ML19326C771

Submits Proposed long-term Mod to Hpis to Alleviate ECCS Small Break Problem Reported in Util 780414 Ltr.Requests NRC Approval of Proposed Design & Proposed 10-15 Minute Operator Response Delay Time

ML19326C771
Person / Time
Site:	Arkansas Nuclear
Issue date:	07/20/1978
From:	David Williams ARKANSAS POWER & LIGHT CO.
To:	Reid R Office of Nuclear Reactor Regulation
References
1-078-14, 1-78-14, NUDOCS 8004280705
Download: ML19326C771 (5)

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- s' REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

DISTRIBUTION FOR INCOMING MATERIAL 50-313 REC: REID R W ORG: WILLIAMS D H NRC DOCDATE: 07/20/78 AR PWR & LIGHT JATE RCVD: 07/24/7: '

DOCTYPE: LETTER NOTARIZED: NO

SUBJECT:

COPIES RECEIVED LTR 1 ENCL 40 FURNISHING INJECTION SYSTEM,APPLICANT"S PROPOSED LONG-TERM MODIFICATION TO THE HIGH P TO ALLEVIATE THE ECCS SMALL BREAK PROBLEM REPORTED TO REGION DIAGRAM IV OFFICE OF INSPEC AND ENFORCEMENT 11Y LTR DTD 04/14/78...W/ATT PLANT NAME: ARKANSAS - UNIT 1 REVIEWER INITI AL: XJM DISTRIBUTOR INITIAL: q oo**no***********

DISTRIBUTION OF THIS MATERIAL IS AS FOLLOWS ******************

GENERAL DISTRIBUTION (DISTRIBUTION CODE AOO1)FOR AFTER ISSUANCE OF OPERATING LICENSE.

FOR ACTION: BR CHIE ORB #4 BC**W/7 ENCL INTERNAL: /450 FILE ** / ENCL NRC PDR**W/ ENCL I & t**w.<2 ENCL OELD**LTR ONLY HANAUER**W/ ENCL CORE PERFORMANCE BR**W/ ENCL AD FOR SYS & PROJ**W/ ENCL ENGINEERING BR**W/ ENCL REACTOR SAFETY BR*nW/ ENCL PLANT SYSTEMS BR**W/ ENCL EEB**W/ ENCL J. MCGOUGH**W/ ENCL EFFLUENT TREA SYS**W/ ENCL EXTERNAL: LPDR'S RUSSELLVILLE, AR**W/ ENCL TERA **W/ ENCL NSIC**W/ ENCL ACRS CAT B**W/16 ENCL THIS DOCUMENT CONTAINS POOR QUAUTY PAGES 4 hISTRIBUTION: LTR 40 ENCL 39 CONTROL NBR: '^^

l@IZE: 3P+1P 70C07'I1E N D o00o000**************************** THE END *) * * *

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H 2 L Pl H G t3 Li l L O AMKsNSAS ARK ANS AS POWER & LIGHT COMPANY STM & LOU #SIAN A SYAEETS . LITTLE AOCK, A AK ANSAS 72203.(5013372-.1311 July 20, 1978 1 078-14 Director of Nuclear Reactor Regulation ATTN: Mr. R. W. Reid, Chief Operating Reactor Branch #2 h,C/1 7 f, U. S. Nuclear Regulatory Commission 'l Washington, D. C. 20555 'i / 9  %

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Subject:

Arkansas Nuclear One - 1[iiM. "?,,, f Docket No. 50-313 '- ,

License No. DPR-51 ECCS Small Break Long-Tern Modification (File: 1510, 0520)

Gentlemen:

As committed in our letter of April 21, 1978, and subsequently reflected in your order for Modification of License dated April 28, 1978, the following is proposed as a long-term modification to alleviate the ECCS Small Break Problem reported to Regien IV Office of Inspection and Enforcement by our letter dated April 14, 1978. This modification, to the High Pressure Injection System, relies on a lesser state of operator readiness than the interim solution outlined in our letter of April 27, 1978.

Our long-term modification allows us to perform the manual opera-tions required in our interim fix remotely from the Control Room with the exception that the HPI header cross connect valves vill be in a normally open position and vill not have to be operated at all if this postulated accident were to occur. As outlined on the attached sketch, each HPI isolation valve vill be connected to both red and green (channels 1 and 2) power. Each channel vill contain redundant contactors between the breaker, at the Motor Control Center, and the valve itself. The contactors on channel 1 vill be interlocks a by a Kirk Key Interlock in the Control Room, with the contactors on channel 2. This interlock will preclude closing the contactors on both channels at the same time and vill provide at least two (2) points of separation between the two channels at all times.

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'l-078-lh Mr. R..W. Reid July 20, 1978 In'the event this postulated small break accident was to occur, the operator would. receive a safety injection alarm, in-the the Control Room, within less than sixty (60) seconds of the break. Our procedures vill require the operator to immediately, upon receipt of the alarm, verify flow through all four (h) safety injection valves. If the operator iden-

.tifies "no flow" in any of the injection legs, he vill immediately proceed to manually transfer, utilizing the Kirk Key Interlock, power to the valve (s) with "no flow" to the other channel of power. This will assure flow through all four (h) injection legs, the necessary criteria to alleviate this postulated yroblem. As discussed in previous submittals, the postulated small break prei in vill not occur unless the small break is accompanied by a 3 of offsite power.

In our situation, the operator vill perform che above actions irregardless of a. loss of offsite power with no degradation to the ability to mitigate the accident.

By letter, James H. Taylor to S. A. Varga, dated July 18, 1978,

. Babcock and Wilcox has submitted additional ECCS small break e analysis for B&W's 177 Fuel Assembly Lovered-Loop NSS (2772 MW).

These analyses incorporate a step input of water to the RCS at ten (10) minutes (consistent with our interim solut' ion) and resultLin a conservative maximum peak clad temperature of 1092F for the worst case break. Based on this and other analysis B&W has performed, assuming a step input of water to the RCS in fifteen (15) minutes as opposed to the ten (10) minutes assumed above, the maximum peak clad temperature for the vorst case break size (utilizing analysis for 2772 MW) is about 2000F (still below the 2200 F criteria of 10CFR 50.46). Therefore, we conclude that a step input of water (initiation of flow through all four (h) injection legs) at fifteen (15) minutes is acceptably within the requirements of 10CFR 50.h6.

As stated in NUREG-0460, operator action may be assumed at the end of ten (10) minutes if adequate information is displayed a.n d

-the actions are very simple in nature which is consistent vieh-past licensing actions and is appropriate for those~ actions which are simple and based on the display of adequate information to the operator. _As discussed earlier, the operator receives a Safety Injection Signal Alarm (audible and visual alarm) in the Control. Room in less than sixty (60) seconds from.the initiation l of.the postulated 1 break. At'that time, he has four (h) flov l indicators available. Based on whether his indicators show ade-qate flow or~"no flow" he must turn two.(2) key controlled switches (located side-by-side) for each valve with "no flow" indication.

Under; single' failure-criteria,Lthe maximum number of valves he l l

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1-078-lh-Mr. R. W. Reid July 20, 1978 would have to transfer would be two (2) or a total of four (h) switches, all located on the same panel.

We.therefore conclude that adequate information is avail-

'able to the operator and the actions he must perform are few and very simple'in nature. We further conclude that ten (10) minutes to perform these actions isia reasonable operator delay time and would successfully align the !!PI system to mitigate-any' size postulated LOCA with substantial margin to 10 CFR50.h6 limits.

However, as stated. earlier, we do have analysis that indicates that at least fifteen (15) minutes are available (for the worst case break) before. operator action is required. A fifteen (15) minute operator delay time will also successfully align tae HPI System to mitigate any size postulated LOCA with margin to 10CFR50.h6 limits.

We request your approval of this proposed design and approval of an operator response delay' time in the range of ten (10) to l' fifteen (15) minutes, inclusive.

t Upon . your approval o f the above, we will submit-analysis I

totally.in conformance with 10CFR 50.h6 (as required by the

.above mentioned Order for Modification of License) documenting that our proposed modification will produce maximum peak clad

' temperatures below 10CFR 50.h6 limits (assuming an operator delay time consistent with the minimun delay time you find acceptable). g

! .Your most expeditious review is' requested as we wish to make this modification during our next refueling outage and we must begin procurement as soon as possible. As you desire, f we vill be glad to support telecons or meetings with you to l discuss-this issue and assist your review.

( Very truly yours,

.l D,.a ~.s-[m ,

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s. c x; Daniel H. Williams Manager, Licensing l- DHW/JTE/ew i

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