ML16209A310
| ML16209A310 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 07/23/1996 |
| From: | King L NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Casto C NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| Shared Package | |
| ML16134A534 | List: |
| References | |
| NUDOCS 9706120369 | |
| Download: ML16209A310 (3) | |
Text
To: C.Casto, Engineering Branch Chief Division of Reactor Safety From: L.King, Reactor Inspector Division of Reactor Safety
Subject:
Oconee Main Steam Line Break Date:
23 July, 1996
Background
At your request I spent the week of July 7th at Oconee nuclear plant reviewing the details of the main aUam line break modification.
The assignment was as the result of my difference of professional viewpoint which is documented in Reference 2.
Reference 1 was an attempt to list my concerns and included the references to pravious memos which I will not duplicate here. These memos were a result of a search of Nudocs for correspondence associated with IEB 80-04.
They included correspondence from NRR, Duke Power and Franklin Institute.
Franklin Institute was contracted by NRR to followup on responses to IEB 80-04.
During the week of July 7th I reviewed the following documents concerned with installation of the modification; electrical schematics, test data, the 10 CFR 50.59 and correspondence written on the modification which included memos documenting phone conversations between the licensee and NRR. I also discussed details of the modification with the engineers and licensing personnel involved.
Reference 3 notified NRR that Duke Power recognized the containment could be overpressurized during a MSLB.
Reference 4 submitted in general the propsed fix for the modification and committed to a time for installation on all three units although details were not available at that time.
I requested at that time to go to Charlotte to discuss the details of the analysis and the design.
My stated concern was that due to the fact that the design was safety related that it could not be installed in the committed time if the details of the design were not available. I was at first contacted to go to Charlotte and than received a phone call at home that I was not to go but needed to return to the Region.
Reference 5 was an NRR response to the proposed fix in Reference 4. It stated, "Although we have not performed a technical review of this design modification the approach provides an acceptable response to address the concerns of IEB 80-04."
I do not understand the NRR response in Reference
- 5. The modification did not meet the safety related or single failure requirements of IEB 80-04.
I had suggested that we review the installation at other B&W plants and specifically Crystal River where I had documented that there was a problem with the closing time of the motor operated feedwater block valves.
Crystal River had installed faster operators on the valves due to MSLB concerns.
Duke Power did not submit at that time the details of the design and most likely were not aware that they could not meet the requirements of IEB 80
- 04.
-9706120369 970610 PDR ADOCK 05000269 G_
Sometime after this a reorganization of responsibilites occured at Oconee and little work was done on the modification.
When work on the modification continued a 10 CFR 50.59 was written.
A review of the 10 CFR 50.59 indicated that due to installed equipment that a much larger modification would have to be installed to meet the requirements of IEB 80-04.
That portions of the installed equipment were not safety related or single failure proof.
This is well documented in the 10CFR 50.59 which is included as reference 9.
In order to attempt to install the modification in a timely manner a decision to proceed in parallel with NRR approval was made.
Reference 6 notified NRR of a delay in the modification and the fact that portions of the modification would qgt be single failure proof of safety related. Reference 7 notified Duke Power of the acceptance of the delay but did not address the issue of single failure proof or safety related.
The licensee was concerned that the response did not address these issues and contacted the NRR project manager to ensure he understood the facts.
They were told to consider Reference 7 as tacit approval. Documentation of this phone call is included as Reference S.
Concerns The 10 CFR enclosed as Reference 9 states on page 3, "Also, even though the circuitry is designed to close both sets of control and block valves, the accident analysis assumptions only take credit for the closing of the control valves.
Thus a single failure of one of the control valves could allow containment pressure to be exceeded."
This problem was eliminated at Crystal River by changing the motor operators on the block valves to high speed operators. The single failure of the control valves would be possible on loss of instrument air where the control valves fail as is.
A second concern is the fast responses required by the operators to be taken during postulated events. This is documented on page 22 and 23 of Reference 10.
Item 2 on page 22 requires the operators to take actions within 25 to 30 seconds to prevent overpressurization of the containment.
It should be noted here that the requirement is a 20 second stroke time.
Testing has shown the actual closure time to be 25 seconds.
If we add to this the 2 seconds it takes for the operators to receive the alarm and assuming they immediately respond the operators would have to take action within 18 to 23 seconds. Item 3 would allow building pressure to reach 140 psig if the operators acted in 2 minutes.
A review of the electrical schematic elementary drawing OEE-247-2 titled elementary drawing of emergency F.W.P.T.
system isolation and misc.
indicated that there is a single coil that is required to be energized to prevent the emergency turbine driven feedwater pump from starting in a MSLB. The normal condition of the coil during operation is deenergized.
This represents a single failure possibility on a MSLB if the coil is not energized and the pump started on decreasing feedwater pressure.
Conclusions
- 1)
Investigate the requirement for changing the motor operators to high
speed operators to avoid overpressurization of the containment on a failure of the control valves to close. This would eliminate the necessary operator responses in items 2 and 3 on page 22 and 23 of Refeerence 10.
- 2)
Reference 1 stated that this modification was not implemented at Surry.
The Region needs to determine if MSLB modifications are required at other plants.
- 3)
The Region needs to allow inspectors to followup on their concerns in a more timely fashion.
- 4)
The same inspectors who are familiar with the modification need to be invloved in reviewing the modification before implementation.
Failure to do this places a burden on licensee engineering and licensing personnel to again explain the issues to a different inspector.
References 1)Letter dated
,1995; L.P. King, Reactor Engineer to Paul Kellog, Operational Programs Chief.
Subject:
MSLB at Oconee.
2)Letter dated April 12, 1996; L.P. King, Reactor Engineer to C. Casto, Engineering Branch Chief.
Subject:
Difference of Professional Viewpoint.
- 3) Letter dated May 27, 1993; J.W. Hampton, Site Vice President Oconee Nuclear Station to L.A. Wiens, Project Manager NRR.
Subject:
Reanalysis of Main Steam Line Break Inside Containment.
- 4)
Letter dated August 19, 1993; J.W. Hampton, Site Vice President Oconee Nuclear Station to L.A. Wiens, Project Manager NRR.
Subject:
Supplement Response to IE Bulletin 80-04.
- 5) Letter dated October 6, 1993; L.A. Wiens, Project Manager NRR to J.W.
Hampton Site Vice President Oconee Nuclear Station.
Subject:
Containment Pressurization Due to Main Steamline Break Inside Containment-Supplement to IEB 80-04.
- 6) Letter dated June 14, 1995: J.W. Hampton, Site Vice President Oconee Nuclear Station to L.A. Wiens, Project Manager NRR.
Subject:
Supplement Response to IE Bulletin 80-04 Delay of NRC Commitment Item.
- 7) Letter dated June 30, 1995; L.A. Wiens, Project Manager NRR to J.W.
Hampton Site Vice President Oconee Nuclear Station.
Subject:
Supplement Response to IE Bulletin 80-04.
- 8) Telephone memo dated August 7, 1995 between David Nix and Ed Burchfield of Duke Power with Len Wiens, NRR.
- 9) MSLB 10 CFR 50.59, dated January 24, 1995.
- 10) PIP 0-093-0239.