ML20127M006

Supplemental Rept to Acrs

ML20127M006
Person / Time
Site:	Monticello
Issue date:	01/05/1970
From:	US ATOMIC ENERGY COMMISSION (AEC)
To:
References
NUDOCS 9211250330
Download: ML20127M006 (11)

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Docket ;o. 50-263 ' '5 i

Suppic aental Report to ACRS

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' MONTICELLO NUCLF AR GEt?ERATI!!C PLA!?T 7,. ,

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l OFFECHAL USE O. .LY 1.0 INTRODl'CTION AND St': _".ARY In our report to the ACKS, dated November 24. 1969, on the Monticelle facility, ve reported the resultc of our safety evaluation. In that report there were a number of items for which the results of our evaluation vere incomplete, primarily because ve did not have sufficient confirmatory information at the tire the report was written. We indicated that we vould report to the Cemmittee the follow-up action on these matters. This supplemental report discusses the status of these tatters:

(1) Non-isolable break in the 11PCI steam supply line (Section 6.1.1).

(2) Limitation en llPCI operation (Section 4.7).

(3) Acceptnbility of jet pump castings (Section 4.3).

(4) Vibratien monitoring of reactor internals (Section 4.3).

(5) Seisr.ic design of structures (Section 5.1.2).

(6) Instrumentatien and centrol items:

a. ECCS low pressure auto-relief interlock (Section 9.2.3).

b. Iemote testing capability of pressure switches on bellows of relief / safety valves (Section 9.2.3.3).

c. Single f ailure criterion (Section 9.2.5) .

d.

Acceatalility of standbv ras treatment systen initiatinP circuitrv (Section 9.2.4).

c.

Seismic tes ting of Class I instrumentation (Section 9.2.7) .

OFFHCEAL USE ONLY

OFFDCHAL USE ONL l' Since issuance of our report to the Cornittec , we have had f urther discussion with the applicant on the foregoing -atters. In addition, further inferration on ser.e of these tatters <as pr' vided in trendments Nes. 23 and 24 'Ibe additional information h&T bien reviewed and our evaluatien is presented in this report.

Our revitw of Technical Specifications is continuing and a revised draft proposed by the applicant (Amendment 23) hos been provided to the C ter.i t t e e . Subject to resciutien of items 1. 4 1:nd 6a above, development of final Technical Specifications, and satisf actory cottpletion of con-struction and preoperatienc1 tests, we conclude that the ?!onticello plant ray be licensed for operation.

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(s N' L 2.0 111 M IT S I ON 2.1 Sen-Isolalle brenk in the !!! C1 Steam Supply idne lhe cpp11 cant has not formally submitted any additional information in rerard to this tntter, llovever, he has informed us orally that a tedificatien vill be rnde to reduce the spectrum of break sires over rhich n ireak in the 5 stenn supply line, occurrin; in the main stencline "ill not initiate autenatic isolation of the broken line. Ue underttand thet this vill be accomplished by repiccing the pressure taps in the liPCIS stonnline with a more sensitive orifice device to reasure an increase in steam flow above rated, which would be indicative of a break in the 11PCI stenmline. Also, the applicant has stated analyses indicate that, in the event of a brenP which cannot 'e detected irredictely, sufficient tine is available to assess cn abnormal condition and then manually actuate the auto-relief system without resultinf in any significant offsite doses.

As stated in our previous report to the Committee, our position is that the applicant will need to (a) demonstrate that the llPCIS and RCICS steam supply lines have adequate isolation capability with the present design, or (b) present information on changes that could be made so that failures in these steanlines could be detected, and the lines isolated as required.

The applicant plans to discuss this matter with us prior to the ACRS neeting.

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DFFECHAL USE ONLP

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l 2.2 Limitatien en HPCI Operation t

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In the TSAR, the applicant indicated that in taking into account all transient stresses expected to occur for the reactor vessel during plant lifetime, five HPCI startups were considered. In Amendment 24, j dated December 19, 1969, the applicant stated that each of the five HPCI utartup cycles included three hot-cold-hot cycles for a total of 15 thernal j cycles. Subsequent analyses, as stated by the applicant, indicate the j usage factor would be less than 1.0 for 80 or more thermal cycles.

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No supporting information was supplied by the applicant to show the

{ c-Iculated peak stresses associated with the HPCI thernal cycles and

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! thus permit us to evaluate the available margin in the reactor vessel usare factor. Therefore, we still intend to place a limitation on HPCIS

operation in the Technical Specifications.

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2. 3. Acceptability of Jet Pump Castings In Amendment 24, the applicant clarified previous statements made

in the FSAR to show that the remaining castings which contain the carburire'd surface are all part of the removable inlet-mixer subassembly, 4

4 which consists of the 180* elbow and nozzle castings shown in the attached 3 sketch. The applicant has stated that none of thece castings has been j found to contain cracks.

a We cannot attribute any direct safety significance to cracking of 4

the inlet-mixer assembly. However, we also find that there were obvious deficiencies in the quality assurance program ur. der which the carburirtd OFFECEAL USE ONLY -

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< JFFECHAL USE ONL J castings were t.ade. Because of these deficiencies and the record of failure involving thcse compenents, ve still believe that additional inservice inspection of these castings should be required, t!e intend to include in the Technical Specifications an inspection program for the remaininr carburized castings which vill include inspection of all castings following the hot functional test and af ter the first refue31ng shutdown, and a lever frequency of inspection thereafter.

We have orally informed the applicant of our intentions. At this time the applicant has not made a commitment to accept this pronosed inservice inspection progrc.*,

2.4 Vibration Menitorint of 1:ecctor Internals The applicant has not changed his position from that previously reported to the Committee, i.e., for the Monticello plant Northern States Power vill rely upon the results of the Dresden 2 vibration tests.

The applicant stated that the results of the Dresden 2 vibration tests vill adequately represent any vibration that may occur in the Monticello reactor, since the fluid velocities within the Dresden 2 vessel are expected to be higher than in Monticello.

As stated in our previous report, we plan to require that the vibration levels of the critical internal and recirculation system components be monitored during plant startup and the initial operatica period.

ONECEAL USE ONLY

- s 4 DFFHCHAL USE ONLL' The applicant has stated that he is prepared to discuss this ttatter in detail with the Comittee at the January meeting.

2.5 Seismic Design of Structures Since the submittal of our report to the Comittee, additional information on stress levels in critical piping systems and discussions en analytical methods employed for dynamic analysis have been provided by the applicant in Amendment 24, dated December 19, 1969. This informa-tion is being evaluated by our seismic design consultant, nr.d his report vill be submitted to the ACRS before the full Comittee meeting. We ,

anticipate that the seismic design methods employed will be acceptable.

2.6 Instrumentation and Control Items 2.6.1 ECCS Low-pressure Auto-relief Interlock The interlock function is provided by on arrangement involving six pressure switches (one switch for each ECCS pump) monitoring pump discharge pressure. The interlock is a permissive-type which allows initiation of auto-relief rhen one of the six switches responds to either the pressure characteristic or to a circuit failure which produces the same signal to the auto-relief system as the pressure characteristic. Therefore, a single f ailure which produces a pemissive condition would defeat the purpose of the interlock in cases when non pemissive circuit orientation is required. We have concluded that this ja not acceptable and that single failure immunity is required. The applicant does not agree to this requirement.

OFFHCHAL USE ONLY

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2.6.2 Monitoring Capability of the Integrity of Bellows en the Tarret Rock Relief /Snfety Valves because the integrity of the bellows is essential to the self-actuated operating mode of the Target Rock relief / safety valves, we conclude thct the testing circuits associated with bellows integrity monitoring should be improved to permit unambiguous testing during operction.

The applicant stated that such capability would be provided in the Monticello design and ve cenclude this is acceptable. We shall review the specific design details prior to issuance of an operating license to ensure that these requirements are satisfied.

2.6.3 Acceptability of Etandby Gas Treatment System (SCTS) Initiating Circuitry Functionally, the SGTS is designed such that one (filter) train is considered to be the " pref erred" system and is actuated initially. If this " preferred" train fails, the redundant filter train is actuated after a time delay of 50 seconds.

Since submittal of our report to the Committee, we have received and reviewed the elementary diagrams for the SGTS. The applicant has stated that the system is designed to those portions of IEEE 279 which relate to testability and the single failure criterion. We conclude that the system is comprised of two electrically independent and redundant initia-ting systems and have not uncovered any deficiencies.

OFFECHAL USE ONLY

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-8 In response to our questioning concerning the ef fect on of fsite doses resultinc from the 50-second delay in transferring operation from one filter trcu. to another, the applicant has informed us orally that this initiatien circuitry will be changed. Upon receipt of the initiation signal, both filter trains will be started simultaneously; when opera-bility is assured one train vill be manually shutdown. We consider this acceptable.

2.6.4 Single Tailure Criterien At the time ve wrote our report to the Committee, some ambiguity existed as to whether the reactor protection and containment isolation systems were designed to meet the single failure criterion as defined in IEEE 279. In Amendment 23 the applicant confirmed that the systems are so designed. This matter is now resolved.

2.6.5 seismic Testing of class I Instrumentation In our earlier report to the Committee, we stated that the applicant had not submitted a completion schedule for the seismic test program related to the balance-of-plant systers; i.e., other than General Electric-supplied systems.

In Amendment 17 the applicant stated that the test program for the General Ele etric-supplied inotrumentation similar to that to be installed at Monticello will be completed by December 31, 1969. In Amendment 23 the applicant stated that, purchase specifications for critical items comprising the balance-of-plant equipment contained clauses requiring that the equipment survive possible seismic accelerations without loss OFFECHAL USE ONLY m_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ . _ . _ _ _ . - _ - - - - - - - - -

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of function. A program is currently underway to ascertain how the equipment manufacturers are able to assure certpliance with that portion of the specifications. The applicant stated that it is currently expected that this effort will be completed by !! arch 15, 1970.

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