ML20129B483
| ML20129B483 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 06/17/1985 |
| From: | Borysiak M TOLEDO EDISON CO. |
| To: | |
| Shared Package | |
| ML20129B463 | List: |
| References | |
| NUDOCS 8507290170 | |
| Download: ML20129B483 (6) | |
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14 TITI.E: Action Plan Report for NI-1 Source Range Channel 7
- REPORT BY
- M. L. Borysiak PLAN NO.: 15A-1 15A-2 DATE PREPARED: June 17, 1985 4
I INTRODUCTION The impact of NI-1 being declared inoperable prior to and during the transient and the subsequent problem of NI-2 failing to respond when the j high voltage was turned on to the detector was to enter the action state-ment of Technical Specification (T.S.) 3.3.1.1 af ter the reactor tripped.
] Action Statement 6 of T.S. 3.3.1.1 simply stated is, if both source range channels are inoperable, verify compliance with the Shutdown Margin
! requirements of T.S. 3.1.1.1 within one hour and at least once per 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> thereafter. The Shutdown Margin requirements were verified and
] documented in the Reactor Operator's log. Thus, there was no significant j impact during or following the transient due to the NI-1 being declared inoperable other than creating an undesirable added distraction to the i operators in having to verify the Shutdown Margin requirements. NI-1 was i subsequently declared operable at approximately 0400-0500 on June 9, 1985,
- l upon the successful completion of ST 5091.01, Source Range Functional j Test.
i The problems with NI-1, as specified in the " Summary of Data" section of
( this report have existed since prior to initial st. art-up. Past efforts to I eliminate these problems have succeeded in reduct.ng these problems, but not the total elimination thereof. The problems with NI-1 appear to be an j annoyance and distraction to plant operations rather than a significant j impact on plant operations.
i j Even though there appears to be no significant impact on plant operations, it is still highly desirable to correct these problems.
SUMMARY
OF DATA i
j 1. Collect and analyze known information/ operational data for conditions
! prior to, during, and af ter the transient.
J
- l. Past history and documentation with respect to the NI-1 problem has been obtained from Information & Records Management System, Davis-Besse
- Maintenance Management System and the M-535 specification file. Due
{
to this review and from discussions with L. C. Stalter, K. A. Yarger, j T. R. Isley, and J. M. DeSando and from personal involvement since
' 1978, these problems have existed since prior to the initial start-up, j The operational data for conditions prior to, during and af ter the transient are as follows. On June 4, 1985, NI-1 was declared inoper-able due to it reading 2 1.5 decades above NI-2 with the High Voltage Cut Off (HVCO) in effect. NI-1 was inoperable during the trip. At approximately 0400-0500 on June 9, 1985, ST 5091.01 was completed and the NI declared operable.
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l There are two, what would appear to be, mutually exclusive problems
! associated with the NI-1 Source Range Nuclear Instrumentation channel.
The first problem deals with the intermittent erroneous count rate
- indication when both the KVC0 is in effect and when it is not. The l second deals wich an intermittent spiking problem which occurs when the HVC0 is in effect and when it is not.
- 2. Review maintenance and test history.
l l A review of the maintenance history indicates that five work orders have been written since January of this year on the problems of l
l spiking and erroneous counts. No significant results were obtained i in determining the root cause at either problem. The required surveillance test, tests the equipment within the RPS cabinets.
Historically, these tests have not shown any problems.
CHANGE ANALYSIS Since 1977, the boron trifluoride detectors, pre-amp and cable in Contain-ment have been replaced, along with modules in the RPS and a reworking of the grounds on the pre-amp and Count Rate Amplifier Module (CRAM) connec-tions with no positive effect on the total elimination of the spiking
- problem nor the erroneous / elevated count rate.
HYPOTHESES I. Possible intermittent problem within the CRAM causing erroneous counts.
j II. Erroneous counts being induced from outside the RPS cabinet, i.e., in j cable from penetration to CRAM.
III. Intermittent spiking problem induced from other equipment / cables in proximity to the manufacturer's supplied non-shielded cable.
IV. Intermittent spiking problem caused from ground loops between systems.
V. Signal cable length for NI 1 is such that the length is terminated in a k, , or full wave lengt2 to be susceptible to a low frequency of 45-60 Hz., i.e, the cables resonant frequency.
NOTE: Past efforts to iden ify the root cause suggest that the planned actions may not be tsttily successful in identifying the root I causes. If these proy ama cannot be eliminated, the only I
alternative would be to.use the future Source Range indications that will be installei. as part of the new Neutron Flux Monitoring Systems as per Regulat. ary Guide 1.97. This particular Facility Change Request (FCR 84-116) has been budgeted and is presently in the detailed design stage.
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N1-1 Source Range Nuclear Instrumentation Channel _ _6/18/85 M. L. Boryslak ses ue .c ona c r e ve Plan for testing hypotheses for the intermittent elevated count rate. (ltypotheses I, II 6 V)
. r DATE
. :,s t e II PHaut t AsseGNE D ST Aff T T Af tGE T To DATE DAIE COMPL E T E D taise,ust M; He $8W4StBIL iI Yl "All steps of this Action Plan are to be performed in accordance _._ . . . _ . - - - . . - - . . - - - . - . _ . ,.
with the latest revision of "Culdelines to Follow When Trouble- _
shooting or Performing Investigative Actions into the Root _.____. _ _ _ _ _ _ _
Causes Surrounding the June 9,1985 Reactor Trip". - - . -. - - - - - _ - - _ . - ..- - - - - - - - . . _ . . . . _ . - -
. -- - .-~ - . . _ . . _ - - - - - -
These Action Plan steps may be performed in any order. _ _ _ _ _ _ . . . . . _ . __x._._
- 1. Determine /further isolate the problem.
_ _ _. _ _ _ _ _ . . . _ _ _ . . _ . - . _ ~ . . . _ . . . _ __ _ _
A. Take readings on the Count Rate Amplifier Modiale (CRAM) test - _
M. Boryslak.
T. Isley Jacks J3 J4 and J5 on both NI-l and NI-2 with and without J. DeSando the liigh Voltage (HV) on, when unit is shutdown (Mode 5).
B. Repeat step A only with HV off when unit is at power (Mode 1) M. Borysiak T. Isley J. DeSando C. When elevated count rate appears, repeat step A or B. II. Borysiak T. Isley J. DeSando I M. Borysiak D. Evaluate results obtained and determine / plan next step in M. Borysiak T. Isley J. DeSando l identifying root cause. Babcock & - - - - . ,
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- 2. { Cable Check, t i i i
( ! A. tising a calibrated Time Ikwaain Reflectometer, accurately [ M. Boryslak T. Isley acasure the signal cable length of N1-1 and NI-2 (NI-2 for ._ . _ _ _ _ _ _ J. De.Sando 1
reference). Also check signal lead, outer shield and inner ._ . . _ . . _
i shield for anomalies.
i B. Calculate resonant frequency of cable ,M._Borysiak T. Isley _ _ _ _ _ _ _ . . _
{? J. DeSando _ _
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, C. WalLJava conduit / cable Ixking for possible sources that i M. Borysiak, .
T. Isley.. -. . - .
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I I may induce noise in close proximity to the conduit / cable. i , J. DeSando
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N1-1 Source Range Nuclean li.strumentation Channel 6/18/85 H. Boryslak sri os.c ou n ctive Plan for testing hypotheses for the intermittent spiking problem. (Hypotheses III and IV)
_ __ . ,__ . - .~ - - -
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/* . . List of cables exiting RPS cabinet, destinstion and routing. H. Borysiak, T. .Isley_._ _. . _ _ . _ . . ._._ _ _ _ _
J. DeSando A. From the above routings, determine what other cables also M. Borysiak. T. Isley _ _ - . ___ _ _ . .
l I i i run in that routing. __
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- 5. ! Analyze the informationobtainedinstepsIthrough4. correlate {M.Borysiaki --
T. Isley _ __ ._
7 fwithpast spiking problems and develop further tests. J. DeSando I .
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