ML19207B375
| ML19207B375 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 07/30/1979 |
| From: | Bixel D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| IEB-79-12, NUDOCS 7908240523 | |
| Download: ML19207B375 (3) | |
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212 West Michigan Avenue, Jackson, Michigan 49201 (517) 788-0550 July 30, 1979 Mr James G Keppler Office of Inspection and Enforcement Region III US Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 DOCKET 50-155 - LICENSE PPR BIG ROCK POINT PL.43T TO IE BULLETIN 79-12: - RESPONSE "SHORT PERIOD SCRAMS AT BWR FACILITIES" The subject bulletin dated May 31 from short periods during reactor startprovide information rela
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requested information.
-up.
This letter provides the in the subject bulletin. Big Rock Point is significantly differe t Big Rock Point has a small, closely cou l dthan ne n
with far fewer control rods than larger differences are significant in relation t plants (32 compared to 177).
pe core Point to snort period scrams and the p These o the susceptibility of Big Rock to prevert short period events In particular, the small number of co tractica start-ups significantly differentrods and the smaller number of no from those of larger plants.er rod make Big Rock P n rol short reactor period. Big Rock Point instrumentation does p Big Rock Point utilizes out-of core neutrovide for a scram instrumentation Thcre are seven channels, three power oper.
ron ation picuammeter) channels.two start-up, two intermediate and provide for a scram on(a short reactor' p ri d (Only the intermediate feature is automatically bypassed whee o 10 seconds or less channels reach 4%.
The start-up channels provide an alarm fn two of the thre this than 20 seconds.
or periods less Responses to the specific questions ask d b below:
e y the subject bulletin are detailed Question 1:
Review and revise, as necessary to each approach to criticalensure that an estimate of the critical rod pattern be made prior The method of estimating critical i
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rod patterns should take into account all important reactivity variables (eg, core xenon, moderator temperature, etc).
Response
Operating procedures already require that an estimate.of critical rod pattern be made prior to each reactor critical approach. The operator is cautioned to use this estimate as a guide only and to expect criticality with each notch withdrawn Question 2: Where inaccuracies in critical rod pattern estimates are anticipated due to unusual conditions, such as high xenon, procedures should require that notch-step withdrawal be used well before the estimated critical position is reached and all SRM channel indicators are monitored so as to permit selection of the most significant data.
Response
Big Rock Point procedures require that " notch-step withdrawal" be used for all rod movements during reactor start-up.
All nucl.ar instrument channels are required to be operable during start-up and the operators are required to monitor all neutrun instrumentation.
Question _3:
Review and evaluate your control rod withdrawal sequences to assure that they minimize the notch worth of individual control rods, especially those withdrawn immediately at the point of criticality.
Your review should ensure that the following related criteria are also satisfied:
Special rod sequences should be considered for peak xenon a.
conditions.
b.
Provide cautions to the operators on situations which can result in high notch worth (eg, first rod in a new group will usually exhibit high rod worth).
Response
The control rod withdrawal sequence specified for Big Rock Point has been selected to minimize notch worths.
The calculations verifying notch worths are detailed in the regions where high notch worths are encountered. All notch worths are significantly less than Technical Specifications limits.
With respect to the specific items addressed in this question:
Analyses have been performed assuming no xenon present and a.
again assuming peak xenor.onditions.
These analyses showed that notch worths do not change greatly between these conditions. A special rod withdrawal sequence for peak xenon conditions is thus considered unnecessary.
b.
The integrated notch worth curve for the approved control rod i.
withdrawal sequence is available for operator use.
As previously noted, the operators are cautioned to anticipate
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criticality with each notch withdrawn and all rod withdrawals are performed in a notch-by-notch mode. This is considered sufficient precaution and obviates the need for special operator attention during unique situations.
Question 4: Review and evaluate che operability of your " emergency rod in" switch to perform its function under prolonged severe use.
Response
Big Rock Point does not have an " emergency rod in" switch.
A jog bypass switch exists which could be used to accomplish continuous rod insertion if it is held in the "run" position simultaneously with the reactivity switch being held in the " insert" position.
The jog bypass switch is utilized for control rod testing performed prior to any critical approach.
Thus, the operability of this feature is verified prior to each start-up.
Question 5:
Provide a description of how your reactor operator training program covers the considerations above (ie, items 1 thru 3).
Response
Reactor physics is addressed in deteil in operator requalification and licensing training. All information in the Big Rock Point Technical Data Book, including approved rod withdrawal sequences, is covered in this training program.
At least evey two years, specific aspects such as reactivity verses
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reactor period, control rod worths, notch worths and Technical Specifications requirements are covered.
Technical Data Book information, such as the approved rod withdrawal sequence, integrated notch worth curve and reactivity verses period tables for beginnirg rnd end of cycle, are used to enable operators to identify pote ntial short period situations.
The administrative controls applied to reactor start-up are also reviewed.
These require the operator to expect criticality with each notch withdrawn and to perform 411 rod withdrawals in a notch-by-notch mode; they also require that the operator prevent stable reactor periods of less than 30 seconds from occurring.
This training is considered very thorough.
Operators completing this training have proven to be knowledgeable of reactor physics and responsive to reactor conditions.
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Jmd David A Bixel Nuclear Licensing Administrator CC Director, Office Nuclear Reactor Regulation
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Director, Office of Inspection and Enforcement
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