ML20062D639

Forwards Review of NRC & Contractor Evaluations of Util Response to SEP Topic VIII-2, Onsite Emergency Power Sys & Diesel Generator

ML20062D639
Person / Time
Site:	Big Rock Point File:Consumers Energy icon.png
Issue date:	08/03/1982
From:	Vincent R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	Crutchfield D Office of Nuclear Reactor Regulation
References
TASK-08-02, TASK-8-2, TASK-RR NUDOCS 8208060178
Download: ML20062D639 (7)

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Consumers Power Company General officet: 1945 West Parnali Road, Jackson, MI 49201 e (5171788 0550 August 3, 1982 Dennis M Crutchfield, Chief Operating Reactors Branch No 5 Nuclear Reactor Regulation 11S Nuclear Regulatory Commission Washington, DC 20555 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - SEP TOPIC VIII-2, ONSITE EMERGENCY POWER SYSTEMS - DIESEL GENERATOR The enclosure to this letter provides Consumers Power Company evaluation of the NRC's June 22,'1982 SER (and its contractors TER) concerning SEP Topic VIII-2, "Onsite Emergency Power Systems - Diesel Generator", for the Big Rock Point Plant. As noted in the evaluation, Big Rock Point's EDG conforms to current NRC licensing criteria.

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' (A T U2. 5 Robert A Vincent Staff Licensing Engineer CC Administrator, Region III, USh3C NRC Resident Inspector-Big Rock Point pages O)

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i CONSUMERS POWER COMPANY BIG ROCK POINT PLANT SEP TOPIC VIII-2 ONSITE EMERGENCY POWER SYS,TEMS - DIESEL GENERATOR i

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i Consumers Power Company Response i

to EG&G and NRC Review of Emergency Diesel Generator Output Frequency July 1982 l

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CONSUMERS POWER COMPANY RESPONSE TO EGSG AND NRC REVIEW OF EMERGENCY DIESEL GENERATOR OUTPUT FREQUENCY I.

ABSTRACT This enclosure serves to provide Consumers Power Company response to 4

I conclusions reached by EG&G (as documented in Reference #1) and by the NRC (as documented in Reference #2) concerning the Energency Diesel Generator (EDG) output frequency transient during initial load assumption at Big Rock Point Plant. As concluded by EG&G, the minimum value of EDG output frequency which occurs during the frequency transient when the Electric Fire Pump (EFP) is started is less than the minimum allowable by current licensing criteria. Based on the.EG&G conclusion, the NRC states that the EDG lov output frequency must be justified by test or analysis or the EDG speed control must be improved.

It is the opinion of the Consumers Power Company that the EDG minimum output frequency during the loading transient is acceptable according to current licensing.

l criteria and according to sound engineering judgement.

II.

DISCUSSION b

A.

EG&G AND NRC CONCLUSIONS As part of the report listed as Reference #1, EG&G states the follow-ing in Section 3.1 regarding the EDG output frequency during initial load assumption:

- "A corresponding frequency transient with a maximun frequency of 62.2 Hz and a minimum frequency of 54.5 Hz occurs over a two-second interval."

. the frequency decrease' encountered when starting the elec-tric fire pump is less than the 95% of nominal frequency required by Paragraph C.h of NRC Regulatory Guide 1.9 and is, therefore, not in compliance with current licensing criteria."

- "NRC Regulatory Guide 1 9, Paragraph C.h requires that the fre-quency and voltage decrease during the diesel-generator loading j

sequence not exceed 95% and 75% of nominal values, respectively; a larger decrease may be justified for a diesel-generator that carries only one large connected load.

Since the Big Rock Point diesel-generator carries more than one load, the frequency drop

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to 5h.5 Hz is not in compliance with current licensing criteria."

In Section h.0 of the report, EG&G summarizes:

"The diesel-generator loading meets the current licensing criteria except that a frequency decrease to 91% of nominal frequency occurs

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vhen starting the electric fire pump.

The maximum allovable decrease, as defined in Paragraph C.h of RG 1.9, is 95%."

Based on the EG&G report, the NRC concludes in Section VI of its Final Safety Evaluation (see Reference #2) that the EDG lov output frequency must be justified by test or analysis or the diesel generator speed control improved.

B.

CONSUMERS POWER COMPANY RESPONSE TO EG&G MID NRC CONCLUSIONS Although Consumers Power Company (CP Co) acknowledges that the EDG output frequency does drop below the Regulatory Guide 1.9 recommen-ded minimum value of 95% of nominal frequency, it is the firm opinion of CP Co that the minimum EDG output frequency of 91% of nominal (as reported in Reference #h) is acceptable for two reasons.

First, it is the opinion of CP Co that the performance of any of the loads comprising the EDG initial step load group is not degraded below their minimum requirements (which is consistent with IEEE 387-1977; see Reference #3).

Second, current licensing criteria allows frequency excursions beyond 95% of nominal frequency in circumstances not unlike those at Big Rock Point.

Although each of these reasons was supported and documented in detail in a recent CP Co submittal (see Reference #h) they are briefly described and, in some cases amplified, in the paragraphs that follow.

Regarding the quality of the EDG output frequency during load assump-tion, Reference #h shows that the output frequency remains within the Regulatory Guide recommended tolerance of 95% of nominal through-out the entire transient with the exception of only 0.65 seconds.

During this 0.65-second period, the frequency drops to a minimum value of 91% and then recovers and rises aoove the lover 95% recom-mended limit.

As described in detail in Reference #h, it is the opinion of CP Co that this frequency excursion vill have an insign-ificant effect on the individual loads that comprise the EDG initial step load group.

The reasons for this opinion (as documented in Reference #h), are listed below.

Component of the EDG Initial Step Load Group

1) EFP

1) The EFP is tested approximately every three days with the EDG supplying a starting frequency similar to that examined in Ref-erence #h.

The EFP has never failed to start and reach running speed during such tests.

2) Core Spray Valves (MO-7070 & MO-7071)

2) Although an increase in torque is electrically imposed by the EDG output voltage and frequency tran-sient for a very short duration (see

1 1 of Reference h and note j-i that the EDG output frequency is lov t-while the output voltage in high for only approximately one second),

this increased electrical torque i

should have no significant effect on valve operation. The engineering 4

staff at Rotork (the valves' man-ufacturer) has indicated that'the valves' torque switch vill not operate to cease the opening stroke.

According to Rotork, cessation of valve travel by torque switch can enly occur by a restrictive shaft ~

load (ie, valve obstruction, j

seizure or seating) which causes a linear shaft movement to result i

in a trip of the torque switch.

L Simply varying the voltage and fre-4 quency of the valves' motor input will not result in torque switch operation.

3) Lighting

3) The lighting may momentarily dim, but should brighten within a couple.

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'of seconds.

h) Gland Seal Exhauster h) The gland seal exhauster does not automatically restart efter power 4

is restored to Bus 2B and, therefore, would not be subject to the fre-l quency transient.

5) I&C Transformer

5) Examples of I&C transformer loads are I&C power supplies ES8512A 4

and ES8512B which are rated for operation at 50 h00 Hz.

6) Airlocks

- 6) By design, the air lock door hydraulic pump motors will not automatically re-sume operation after power is restored tc Bus 2B and, therefore, vill not be' sub-

.jected to the EDG output transient.

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air lock control circuits (like the EFP), however, are subjected to such transients approximately every three days.

The ability of'these circuits to sustain such transients and operate as designed has been proven frequently in the past.

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Regarding the acceptability of the EDG output frequency transient according to current licensing criteria, it.chould be reemphasized that Paragraph C.h of Regulatory Guide. (RG) 19 recommends: "The

' diesel-generator unit design should be such that at no time during the loading sequency should the frequency and voltage decrease to less than 95 percent of nominal and 75 percent of nominal, respec-tively.

(A larger decrease in voltage and frequency may be justified for a diesel-generator unit that carries only one large connected load.)"

Since the RG 19 description of under what circumstances a larger decrease in frequency may be justified is quite vague, there is room for quite dissimilar interpretations. As interpreted by EG&G and 0.ocumented in its interim report (see Reference #1), RG 1.9 allows justification of a frequency decrease belov 95% of nominal if the diesel generator carries only one large connected load.

The EG&G interim report states:

"Since the Big Rock Point diesel-generator carries more than one load, the frequency drop to 5h.5 Hz is not in compliance with current licensing criteria".

CP Co con-siders the EG&G interpretation to be incorrect since this interpre-tation vould require that the EDG carry only one load and that this load be a large load in order that justification for a frequency

<95% be permitted.

As documented in Reference #h, CP Co assumes a more realistic ap-proach in its interpretation of RG 19, Paragraph C.h.

Utilizing the NEMA MG-1 definition of "large apparatus" to be 100 hp or greater (see Reference #5), it becomes apparent that only one large load is connected to the EDG during initial load assumption; namely the 100 hp (nameplate rating) EFP. Utilizing full load ratings, the EFP alone constitutes a load equivalent to 108 kVA/250 kVA = L3.2%

of the EDG full load rating. The balance of the EDG loads that comprise the initial step load group (namely the core spray valves, the lighting, the gland seal exhauster, the I&C transformer and the air locks) represent only 58.1 kVA/250 kVA = 23.2% of the EDG full load rating. During starting conditions, the EFP alone comprises between 80% and 90% of the total starting kVA load imposed on the EDG.

For these reasons, CP Co feels justified in stating that the Big Rock Point EDG carries only one large connected load.

In an attempt to eliminate the requirement of interpreting RG 19, CP Co prefers utilizing one of the basis documents for RG 19; namely IEEE 387-1977 Paragraph 51.2(5) of the standard (see Reference

1. 3) states that a diesel generator unit shall be capable of " main-taining. voltage and frequency at the generator terminals within limits that will not degrade the performance of any of the loads comprising the diesel load below their minimum requirements, in-cluding the duration of transients caused by load application or removal".

It is the opinion of CP Co that the Big Rock Point EDG provides an output in accordance with this criteria.

CONSUMERS POWER COMPANY RESPONSE TO EG&G AND NRC REVIEW OF EbERGENCY DIESEL GENERATOR OUTPUT FREQUENCY LIST OF REFERENCES (Sheet 1 of 2)

Reference Number Reference Description 1.

EG&G Interim Report # EGG-EA-5882, " Systematic Evaluation Program, Topic VIII-2, Diesel Generator, Big Rock Point",

dated May 1982.

2.

NRC Final Safety Evaluation as transmitted to CP Co in letter:

DMCrutchfield to DJVandeWalle, "SEP Topic VIII-2, Onsite Emer-gency Power Systems - Diesel Generator, Final Safety Evaluation For Big Rock Point", dated June 22, 1982.

3 IEEE 387-1977 "IEEE Standard Criteria for Diesel-Generator Units Applied as Standby Power Supplies for Nuclear Power Generating Stations", Para 5.1.2(5) " Quality of Power".

h.

Letter: RAVincent to DMCrutchfield " Big Rock Point Plant -

SEP Topic VIII-2, Onsite Energency Power Systems - Diesel Generator", dated April 21, 1982.

5 NEMA MG-1 " Motors and Generators", Part 20 "Large Apparatus Induction Motors", June 1981.