ML17037B543

Letter Regarding Responses to June 9, 1976 NRC Question

ML17037B543
Person / Time
Site:	Nine Mile Point
Issue date:	08/03/1976
From:	Schneider R Niagara Mohawk Power Corp
To:	Lear G Office of Nuclear Reactor Regulation
References
Download: ML17037B543 (12)

Text

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50-220 FI' NVMOEB NRC DISTRIBUTION FOB,P, T GO DOCICET MATERIAL FROM: DATE OF DOCUMENT

'l 8/3/76 Mr. George 'Lear Niagara Mohawk Power Corp.

Syracuse, New York DATL= RECEIVE D ABETTER Mr, Rudolph R. Schneider 8/6/76 ONOTOB IZED PROP INPUT FORM NUMBER OF COPIES RECEIVED PjjjDB IOINAL PKVNCLASSIF I ED Q COP V One signed DESCRIPTION ENCLOSU RE Ltr, w/attached,;,re their 5/1'9/76 ltr, and our 6/9/76 ltr. ~ ~ .furnishing additional in information concerning Assembly Averaged Relationship .Tech Spec,- 'ower-Void ACKNOWLEDGED (5-P)'O

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PLANT NAME:

Nine Mile Point gi NOT RziMOVZ .

SAFETY. FOR ACTION/INFORMATION ASSXGNED AD: ASSI NED DE BRANCH CHIEF: Lear i

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NIAGARA MOHAWK POWER CORPORATION NIAGARA 300

~ MOHAWK ERIE BOULEVARD WEST SYRACUSE, H.Y. l3202 August 3, 1976 Director of Nuclear Reactor Regulation Attn: Mr. George Lear, Chief Operating Reactors Branch III3 U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Re: Nine Mile Point Unit 1 Docket No. 50-220 DPR-63

Dear Mr. Lear:

Our letter of'ay 19, 1976 transmitted proposed changes to the Assembly Averaged Power-Void Relationship Technical Specification for Nine Mile Point Unit 1. 1'our letter of June 9, 1976 requested additional information regarding that'roposed change. The attached responses address the questions contained in your letter.

Sincerely, NIAGARA MOHAWK POWER CORPORATION Rudolph . Schnei der, peg(P~o po Vice President Electric Operations S. gang P Attachment

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c RESPOND. S TO JUNE 9, l976 NRC QUESTION NINE HILE POINT UNIT 1 Docket No. 50-220 DPR-63 RecCuest Provide a quanti tative explanation of'ow exposure dependent "B" values are calculated. Include examples which show how different values of "B" were calculated for two different exposures of the same fuel. The examples should show (1) the relationships (equations) assumed, and (2) the source and numerical values of all terms in the relationship for:

1. maximum Average Planar Linear Heat= Generation Rate (EQPLHGR) and Average Heat Generation Rate (q) (i.e., assumed peaking factors) .

2. Dryout Time. (i.e., h,g'n'"h., flow, average density, q).

3. "B" values (i.e., void fraction, peaking factor, power).

R~es ense The duration of nucleate boiling for non-jet pump plant ECCS analyses has been determined using the correlation (Equation 1, below) described in "General Electric Compliance with 10CFR50 Appendix K-Acceptance Criteria I.C.4." That correlation shows the time to boiling transition (dryout time) is a function exclusively of liquid volume fraction and power input to the bundle. Converged HAPLHGR limits and conservative axial power distributions were assumed for the dryout time determinations.

Both HAPLHGR limits and dryout times are exposure dependent. The following development shows how "B" values are calculated.

(0 ~ 31) (Pf) (hf ) Equation 1 gt II ht = time to transition boiling, hr.

3 p = saturated liquid density, ibm/ft h

enthalpy of'aporization, BTU/ibm fg gist V (1--a)

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q = Powor generation in bundle, BTU/hr = (PF) (FCP) (ABTU)

PF = bundle radial power factor FCP ~ fractional core power relative to 1850 Hh'BTU

= average bundle output at 1850 Hft, BTU/hr V = active coolant volume, ft3

a. = void fraction Therefore ht ='0.31) (P ) (hf ) (V) (1 - a.)

Equation 2 (ABTU) (PF) (FCP)

"B" Factor = (1 i

a.)

Equation 3 ~

(PF) (FCP) t Limiting this "B" factor relatioriship will assure that local power void values will not result in dr@out times shorter than those used.

in the ECCS Analysis.

Using Equation 2:

"B" Factor = (ABTU) Qt) Equation 4 (0.31) (P f) (hffg) (V)

Assumed nominal values are:

7 ABTU = 1.1869 x 10 BTU/hr pf ~ 45.977 ibm/ft3 hffg = 641 . 36 BTU/1 bm V ~ 1.2696 ft, Znitial Core V = 1.2948 ft3 , Reloads 1, 2, 3

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V = 1.2936 ft3 , Reloads 4, 5 Substituting the above values in Equation 4 yields the "B" factor relatiori-ships for the different reloads:

"B" Factor = (1022.688) (ht) 2'ni tial Core Equation 5 "B" Factor = (1002.784) (ht) Reloads 1, 2, 3 Equa,tion 6 "B" Factor = (1003.714) (b t) Reloads 4, 5 Equation 7 The folloving examples shov hov different values of "B" vere calculated for tvo different exposures of the same fuel (Reload 3):

~Ex osure ECCS Anal sis Dr out Times HAPLHGR 5000 7fVD/T 1.48 sec 10.68 25000 HVD/T 1.59 sec 9.92 Sunsti tuting the above dryout times in Equation 6 yields:

For 5000 IWD/T:

"B" Factor = (1002.784) (ht)

"B" Factor = 1002.784lhr) (1.48 sec) 3600 sec/hr "B" Factor = 0.412 For 25000 IWD/T:

"B" Factor = (1002.784) gt)

"B" Factor = (1002.784/hr) (1.59 sec) 3600 sec/hr "B" Factor = 0.443

e~eeest:

Demonstrate how "B" values are calculated to assure conservatism when using the dryout times assumed in the ECCS analysis.

R~es see As indicated in the above response, nominal values were .used to calculate, the "B" factors. Converged HApLHGR limits and conservative axial power distributions were assumed for t'e dryout time, determinations. 'In addition, a conservative c4rrelation (G.E. compliance with 10CFR50, Appendix K criteria I.C.4:) was used which was previously approved by the Commission.

A "B" Factor Limiting Condition for Operation is not necessary to assure that actual dryout times are conservative. Dryout time is only one of many conservative inputs used to determine HAPL/EGR limits, the ultimate restriction of interest. Sensitivity analyses performed by our fuel supplier have determined that the parameters used to calculate dryout time (void fraction, axial power distributions) are conservative when compared to normal plant operation.

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