

.Page #2 N

Based on a conservative assumption that the measured RCS flow will be-no lower than 954.of TD flow, it is requested that a region of acceptable operation be added to Figure 3.2.3 for:

95% TD. Flow 1-RCS Flow $ 1004 TD Flow Considering the relationship given by Equation 3, it is

[p' recommended that the maximum power level for this region be P

reduced by-24 for each 14 reduction in measured flow below TD flow.

This conservative restriction of core power is the equivalent of-an RCS flow-increase ranging from approximately ke 2.6% -N13.0% in terms of DNB margin for flow deficits up to St.

Operation of the plant in this region within the specified power restriction does not result in increased Tavg, thus there

-is nu temperature impact on the DNB margin.

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. s The Technical Specifications and accident analyses -results have

$3 been evaluated to determine the impact of operating within the 7

definedsnew region of Figure 3.2-3 with the imposed i

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.y restrictions.

In all cases, sufficient margin exists to allow I

continu.ed' plant operations.

No Technical Specification limits require modification, including core limits, OT A T, OP A T, and Power Range. Neutron Flux High setpoints.

.Theebrolimitsremainthesameduetotheincreasedmarginto DNB afforded by the power reduction and interpretation that i

they will be valid for the restricted power levels.

This l'

implies that under these conditions the restricted power level should,be considered to be 100% of Rated Thermal. Power (RTP)

[

for Figure 2.1-1.

With this restriction applied to the Safety 1

limits, there,is no change in the core limits thus the OTA T and OP A T trip setpoints remain unchanged.

Utilizing the latest Westinghouse data, the uncertainty in the s

instrumentation for the Power Range Neutron Flux High trip function is 4.7% span (or.5.7% RTP).

With.a~ normal assumption I

of reactor trip at 109%.RTP, the uncertainty analysis verifies

.that a trip will take place at 109% RTP plus 5.7% uncertainty or 114.7% RTP.

A 5% reduction in RCS flow requires a trip at

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115.2% RTP.

Therefore, adequate margin exists in the j

instrumentation such that no' change in the nominal setpoint is

'necessary.

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ATTACHMENT 2 (cont' d)

Page #3 l

If the measured RCS flow is equal to or greater than TD flow, operation will be'in the acceptable region of the present Figure 3.2-3 and the requirements of this specification will remain unchanged.

The addition of the new region to Figure 3.2-3 is only requested to preclude a needless. reduction,to 5%

RTP should the measured RCS flow be less than TD flow.

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ATTACHMENT 3 SIGNIFICANT HAZARDS CONSIDERATION The proposed amendment to the Technical Specifications does not involve a significant hazards consideraton for 1the-following reasons:

No significant increase in the probability or consequences of an accident previously evaluated is involved because the probability of an accident does not change and sufficient margin for plant operations remains to prevent a significant increase in acci6ent consequences.

The possibility of a new or dif ferent kind of accident f rom any previously evaluated is not created because the plant systems and physical design remain the same.

No significant reduction in a margin of safety is involved because the 2% power reduction for every 1% flow reduction ensures a sufficient margin of safety remains.

_. -.. _ _. _,. _ ~

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