ML20137B440

Forwards Justification for Conclusion That Magnitude of Penalty for Pumped Injection Could Be Reduced from 0.8 Psid to 0.15 Psid.Change Incorporated Into LOCA Models & Will Be Used for Cycle 18 Reload Licensing Submittal

ML20137B440
Person / Time
Site:	Yankee Rowe
Issue date:	08/16/1985
From:	Papanic G YANKEE ATOMIC ELECTRIC CO.
To:	Zwolinski J Office of Nuclear Reactor Regulation
References
FYR-85-88, NUDOCS 8508220009
Download: ML20137B440 (11)

Text

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Tc'=pho"e (6 ") * ' " '00 YANKEE ATOMIC ELECTRIC COMPANY TWX 710-380-7619

^*

1671 Worcester Road. Framingham, Massachusetts 01701 2.C.2.1 8 j m: } FYR 85-88

. i e , J K 1:p August 16, 1985 United States Nuclear Regulatory Commission Washington, DC 20555 Attention: Mr. John A. Zwolinski, Chief Operating Reactors Branch No. 5 Divicion of Licensing

References:

(a) License No. DPR-3 (Docket No. 50-29)

Subject:

LOCA Injection AP Penalty

Dear Sir:

During our meeting of August 8,1985, Yankee presented information on the Injection AP Penalty as it is applied to Yankee's LOCA analyses. Our conclusion was that the magnitude of the penalty for pumped injection could be reduced from 0.8 psid to 0.15 psid as had been generically approved for Exxon LOCA models in 1979. The attachment provides further justification for our conclusion.

This change has been incorporated into the Yankee LOCA models and will be used for the Cycle 18 reload licensing submittal, which will be sent to you in September. Based on our discussions on August 8, 1985, we would appreciate your review and approval of this submittal on an expedited basis.

Very truly yours t

George, ic, r.

Senior Project Engineer Licensing CP/tn 0

0500220009 050016 h0 PDR ADOCK 05000029 P PDR \

ATTACHMENT Steam-Emergency Core Coolina (ECC) Water Interaction Model INTRODUCTION Appendix X to 10CFR50 Requirement I.D.4 directs that the thermal-hydraulic interaction between steam and all emergency core cooling water shall be taken into account in calculating the core reflooding rates. This requirement was met for our currently approved ECCS model by the introduction of a frictional pressure loss penalty @P penalty). Experimental data are available that show that the AP penalty used in our currently licensed model is overly conservative. Information is provided in the following sections to justify the replacement of the currently approvedAP penalty with aAP penalty which {

is more representative of the steam-ECC water interaction phenomenon expected during LOCA conditions.

Currently Licensed Model l

The AP penalty model used in our current licensing calculations is described l in Reference 1. TheAP penalty is a function of the angle of injection and whether ECC flow is delivered from the accumulators or ECC pumps. Table 1 provides theA P penalty for various angles of injection. Yankee has a 900 angle of injection and in accordance with Table 1 utilizes a AP penalty of 1.8 psid during accumulator flow and 0.8 psid during ECC pump flow.

Proposed Model l l

Since the AP penalty model described in Reference 1 was ap' proved, tests have (

been performed by EPRI to examine the effects of steam water interaction in  !

PWR cold legs. These tests were performed with 1/14 and 1/3 scale geometries j and are described in References 2 and 3 respectively. '

l Test section geometry and pressure tap locations for the 1/14 scale test is I provided in Figure 1. The cold leg was simulated with a 2" pipe. The safety j

injection pipe used a rebored 20 diameter length 3/4" SS of 0.636" ID.

Various interchange.ble spool pieces were used to obtain data with 450, 600 and 900 inject'on nozzles.

Test parameters and their ranges are described in Table 2. Relevant information on the test are provided in tabular form in the report. As seen l in Figure 1, AP across the cold leg is given as: '

APcold leg a DP10 - DPg.

includes the conventional frictional loss in the pipe as well as APeold the impaclek of the ECC injection on the cold les pressure drop. Appendix D of the report provides a scheme to estimate the frictional pressure drop in the cold leg.

A test configuration similar to that of Figure 1 was used in 1/3 scale tests as well. The cold leg was simulated with a 10.4" ID pipo. The injection line used a 3.325" ID pipe. 450 and 900 injection nozzles were utilized. Test parameters and their ranges are described in Table 3. Relevant information on the test are provided in tabular form in the report. The pressure drop across

the cold leg is given by DP o.l Similar to the 1/14 scaib d,to, DP lo  ;

includes the conventional pressure loss in the pipe along with the impact of '

the ECC injection on the cold les pressure drop.

Reflood analysis performed for the Yankee plant calculates the cold les pipe friction as a separate calculation. Therefore, the injection AP penalty accounts for the impact of the ICC injection on the cold les pressure drop.

To obtain the magnitude of the injectionAP penalty from the above tests, it is appropriate to remove the experimental pipe friction from the total pressure drop across the cold les pipe. Exxon Nuclear Company has calculated .

the injection AP by appropriately removing the pipe friction losses (Reference 4). Their results are shown in Figure 2 where injection AP for all pumped ECC data is reported as a function of the steam dynamic head at inlet i

to the cold les pipe.

The mean of the data shown in Figure 2 is a pressure loss of -0.06. This -

indicates that the ECC injection condenses the core steam and instead of i acting as a hindrance to the core steam venting, it helps the process. The i results show thatAP penalty can be bounded by 0.15 psid pressure. Only one point out of 131 was above the 0.15 psid bound, and this did not replicate; the duplicate run for the point had a pressure loss of 0.06 paid.

Anoticability of EPRI Results to the Yankee Plant b i

The following values are calculated for the Yankee plant during reflood conditions:

Core Pressure approximately 32 psia steam Momentum approximately 0.1 psi l ECC ?.njection Flow Velocity approximately 45 ft/sec BCC Water Temperature approximately 1350F  !

I All of the above parameters except the NCC injection flow velocity are within I range of the test conditions. The ICC injection flow velocity was varied between 1-16 ft/see in the test as opposed to 45 ft/sec expected in Yankee.  !

References 2 and 3 were reviewed to ast.ess the impact of the higher injection f velocity on injection AP penalty.

The injection-water flow rate effect on cold les pressure drop was considered' in Reference 3. As shown in Figure 3, no injection velocity effect is noticed if all the data points are considered. However, at a steam momentum value of 0.2, the cold les AP is lower for higher injection velocities.

Reference 3 also documents an effort which was aimed at developing a two-phase slip model based on the experimental data to improve the prediction of cold  !

les pressure drops. Figure 4 shows the predicted cold les AP for injection  ;

velocities of 4, 8 and 12 ft/sec. The predicted AP is lower for higher

~

injection rates which indicates that the injection velocity for the Yankee  ;

plant will be bounded by the test AP results.  ;

I since a higherAP penalty yields conservative flooding rate, use of a bounding value of 0.15 in our calculations is proposed.

I

SUMARY It is proposed that the current AP penalty of 0.8 psid during pumped ECCS flow be replaced byAP penalty of 0.15 paid af ter the accumulator has been calculated to be empty. The use of the proposedAP penalty during pumped ICC injection is based on applicable experimental data and is, therefore, in compliance with Appendix K Requirement I.D.4.

REFERENCES

1. XN-75-41, Supplement 5 Revision 1 " Exxon Nuclear Company WREM-Based Generic PWR ECCS Evaluation Model," October 3, 1975.

2. " Mixing of Emergency Core Cooling Water With Steam: 1/14 Scale Testing Phase," EPRI-294-2, Key Phase Report, January 1975.

3. " Mixing of Emergency Core Cooling Water with Steam: 1/3 Scale Test and Summary," EPRI-294-2, Final Report, June 1975.

4. XN-NF-78-30, " Exxon Nuclear Company WREM-Based Generic PWR ECCS Evaluation Model Update ENC-WNEM-ITA," May 1979.

i i

IAEleI 1 In.loction Section Pressure Loss Differential Pressure Anale of Iniection Durina Accumulator Injection Durina Pump In.iection 908 1.8 0.8 758 1.5 0.35 608 0.4 0.35 45' O.6 0.30 i

(

i

TABLE 2 Test Parameters and Ranmes for Reflood Tests l

Reference Test Parameter Test Ranae Condition Cold Les Pressure (psis) 20, 40, 60 60 Injection Water Velocity (ft/sec) a) Accumulator Range 40, 70 70

! b) SIS Range 4, 8, 12 8 I

l i

TABLE 3 Parameters and Ranges for Reflood - SIS and Post-Reflood Tests Parameter Range Cold Les Pressure (psia) 22, 50 l Injection Water Velocity (ft/sec) 1, 16 Injection Water Temperature (OF)- 80, 120, 150 Injection Angle (deg) 90, 45 Steam Temperature (DF) SAT, 500 Steam Flow (lbm/sec) 1.4, 3.0, 6.1 l

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