NRC-89-0049, Forwards Response to Suppl 1 to NRC Bulletin 88-007, Power Oscillations in Bwrs. Actions Have Been Taken to Ensure That Safety Limit for Plant Min Critical Power Ratio Not Violated

Forwards Response to Suppl 1 to NRC Bulletin 88-007, Power Oscillations in Bwrs. Actions Have Been Taken to Ensure That Safety Limit for Plant Min Critical Power Ratio Not Violated

ML20236B337
Person / Time
Site:	Fermi
Issue date:	03/10/1989
From:	Sylvia B DETROIT EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-89-0049, CON-NRC-89-49 IEB-88-007, IEB-88-7, NUDOCS 8903210032
Download: ML20236B337 (8)

Text

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'*g B. Ralph Sytela Senior Vice President i

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U. S. Ibclear Rcsulatory Commission Attn: Document Control Desk Washington, D. C.

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References:

1) Fermi 2 tHC Docket No. 50-341

.tRC License No. NPF-43 2)

!HC Bulletin No. 88-07, " Power Oscillations x

in Doiling Water Reactors (BWRs), dated June 15, 1988

3) Detroit B31 son Letter to NIC, " Response to 15C Bulletin No. 88-07", NIC-88-0227, dated Septerrber 16, 1988 4)

NIC Bulletin No. 88-07, Supplement No.1,

" Power Oscillation in Boiling Water Rea::toJ:s (BWRs)," datu3 Decenber 30, 1988

Subject:

Besnonse to Surolwnnt_J to tK.' Bullet;in 88-07 ibis in to provide Dctroit D31 son's response to Supplement 1 to the NFC Bulletin 68-07 (Reference 4). Detroit Edison has reviewed the Supplement 1 and has taken actions to ensure that the safety limit for the Fermi 2 Mininum Critical Power Itatio (11CPR) is not violated.

Detailed specific responce to the actions requested by Supplement 1 to the Bulletin 88-07 is provided in Enclosure 1 of this letter.

If you have any questionr, please contact Mr. Girija Shukla at (313) 586 4270 8903210032 890310

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I, B. PMPH SILVIA, do hereby affim that the foregoing statements are based 1on facto arl circumstances which are true ard accurate to the best of nry knowledge and belief.

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personally appeared B. Ralph Sylvia, being first duly sworn and says that he-executed the foregoing as his free act and deoS.

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RESP 0tER TO SUPPLEMENT 110 NIC BULLFIFIN 88-07 y

Detroit Edison's response 'to each item of-the MC' Bulletin 88-07,.

Supplenent l is given below:

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o RfC_Bulletit.88-07_. Surolement 1. Action 1 q

.p Within 30 days of receipt of this Supplement, all BWR licensees l'-

, shottla. implement the GE Interim Stability Rmommendations described in Attachment 1.

However, for ttose plants' that do not 1

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. have effective automatic scram protection in the event of regional oscillations, a manual scram should be initiate] under all-operating conditions'when two recirculation punps trip (or "no punps operating") with the Reactor in the RUN mode.

o DgtiqitJtliagn_ Response-to Action 1 Fermi 2 has alrea3y implemented a manual scram requirement when

- two recirculation punps trip with the reactor in the WN mode.

Mo implementation of the GE interim stability recommenclations is Jescribed below.

A.

GE Interim Correcti" Actions 1, 2 and 3 state:

1 Intentional. operation shall not be allowed in Region A or

. Region B of Figure 1.

2.

If Region A is unintentionally entered:

Group 2 plant operators (Fermi 2) shall manually scram the reactor to exit the region.

3.

If Region B is unintentionally entered:

. Group 2 plant operators (Fermi 2) chall take immediate action to exit the region. Immedlate aocion consists of:

h Insertion of a predefined set of control rods which will most effectively reduce core thermal power.

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Increasing recirculation punp speed if one or more pumps are in operation. Starting a recirculation punp to exit this region is NCH' an appropriate action.

1 1

Fermi 2 is unique to other plants in' that the "minintm" recirculation ponp speed in 30%. Although the lower mechanical stops are set at,20% speed, the limiter #1 sotpcint is approximately 31% speed.' Because 'of ra:irculation M-G set

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instabilJtica exhibited at speeds from 24-28%, once a punp is started, it is backed just off the limiter #1 to verify control and is left at 30% punp speed.

Operations procedure NPP-22'.000.03, " Power Operation 25% to 100%

to 25%," has been revised to ensure that during startup, prior to exceeding the 80% rod line that core flow be greater than 45%

unless specifically directed by the NSS and Reactor Engineer for 1

Pre-Conditioning Interim Operating flanagement Recommendations (PCIWR). NPP-22.000.03 has also been revised to prohibit operation at >80% rod lines with core flow <45% of rate during controlled shutdowns. At 30% recirculation punp speeds, it is not currently possible to drop below 40% core flow at rod lines greater than the 80% rod line. Core flows of 45 to 46% are typically seen with Pccirculation punp speeds at 30%.

Because of this unique feature, Regions A and B cannot be entered unless a recirculation punp trip occurs, Procedure NPP-20.138.01 was revised to include the appropriate actions for entry into regions A, B and C.

The revision to these procedures satisfy GE Interim Corrective Actions 1, 2, and 3.

B.

GE Interim Corrective Acticn 5 States:

5.

If at any time during operation in Region A, B or C, core

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thermal hydraulic instability occurs, the plant operator

. shall manually scram the Beactor.

Evidence of thermal hydraulic instability consists of APM peak to peak oscillations of greater than 10% or periodic LPFM upscale or downscale alarms in addition to the guidance provided in SIL 380, Revision 1.

During July of 1988, Reactor Engineering and Operations hcd already taken actions to inplement corrective actions similar to that of interim Corrective Action 5.

The initial procedure revisions were based on the inSustry recommendations at that time, which allowed two minutes to correct oscillations with control red insertions or flow increases befort requiring a manual scram if oscillations continued. Training emphasized the ned for a manual scram if large oscillations cccurred, regardless of the allowed two minate durations. These recommendations were based on industry expectations of adequate margins to the MCPR safety limit for oscillations with durations of less than two minutes.

Because the above mentioned recorc:rendations were already in place in plant precedures, the " allowed" two minute duration was deleted and an inn,adiate Renator scram was directed. Fermi 2's definition

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' Lef the _ oscillation level at'which the manual scram nush be~ taken.

ils more conservative than Interim Corrective Action 5 in that an LPHi oscillation -of >10% ' peak-to-peak aha requires. a manual scrami-i Procedures -were also revised to emphaside.that nultilple LPM-I upscale-alarms are one of tne events.- that trigger ~ corrective actions for stability.

o The following Operations and. Reactor Engineering procedures were.

revised to implemnnt Interim Corrective Actions 1, 2,:3 and 5 as

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NPP-20.138.01 Recirculation Punp. Trip NPP-20.138.02 Jet Pump failure

NPP-20.107.02 Loss of Feedwater Heacing NPP-55.000.06 Power' Ascension and Shaping Using Control Rods NPP-22.000.03 Pcwer operation 25%'to 100% to 25%

h' i NPP-20.125.01.

Loss of Condenser Vacuum q'~

NPP-20.000.07 Fuel Cladding Failure NPP-20.131.01 Loss of General Service _ Water System NPP-23.13 8.01 -

Reactor Recirc System a

ARP 3D106-LP m. Upscale 1

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ARP 3D107 i LP M Downscale i

ARP 3D102 AP M Upscale ARP 3D103

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These procedure changes satisfy GE Interin: Correctivo Actions,1, 2, 3 and 5.

C.-

GE Interim Corrective Action 4 States:

4.

Intentional operation in Region C chall be allowed only for control rod. withdrawals during starc.4s requiring-PCIGIR.

T.'11s. region should be avoided for control rod i

sequence exchanges, surveillance testing and reactor shutdowns.

During control rod with3rawal, flux nanitoring should be cory3ucted in cecordance with SIL 380, Revi8icn 1.

Reactor Engineering procedure 53.000.06, " Power Ascension and Shaping Using Control Rods", already covers the recommendation of SIL 380,. Revision l' and contains guidance to only enter Ragion C during startup3 if required due to PCIOiR limitations. The procedure has been revised to more clearly define the boundaries of Region C.

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' Enclosure to tEC-89-0049 Page 4 Beactor Engineering proccdure 57.000.06, " Control Rod Pattern Exchange", already contains steps forbidding entry into Region C i

during control rod sequence exchanges, j

As mentioned in response to Action 1, Operations procedure NPP-22.000.03, " Power Operation 25% to 100% to 25%", has been revised to prohibit operation below 45% of rated core fJow at rod

lines greater than 80% unless specifically directed by the NSS anc

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Reactor Engineer. This will only be used during startupJ -

reqJiring PCICMR. The procedure has also been revised to pr inibit I

operation below 45% core flow at rod lines > 80% fat powet reductions. This requirement will also eliminate the entry into Region C for = Sequence Exchanges and surveillance testirg that require downpower maneuvers and shutdowns. Even with the Recirculation punps at "mininum" speed (~31%) at rod lines >80%,

core flow is typically 45 to 46%, minimizing the impact of these l

additional administrative requirements.

f These procedure changes satisfy GE Interim Corrective Action 4.

o NIC Bulletin 88-07. Sucolemmt 1. Action 2 The boundaries of Region A, B, and C shown in Figure 1 of the GE recommendations (Attachment 1) were derived for those BWRs using NIC approved GE fuel. For BWR9 using fuel supplied by other vendors, these regions should be adopted in principle, but the power / flow boundaries should be based on existing boundaries that l

have been previously approved by the IUC. For proposed new fuel.

designs, stability boundaries should be re-evaluated aM justified based on any applicable operating experience, calculated changes in core decay ratio using NIC approved methodology, and/or core 1

decay ratio measurerrents. There should be a high degree of assurance that instabilities will not occur under any circumstances of operation in Region C.

o Detroit Itlison's_Fesponse to Action 2 Felmi 2 is currently in the internal technical review prccess for the Reloa31 licensing submittal. The section of the submittal concerning stability will cover the subject of bouMaries for corrective actionc due to stability concerns.

Becauce an indepeMent section in the standard reloa3 licensing submittal format exists to discuss cycle specific issues, it is

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ensured that in subsequent reloads stability will be discussed.

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'o: - Hip Bulletin 88-07. a-mic==mt 1. Action 3 The BWROG recommendations of Attachment 1 Are ambiguous with respect to permissible conditions for entry into Regions B ard C.

Although the reco vnendations state that intentional operation' in Pegion B 119 not permitted and opdration in Region C is permitted

'only for purposes of fuel conditioning during rod withdrawal for startup operations, intentional entry into Region B or C is also allowable in situations where rod insertion or a flow increase is required by procedures to exit Regionc A and B after unintentional entry. Licencees should ensure that the procedurce and training enployed for implementation of these recommendations avoid any similar ambiguity. which could lead to operator confusion.

o' M;roit R11sonis Response to Action 3 As' discussed in response to Action 1, Fermi 2's unique

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recirculation punp mininum speed prevents operation in Region A or B, except during ; circulation pump trip events. Procedure i

NPP-20.138.01 adequately covers required actions upon entry into Regions A dnd B.

Actions per MPP-20.138.01, " Recirculation pung N

trip", are acre conservative than the Interim Corrective Actions in that our procedure directs that the rod line be reduced to less-

.than 80% if the punp trip pitces the unit in either region B or C.

'l There' is very little ambiguity in this arrangement and any perceived ambiguity inplied by entering Regions B or C by exiting Region A is eliminated by the requirement for a manual scram if Region A is entered.

A training summary was issued for urgent required reading to

. l address this supplement. In particular, the training suntnary I

discussed " intentional" entry into Regions A and B and listed the affected procedures. A more detal. led discussion of the topic was issued as required recding for Operations personnel on March 8,1989.

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'This training, along with the procedural changes discussed in response to Actions 1, 2 and 3 would satisfy all of the requirements,of tDC Bulletin 88-07, Supplenent 1, " Power 1

Oscillations In Boiling Water Reactore;".

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~ Attachment gFi^gure'1 from GE Interim.

Recommendations for

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