ML20196D792

Forwards Comments Related to Staff Responses to follow-up Actions Re Dynamic Testing of Instrument Channels at Braidwood

ML20196D792
Person / Time
Site:	Braidwood
Issue date:	10/02/1998
From:	Burrows F NRC (Affiliation Not Assigned)
To:	Collins S NRC (Affiliation Not Assigned)
References
NUDOCS 9812020326
Download: ML20196D792 (4)

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1. J p' UNITED STATES I g, j NUCLEAR REGULATORY COMMISSION l

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l October 2, 1998 ,

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l MEMORANDUM TO: Samuel J. Collins, Director ..

Office of Nuclear Reactor Regulation 98 tel 18 f00 M FROM: Frederick H. Burrows, Electrical Engineer,

! Electrical Engineering Branch qg >

Division of Engineering -

j Office of Nuclear Reactor Regulation j

SUBJECT:

CONCERNS RELATED TO DYNAMIC TESTING OF INSTRUMENT CHANNELS AT BRAIDWOOD in a niemorandum dated October 17,1996, I expressed a Differing Professional View l (DPV) concerning the dynamic testing of instrumentation channels at Braidwood.

Specifically, I expressed my view that dynamic testing of safety-related instrument l

channels was outside the plant's licensing basis and represented an unreviewed safety question. In a January 2,1997, memorandum, Frank Miraglia, Acting Director, NRR, provided the ad hoc DPV panel's recommendations for this issue. A follow-up action memorandum was sent to Brian Sheron, Acting Associate Director for Technical Review, NRR, on the same day with subsequent forwarding to Bruce A. Boger, Director, Division of l Reactor Contrals and Human Factors, NRR. In .*. September 21,1998, memorandum, you have now pim.ded the results of the staff's review of the follow-up actions.

I have reviewed the staff's response contained in the September 21 memo and conclude l that those fc!!ow-up action efforts fall short of completely addressing my concerns. To spare myself furthes frustration and to limit the detrimental effects resulting from the j DPV/DPO process, I will not at this time pursue further formal staff review (via the DPO }

i process) of the issues associated with dynamic testing of in ament channels at Braidwood and adjustment of the time constants in reacte- otection instrument channels f in Westinghouse plants.

l In an effort to bring some closure for my concerns, I have attached hereto my comments l related to the staff's responses to the follow-up actions. My hope is that you will consider

! my comments and take whatever action you deem appropriate.

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Also, I now request that the DPV and this letter (if appropriate) be made public, elong with the release of my name, per NRC Handbook 10.159.

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I CONTACT: Frederick H. Burrows, EELB/DE/NRR 415-2901

Attachment:

As stated 1 -

9812O20326 981002 PDR ADOCK 05000456 p PDR .

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l COMMENTS ON THE STAFF'S RESOLUTION

_OF FOLLOW-UP ACTIONS TO DYNAMIC TESTING OF BRAIDWOOD INSTRUMENTATION l

1. The staff concludes in the September 21,1998, memorandum from R. Lee Spessard to Brian Sheron that the dynamic testing (MESAC) is consistent with the Westinghouse setpoint methodology and the Braidwood Technical Specifications (TS) and equivalent to channel operational or functional tests performed at other plants. I disagree; as I have stated before the periodic required channel functional tests for Westinghouse plants are based on a static test method. That is, the input test signal is slowly changed (manually, not a ramped input from a signal generator) with the dynamic components bypassed until the associated bistable (or comparator) changes state. The value of the input signal at which the bistable trips is written down and verified to be within the setpoint (or allowable value) limits contained in the TS. At Braidwood (and possibly Vogtle) a ramp input signalis used and the dynamic components are not bypassed. The time of the bistable trip is determined and the value of the input signal at the time the trip occurred is read off the input signal, recorded and compared to the TS setpoint limit. Obviously the Braidwooo trip value is affected by the dynamic component uncertainties. Since the Braidwood TS are the same as Byron TS and their setpoint limits contained therein are based on typical Westinghouse setpoint methodology which does not account for dynamic component uncertainties, Braidwood's method of satisfying the TS channel operational test requirements (based on a literal interpretation) remain questionable and not completely evaluated by the staff in my opinion. Although the licensee's evaluation of the channel's static string tolerance does provide some usefulinformation (especially if the comparator/ bistable is included in the string), it does not satisfy (in my opinion) the requirements of a channel functional or operational test (once again based on a literal interpretation).

2. The staff concludes in the September 21,1998, memorandum from R. Lee Spessard to Brian Sheron that although the " margins of safety" were decreased in the sensitivity analyses, the Braidwood accident analyses bound the effects of time constants nonconservatively offset by 10 percent. I disagree that the Braidwood accident analyses bound the time constant tolerances--The Westinghouse sensitivity studies do. While it is true that the safety limit used in the Braidwood Chapter 15 is bounding, the individual analyses contained therein do not bound since they currently do not account for the time constant adjustment uncertainties. It is my belief that the most conservative assumptions and conditions should be utilized in FSAR Chapter 15 analyses.

l l Since the licensee plans to continue to use dynamic testing, I believe that the current Chapter 15 analyses should be updated to reflect the results of the Westinghouse sensitivity studies. If they are not updated, it is my opinion that they are then not t

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bounding and the validity of future Chapter 15 type sensitivity studies may be questionable due to lack of formal documentation associated with the impact of time constant uncertainties.

3. The staff concluded that the "mergin to safety"in selected Braidwood FSAR safety analyses will be reduced due to offsetting some of the time constants by 10%.

The staff also assumed that MESAC had been installed under 10 CFR 50.59 although the licenses could not readily verify this. It is my position (based on discussions with Eileen McKenna) that the use of the MESAC system and the associated dynamic testing of instrument channels represented an unreviewed safety question (because l the " margin to safety" was reduced) when it replaced the static testing method l approved by the staff as part of the Byron /Braidwood initiallicense activity. Instead l of addressing the safety impact of adopting dynamic testing when it was implemented, it $ pears that the licensee, with some reluctance, only recently ask l Westinghouse to perform sensitivity studies. Also, during the staff's review of the DPV, the licensee appeared unwilling to address some of the staff's questions. In lieu of addressing the licensee's apparent failure to follow 10 CFR 50.59 and the un7sponsiveness, the staff sent a September 21,1998, letter of appreciation to the l licensee for the technical support provided during the review of this DPV issue. l l

believe this sent an inappropriate message to the licensee.

4. As noted above the staff concluded that the " margin to safety"in selected Braidwood FSAR safety analyses will be reduced due to offsetting some of the time constants by i10%. Based on licensee analyses that show that the safety limits will not be exceeded in any Braidwood Chapter 15 accident analyses, the staff further concludes that the public health and safety is not affected by 10% time constant uncertainties in other Westinghouse plants. I disagree with this far reaching conclusion. I believe each Westinghouse plant has its own et of Chapter 15 accident analyses with accompanying assumptions, etc. that change over the life of the plant. Based on this, how can one conclude that sensitivity studies performed for Braidwood answer the unreviewed safety question for other plants? Without performing the individual sensitivity studies for the other Westinghouse plants, how can orie conclude that their safety limits are not exceeded? That is, how can one conclude that there was, is, and will be margin available in other plant's Chapter 15 analyses based solely on recent Braidwood sensitivity studies?

5. The staff has repeatedly stated that Braidwood's dynamic testing is in accordance with the Westinghouse setpoint methodology and the plant's Technical Specifications (TS). The staff also concluded that 110% tolerance for industry time constant calibration procedures is acceptable and that the Westinghouse Standard Technical Specifications (STS) already implement this recommendation. I do not understand these conclusions. The current Westinghouse STS require the lead / lag j time constants to be set s or a to specified values for OTAT and OPAT. Braidwood l TS require those time constants to be set equal to specific values. How can the l *10% satisfy a s requirement? How can the 110% satisfy a = requirement? Are TS to be interpreted literally? I believe they should be.

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Also it should be noted that the Westinghouse STS and the Braidwood TS do not l specify value:t for time constants in all channels that have dynamic corr ponents. ,

That is only the setpoints and allowable values for OTAT and OPAT protective l functions explicitly contain values for dynamic components; other channels such as I l pressurizer pressure low do not. How does the Westinghouse STS implement the staff's 10% recommendation if they do not even specify any values?

6. The' staff stated that the MESAC system had received a " tacit approval" as discussed in an August 4,1998, memorandum. The August 4 memo states that I

since the licensee did not exclude the use of MESAC from an amendment request that was granted on April 13,1993, and it was installed at that time, the staff granted " tacit approval" for its use. The staff's use of " tacit"in the case of MESAC l and in other licensing issues concerns me. One can conclude, for example (based on j l the staff's use and interpretation of " tacit approval"), that just about any inspection  !

finding encompassing a plant equipment shortcoming involves a backfit since most i

equipment was installed in the power plant when it was originally licensed and therefore received " tacit approval."

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A quick review of the staff's safety evaluation associated with the April 13,1993, I amendment approval indicates the word MESAC or the words, dynamic testing, are i l not found therein. This indicates that the licensee probably did indeed not exclude '

l the use of MESAC from the amendment request: but the licensee did not explicit

! state that he was using MESAC and seeking its approval either. Using my Random

( House College Dictionary, tacit approval means " understood without being openly expressed; implied." I am not an NRC icwyer, but " tacit approval" has always meant to me that I at least had a little knowledge of the thing I was " tacitly approving."

Can the staff say that about the Braidwood MESAC " tacit approval?" ,

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