ML17037B535
| ML17037B535 | |
| Person / Time | |
|---|---|
| Site: | Nine Mile Point  |
| Issue date: | 09/03/1976 |
| From: | Schneider R Niagara Mohawk Power Corp |
| To: | Lear G Office of Nuclear Reactor Regulation |
| References | |
| Download: ML17037B535 (34) | |
Text
ERG FORM 195 (2.1 0 I U.So NUCLEAR REOULATOF MMISSION DOCKET NUMBER 0- RXo NRC DISTRIB5TION Fon PART 60 DOCKET MATERIAL FILE NUMOER MR G LEAR "ROM'IAGARAMOHAWK POWER CORP SYRACUSE'Y R R SCHNEIDER DATE,OF DOCUMENT DATE RECE<<VED
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DESCRIPTION t ~,. LNR RNF OGR 1-7-76;IJNI RNQUNSTING INFO
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NIAGARA MOHAWK POWER CORPORATION September 3, 1976 CO 4@pg F4S'@
Re:
Nine Mile Point Unit Docket No. 50-220 DPR-63 1
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Mr. George Lear, Chief Q
Operating Reactors Branch g3 S. Nuclear Regulatory Commission
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Dear Mr. Lear:
Your letter of January 7, 1976 requested inf'ormation regarding the Mark I'ontainment Evaluation Short Term Program and Proposed Long Term Program.
My May 19, 1976 letter refer-enced an April 30, 1976 letter from Mr. E. A. Hughes (General Electric) to Mr. V. Stello (Commission) transmitting responses to a portion of'hose questions.
Subsequent to the above, additional letters dated May 24, 1976 and June 18, 1976 from Mr. E. A. Hughes (General Electric) to Mr. V. Stello (Commission) transmitted the responses to the remainder of the questions.
This letter is to inform you that the information contained in the above transmittals apply to Nine Mile Point Unit l.
However, responses to certain questions, or portions thereof, indicated that we would supply plant unique information.
This information is attached.
Very truly yours, NIAGARA MOHAWK POWER CORPORATION p'RE R.
SCHNEIDER Vice President-Electric Production
/sz Attachment
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RESPONSES TO 0UESTIONS ON HARKI CONTAINHENT EVALUATION MECHANICAL ENGINEERING'RANCH
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Question No.
4 Assess the functional operability of the section of ECCS piping near the torus penetration if the torus supports fail to hold torus in place during pool swell.
R~es ense The "Plant Unique Analysis Report for Torus Support System and Attached Piping for Nine Mile Point Nuclear Power Station" shows through detailed analysis, that the torus supports and tie-down restraints can successfully withstand the combined Loss of Coolant Accident and earthquake loads.
Sections 7.2 and 8.2 of the report also show that all piping attached to t'e torus can withstand the local motions of the torus structure without loss of function; i.e., all piping both vital and non-vital, meet the requirements presently established for the torus analysis program.
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guestion No.
7 Provide original design cri teria for the section of BSRV line in-side t'e torus.
As a minimum, the criteria should include the quality group classification in terms of ASP1E Code class and/or ANS Safety Class, and stress limits for design and operational conditions.
R~es oose The original design criteria for the section of PIain Steam Relief Valve discharge lines inside the torus was ASA B3l.l.
At the time that these were designed, there were no quality group classifications.
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RESPONSES TO gUESTIONS ON HARKI CONTAINMENT EVALUATION CONTAINMENT SYSTEMS BRANCH
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guestion No.
8 The screening of structural elements was discussed in Section 4
of Volume III.
However., the screening analysis did not include instrument air lines in the torus.
One utility with a Mark l'ontainment has examined the possibility of modifying these lines to protect them from pool swell.
This was discussed during the December 4, l975 meeting.
Describe the type and location of instrument air lines found in the Mark I containment.
Provide a screening analysis similar to that performed for other components iri Volume IIIfor instrument air lines in the torus.
R~es ense There are no instrument air lines inside of the torus at Nine Mile Point Unit l.
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guestion No.
9 The failure of baffling screening in the torus is discussed on Page 34 of Volume III. In addition, on Page 6-7 of Volume IV, it is stated that the catwalk system in plants with solid deck plates could suffer extensive damage during the pool swell event.
The potential for both baffles and solid deck plates to act as potential missiles is. suggested in the STP reports.
Damage to the chorus walls and vacuum breakers due to these potential missiles has been evalu-ated.
Discuss potential damage to other critical structures in the torus due to missiles including the vent-ring header-down comer
- system, vent bellows, instrument air lines and the vent drain lines.
R~es ense See our August 27, l976 letter from Mr. R. R. Schneider to Mr. George Lear.
guestion No. l9 Provide the following information related. to the analyses used to determine torus uplift.
a.
A detailed description of the methods of analysis used to pre-dict torus lift, with and without consideration of ring header column reaction loads.
b.
Results of torus liftanalyses, with and without consideration of ring header column reaction loads.
R~es oose A detailed description of the method and results of the torus uplift evaluation is included in Section 5.4 of "Plant Unique Analysis Report'or Torus'Support and Attached Piping foz Nine Mile Point Nuclear Power Station."
The report discusses analyses which include ring header column reaction loads; no analyses are reported without ring header column 'reaction loads.
This is in line with the guide-lines established for the program after accurate plant specific ring header column reaction loads became available.
Only combined actual load cases were evaluated.
As a part of the development of the report, load cases without ring header column reaction loads were evaluated and in all cases, uplift was decreased.
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guestion No.
20 Provide the following informat'ion regarding torus support design for upward and dovnvard loads.
a.
A description and sketches of'typical supports currently in use.
b.
Upward and dovnward loads originally considered in the design of the supports.
c.
A t'able showing t'e'ypes of torus supports for both upward and downward loads for each of the Mark,I plants.
d.
A description of the types of structural modifications under consideration for torus supports for froth upvard and down-vard loads.
R~es esse a.
A complete description of the torus support system for Nine Mile Point Unit 1 is included in Section 3.1 of "Plant Unique Analysis Report for Torus Suppozt and Attached Piping for Nine Mile Point Nuclear Power Station."
This section provides a verbal description, illustrations, and a t'abulation of the import'ant physical characteristics of the support syst'm.
b.
The original downvard loads used in the design of the torus support columns are taken from CBsI Dwg. 9-1370, F-l, Rev. 3.
Maximum Loads Per Column (lbs)
Descri t'ion Outsi de Inside Dead Load and Water Pressure Vertical Earthquake (54K)
Horizontal Earthquake (150)
TOTAL - lbs Horizontal Shear Flooded Condition (Water and Steel) 197,000 20,800 10,850 13,400 242, 050 109, 000 442,900 163,000 20I 800 10,850 194R650 2,100 375,900
b.
Continued It appears that no upvard loads in excess of deadveight were considered.
c.
See response
- a. of this question.
d.
The results reported in "Plant Unique Analysis Report for Torus Support and Attached Piping for Nine Mile Point Nuclear Pover Station" shov that all structure and tie-down restraints meet the present program requirements and therefore no modi-fications are being considered at this time.
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RESPONSES TO QUESTIONS ON MARKI CONTAINMENT EVALUATION STRUCTURAL ENGINEERING BRANCH
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guestion No.
4 According to this report, several components, structural elements or connections would failif subjected to the "most probable" LOCA induced pool swell loads.
No short term repairs have been proposed to prevent or mitigate such failures.
Describe your conceptual plans for short term repairs, ifit is determined that such repairs are necessary.
R~ds onse Our August 27, l976 letter from Mr. R. R. Schneider to Mr. George Lear described plans for replacement of our solid catwalk with a grating catwalk during the scheduled Spring, l977 refueling outage.
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Question No.
5 Describe your plan, if any, for in-service surveillance prior t'o long term repairs of critical structural elements determined to be near yield due to pool svell loads.
R~es ese The following in-service surveillance program will be 'conducted during the duration of the Hark I Containment Long Term Program.
This inspection vill be conducted at each refueling out'age.
Di-mensional verifications will be performed on a one-time basis at'he next refueling outage.
Element Zns ection l.
Catwalk 2.
Torus Supports a.
Connection t'o Shell b.
Columns c.
Pi n Connect'ors d.
Anchor Bolts Verify proper hold-dovn Verify plate thickness of attachment to shell, gauge attachment welds, Hagnetic Parti cle Test'ttachment welds Verify section dimensions Verify pin size and keepers Verify proper number and that nuts are properly instal led
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guestion No.
7 The Addendum which should address the torus and its supports (see foot note on page 1-2 of Volume I) has not been received.
Indicate the expected dates when the NRC staff could be briefed on this topic and when Addendum 2 would be submitted for NRC staff review.
Provide information on t'e adequacy of the torus and its supports in as much detail as that provided Sor other structures, with particular attention to the combined effects of LOCA-induced loads and seismic loads, and the effectiveness of current or proposed ti e down assemblies.
~Res oose The "Plant Unique Analysis Report for Torus Support and Attached Piping for Nine Mile Point Nuclear Power Station" Sully addresses this question.
The torus and its support structure have been analyzed relative to the accepted guidelines for the short-term phase of the torus program.
The safety margins of all components of the structure are listed in Tables 9 and 10 of the report.
The loads used for this evaluation include both Loss of Coolant Accident induced loads as well as plant specific seismic loads developed for the Nine Mile Point Unit 1 torus from the appropriate ground accelerati ons.
guestion No.
8 In item (h) of page 1 3 of Volume I and in Section 6.1.3 of Volume IV, it is indicated that catwalks and platforms with solid floor decking "may potentially fail" due Co bulk pool swell loads and may subsequently generate missiles.
Provide the basis for con-cluding that such missiles will not hinder the function of any safety related equipment', electrical lines, instrument lines, piping or structures located above Che catwalk or elsewhere with-in Che torus.
Describe the missile impact'nalysis and provide a summary of the results for the plate impacting on the torus or a vent pipe.
In view of this potential hazard, provide justification why the solid checkered plate platforms should not be replaced with grating, where appropriate, as a short term safety measure.
Furthermore, it is also indicated Chat local yielding will occur,,
at the torus/beam connections.
Indicate if this yielding.will occur in Che torus shell itself and, if so, provide the expected strain and deformation and discuss" the potential effect on leaktight integrity.
Also, discuss the possibi.lity of torus compressive loads causing buckling at these locations, expecially when sub-jected Co seismic loads.
R~es sse See. our August 27,.1976 letter from Mr. R. R. Schneider to Mr.
George Lear.
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Question No. 30 Describe your plans for increased in-servi ce surveillance during the long-term program for structural elements found to be critical during the short-term progra'm.
e R~es oose See the response to Question No.
5 of this section.
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