ML18082B193

Forwards Supplemental ECCS Calculations in Response to NRC 800829 Ltr Re NUREG-0630

ML18082B193
Person / Time
Site:	Salem
Issue date:	09/05/1980
From:	MITTL R L Public Service Enterprise Group
To:	MIRAGLIA F J Office of Nuclear Reactor Regulation
References
NUDOCS 8009180465
Download: ML18082B193 (5)

Text

I Public Service Electric and Gas Company 80 Park Place Newark, N.J. 07101 Phone 201/430-7000 September 1980 Director of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Attention:

Mr. Frank J. Miraglia, Chief Licensing Branch 3 Division of Licensing Gentlemen:

CLADDING SWELLING AND RUPTURE CALCULATIONS NO. 2 UNIT SALEM NUCLEAR GENERATING STATION DOCKET NO. 50-311 PSE&G hereby submits, in the enclosure to this letter, the supplemental ECCS calculations related to "Cladding Swelling and Rupture Models for LOCA as requested in your letter of August 29, 1980. Should you have any questions in this regard, do not hesi-tate of contact us. CC: Mr. Leif Norrholm Salem Resident Inspector C02 The Energy People soo91ao 11c6 R. L. Mittl General Manager -Licensing and Environment Engineering and Construction 1// 95-0942 I " . :... * . .. e ATTACHMENT l A. Evaluation of the potential impact of using fuel rod models sented in draft NUREG-0630 on the Loss of Coolant Accident (LOCA) analysis for Salem Units 1 and 2. This evaluation is based on the limiting break LOCA analysis fied as follows: BREAK TYPE -DOUBLE ENDED COLD LEG' GUILLOTINE BREAK DISCHARGE COEFFICIENT

0.8 WESTINGHOUSE

ECCS EVALUATION MODEL VERSION FEBRUAR 1978 CORE PEAKING FACTOR 2.32 HOT ROD MAXIMUM TEMPERATURE CALCULATED FOR THE BURST REGION OF THE CLAD -2130°F = PCT 8 ELEVATION

-6.0 Feet HOT ROD MAXIMUM TEMPERATURE CALCULATED FOR A NON-RUPTURED REGION OF THE CLAD -

= PCTN -ELEVATION

-7.5 Feet CLAD STRAIN DURING SLOWDOWN AT THIS ELEVATION

3.3 Percent

MAXIMUM CLAD STRAIN AT THIS ELEVATION

-6.2 Percent Maximum for this node occurs when the core reflood rate is greater than 1.0 inch per second and reflood heat transfer is based on the flecht calculation.

AVERAGE HOT ASSEMBLY ROD BURST ELEVATION

-6.0 Feet HOT ASSEMBLY BLOCKAGE CALCULATED

-45 Percent 1 . BURST NODE The maximum potential impact on the ruptured clad node is expressed in letter NS-TMA-2174 in terms of the change in the peaking factor limit (FQ) required to maintain a peak clad temperature (PCT) of 2200°F and in terms of a change in PCT at a constant FQ. Since the clad-water reaction rate increases significantly at temperatures above 2200.°F, dividual effects (such as due to changes in several fuel rod models) indicated here may not accurately apply over large ranges, but a simultaneous change in FQ which causes the PCT to remain in the neighborhood of 2200.°F justifies use cf this evaluation procedure.

From NS-TMA-2174:

For the Burst Node of the clad: 0.01 AFQ 150°F BURST NODE APCT Use of the NRC burst model could require an FQ reduction of 0.015 The maximum estimated impact of using the NRC strain model is a required FQ reduction of 0.03. Therefore, the maximum penalty for the Hot Rod burst node is: APCT 1 = (.015 + .03) (l50°F/.Ol)

= 675°F Margin to the 2200°F limit is: APCT 2 = 2200.°F -PCT 8 = 70°F The FQ reduction is required to maintain the 2200°F clad ture limit is. AFQ 8 = (APCT 1 -APCT ) (.Ol AFQ) 2 l 50°F = (675 -70) co1) 150 = .04 (but not less than zero). 2. NON-BURST NODE The maximum temperature calculated for a non-burst section of clad typically occurs at an elevation above the core mid-plane during the core reflood phase of the LOCA transient.

The tial impact on that maximum clad temperature of using the NRC fuel rod models can be estimated by examining two aspects of the analyses.

The first aspect is the change in pellet-clad gap conductance resulting from a difference in clad strain at the non-burst maximum clad temperature node elevation.

Note that clad strain all along the fuel rod stops after clad burst occurs and use of a different clad burst model can change the time at which burst is calculated.

Three sets of LOCA analysis results were studied to establish an acceptable sensitivity to apply generically in this evaluation.

The possible PCT increase resulting from a change in strain (in the Hot Rod) is +20.°F per percent decrease in strain at the maximum clad temperature locations.

Since the clad strain calculated during the reactor coolant system blowdown phase of the accident is not changed by the use of NRC fuel rod models, the maximum decrease in clad strain that must be considered here is the difference bet\ .. !een the 11 maximum clad strain 11 and the 11 clad strain during blowdown 11 indicated above.

{-. '.......... Therefore:

t,PCT 3 20°F = C.Ol strain) (MAX STRAIN -SLOWDOWN STRAIN) = ( 20) (.062 -.033) . 01 = 58 The second aspect of the analysis that can increase PCT is the flow blockage calculated.

Since the greatest value of blockage indicated by the NRC blockage model is 75 percent, the maximum PCT increase can be estimated by assuming that the current level of blockage in the analysis (indicated above) is raised to 75 percent and then applying an appropriate sensitivity formula shown in NS-TMA-2174.

Therefore, t,PCT 4 = l.25°F (50 -PERCENT CURRENT BLOCKAGE)

+ 2.36°F (75-50) = 1.25 (50 -45) + 2.36 (75-50) = 65°F If PCTN occurs when the core reflood rate is greater than 1.0 inch per second t,PCT 4 = 0. The total potential PCT increase for the non-burst node is then Margin to the 2200°F limit is = 2200°F -PCTN The FQ reduction required to maintain this 2200°F clad perature limit is (from NS-TMA-2174) ) t,FQN = -0. 14 but not less than zero. = 0 The peaking factor reduction required to maintain the 2200°F clad temperature limit is therefore the greater of t,FQ 8 and ACn ACn -

VI'

-*-*

,,.. -B. The effect on LOCA analysis results of using improved analytical and modeling techniques (which are currently approved for use in the Upper Head Injection plant LOCA analyses) in the reactor ant system blowdown calculation (SATAN computer code) has been via an analysis which has recently been submitted to the NRC for review. Recognizing that review of that analysis is not yet complete and that the benefits associated with those model improvements can change for other plant designs, the NRC has established a credit that is acceptable for this interim period to help offset penalties resulting from application of the NRC fuel rod models. That credit for two, three and four loop plants is an increase in the LOCA peaking factor limit of 0. 12, 0. 15 and 0.20 respectively.

C. The peaking factor limit adjustment required to justify plant operation for this interim period is determined as the appropriate credit identified in section (B) above, minus the calculated in section (A) above (but not greater than zero). FQ ADJUSTMENT=

.2 -.04 -7 0