ML20080C184
| ML20080C184 | |
| Person / Time | |
|---|---|
| Site: | Crane  |
| Issue date: | 08/15/1983 |
| From: | Hukill H GENERAL PUBLIC UTILITIES CORP. |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0737, RTR-NUREG-737, TASK-2.K.3.05, TASK-TM 5211-83-219, NUDOCS 8308190254 | |
| Download: ML20080C184 (5) | |
Text
- e-GPU Nuclear Corporation g
gf Post Office Box 480 Route 441 South Middletown, Pennsylvania 17057-0191 717 944 7621 TELEX 84 2386 Writer's Direct Dial Number:
August 15, 1983 5211-83-219 Office of Nuclear Reactor Regulation Attn:
D. G. Eisenhut, Director Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C.
20555
Dear Sir:
Three Mile Island Nuclear Station, Unit 1 (TMI-1)
Operating License No. DPR-50 Docket No. 50-289 Auto RC Pump Trip (NUREG 0/37, II.K.3.5)
Our letter of March 31, 1983 (5211-83-017) notified you of our plans to revis-the RCP trip criterion from 1600 psig ESas to 25 F subcooling margin. This has been accomplished. Our letter of June 8, 1983 also advised you of our intent to join the B&W Owners Group on this subject to further analyze and quantify the margins associated with the new criterion we have adopted.
Enclosed is a description of the plan for the submission of the supplemental information consistent with the other B&W Owners.
GPU vill provide the information consistent with other B&W Owners in May, 1984.
Sincerely,
{
- l. D. Hukil D rector, TMI-1 11D11:LWil:vj f cc:
R. Conte J. F. Stolz J. Van Vliet B. Sheron
/o%
I/I P308190254 830815 PDR ADOCK 05000289 P
PDR GPU Nuclear Corporation is a subsidiary of the General Public Utilities Corporation
+-
t PLAN FOR RESOLUTION OF 'DiI ACTION ITDi II.K.3.5
" Automatic Trip of Reactor Coolant Pumps" INTRODlX. TION The criteria for resolution of NUREG-0737, Item II.K.3.5, " Automatic Trip of Reactor Coolant Pumps", are provided in a letter from D. G. Eisenhut (NRC) to GPU Nuclear on March 4,1983. As discussed in our letter of March 31, 1983, GPUN has revised the RCP Trip Criteria from 1600 psig ESAS to 25*F subcooling margin under 10CFR 50.59. The B&W Owners Group has been formulating a plan to demonstrate compliance with those criteria. 'Ihe following represents this overall position and plan.
PLAN EDR TREAWENT OF RC PUMP OPEPATION 1
The treatment of reactor coolant pumps during accidents and transients has l
received extensive attention over the past several years. THE B&W Owners i
Group has performed analyses evaluating the effect of a delayed RC pump trip using Appen3ix K assumptions during the course of a small break IOCA accident and has determined that an early trip of E pumps is required to show conformance to 10CFR 50.46 for a range of break sizes. Therefore, to be I
consistent with the conservative analyses performed, it is our position that the reactor coolant pumps should be tripped if indications of a small break LOCA exist.
The B&W Owners Group and B&W maintain that it is highly desirable to maintain RC pu:rp operation during non-LOCA events, as an aid in the mitigation of transients. Consistent with this phiolosophy, the concept of subcooling margin was chosen as an indicator for the need to trip IC pumps. It is our intention to demonstrate that this concept is consistent with our philosophy for handling RC purps during transient conditions and complies with the intent of the criteria stated in your letter of March 4, 1983. The synptom approach of subcooling margin, developed as part of the Abnormal Transient Operating Guidelines Program, is intended to replace the present guidelines of tripping solely on the presence of a low RC pressure ESFAS signal.
It is the position of the B&W Owners Group and B&W that reactor coolant pump trip can be achieved safely and reliably by the operator. It has been determined that a loss of subcooling margin will occcur for those SBIOCAs where a pump trip is required for compliance with 10 CFR 50.46.
The B&W Owners Group will undertake a program based en the above positions to denonstrate that the concept of subcooling margin is an appropriate indicator of the need to trip FC puq o, "et still allows continued FCP operation for steam generator tube ruptures SGIR). 'Ihe concept of subcooling margin will be examined for the more likely non-IDCA transients to denenstrate that under realistic conditions an indication requiring RC pump trip is unlikely.
This program is also interded to provide the justification for manual BCP trip on indication of loss of subcooling margin. Tripping on loss of subcooling margin will assure pump trip prior to the development of significant system voids. No attempt will be made to demonstrate acceptability of continued RCP operation during small break conditions. No request for an exemption of 10CFR 50.46 will be made to allow continued R'P operation during SBIDCA.
The specific plan for resolution of the RC punp trip issue is structured to address the specific criteria stated in the March 4, 1983 letter. A description of the plan, related to the criteria with which it is intended to address, follous:
I.
Pump Operation Criteria Which Can Result in RCP Trip During Transients and Accidents 1.
Setpoints for BCP Trip:
4 a.
The RCP trip criterion, based on loss of subcooling margin, was developed with the intent of assuring that an indication for PC pump trip would occur for those SBIDCAs where pump trip was required to meet the criteria of 10CFR 50.46. A spectrum of analyses has been performed using Appendix K assumptions which demonstrate that a loss of subcooling will always occur for small breaks that have the potential to uncover the core and exceed 10 ER 50.46 criteria if the RCPs are tripped unoer certain two-phase conditions.
'Iherefore, loss of subcooling can be used as an indicator of the need for BCP trip. The actual value of the setpoint (25'F) will be verified to ensure that this indicator will allow continued forced RCS flow during realistic SGTRs up to ard including the design basis SGTR - a single double ended rupture. The setpoint will also be verified to include consideration for minimizing the indication for need to trip BC pumps for more likely non-IOCA events such as a mild overcooling transients.
No partial or staggered RCP trip schemes will be considered except for the extreme case where mechanical damage to the l
pump is likely as this adds to increased decision making on l
the part of the operator during transient conditions. I r
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b.
Le RCP trip criterion based on s6 cooling margin precludes operation of the RC puIps in a highly voided system (except for ICC conditicus).
c.
A prfmary objective of the parameter and setpoint verification is the avoidance of reactor coolant pq trip for non-IDCA events particularly SGIR. Realistic operator actions in accordance with the procedures are expected to avoid loss of subcooling and the need to trip the reactor coolant pu::os for this event. Furthernore, since subcooling trargin would l
be quickly regained fol. lowing trakeuo or EPI initiation, with-out loss of natural circulation even if the coerator failed to take actions to prevent RCP tripping and FSFAS actuation, restart of the puups would be allowed.
Consequently, reliance on the PORV for depressurization is unlikely.
d.
The significance of primary systen voiding due to flashing of hot coolmt is disucssed as part of operator training.
The subject void treatrent is being supplemented by additional guidance on preventicn, detection, and mitigation of voids.
l This is considered outside of the ATOG scope but will be addressed.
e.
Actions following <.cntainment isolation signals will be 4
reviewed to ensure consistency in the treatment of i
availability of cooling water and seal injection to prevent pump damage. Instructions for pu p trip are provided in the i
ATOG guidelines in the unlikely event of rechanical putp i
damage. Crtieria for restart of RC pu:ps include assuring that cooling water and seal injection are available.
Existing TMI-l procech:res also include the guidance.
f.
Instructions for maintaining or reinitiating forced RC flow are contained in ATOG for ICC conditions.
2.
Guidance for Justification of Manual FfP Trip a.
A soectrun of small break IDCAs has been analyzed for 177 and 205 FA plant types using the CRAFT 2 code. Using the Anpendix K evaluation techniques, there exists a cocbination of break sizes and RC puTp trip times which result in exceeding 10 CFR 50.46 limits.
For the worst break size, i.e., that size which requires the earliest pu o trip, trip must occur within 2 minutes of the indication of need for pump trip.
As break size decreases, nore time is available for operator action, the critical time period of high void fonmtion
(>70%) when RC puTp trip is not recocrended, has also been.
determined. The critical. time period for the break requiring the earliest operation action tire is short (5 minutes) when puTp trip could result in exceeding 10 CFR 50.46 criteria. i
b.
A best estimate SBIICA analysis will be performed for each general plant type, over the spectrum of sizes determined by the conservative analyses to determine (a) the time available for a required RC pump trip, and the period of time when RC pump trip is not recomended or (b) the lack of indication for a required pump trip. If it is determined that a need for IC pump trip exists, the time for operator action will be determined and justified by comparison to ANSI Standards and operating experience. An indication of reasonable operator action time is expected to justify manual RCP trip.
3.
Other Considerations a.
The level of quality of instrumentation, as described in the enclosure to the March 4, 1983 letter, used to produce the signal irdicating the need for PC punp trip, will be provided by GPUN to supplement the B&WOG generic subnittal for treatment of RC pumps during transientc.
b.
The A'IOG guidelines and plant specific Dnergency Operating Procedures contain criteria for the timely restart of reactor coolant pumps when conditions which will support safe pump operation exist. Table 6 of the Equipment Operator chapter of A'IOG provides the conditions when RC pumps can be restarted.
Plant operators have been trained in their responsibility for c.
performing ICP trip in the event of a small break IOCA.
Current plant procedures (non-A'IOG) require RC pu:rp trip on 25"F subcooling margin. Instructions for plant operation are reinforced by regular requalification class and simulator training. Operators have been trained on the concept of RC pump trip on subcoolirg margin.
II.
Pumo Operation Criteria Which Will Not Result in RCP Trio Durinc Transients and Accidents Since it is the position of the B&WOG ard B&W that the safest method for RC pump operation following SBIDCA is (manual) trip, the criteria stated in this section will not be addressed.
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