ML20112J742

Affidavit of Fr Stead Re Actions Taken to Improve Design of Wide & Narrow Range Water Level Measurement Sys & Ability to Detect Inadequate Core Cooling

ML20112J742
Person / Time
Site:	Perry
Issue date:	01/11/1985
From:	Stead F CLEVELAND ELECTRIC ILLUMINATING CO.
To:
Shared Package
ML20112J676	List: ML20112J668 ML20112J694 ML20112J726 ML20112J742 ML20112J753
References
OL, NUDOCS 8501180358
Download: ML20112J742 (7)

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4 C l ' " 5 i.ED January 11, 1985

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-UNITED STATES OF AMERICA ~ ~

NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD In the Matter of )

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THE CLEVELAND ELECTRIC ) Docket Nos. 50-440 ILLUMINATING COMPANY, ET AL. ) 50-441

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(Perry Nuclear Power Plant, )

Units 1 and 2) )

AFFIDAVIT OF FRANK R. STEAD STATE OF OHIO )

) ss COUNTY OF LAKE )

Frank R. Stead, being duly sworn, deposes and says as fol-lows:

1. My name is Frank R. Stead. I am employed by The Cleveland Electric Illuminating Company as Manager of Nuclear Engineering. My business address is Perry Nuclear Power Plant, 10 Center Road, Perry, Ohio 44081. I have responsibility for the system design of all nuclear systems of the Perry Nuclear Power Plant, including the reactor vessel water level measure-ment system. A statement of my professional qualifications is attached hereto as Exhibit A. I have personal knowledge of the matters set forth herein and believe them to be true and cor-rect.

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2. Tbepurposeofthisaffidavitis.todescribetheac-tions taken at Perry Nuclear Power Plant ("PNPP") to improve

.the design of PNPP's wide and narrow range water level measure-ment systems and to enhance PNPP's ability to detect inadequate core cooling ("ICC"). PNPP i s water level measurement systems are described fully in 11 7-9 of Charles Johnson's affidavit. ,

These actions have been taken in response to the recommenda-tions of two reports prepared for the Boiling Water Reactor

("BWR") Owners Group; Review of BWR Reactor < Vessel Water Level Measurement Systems, July 1982 (SLI-0211), and Inadequate Core Cooling Detection in Boiling Water Reactors, November, 1982 (SLI-8218). These reports were prepared in response to agree-ments between the BWR Owners Group and the NRC Staff, first, that a general study of ICC detection In BWRs was needed and second, that although water le' vel measurement systems used in BWRs such as PNPP have performed with, cut any serious difficul-ties, a critical review might identify improvements which would enhance the systems' reliability and accuracy. SLI-8211 iden-T tified a number of ways in which the water level measurement i

systems in BWRs such as PNPP might be modified to achieve greater reliability. SLI-8218 contains a general analysis of ICC detection in BWRs.

3. The recommendations of SLI-8211 which are applicable to PNPP deal with the effects of high drywell temperature. Ex-cessively high drywell temperatures can be caused by loss of drywell coolers and/or a loss of coolant accident ("LOCA").

When such temperatures exist and the reactor vessel is de-2 pressurized, " flashing" and subsequent boiloff of the water in the reference legs can occur. Level instrumentation readings would be erroneously high if this happened. The amount of error indicated by the water level measurement system could be as much as 16 inches per foot of reference leg vertical drop in the drywell, once flashing has occurred. Prior to modifica-tion, PNPP's reference legs had vertical drops (from the condensing chamber to the drywell penetration) of six feet ten inches to seven feet ten inches. This meant that errors in measured water level of as much as 9 feet 1 inch to 10 feet 5 inches could have occurred after flashing. To eliminate this .

problem, SLI-8211 recommended that the vertical drop of the reference legs in the drywell be minimized.

4. SLI-8211 also noted that excessively high drywell temperatures can cause density changes in the water in the drywell piping. These density changes can cause the level in-strumentation to be off by as much as 12% of the difference in vertical drop between the reference and variable leg piping in the drywell. PNPP's piping, as it existed at the time the l

analysis in SLI-8211 was performed, had vertical drops in the variable legs (from the vessel nozzle to the drywell penetra-tion) of six inches to three feet 11 inches. The difference in vertical drop between the variable legs and the reference legs could have caused erroneous level indications of as much as 9 inches. To eliminate this problem, SLI-8211 recommended that the vertical drops in the reference and variable legs in the drywell should be approximately equal.

1 5 ., SLI-8211 recommended one additional change to mini-mize the effects of drywell overheating. The report noted that the magnitude of instrumentation error caused by flashing in tr.e reference legs is related to the location of the flow-limiting orifices in those legs. If the orifices are lo-cated close to the reactor vessel and flashing occurs, a pres-sure gradient across the orifice is created which contributes to error in water level measurement, particularly when the pressure in the reactor vessel is low. If the flow-limiting orifices are located close to the points where the reference legs pass through the drywell wall, the pressure gradient dur-

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ing flashing is virtually eliminated. The orifices at PNPP were located close to the reactor vessel. SLI-8211 recommended that flow-limiting orifices in the reference legs be moved as close to the drywell penetratioas as possible.

6. In response to these three recommendations, PNPP has taken a number of actions to modify the design of its water.

level measurement systems. First, the design of the reference legs has been changed to incorporate new penetrations for them in the drywell walls. Reference leg piping has been redesigned so that all vertical drops from the condensing chambers to the drywell penetrations will be between one and two feet. As noted in the Affidavit of Gary R. Leidich, one reference leg actually has a vertical drop of two feet three inches. These drops are acceptable because if flashing were to occur, the maximum error which could be introduced would be between one i

i foot four inches and three feet. Since PNPP operator guidelines require the operator to maintain water level at least fourteen feet above the top of active fuel, satisfactory control of water level can be maintained even if worst flashing conditions are assumed and the operator does not recognize that the level indicators are giving erroneous readings.

7. Redesigning the routing of the reference legs has also resulted in most of the differences in vertical drops be-

~ tween associated reference and variable legs being equal to within approximately one foot. In two cases, however, the ver-

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tical drop difference is approximately two feet. he

. largest deviation is less than two feet two inches which can cause a maximum potential error of only about three inches.

8. The second design change implemented at PNPP responds to the recommendation of SLI-8211 concerning the location of j

the flow-limiting orifices in the reference legs. Reference leg orifices formerly located at the reactor vessel nozzles have been redesigned so that they will now be located as close to the drywell penetrations as is feasible. The Leidich Affi-davit describes the actual installed locations of the orifices.

Appendix B of SLI-8211 indicates that placing the orifices in these locations will prevent the occurrence of pressure gradi-ents large enough to significantly affect water level indica-tions.

3 Thus, the design modifications implemented at PNPP are respon-sive to all the recommendations of SLI-8211 for PNPP-type BWRs.

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Frank R. Stead Subscribed and sworn to before me this.// day of January, 1985 Recin__L ' PrlLbi Notary Public #

PATRICIA G. DEDEK, Notary Pubic STATE OF CH'O (Lake CounM My Commission Ewires April 16,1335 Q

RESUME OF FRANK R. STEAD EDUCATION AND TRAINING: - Bachelor of Mechanical Engineering, Cleveland State University, 1970

- Master of Science Degree in Mechanical Engineering, Ohio State University, 1972

- Three-week In-Core Fuel Management Course, Purdue University, 1972

- Westinghouse Large Steam Turbine Operator Awareness Program, Dutton Mill, 1980 EXPERIENCE:

1965-Present - The Cleveland Electric Illuminating Company Joined CEI in 1965 and held various engineering positions at CEI's Perry Project including Senior

. Design Engineer of Nuclear Fuels, gaining seven years experience in the Fuel Management area.

Also held positions in Nuclear Licensing, Balance-of-Plant Equipment, and Civil Engineering.

Most recently, rotated through several General Supervisor positions in Maintenance and Operations at CEI fossil plants.

In July 1982, named to present position of Manager, Nuclear Engineering Department, with responsibilities for operational support and modification engineering, reliability and design assurance, and nuclear licensing and fuel management at the Perry Nuclear Power Plant.

Reports to the Vice President, Nuclear Operations Division.

PROFESSIONAL MEMBERSHIPS: - American Society of Mechanical Engineers

- American Nuclear Society

- Registered Professional Engineer, State of Ohio Exhibit "A" 7 - . . . , ., - --.---- .--v -.--o .~v . . , . - , , --e, , -.-.._..,,.y, ,_.,..-,_,r, - ., , . - ,