ML20072M040
| ML20072M040 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 08/23/1994 |
| From: | Sylvia B NIAGARA MOHAWK POWER CORP. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NMP2L-1488, NUDOCS 9409010172 | |
| Download: ML20072M040 (3) | |
Text
1 M V NIAGARA HuMOHAWK NIAGARA MOHAWK POWER COnPoRAT1oN/NINE MILE POINT, Po. BOX 63, LYCOMiNG, NY 13093/ TELEPHONE (315) 349-2882 8 Ralph Sylvia N*c[al* * "'**
August 23,1994 NMP2L 1488 1
i U. S. Nuclear Regulatory Commission
. Attn: Document Control Desk j
Washington, DC 20555 l
RE:
Nine Mile Point Unit 2 Docket No. 50-410 NPF-69 Gentlemen:
Subject:
Proposed License Amendment - Upmted Opemtion, Response to Requestfor AdditionalInfonnation In a letter to the NRC dated July 22,1993 (NMP2L 1397), Niagara Mohawk Power Corporation (NMPC) proposed a license amendment to allow Nine Mile Point Unit 2 (NMP2) to operate at an uprated power of 3467 megawatts thermal. During the course of the Staff's review of this proposed license amendment, the NRC has determined that additional information, as identified in its July 26,1994 letter to NMPC, is required to complete its review of this matter. Attached to this letter are the Staff's questions and the requested addit:enal information.
Niagara Mohawk has provided a copy of this response to the appropriate state representative.
Very truly yours, kM B. R. Sylvia Exec. Vice President - Nuclear 3RS/KWK/ksj Attachment xc:
Regional Administrator, Region I Mr. B. S. Norris, Senior Resident Inspector Mr. M. L. Boyle, Acting Director, Project Directorate I-1, NRR Mr. D. S. Brinkman, Senior Project Manager, NRR Ms. Donna Ross Division of Policy Analysis and Planning New York State Energy office Agency Bui' ding 2 Empire State Plaza COOC2U Albany, NY 12223 Records Management 94o9010172 940823 PDR ADOCK 05000410 i
i p
PDR k
ATTACIBLFEI Question 1 - Topical Report (NEDC-31994P, revision 1) prepared by General Electric states that "the time windows establishedfor the humanfactors analysis are typically the order of several minutes to hours. " Please clanfy the meaning of the word " time window. " It is not clear whether the term " time window" refers to the window of opportunity for an operator to take action or the estimated time for the operator to perform specific required action.
The term " time window" is de6ned as the amount of time between when an operator is provided a cue to take a specific action and the time at which the consequence of failing to perform the action in unavoidable. As such, equating " time window" with " window
- of opportunity", above, is correct.
Question 2 - Please explain the method used to determine the length ofthe time windows, e.g., by operator walk throughs or through accident sequence analyses.
The method used to develop the " time windows" is accident sequence analysis. More specifically, accident sequences are developed to describe the progression of a severe accident including the operator and component failures that can occur as a sequence progresses. The calculation of event timing is based on calculations which simulate the response of the core, vessel, and containment.
Question 3 - Please discuss whether the power uprate will change the type, scope, or time requirements of operator actions neededfor accident mitigation, including the type and scope ofplant procedure changes, and any anticipated changes in the scope or nature of operator response.
Timing of events has a direct influence on the probability of successful operator actions.
The impact of timing is developed by considering time windows, as above. The time for specific actions to be taken within the time window, i.e. the task time, is developed using walk throughs of procedures to direct the specific task. Generally, the greater the ratio of the time window to the task time, the greater the success probability. This occurs since the operators have a longer time to appraise, respond and correct, as nece::sary.
In this regard, the potential for power uprate to affect accident timing has been considered relative to operator reliability.
Page 1 of 2
Q The timeline below depicts the IPE treatment of time windows:
IPE IIuman Factors Modeling Timeline i
i PRE-UPRATE WINDOW i
t t,
tr o
iTASK TIME :
I I
s b
POST-UPR ATE WINDOW i
i i
't t,'
tr' o
In the above, t represents the start of the event, t represents the time of the cue to the o
y operator to take a specific action, and tr is the latest time at which the action can be successful. Similarly, the time from t to to, the task time, represent the time necessary o
for the operator to take the specific action. The timeline for t, to to must be accomplished sometime within the period t to tr, the time window. The power uprate has the potential y
to affect the actual times for specific accident mitigation task time windows. However, severe accident time windows are on the order of several minutes to many hours in duration and uprate related changes to event timings will be on the order of seconds to tens of seconds. In this regard, time window changes on the order of a few seconds, more or less, will have an inconsequential effect on the probability of operator success.
As such, t,' may actually occur a short time before t, and likewise for tr. However, in both cases the task time, i.e. the time from t, to to is the same and comfortably fits either time window. For example, the task time for aligning suppression pool cooling is approximately 10 minutes and is primarily a function of the time it takes to start and stop pumps and change valve positions. In both pre and post power uprate configurations much more than 10 minutes, (i.e., approximately 15 hours1.736111e-4 days <br />0.00417 hours <br />2.480159e-5 weeks <br />5.7075e-6 months <br /> in the NMP2 IPE), is available for the action to be successful.
As such, the power uprate will not significantly change the operator reliability values or overall plant safety measures as calculated by the IPE. In addition, the new uprate plant conditions will not create any new operator tasks or affect the scope of existing tasks.
Minor changes to plant operating conditions will not affect the nature of plant response or create new criteria upon which to measure system or operator response. As such, uprate changes will be limited to minor changes (i.e. on the order of seconds) in severe accident timing.
Where appropriate the threshold cues for operator action in the emergency operating procedures are being adjusted for uprated conditions, but in all cases the changes are small and no task scope change is involved.
In summary, the uprate will create minor changes to the timing of overall severe accident mitigation. In this regard, no changes to the type or scope of related procedures are required.
In addition, no changes to the scope or nature of operator response are necessary.
Page 2 of 2