ML20125A483

Requests Response to Encl Concerns on NEDO-20846,plant ATWS Submittal

ML20125A483
Person / Time
Site:	Monticello
Issue date:	08/01/1975
From:	Stello V Office of Nuclear Reactor Regulation
To:	Goller K Office of Nuclear Reactor Regulation
Shared Package
ML20125A480	List: ML20125A477 ML20125A483
References
NUDOCS 9212080363
Download: ML20125A483 (3)

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i DocketFile(

AUG 01 1975 NRR: Reading File J

Docket No. 50-263 RSB Reading File 1

V. Stello

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RS Administrative Asst.

.i Karl R. Goller, Assistant Director for Operating Reactors, Group 2. RL I

REVIEW OF NEDO-20846, MONTICELLO ATWS SUBMITTAL a

i Report

Title:

NEDO-90846, " Anticipated Transients Without Scram Study for the Monticello Generating Plant"'

Docket No.:

50-263 Originating Branch and Project Manager: ORB-2, B. Buckley 4

1 i

Technical Review Branch Involved: Reactor Systems Branch 1

Description of Review:

First Round Questions Review Status: Awaiting Information j

In order that we.may continue our review of.the subject topical, j

additional information is requested. The analysis submitted included 3

j the effects of, proposed plant modifications.

In order to satisfy-l l

paragraph II.c of Appendix A to WASH-1270 either revise the analysis l

to reflect the plant as it is, or submit plans for any proposed plant changes and a schedule for implementation of these changes.

4 1

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Victor Stello, Jr., Assistant Director for Reactor Safety i

l Division of Technical Review Office of Nuclear Reactor Regulation

Enclosure:

Concerns-on NEDO-20846 l

cc:

S. Hanauer F. Schroeder A. Giambusso 1

0. Ziemann B. Buckley T. Novak j

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CONCERNS ON NED0-20846 1.

Provide the peak torus water temperature reached during the MSly closure ATWS.

Provide and justify a torus water temperature limit.

If the calculated temperature exceeds the limit, discuss the plant modifications needed to keep torus water temperature below the proposed limit.

NE00-20626 suggests a pool temperature limit of 170*F.

If the peak torus water temperature exceeds 170 F discuss plant modifications needed to keep this temperature below 170'F.

2.

The analysis takes credit for the operator initiating the standby liquid control system five minutes after the ATWS event.

Discuss the indications available to the operator to assure this manual initiation of the SLC.

3.

In figure 4-3 the relief valve flow oscillates between about 3,000 and 7,000 lb/sec from about 30 seconds to 95 seconds after t

the ATWS. At about 108 seconds the relief valve flow begins to oscillate between 3,000 and 14,000 lb/sec.

Explain this difference in the peak relief valve flow.

4.

The Technical Specifications present sodium pentaborate solution concentration versus net tank volume in Figure 3.4.1.

The concentration varies from 10.8% to 21.4%.

Perform the analysis using each of these concentrations.

Justify the use of 13% as an initial condition listed in Table 3-1 of NED0-20846. Also justify the poison reactivity worth and provide vessel volume.

5.

In Section 4.4 of the Technical Specifications a minimum flow rate of 24 gpm for each of the standby liquid control system pumps is listed as a surveillance requirement.

Perform the analysis using this value.

In Table 3-2 of NED0-20846 a 28 gpm flow rate per pump is listed.

Provide your basis for using this L

value in your analysis.

Provide the total volume of poison in-jected following the ATWS for both hot shutdown and cold shutdown.

i 6.

It is stated that no accounting for possible non-homogeneous mixing was made since this would take a detailed evaluation.

However, GE stated at a meeting with the staff on August 7, 1974, that tests were being conducted on borated water mixing ohenomena.

Demonstrate that your assumption of uniform mixina is consistent-with the experimental data. Otherwise, perform a sensitivity study to show the effects.of nonhomogeneous mixing of the liquid -

poison, varying the mixing efficiency from 50% to 100%.

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7.

The staff has submitted to General Electric questions on NED0-20626 (letter from V. Stello to I. Stuart, January 28, 1974, and letter from W. Butler to I. Stuart, April 9, 1975).

Respond to the following questions as they apply to Monticello:

1, 4, 5, 6, 9, 12, 13, 16, 17, 310.1, 310.3, and 310.5.

8.

Provide the bases for assuming thirty seconds for transport time 3

of the sodium pertaborate solution from the storage tank to the vessel and for the liquid to become effective in the core.

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