ML20203A586
| ML20203A586 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 02/04/1998 |
| From: | Savio R NRC (Affiliation Not Assigned) |
| To: | Jeffery Wood TOLEDO EDISON CO. |
| References | |
| TAC-MA0163, TAC-MA163, NUDOCS 9802240066 | |
| Download: ML20203A586 (6) | |
Text
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UNITED STATES
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NUCLEAR REGULATORY COMMISSION 2
WASHINGTON. D.C. 30086 4 001
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February 4, 1998
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Mr. John K. Wood Vice President - Nuclear, Davis-Besse Centarior Service Company c/o Toledo Edison Company Davis-Besse Nuclear Power Station 5501 North State Route 2 Oak Harbor, OH 43449-9760
SUBJECT:
DAVIS-BESSE NUCLEAR POWER STATION, UNIT 1 - INTERPRETATION OF SCHEDULE REQUIREMENTS FOR TECHNICAL SPECIFICATION SURVEILLANCE l
TESTS CONDUCTED ON A STAGGERED TEST BASIS (TAC N0. MA0163)
Dear Mr. Wood:
This document has been prepared in rosponse to your letter (enclosed) dated November 3,1997, in which you requested the Nuclear Regulatory Commissian (NRC) staff to provide an interpretation of schedule requirements for Technical Specification (TS) surveillance tests conducted on a staggered test basis at the Davis-Besse Nuclear Power Station.
Backaround Davis-Besse TS 1.0, " Definitions," defines staggered test basis as follows:
"TAGGERED TEST BASIS 1.21 A STAGGERED TEST BASIS shall consist of:
a.
A test schedule for n systems, subsyr' ems, trains or designated components obtained by dividing the specified test interval into n equal subintervals, b.
The tcsting of one system, subsystem, train or designated components at the beginning of each subinterval.
Davis-Besse TS 4.0.2 states:
4.0.2 Each Surveillance Requirement [SR] shall be performed within the specified time interval with a maximum allowable extension not to exceed 1
25 percent of the specified surveillance interval.
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TS Bases 4.0.2 states, in part:
4.0.2 The provisions of this specification provide allowable tolerances for performing surveillance activities beyond those specified in the nominal surycillance interval....It is not intended that the allowable tolerance be used as a convenience to repeatedly schedule the performance of surveillances at the allowable tolerance limit.
1 h
346 PDR
... i a * * -
J. Wood.
Reauest for Internretation You requested an interpretation from NRC on the appropriate application of the 25 percent maximum allowable extension (TS 4.0.2) to TS surveillance testing perfo.. led on a staggered test basis.
Internretation As an example, consider a 4-channel system with channel functional testing required to be performed once per 32 days on a staggered test basis (32 days chosen for mathematical simplicity).
Per TS 1.21:
Subinterval = 32/4 a 8 days If a functional test is not performed within the 8 days, then TS 4.0.2 allows up to a 25 percent extension.
In your letter, you offered two possible interpretations of the application of TS 4.0.2:
(1)
Since each channel must be tested once per 32 days, then TS 4.0.2 allows:
Extension - 0.25
- 32 - 8 days (2)
Since each subinterval requires testing each 8 days, then TS 4.0.2 allows:
Extension - 0.25
- 8 - 2 days.
For the Davis-Besse TSs, the staff has determined that the 25 percent i
extension of TS 4.0.2 addresses the overall length of the surveillance interval, while the subintervals of the staggered testing deftaition only deal with how the beginning of the overall intervals for different subsystems are arranged. Therefore, TS 4.0.2 should be applied to the overall interval requirement. Thus, as in the example above, Extension - 0.25
- 32 - 8 days.
You also state in your letter that:
...the intent of performing testing on a staggered basi: is to limit the length of time that a common cause system failure could go undetected.
Though staggered testing does have a benefit with regard to reducing the risk due to common cause failures, it also provides for operational convenience.
The requirement in the Davis-Besse TSs to perform designated testing on a staggered basis (each 8 days in the example above) uoes not take precedence over each system-specific surveillance requirement to test all channels within the specified interval (32 days in the example).
J. Wood,
Since TS 4.0.2 cannot be used on a routine basis, a test (say, on Channel 2) conducted subsequent to the application of TS 4.0.2 would still have to be performed again in the next subinterval as previously scheduled (for Channel 2).
For example, if the entire 8-day extension was utilized for the test of Channel 2, then the next test of that channel would have to be performed in 24 days, as shown by the following table:
ILa.y Chennel a
8 1 completed (normal schedule) 16 (2 scheduled, not completed, TS 4.0.2 invoked) 24 2 completed (including TS 4.0.2 25 percent extension) 3 completed (normal schedule) 32 4 completed (normal schedule) 40 1 completed (normal schedule) l 48 2 completed (return to ncrmal schedule) 56 3 completed (normal schedule)....
The above interpretation applies to Davis-Besse.
For plants that have opted the improved Standard Technical Specifications (iSTS), SR 3.0.2 (which provides for a 25 percent extension similar to Davis-Besse TS 4.0.2) specifically refers to the frequency which, due to the changed definition of staggered testing in iSTS, is the subinterval.
Therefore, the above interpretation does not apply to plants that have adopted the iSTS.
Please contact Allen Hansen of my staff at 301-415-1390 if you have any questions.
Sincerely, b
%-V h.
Richard P. Savio, Acting Project Director i
Project Directorate III-3 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulatior.
Docket No. 50-346
Enclosure:
As stated cc: See next page
Since TS 4.0.2 cannot be used on a routine basis, a test (say, on Channel 2) n conducted subsequent to the application of TS 4.0.2 would still have to be i
performed again in the next subinterval as previously scheduled (for I
' Channel 2).
For example, if the entire 8-day extension was utilized for the test of Channel 2, then the next test of that channel would have to be performed in 24 days, as shown by the following table:
Dity Channel 8
1 completed (normal schedule) 16 (2 scheduled, not completed, TS 4.0.2 invoked) 24 2 completed (including TS 4.0.2 25 percent extension) 3 completed (normal schedule) 32 4 completed (normal schedule) 40 1 completed (normal schedule) 48 2 completed (return to normal schedule) 56 3 completed (normal schedule)....
The above interpretation applies to Davis-Besse.
For plants that have adopted the improved Standard Technical Specifications (iSTS), SR 3.0.2 (which provides for a 25 percent extension similar to Davis-Besse TS 4.0.2) l specifically refers to the frequency which, due to the changed definition of staggered testing in iSTS, is the subinterval.
Therefore, the above interpretation does not apply to plants that have adopted the iSTS.
Please contact Allen Hansen of my staff at 301-415-1390 if you have any questions.
Sincerely, Original signed by D. Pickett for:-
Richard P. Savio, Acting Project Director Project Directorate III-3 Division of Reactor Projects III/IV Office of Nuclear Ree 'ar Regulation Docket No. 50-346
Enclosure:
As stated cc:
See next page DISTRIBUTION:
Docket File PUBLIC JLieberman JZwolinski PD3-3 R/F EAdensam (EGAl)
HICB/DRCH RSavio JJohnson, RII TSB OGC GGrant, RIII MBoyle (MLB4)
ACRS SCampbell, RIII SBloom (SDB1)
CHeyl, RI TGwynn, RIV SRichards DOCUMENT NAME: G:\\DAVISBES\\DBA0163.LTR
- See previous concurrence OFFICE PD33:LA l C PD33:PMl HICB:BC l TSB:BC d,nd PD33:Pd ['E NAME EBarnhillEtk AHansen JWermiel
- WBecknef ~
RSavid " V DATE d)/a /C/f t/1/9F 1/27/98 A /4 / 4 '6 A/4/%
OFFICIAL RECORD COPY
J. Wood.
Since TS 4.0.2 cannot be used on a routine basis, a test (say, on Channel 2) conducted: subsequent to the application of TS 4.0.2 would still have to be performed again in the next subinterval as previously sr.heduled (for
' Channel 2).
For example, if the entire 8-day extension was utilized for the test of Channel 2, then the next test of that channel would have to be performed in 24 days, as shown by the following table:
l D3y Channel 8
1 completed (normal schedule) 16 (2 scheduled, not completed, TS 4.0.2 invoked) 24 2 completed (including TS 4.0.2 25 percent extension) 3 completed (normal schedule) 32 4 completed (normal schedule) 40 1 completed (normal schedule) 48 2 completed (return to normal schedule) 56 3 completed (normal schedule)....
The above interpretation applies to Davis-Besse.
For plcnts that have adopted the improved Star.dard Technical Specifications (iSTS), SR 3.0.2 (which provides for a 25 percent extension similar to Davis-Besst TS 4.0.2) specifically refers to the frequency which, due to the changed definition of staggered testing in iSTS, is the subinterval.
Therefore, the above interpretation does not apply to plants that have adopted the iSTS.
Please contact Allen Hansen of my staff at 301-415-1390 if you have any questions.
Sincerely, Original signed by D. Pickett for:
Richard P. Savio, Acting Project Director 1
Project Directorate III-3 Division of Reactor Projects III/IV Office of Nuclear Reactor Regulation Docket No. 50-346
Enclosure:
As stated cc:
See next= page DISTRIBUTION:
Docket File PUBLIC JLieberman JZwolinski PD3-3 R/F EAdensam (EGAl)
HICB/DRCH RSavio JJohnson, RII TSB OGC GGrant, RIII MBoyle (MLB4)
ACRS SCampbell, RIII SBloom (SDB1)
CHeyl, RI TGwynn, RIV SRichards DOCUMENT NAME:
G:\\DAVISBES\\DBA0163.LTR
- See previous concurrence OFFICE PD33:LAl C PD33:PM l HICB:BC l TSB:BC e,,n/l PD33:PD l_ C NAME EBarnhillEff AHansen JWermiel
- WBecknef ~
RSavio* V DATE cW3/CN-t/1/9F 1/27/98 A /4 / '11 1/4/%
OFFICIAL RECORD COPY'
John K. Wood Davis-Besse Nuclear Power Station, Unit 1 Toledo Edison Company cc:
Mary E. O'Reilly Robert E. Owen, Chief Centerior Energy Corporation Bureau of Radiological Health 300 Madison Avenue Service Toledo, OH 43652
- Ohio Department of K c P.O. Box 118 James L. Freels Columbus, OH 43266-0118 Manager-Regulatory Affairs Toledo Edison Company James R. Williams, Chief of Staff Davis-Besse Nuclear Power Station Ohio Emergency Management Agency 5501 North State - Route 2 2855 West Dublin Granville Road.
Oak Ha.uor, OH 43449-9760 Columbus, OH 43235-2206 Gera'd Chamoff, Esq.
Donna Owens, Director Shaw, Pittman, Potts Ohio Department of Commerce and Trowbridge Division of Industrial Compliance 2300 N Street, NW.
Bureau of Operations & Maintenance Washington, DC 20037 6606 Tussing Road P.O. Box 4009.
Regional Administrator Reynoldsburg, OH 43068-9009 U.S. Nuclear Regulatory Commission 801 Warrenville Road -
Ohio Environmental Protection Agency Lisle, IL 60523-4351 CERR-Compliance Unit ATTN: Zack A. Clayton Robert B. Borsum P.O. Box 1049 Babcock & Wilcox Columbus, OH 43? eau 149 Nucle.ar Power Generation Division
-1700 Rockville Pike, Suite 525 State of Ohio Rockville, MD 20852 Public Utilities Commission 180 East Broad Street Resident inspector Columbus, OH 43266-0573 U.S. Nuclear Regulatory Commission 5503 North State Route 2 -
Attomey General Oak Harbor, OH 43449 Department of Attomey 30 East Broad Street James H. Lash, Plant Mas ager Columbus, OH 43216 Toledo Edison Comoany Davis-Besse Nuclear Power Station President, Board of County 5501 North State Route 2 Commissioner of Ottawa County
'Jak Harbor, OH 43449-9760 Port Clinton, OH 43252
- Roy P. Lessy, Jr.
Akin, Gump, Srauss, Hauer & Feld, LLP 1333 New Hampshire Ave., NW., Ste. 400 Washington, DC 20036
CENTEREOR ENERGY
$501 N stare Route 2 419-249 2300 John K. Wood Oak Harbor, oH 43449 fax 419-321-8337 Vce Prescern Nocheer Dav's-Besse License Number NPF-3 Serial Number 2495 Docket Number 50-346 November 3, 1997 United States Nuclear Regulatory Commission Document Control Desk Washington, D. C. 20555-0001
Subject:
Request for Interpretation of Schedule Requirements Regarding Technical Specification Surveillance Tests Conducted on a Staggered Test Basis Ladies and Gentlemen:
The purpose of this letter is to request an NRC interpretation of schedule requirements regarding Technical Specification surveillance tests conducted on a " Staggered Test Basis".for the Davis-Besse Nuclear Power Station (DBNPS), Unit Number 1. Operating License Number NPF-3. The
. details of this request are provided in the Enclosure. A response is requested by June 1,1998.
Should you have any questions or require additional information, please contact Mr. James L. Freels, Manager - Regulatory Affairs, at (419) 321-8466.
Ve truly yours, dw-
$1 M Ulaj g
Enclosure
/
A. B. Beach, Regional Administrator, NRC Region III cc:
S. J. Campbell, DB-1 NRC Senior Resident laspector A. G. Hansen, DB-1 NRC/NRR Project Manager Utility Radiological Safety Board lill!!Istmumen,,,,
_9711070102 971103 closure gDR ADOCK 05000344 PDR
Docket Number 50-346 0,
License Number NPF-3 Serial Number 2495 Enclosiire Page1 Request for Interpretation of Scheduk P.equirements Regarding Technical Specification Surveillance Tests Conducted on a Staggered Test Basis Backcround:
The Davis Besse Nuclear Power Station (DBNPS) Technical Specifications (TS) Defiriition 1.21 states as fo!Lws:
A STAGGERED TEST BASIS shall consist of:
A test schedule for n systems, subsystems, trains or designated components a.
obtained by dividing the specified test interval into n equal subintervals, l
b.
The testing of one system, subsystem, train or designated components at the beginning of each subinterval.
There are no TS Bases associated with the Definitions Section of TS, however, the intent of performing testing on a staggered basis is to limit the length of time that a common cause system failure could go undetected.
Section 4.0.2 of the DBNPS TS states as follows:
Each Surveillance Requirement shall be performed within the specified time interval with a maximum allowable extension not to exceed 25 percent of the specified surveillance interval.
The associated Bases for DBNPS TS Section 4.0.2 states,in part:
The provisions of this specification provide allowable tolerances for performing starveillance activities beyond those specified in the nominal surveillance interval. These tolerances are necessary to provide operational flexibility because of scheduling and performance considerations. The phrase "at least" associated with a surveillance frequency does not negate this allowable tolerance value and permits the performance of more frequent surveillance activities.
The allowable tolerance for performing surveillance activities is sufficiently restrictive to ensure tFat the reliability associated with the surveillance activity is not significantly degraded beyond that obtained from the nominal specified interval. It is not intended that
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Docket Number 50-346 Q
License Number NPF-3 Serial Number 2495 Enclosure Page 2 l
the allowable tolerance be used as a convenience to repeatedly schedule the performance of surveillances at the allowable tolerance limit.
Exclanation of Issue:
The issue of interpretation is how to apply the maximum allowable extension provisions of TS Section 4.0.2 to surveillance testing conducted on a STAGGERED TEST BASIS. To illustrate the issue, assume a typical four channel instmmentation functional unit, with channel functional testing required to be performed at least once per 31 days on a STAGGERED TEST BASIS.
Using the above example, under TS Definition 1.21, the 31 day specified test interval is divided into four equal subintervals of 7.75 days, and one channel is ested at the beginning of each subinterval. As a practical matter, at the DBNPS, such a channel functional test would typically be scheduled once e week on the same day of the week, with each channel being tested every 4 weeks. In the ev... that the channel functional test schedule is disrupted, for whatever reason, end it becomes necessary for the provisions of Specification 4.0.2 to be applied, there are differing interpretations as to how this should be done.
One interpretation is that the 25% allowance must be applied to the subinterval time frame.
Under this interpretation, if last week's channel functional test (for channel "x") was completed at arbitrary time "zero", then this week's channel functional test (for channel "y") must be completed no later than 125% of the 7.75 day subinterval, or by day 9.6875.
A differing interpretation is that the 25% allowance may be applied to the 31 day interval for the particular channel of interest, irrespective of the test completion history for the other channels.
Under this interpretation, the maximum allowable extension for any channel is 125% of 31 days, or 38.75 days from the last performance of the channel functional test for that same channel.
The first interpretation ensures that if the chaanel "y" test is completed at day 9.6875, that time will be within 125% of 31 days since the last performance of the channel"y" test, even if each test in the past month utilized the 25% allowance. Tnis method also_ ensures a relatively uniform test spacing over the 21 day interval, regardless of whether the 25% allowance is used. However, this method is potentially overly conservative in the sense that if each of the three previous channels were completed on the normal 7 day schedule, and the need arose to use the maxirnum 9.6875 day allowance for channel "y", then channel "y" testing would be required to be completed within 3v.6875 days ( 3 x 7 + 9.6875 days) of the last performance of the channel"y" test. Or,if each of the three previous channels were comple d on a 7.75 day schedule, and the need arose to use the maximum 9.6875 day allowance for channel "y", then channel "y" testing would be required to be completed within 32.9375 days ( 3 x 7.75 + 9.6875 days) of the last performance of the channel "y" test. In either case, the current channel "y" test would be required to be completed well within the 38.75 day limit, were the extension applied to the 31 day interval, as would be allcwed by the second interpretation. The end result is that, under the
Docket Number 50-346 License Number NPF-3 1
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Serial Number 2495 I
Enclos'ure
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Page 3 first interpretation, a channel may need to be declared inoperable and placed in a tripped l
condition earlier than under the second interpretation. This could place the plant in a less reliable configuration since under a typical 2 out of 4 actuation logic, a spurious signal in a second channel could cause inadvertent initiation of a protective action, for example a reactor trip or a Safety Features Actuation System actuation.
However, while the second interpretation potentially allows a greater time margin to perform a test, it does not ensure that testing is uniformly spaced. Under the above example, a series of channel functional tests for each of four channels could be conducted with three 7 day subintervals and one 17.75 day subinterval.
Reauest for Interoretation:
The DBNPS surveillance test program is presently being conducted under the more conservative scheduling approach of applying the 25% maximum allowable extension of TS Section 4.0.2 to the STAGGERED TEST B ASIS subinterval. However, as described above, this approach may be overly conservative and could result in equipment being prematurely declared inoperable, potentially placing the plant in a less reliable condition.
For this reason, the DBNPS requests a written response from the NRC on the appropriate application of the 25% maximum allowable extension of TS Section 4.0.2 to TS surveillance testing performed on a STAGGERED TEST BASIS.
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