ML19338E936

Proposed Revision to Tech Specs 3/4 2-3 for Amend 55 to License DPR-65.Authorizes Performance of Tests at Reduced RCS Inlet Temps in Order to Quantify Secondary Plant Performance Losses.Low Temp Testing Safety Review Encl

ML19338E936
Person / Time
Site:	Millstone
Issue date:	09/30/1980
From:	NORTHEAST NUCLEAR ENERGY CO.
To:
Shared Package
ML19338E933	List: B10092, Application to Amend License DPR-65 Authorizing Performance of Tests at Reduced RCS Inlet Temps in Order to Quantify Secondary Plant Performance Losses ML19338E936
References
TAC-11348, TAC-11561, TAC-12505, TAC-42846, NUDOCS 8010060330
Download: ML19338E936 (6)

Text

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lO DOCKET NO. 50-336 1

ATTACB ENT 1 l

MILLSTONE EXX.BAR POWER ' STATION,' UNIT NO. 2 LOW TEHFERATURE TESTING QUANTIFICATION OF SECOMMRY PLANT LOSSES SEPTEMBER, 1980 8 *10060 3,3 0

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Figure 3.21 Allowohle P.uk Lineer Host flues vs Burnup

• During Cycle 4, low temperature testing is authorized for periods not exceeding i

g 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> with the inlet temperature greater than or equal to 5370F and without

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s DOCKET NO. 50-336 J

1 ATTACBENT 2 l

MILLSTONE NUCLEAR POWER STATION, UNIT NO. 2 1

LOW TBIFERATURE TESTING SAFETY ANALYSIS REVIEW i

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SEPTEMBER, 1980

SAFETY ANALYSIS R VIEW The performance of the test will reduce the inlet temperature such -that the temperature will be outside of the region normally analyzed. For this reason, NNECO has determined that the test constitutes an unreviewed safety question as defined in 10CFR50.59. The following paragraphs address the effects of the short duration test and the steps that will be taken to assure conservatism with respect to the existing safety analyses.

CEA Withdrawal The parameters of concern for this transient are high power Invel following withdrawal and DNB. Since the MTC is within the analysis bouids and the i

lower temperature is a DNB credit, consequences of this transient initiated from test conditions would be within the analysis bounds.

Boron Dilution The test conditions do not exceed the bounds of this analysis.

Excess Ioad and Excess Heat Removal Due to Feedwater Malfunction Since the steam flow dn'ing the test is higher than normal, the potential mis-match between the primary and secondary system caused by these events is pro-portionally smaller than assumed in the analysis. These transients are bounded by the steam line break analysis which has been determined to be the limiting cooldown event.

Loss of Load

' Initiation of this transient from a lower temperature could possibly delay reactor trip due to the increased energy required to heat the RCS. This would not worsen the effects of this transient, but rather, just delay them.

Loss of Feedwater

'he current safety analysis conservatively assumes that the reactor trips on low steam generator water level, tithough other trip conditions would be created prior to the low steam generater water level trip.

The increased mass of the reactor coolant system (RCS) at the lower primary system temperature is offset by a smaller change in RCS specific volume during the associated temperature transient. These competing effects have been evaluated and NNECO has determined that the expansion of the RCS from a lower temperature during a loss of feedwater event is within the bounds of the current loss of feedwater analysis.

. As such, the initiation of a loss of normal feedwater from a lower RCS tempera-ture is within the bounds of current analysis. In addition, assumptions related to acderator temperature coefficients and reactor trip conditions ensure that the results of a loss of normal feedwater event, as analyzed, are conservative.

RCS Depressurization. Loss of Flow. CEA Drop. Loss of Load to One Steam Generator and Seized Rotor The DNB credit obtained by operating at a lower temperature will keep the results of these transients within the bounds of the current analysis.

Quantification of the magnitude of the DNB credit is not presented because the additional credit is conservative with respect to the docketed analyses.

The lower temperature would result in a DNBR value greater than that previously calculated.

CEA Ejection Since the RCS will be at a lower temperature, there will be less stored energy in the fuel and clad. Thus, for the same ejected CEA, the total enthalpy of the fuel and clad following ejection will be less than that shown in the current analysis.

Steam Generator Tube Rupture This accident initiated from test conditions would result in more primary coolant transport to the secondary side. This is a result of the larger pressure differential between the primary and secondary side and the greater subcooling of the primary side fluid. The analysis of this transient for Cycle 3 is applicable to Cycle 4 as the reload does not affect the event.

The Cycle 3 analysis assumed that the RCS pressure is 2300 psia, 50 psi above normal operating pressure. This conservatism of fsets the effect of reduced steam generator pressure and keeps the consequences of this event within, analysis bounds.

Steamline Break Initiation of this transient from test conditions may slightly increase the cooldown rate because the latsut heat of vaporization is higher at the lower steam generator pressure. This non-conservatism is.of fset for the following reasons. First, the increased cooldown is bounded by the no load case which starts at a lower temperature than the test. Second, the more rapid RCS pressure decrease will allow sooner delivery of boron from the HPSI pumps.

Third, the charging system which is a' qualified ECCS subsys. tem is not credited in the analysis. This system can ~begin immediate boration once the SIAS is generated. These three reasons mitigate ' concerns caused by an increased cool-down and the consequences of this event remain bounded by the current analysis.

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. LOCA An ECCS analysis performed for Calvert Cliffs 1 (Reference (1)), a sister plant to Millstone Unit No. 2 showed that a l'F reduction in inlet temperature could produce up to a 4*F increase in peak clad temperature. Although Millstone Unit No. 2 has PCT margin to accomodate such an increase, the limits of the Calvert Cliffs' analysis will be applied to Millstone during the test to provide additional conservatism. Specifically, the inlet temperature will not be allowed to drop below 537'F, a 12*F maximum decrease and the Linear Heat Rate limit will be reduced from 15.6 Kw/ft to 14.2 Kw/ft. Application of these limits during the test will' assure that the consequences of a LOCA initiated from test conditions will be ne more limiting than currently shown.

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