ML20211L494
| ML20211L494 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 12/11/1986 |
| From: | Gridley R TENNESSEE VALLEY AUTHORITY |
| To: | Youngblood B Office of Nuclear Reactor Regulation |
| References | |
| 0458C, 458C, NUDOCS 8612160052 | |
| Download: ML20211L494 (9) | |
Text
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TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEE 374ot SN 157B Lookout Pisce DEC 11886 Director of Nuclear Reactor Regulation Attention:
Mr. B. Youngblood, Project Director PWR Project Directorate No. 4 Division of Pressurized Water Reactors (PWR)
Licensing A U.S. Nuclear Regulatory Consission Washington, D.C. 20555
Dear Mr. Youngblood:
In the Matter of
)
Docket Nos. 50-327 Tennessee Valley Authority
)
50-328 SEQUOYAH NUCLEAR PLANT - ADDITIONAL INFORMATION ON SEQUOYAH DESIGN BASELINE AND VERIFICATION PROGRAM In response to NRC's request for additional information on the Sequoyah Design Baseline and Verification Program (DB&VP) dated September 9, 1986, enclosed is "Sequoyah Nuclear Plant - NRC Technical Information Request on Design Baseline and Verification Program." The particular efforts involved in implementing the Sequoyah DB&VP, supplementary to information presented in the TVA Nuclear Performance Plan, Volume 2, will be provided in a separate submittal. TVA will transmit this it. formation to NRC by December 19, 1986. to this letter consists of a list of commitments contained within enclosure 1.
If you have any questions concerning this issue, please call Beth L. Hall of the Sequoyah Site Licensing Staff at (615) 870-7459.
Very truly yours, TENNESSEE VALLEY AUTHORITY R.
- ridley, rector Nuclear Safety and Licensing Sworntogndsubsc d before me this
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An Equal Opportunity Employer
. Director of Nuclear Reactor Regulation gg[gjjgggg ec (Enclosures):
U.S. Nuclear Regulatory Commission Region II Attn:
Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW Suite 2900 Atlanta, Georgia 30323 Mr. Carl Stahle, Sequoyah Project Manager U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, Maryland 20814 Mr. G. G. Zech Director TVA Projects U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 e
ENCLOSURE 1 SEQUOYAH NUCLEAR PLANT NRC TECHNICAL INFORMATION REQUEST ON DESIGN BASELINE AND VERIFICATION PROGRAN la.
NRC CONCERN For the ice condenser system why is only the containment isolation penetration included?
RESPONSE
The Ice Condenser system is a static system in which the ice bed requirements are maintained adequately by technical specification requirements and surveillance requirements. These will ensure that sufficient ice and required flow paths through the ice bed are always available. The refrigerant piping system is used to maintain the ice bed in technical specification requirements and does not perform a safety function except for containment isolation.
Ib.
NRC CONCERN Why is the hydrogen analyzer subsystem not included in the hydrogen mitigation system?
RESPONSE
The restart portion (Phase I) of the Design Baseline and Verification Program (DB&VP) is reviewing systems and subsystems required to mitigate Final Safety Analysis Report (FSAR) Chapter 15 design basis accidents.
For such an accident, several days will pass before the hydrogen concentration would reach a sufficient level as to be a concern according to Sequoyah FSAR Chapter 15 analysis. Present system operating procedures (SOI-83.1) require the hydrogen recombiners to be placed in operation within the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> after an event or when hydrogen concentration reaches a preset level as measured by the i
hydrogen analyzers. This preset level measured by the hydrogen analyzers is required to mitigate events beyond our design basis (i.e., inadequate core cooling events).
Events discussed in Chapter 15 of the FSAR would be mitigated adequately by placing the hydrogen recombiners in service within the first 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.
For this reason, the hydrogon analyzers were not considered in Phase I of the DB&VP.
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NRC CONCER5 Since the issuance of the 10 CFR 50.54(f) letter in September 1985, there have been several areas where it could not be demonstrated that the sequoyah plant met the design criteria.
Examples of these include containment isolation, electrical calculations, pipe hangers, and cable tray supports. Because of this the staff believes that the as-built plant should be covered by the DB&VP.
For those systems within the scope of the DB4VP, will the program verify that the as-built systems (or portion of systems) meet the appropriate design criteria? If only plant modifications made since licensing are covered by the DB&VP, justify covering only modifications made since licensing and not the as-built plant.
RESPONSE
TVA's restart program for Sequoyah was designed after a comprehensive review of various findings by both outside and internal organizations including:
1.
Findings from TVA's quality assurance (QA) audits; conditions adverse
.to quality (CAQ) at Browns Ferry, Sequoyah, Watts Bar, and Bellefontet and from TVA's cancelled construction projects.
2.
Nuclear Safety Review Staff (NSRS) and Nuclear Safety Review Board
~ (NSRB) reports.
- 3..TVA Employee Concern Program.
4._ Industry experience and response to NRC IE Bulletins, Information
. Notices, etc.
~
- 5.. Audits and reviews by INPO at Bellefonte, Watts Bar, Sequoyah, and Browns Ferry.
7.
Design and Engineering reviews by Gilbert / Commonwealth (two reviews) land Duke Power Co. (Piping program, stress design review at Watts Bar).
8.
Black and Vestch independent review of Watts Bar auxiliary feedwater system.
9.
Engineering review by Bechtel.
10.
WESTEC Environmental Qualification Program audit.
11.
SWEC Systematic Analysis of Identified Issues / Concerns at TVA.
O
- The above reviews concluded that Sequoyah had a weak design control program after issuance of the operating license (OL). This conclusion was reinforced by the fact that there are several specific factors, coming into y
effect since OL, that reduced the effectiveness of the adequate design control process.
First, once the plant went into operation, the engineering organization and plant operations organization worked to different procedures.
This resulted in a two-drawing system ("as-designed" and "as-constructed"), with each organization using its own system.
This system could work properly, had adequate procedures and controls been in place.
Second, engineering attention was diluted by the aggressive engineering construction program underway.
The plant operations organization consequently created its own control systems and engineering-type functions.
Third, the engineering change notice (ECN) used for plant changes is a document implemented during the original construction period that was intended to notify const.uction of upcoming changes to drawings.
This ECW program, in effect post-OL, was not an effective design change integration mechanism for an operating plant.
Fourth, the engineering organization allowed many design criteria to become out of date.
In addition, the FSAR was not maintained.
In rummary, theso changes made the design engineer's task difficult, as he did not have up-to-date criteria, his design change mechanism was originally intended for another purpose, and his path.to current configuration information was often difficult.
Based upon this assessment. TVA has designed the DB&Vp to supplement other restart programs by:
1.
gvaluating changes to Sequoyah since issuance of the OL.
A major part of this evaluation process is to verify adherance of the changes to the recently reassembled design criteria. This effort is directed at providing confidence that plant modifications implemented since issuance of the OL can be supported by engineering analysis / documentation and that these modifications do not degrade the system's abilities to mitigate Chapter 15 accidents and safely shut down the plant.
2.
Resolving differencer between "as-constructed" and "an-designed" t
drawings for the control room drawings within the program scope.
3.
Providing the foundation for an improved design control process.
A transitional design program is in effect, leading to the permanent chango control process.
I 4
The DB&VP interfaces with many of the other Nuclear Performance Plan (NPP).
Volume 2 programs to provide the necessary high level of confidence that Sequoyah is in conformance with its design basis and can be restarted and operated safely.
The DB&VP is an integral part of the Sequoyah restart program.
It should be considered in concert with the NPP, Volume 2 programs which address the issues required for restart of Sequoyah, including programo such as welding, alternate analysis, and electrical calculations which were specific pre-OL program weaknesses.
Calculations are also being reviewed within the other disciplines to ensure that similar concerns do not exist.
3.
NRC CONCERN Verify that the main steam isolation valves are included in the DB&VP.
RESPONSE
The main steam system from the steam generators through the main steam:
1 solation valves and the main steam check valves to the anchor where the piping exits the main steam valve vaults are included in the program for restart.
4.
NRC CONCERN For the auxiliary feedwater system, provide the rationale for not including the pump suction and pump recirculation. lines from the condensate storage tank.
RESPONSE
The safety-grade water supply for the auxiliary feedwater system is the essential raw cooling water (ERCW) system. The normal supply is from the condensate storage tank. When a low suction pressure on the supply from the condensate storage tank is detected, the ERCW will automatically supply safety-grade water to the auxiliary feedwater pumps. The requirements to have a qualified water supply are met by the ERCW system and the instrumentation that provides the pump suction switchover signal.
The minimum flow requirements for the auxiliary feedwater system are met, assuming the loss of all the wa(pr in the miniflow line. The portion of the line that contains the orifice that controls the miniflow is included in the boundary to ensure that proper flow will exist.
The return of the flow to the condensato storage tank is not required, as the water in the tank performs no safety function. The safety-grado water supply is provided by the ERCW system.
.,- 5.
NRC CONCERN In order for the staff to assess the timeliness of implementation of
.=
the permanent design change program, including transition to a single configuration drawing system, provide a schedule or timetable for complete implementation of the permanent design control system.
RESPONSE
There are two steps planned to implement the permanent design control system. These are the transitional system and the permanent system. The transitional design change control process, as well as the permanent design control system, is based upon the " single drawing concept." The " single r
drawing" will be developed, utilizing "as-designed" information and "as-constructed" information and will be issued either in advance of 2
providing a design change authorization for the change in the area of interest or when the work is completed. This change will be reviewed i
before its issuance for configuration and constructibility whenever appropriate.
1 The transitional design change control process will begin the conversion from the two-drawing system to the " single drawing." The actual production of the " single drawings" and replacement of the "two drawings" will be on an "as-needed" basis to support new modifications, except that DB&VP primary drawings for unit 2 will be completed by the end of the cycle 4 outage (the second refueling outage after restart) for unit 2.
TVA will begin implementation of the permanent design control system after the completion of the remainder of safety-related system design criteria.
These design criteria are planned for completion by December 31, 1987.
6.
NRC CONCERNS Discuss the TVA plan for providing detailed information describing the postrestart phase of the DB&Vp.
In particular, provide information addressing which specific systems are to be included, which attributes of the Phase I scope are to be applied, and a schedule for completion.
RESPONSE
The detailed scope and schedule _for the postre' start (Phase II) phase of the 3
084VP has not been determined. The scope and Phase I attributes that will 4
be applied will be determined by the results of Phase I.
Based on this analysis, TVA will submit to NRC the scope and schedule for Phase II of the
)
DB4VP by March 21, 1987.
TVA intends to maintain program continuity on unit 2.
Activities that are required, regardless of the outcome of Phase I, include those regulred to 4
continue the baseline portion of the activities such ass (a) developing design criteria for the romaining safety-related systems by l
December 31, 1987, and (b) conducting functional walkdowns for the i
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. remaining safety-related systems by the end of the cycle 4 refueling outage (the second outage after restart).
The scope of the verification portion (i.e., technical review of various change documents) will be detemined and justified by the Phase I.
7.
NRC CONCERN Provide additional information on the criteria and analytical results for anchor bolts and containment stiffeners evaluations. The staff visit during the week of July 31, 1986, did not provide enough time to review this information.
RgSPONSg i
The anchor bolts information was provided by a letter from R. L. Gridley to B. J. Youngblood dated August 18, 1986, and the containment stiffeners information was transmitted by a letter from R. L. Celdley to B. J. Youngblood dated September 24, 1986, r
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ENCLOSURE 2 SEQUOYAH NUCLEAR PLANT LIST OF COMMITMENTS MADE IN ENCLOSURE 1 1.
Complete design verification of DB&VP primary drawings for Sequoyah unit 2 by and of cycle 4 refueling outage.
2.
Complete remainder of safety-related system design criteria for unit 2 Phase II by December 31, 1987.
3.
Submit unit 2 Phase II scope and schedule to NRC by March 21, 1987.
4.
Complete unit 2 Phase II functional walkdowns by end of cycle 4 refueling outage.
5.
Submit DB&VP information that supplements the Nuclear Performance Plan (NPP), Volume 2, by December 19, 1986.
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