ML19316A068

Forwards Request for Info Addl Re B&W Repts BAW-10055 & BAW-1388 Re Fuel Densification.Requests Response by 730413

ML19316A068
Person / Time
Site:	Oconee
Issue date:	03/14/1973
From:	Deyoung R US ATOMIC ENERGY COMMISSION (AEC)
To:	Thies A DUKE POWER CO.
References
NUDOCS 7911210638
Download: ML19316A068 (9)

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Docket Hos. 5 270/287 Af4R 14 1973 Duke Power Company

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ATTN Mr. A. C. Thies.

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Senior Vice President

,t Production and Transmission' P. O. Box 2178 charlotte, North Carolina 28201:

Gentlement-

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i-Our November 20, 1972 letter to you requested that you provide us with the necessary analysis and other relevant data for determining

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the consequences of fuel densification in the Oconee Nuclear Station, Units 1, 2 and'3.'

In response to our requests you have

, ',h provided B&W topical reports BAW-10055 and BAW-1388 which report the results of your study and analysis. Our review of these documents N W has revealed a number'of areas where additional information will be O,

required for us to complete our evaluation. These areas are listed k

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in the enclosure to this latter. Also included in the antinsure

-f are statements of our positions' on conservative assumptions to be j

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used regarding vent valve malfunction and departure from nucleate boiling..

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The bulk of the enclosed material has'aiready been discussed i-with you and therefore we anticipate you will be able to respond -

in a short period of time. In order to meet our May 1, 1973 target date for completing our review of BAW-10055 and BAU-1388 r

we will need your complete response by April 13, 1973. If fou have questions regarding the enclosure please contact us.

a Sincerely.

Original Signed by L C. DeTerng j.

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1. C. DeYoung, Assistant Director f

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for Pressurized Water Reactors

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, Request for Additional Information 7911210 ec:.See' attached page '

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JUEST FOR ADDITIONAL OCONEE 1_

, p, FUEL DENSIFICATION INFORMATION t=

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1.

Provide the values for the following physical properties and dimensions of the Oconee Unit 1-fuel pins:

a.

fuel pellet length, diameter, dished end volume and chamfer volume b.

fuel pellet density clad inside and outside diameter, initial ovality, and wall c.

thickness.

each of 'these parameters, provide the nominal value, the For

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specified value and tolerances, and the average value (as built) with V

standard deviation as well as maximum and minimum measured values.

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Describe the method of measuring that was used, the frequency of measuring samples, and the production step at which the measurements are performed in the production process of the fuel assembly. If any of these parameters is measured at different times in the production process, e.g., at the fuel pellet manufacturer and at B&W, with id entical or different measuring techniques compare the results and discuss any differences.

2.

In order to assess the B&W evaluation model, TAFY, for stored L energy, fuel pellet to clad gap conductance, and clad temperature bf a i el pin for Oconee ynit 1, a detailed description of the foll wing items is requir d.

Where applicable, equations and empirical formulations should be provided.

The amount and composition of the sorbed gases assumed to be a.

present in the fuel including the analytical methods used to describe the release rate of the sorbed gases.

i

j.

b.

The amount and content of the gas in the gap between fuel pellet and clad.

Description of the gas mixture conductivity model for the' gas c.

in the fuel pellet-clad gap, and the thermal expansion model for the fuel pellet and the clad. Discuss how the fuel cracking is treated.

(

I d.

A listing of input' values used for the TAFY code, including fuel i

and clad surface *, roughness and the fuel pin plenum volume.

A listing of the\\following parameters calculated with TAFY:

e.

\\l hot gap size, fuelt pellet diameter, conductivity of gas mixture, temperature jump distance, gap conductance and the contribution of each of the additive terms in the gap conductance.

The information should be provided as a function of linear heat generation rate (kw/f t) and as a function of fuel burnup.

f.

A comparison of TAFY calculated gap conductance (see item e) with applicabic fuel performance data.

3.

Provide additional information on the fuel cladding creep tests that were performed in the BAWTR and that form the basis for the B&W clad creep model, CRECOL, which is used to calculate the expected collapse time for the Oconee Unit 1 fuel cladding.

The requested information should include:

Physical properties of samples including yield stress., Young's a.

modulus, Poissoa's ratio and cold work.

b.

Physical dimensions of samples including meacured outside diameter, ovality, and thickness 4

-- 5

c=e t

8 Three profilometer measurements of the pellet diameter (one c.

typical and two extremes).

4.

In order to assess the B&W collapse model, CRECOL, that is used to calculate expected collapse time for the fuel pins in Oconee Unit 1, the following additional information is required:

The equation used to calculate collapse ovality and a justi-a.

fication for not using the creeprate of irradiated fuel in t

t!at calculation b.

A detailed descr ption and justification for the extrapolation

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of BAWTR test data to the collapse time by use of the Larson Miller Parameter (LMP) including specific literature references to this method of extrapolation.

A justification for not including in the cladding stress analysis c.

such axial forces as caused by pellet hangup, rod interference on the grid plates, and rod bending at the spacer grids.

d.

A comparison of CRECOL calculated critical ovality and collapse time with experimental clad performance data.

A discussion of how flow induced fuel pin vibrations could e.

affect the fuel pin collapse time.

I f.

A discussion of the clad temperature used in the CRECOL cal-culation.

g.

A comparison of the B&W CRECOL code and the CRECOL code des-cribed in USAEC Report GAMD 9623, GGA,196.

The comparison should identify any changes ma,de to result insthe present B&W version.

I I

o-o.

4 3.

In order to perform an independent staff evaluation of the clad integrity for Oconee Unit 1, the following information is requested:

Detailed discussion of the 0.9 value for the usage factor and a.

of the damage catagories included in the analysis, b.

Collapse time calculated with CRECOL with'a comparison to one cycle and three cycle operating times.

t I

A list of operat.ing conditions and physical properties including:

c.

't maximum *. operating time

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maximum external fuel pin pressure

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clad temperature clad outside diameter clad thickness initial ovality yield stress vs temperature and fast flux elastic modulus vs temperature Poisson ratio vs temperature internal fuel pin pressure vs time fast flux d.

Discussion of the assumptions for the internal fuel pin pressure i

time, including the cold and hot BOL pressure with and without v

l fuel densification.

t

5-t 6.

In order to a ssess the B&W evaluation of transients and accidents, provide a complete and consistent set of design values and operating parameters for conditions with and without fuel densification.

Where applicable, appropriate information in the Final Safety Evaluation Report, FSAR, for Oconee Unit 1 should be referenced.

The information requested should include:

core wide radial power map a.

b.

radial local peak for hot assembly

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c.

axial flux shape '

d.

local flux distribufion in hot assembly

\\f mass inlet velocity. to hot assembly (with and without one vent t

e.

valve assumed open).

f.

loss coefficients for spacer grids and upper an. ;ower end fittings.

7.

Provide an analysis of the (1) loss of flow transient and (2) Locked rotor accident for Oconee Unit 1 without and with the assumption of densified fuel.

The inforniation provided should include the following:

nuclear power decay a.

,b.

core coolant flow decay i

66re inlet pressure c.

i d.

DNBR vs time

{

e.

peak clad temperature vs time f.

peak fuel centerline temperature vs time g.

average heat flux vs time l

h.

gap conductance vs time

i. clad to coolant heat transfer coefficient

8.

Provide the technical bases and supporting analyses for your conclusion that the 8.55 ft split break would remain the worst break for a loss of coolant accident within the break spectrum considering the effects of fuel densification.

For the worst break size provide curves showing:

Hot rod axial flux distribution for the steady state condition c.

f b.

Maximum clad temperature and local hot rod heat transfer coeffic.ientas5functionoftime

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Hot channel flowrate as a function of time.

c.

Provide details \\'f the assumptions and justification for 9.

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establishing the design transient 100% - 30% - 100% power as the limiting transient.

Discuss the axial xenon oscillations that are included in the design transient analysis.

10.

Discuss, in detail, and justify how the effects of fuel densification are included in the rod ejection accident analysis and compare this analysis to the one in the FSAR without fuel densification.

In particular, for full power cases, provide the initial peaking factors and their relationship to the power spike

,nodel and to design limits in the Technical Specifications for Oconee Unit 1.

Describe how the initial pellet density variation has been accounted for if other than by a 2 variation on heat flux i

and gap increase.

Provide the peak fuel temperature (average and centerline) and clad temperature as a function of time during the accident. Indicate the number of fuel rods that experience DNB and

. will fail during the course of the accident.

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11. The appropriate conservative assumptions for an assumed vent valve malfunction and the criteria for determining departure from nucleate boiling and subsequent degraded heat transfer are:

(a) Since the status of vent valves (open or closed) are not directly monitored and there is limited operating experience with these devices one vent valve should be i

assumed to malfunction in ei.ther the closed or open position '(whichever is more conservative) for srfety analyses. \\

(b) Departure fr'om nucleate boiling (DNB) and a subsequent degraded heat transfer condition should be assumed whenever a DNBR equal to or less than 1.3 is predicted.

For this purpose the use of the TEMP code and the B&W-2 correlation is acceptable.

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