ML19296C525
| ML19296C525 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 02/22/1980 |
| From: | Dewitt R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| RTR-NUREG-0578, RTR-NUREG-578 NUDOCS 8002260507 | |
| Download: ML19296C525 (6) | |
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Consumers Russell 8. DeWitt
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Vice President Nuclear Operations
![jQ7 General Offices. 212 West Mic hsgan Avenue. Jack son. Michigan 49201. Area Code 517 7H8-0550 W
February 22, 1980 Mr Harold R Denton, Director Office of Nuclear Reactor Regulation US Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - PROPOSED OVERALL RISK ASSESSMENT Representatives of Censumers Power Company met with members of your staff en January 2h,1980, to discuss plans for improving the overall safety of our Big Rock Point plant. The meeting was prompted by Consumers Power Ccmpany concerns regarding the appropriateness of certain modifications required by recent NUREG documents or those which might result from ongoing Systematic Evaluation Program (SEP) reviews. Big Rock Point is one of the oldest boil-ing water reactors and is unique with respect to plant design, size and loca-tion.
The recent URC requirements, on the other hand, result largely t' rom review of potential problem areas at never, more standard plants.
Consumers Power Company is cencemed that direct applicaticn of these requirements to Big Rock Point may not be cost effective in terms of overall plant safety.
Strong incentives exist for continued operation of Big Rock Point. These are briefly discussed below. Nonetheless, review of the potential costs of the NRC required modificatiens mentioned above indicates that continued oper-ation may be rendered economically unfeasible unless the safety benefits of each of these modifications is thoroughly evaluaced.
Big Rock Point is an important asset to the co=merical nuclear power program in the United States. Among the factors which provide an incentive for con-tinued operation are:
a.
It is one of the few operating reactors at approximately the midpoint of its design lifetime.
It is also a small and comparatively simple plant. The plant therefore provides a somewhat unicue opportunity to obtain mid-and late-life operating experience, including identifica-tien of possible unforeseen problems, at a lover public risk than if such experience were to be gained solely at larger plants.
DQ 8002260
Mr Harold R Denton 2
b.
An active Department of Energy light water reactor fuel research program is ongoing at Big Rock Point.
The new fuels being evaluated have a potential fbr improving operation and reducing acci ent risk at all nuclear power plants.
This urogram may not be capable of being economic-ally pursued at larger plants.
c.
The plant provides the power equivalent of approximately 3,000 barrels of oil per day.
System design is such that replacement power for Big Rock Point is essentially all generated in oil-fired units.
d.
Big Rock Point's remote location vould require replacement power to be transmitted several hundred miles with attendant problems of transmission losses and deleterious effects on grid stability.
e.
Big Rock Point has operated safely for over 17 years.
Many members of the present plant staff have worked at the plant since initial criticality.
The cor.tinuity and experience of the plant staff is believed to be a signifi-cant contributor to overall plant safety and minimization of risk to the public.
Analytical tools are somewhat lacking to permit an accurate quantitative evalua-tion of the cost benefit of various safety modifications.
Consumers Power Company intends to provice such tools by performing an overall plant risk assess-cent.
This assessment will utilize probabalistic analysis methods similar to those employed in WASH-lk00, the Reactor Safety Study. The primary purpose of the risk assessment vill be to identify those plant characteristice which have the greate=t effect on health and safety of the public.
Proposed modifications to reduce risk would then be evaluated using the probabalistic model. This pre gram is consistent with recoemendations of NUREG-0585, "TMI-2 Lessons Learned Task Force Final Feport" to perfbrm a systematic reliability evaluation of plant systems and to define a quantitative risk goal as a threshold for backfitting of new requirements to existing plants.
The probabalistic model would be maintain-ed current so that future changes in plant design and operation can be based on the best available technical information.
The analysis described above vill identify those areas which might benefit from plant modifications, and these modifications might be different from those pro-posed in recent NRC requirements (NUREG-0578, NUREG-0585, HUREG-0626, NUREG-0660) or which might result from SEP requirements. For this reason, Consu=ers Power Company proposes to defer action on the plant modific ations listed in the attach-ment to this letter. Upen completion of the above assessment, these modifications vill be evaluated using the probabalistic model; if they are then deemed necessary, their i=plementation vill have been delayed only as long as the duration of the risk assessment.
Based upon discussions with two pctential consultants, the proposed assessment is estimated to require approximately five man-years of effort and could be completed by the end of this year.
Consumers Power Company considers the program described above to be of benefit for the remainder of the nuclear industry as well.
It will provide the oppor-tunity to establish techniques to quantify risk goals and reduce uncertainties within the industry and within the NRC.
It provides the opportunity to ensure the maximum risk reduction benefit from plant modifications.
Vr Ha mld R Denton Consumers Power Company intends to select a consultant and begin work on this project within one month. An indication of your concurrence with this program would be appreciated by April 1,1980.
Russell B DeWitt (Signed)
Russell B DeWitt Vice President Nuclear Operations pages
BIG ROCK POINT MODIFICATIONS TO BE DEFERRED PENDING CCMDLE" ION OF THE RISK ASSESSMENT 1.
High steam drum level feedvater trip - This modification was originally discussed in Consumers Power Company letter dated October 30, 1979 It was discussed as a possible means of eliminating the need for high pressure testing of relief valves.
The BWR Owners Group has recently decided not to recommend installation of such trips in lieu of testing.
Consumers Power Company considers that automatic termination of a principal vater source to the reactor requires further consideration from the standpoint of effect on overall plant safety.
2.
Post-incident shielding (NUREG-0578, Item 2.1.6.b) - The technical reascns and justification for deferring this ite= until the completion of the SEP program were discussed in detail in Consumers Power Company letter dated December 27, 1979. The cost of this single modification is significant with respect to continued economical operation of the plant.
The need for and specifications of this modification vill be reevaluated upon completion of the risk assessment.
3.
Technical Support Center (NUREG-0578, Item 2.2.2b) - The reasons for deferr-ing this item vere also discussed in our December 27, 1979, letter.
The cost of this modification, as currently envisioned, is also significant with respect to continued economical operation.
It vill also be reevaluated upon completion of the risk assessment.
h.
Post-incident sampling system (NUREG-0578, Item 2.1.8.a) - The reasons for deferring this item were also discussed in our December 27, 1979, letter.
5 Alternate shutdown panel (fire protection requirement of Amendment 25 to License DPR-6) - Deferral of this ite= until the completion of the SEP program was requested by insumers Power Company letter dated August 2h,
1979.
6.
Containment Hydrogen Mcnitor (NRC letter dated September 13, 1979) - The small size of the Big Rock Point core and the large free volume inside containment result in a maximu= credible hydrogen concentration of approxi-mately 6 volume percent.
This situation was discussed in Consumers Power Company letters dated May h,1979, and October 30, 1979 The need to moni-tor centainment hydrogen concentration at Big Rock Point is thus much less than at other plants and needs to be evaluated as part of the risk assess-ment.
7.
ATWS Modifications or Analysis including Recirculating Pump Trip and ATWS Rod Injection - Big Rock Point's response to a postulated ATWS event is different than that of other boiling vater reactors due to significant design differences.
The need for modificatiens to prevent and/or mitigate ATWS vill be considered as part of the risk assessment.
BIG ROCK POINT MODIFICATIONS TO BE DEFERRED (cont'd) 2 8.
Automatic Isolation of Emergency Condenser (Draft NUREG-0626, Item A.2) -
NUPEG-0626 discusses this modification as a change in automatic isolation logic to iso?. ate the condenser on high radiation detected in its vent rather than on high radiation detected in the main steam line.
In fact,
no automatic isolation logic of any kind currently exists at P. g Rock Point; this modification is thus considerably more difficult than implied in NUREG-0626.
Consumers Power Company is concerned that autome. tic isola-tion vould eliminate the emergency condenser as a heat sink.
The risk assessment vill provide cpantitative data to evaluate the cost benefit of this modification.
9 Installation of Interlocks on Pecirculation Loops (Draft NUPEG-0626, Item A.8) - Operability of Big Pock Point recirculation loops is now controlled administratively in accordance with a recently approved Technical Specifi-cation chanEe.
Consumers Power Company consMers that this control provides adecuate protection of the health and safety of the public.
The risk assess-ment will enable quantitative determination of the benefit of interlocks.
BIG ROCK POINT MODIFICATIONS WHICH WILL CONTINUE IN ARALLEL WITH THE RISK ASSESS!ENT 1.
Emergency Condenser (Reactor Coolant High Point) Vent (NPC letter dated September 13, 1979) - This appears to be the only practical method of releasing non-condensible gases from the primary system and is important to assure continued availability of the emergency condenser as a heat sink.
2.
a.
Containment Radiation htnitor (NUREG-0578, Item 2.1.8.b) b.
Improved Iodine Instrumentation (NUREG-0578, Item 2.1.8.c) c.
Containment Pressure Monitor (NBC letter dated September 13, 1979) d.
Containment Level Monitor (!TRC letter dated September 13,1979) e.
Modification / Replacement of Existing Steam Drum / Reactor Vessel Level Instrumentation (CPCo letter dated December 27,1979)
These modifications vill all aid in safe operation of the plant.
Their impact on continued economical operation does not necessitate deferral.
3.
Fire Protection Modifications Required by Amendment 25 to License DPR (except alternate shutdown panel) - Work on these items is underway.
Their completion vill enhance plant safety.
h.
a.
Relocate Backup E=ergency Diesel Generator (CPCo letter dated December 27, 1979) b.
Provide Fedundant Cooling Water Supply for Core Spray Heat Exchanger (CPCo letter dated December 27,1979) c.
Provide Larger Emergency Diesel Generator Fuel Supply (CPCo letter dated December 27, 1979)
These items are all considered necessary to further ensure ability to safely control the plant in the event of an accident involving significant core damage and loss of off-site power.