ML20126J267

Forwards Request for Addl Info Re Steam Condensing Mode of RHR Sys.Info Requested by 850715

ML20126J267
Person / Time
Site:	Grand Gulf
Issue date:	06/11/1985
From:	Adensam E Office of Nuclear Reactor Regulation
To:	Richard J MISSISSIPPI POWER & LIGHT CO.
References
TAC-55759, TAC-57139, TAC-57140, NUDOCS 8506180573
Download: ML20126J267 (6)

Text

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UNITED STATES RC R

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NUCL AR REGULATORY COMMISSION Local,PDR j

WASHINGTON, D. C. 20555 i

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June 11, 1985 l

iDocket No. 50-416 Mr. Jackson B. Richard Senior Vice President, Nuclear Mississippi Power & Light Company

P.O. Box 23054 Jackson, Mississippi 39205 De~ r Mr. Richard

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Subject:

Grand Gulf Unit 1 - Request for Additional Information Regarding

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Steam Condensing Mode of Residual Heat Removal (RHR) System The NRC staff is reviewing condensation oscillation loads which could result from steam discharges through the RHR relief valve discharge pipe when the RHR is. operating in the steam condensing mode.

Infonnation on these loads was prov.ided by Mississippi Power & Light Company letters dated March 23, 1983, September 7,1984 and January 24, 1985.

Additional information described in the enclosure is needed to complete our evaluation.

In order to meet the schedule for completion of this review, you are requested to provide the information identified in the enclosure by July 15, 1985.

If you cannot meet this date, you should advise the NRC Project Manager, L. L. Kintner, within 7 days of receipt of this letter.

The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten responderits; therefore, OMB clearance is' not required under P.L.96-511.

Sincerely, Elinor G. Adensam, Chief Licensing Branch No. 4 Division of Licensing

Enclosure:

As stated cc:

See next page 8506180573 850611 PDR ADOCK 05000416 P

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GRAND G LF Mr. Jackson S. Richard Senior Vice President, Nuclear Mississippi Pcwer & Light Carpany P.O. Box 23054 Jackson, Mississippi 39205 cc: Robert S. McGehee, Escuire The Honorable Willia: J. Guste, Jr.

Wise, Carter, Child, Steen and Caraway Attorney General P.O. Box 651 Departsent.of Justice Jackson, Mississippi 39205 State of Louisiana Baton Rcuge, Louisiana 70804 Nicholas S. Reynolcs, Esquire Bishop Liberman Ceak, Purcell Mr. Oliver.D. Kingsley, Jr.

and Reynolds Vice President, Nuclear Operations 1200 17th Stre at, % W.

Mississippi Power & Light Corpany Washington, D, C.

20036 P.O. Box 23054 Jackson, Mississippi 39205 Mr. Ralph T. t:lly Manager of Out: ity Assurance Middle South Services, Inc.

P.O. Box 61000 New Orleans, Louisiana 70161 Mr. Larry F. Dale, Director Nuclear Licensing and Safety Mississippi Power & Light Company P.O. Box,23054 3

. Jackson, Mississippi 39205 Mr. R. W. Jackson, Project Engineer Bechtel Power Corporation 15740 Shady Grove Road Gaithersburo, Maryland 20760 Mr. Ross C. Butcher Senior Resident Inspector U.S. Nuclear Regulatory Commission Route 2, Box 399 Port Gibson, Mississippi 39150 J. Nelson Grace, Regional Administrator

!!,S. Nuclear Regulatory Ccrmission, Aegion II 101 Marietta Street, N.W., Suite 2900 Atlanta, Georgia 30323 Mr. J. E. Cross, General Manager Grand Gulf Nuclear Station

. Mississippi Power & Light Caepany P.O. Box 756 Port Gibson, Mississippi 39150

Enclosura 5

REQUEST FOR ADDITIONAL INFORMATION

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GRAhD GULF, UNIT 1 HUMPHREY CONCERN 3.0 1.

In Reference 1 ik is stated that "The heat exchangers in the Grand Gulf Nuclear Station (GGNS) Residual Heat Removal (RHR) ' Systems are each designed with vents at two locations on the steam side of the heat i-exchanger. The vents remove non-condensible gases which could collect in-4 the heat exchangers and. degrade their performance. When the RHR system is operating in the steam condensing mode, (SCM), these vents provide a small but continuous dump of steam to the suppression pool through the j

RHR heat exchanger relief valve discharge line. The flow rate of steam 4

through the relief valve discharge line is such that chugging could occur 4

in the pool as long as the RHR system operates in this mode." Therefore, either justify why chugging need not be considered during RHR operation in the steam condensing mode or. include these chugging cycles.in the development of the load specification.

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2.

.To estimate the corresponding lateral loads on the discharge line, MP&L employs the Mark II load methodology of Reference 2.

The Mark II lateral load methodo' logy of Reference 2 was modified by the NRC staff's acceptance criteria (Reference 3) to take into account the stochastic l

nature of the chugging phenomenon. The modification consists of an f

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+ adjustment to the design load amplitude, F, according to the relation F = - r in (P)

(1) where P is the exceedence probability of the load F and d-is an empirical constant derived from the pertinent data base. A detailed description of the basis for this modification and its derivation is provided in Reference 4.

Based on our evaluation of your submittal, it does not appear that.the NRC modification has been incorporated into the load specification.

Provide an amended a'alysis'which is consistent with the staff's

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acceptance criteria or justify the apparent deviation.

3. ' Provide the number of chugs, and the basis for this value, that would be' experienced on the relief valve line during the life of the plant. Also include the value of exceedence probability described in que tion (2), if appropriate.

4.

Indicate if one or both RHR heat exchangers would be used during SCM operations.

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If the number of chugs considered for design exceeds 10, discuss how fatigue considerations have been included in the analysis.

The discussion should include not only the discharge line but any submerged structures that may experience loads due to the chugging at the vent exit.

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. It is stated insReference 1 that the lohd on the discharge line is 6.

"... uniformly distributed over the bottom 4 feet of the discharge pipe exit." This seems to be an incorrect interpretation of the Mark II methodclogy which requires that the load be ' distributed uniformly over 1 to 4 feet of the downcomer end.

Secondly, the load should be scaled to pipe diameter. An acceptable approach would be to take the ring of application as i to 2 pipe diameters.from the discharge line exit.

Indicate if you plan to confonn to this Mark II methodology or provide justification for all deviations.

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REFERENCES:

6, dated March 23, 1983, from e, M L to Dn n 2.

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" Mark II Main Vent lateral Loads," GE Report NEDE-23806-P, 3.'

Anderson,' C., " Mark II Containment Program Load Evaluation and Acceptance Criteria,"~NRC NUREG-0808, 4.

Lehner, J.,

" Selected Evaluations of Mark II LOCA Loads Performed by BNL and its Consultants for the Mark II Generic Program," BNL NUREG/CR-2191,-

March 1982.

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