ML20024G530
| ML20024G530 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 07/05/1972 |
| From: | Wachter L NORTHERN STATES POWER CO. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML20024G522 | List: |
| References | |
| IEB-72-01, IEB-72-1, NUDOCS 9102120608 | |
| Download: ML20024G530 (5) | |
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NORTHERN STATES
'P O W E R COMPANY i
M I N N E A PO L.l e. M I N N E S OTA 5 5 400 1
1 July 5, 1972
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i Mr B H Grier Regional Director United Stateo Atomic Energy Commission Directorate of R(gulatory Operations Region III, 799 Roosevelt Road Glen Ellyn, Illinoin 60137 D ar Mr Oriert I
MONTICELLO NUCLEAR GENERATING PLANT Docket No. 50-263 Licence No. DPR-22 Inspection of Support Hangers for Emergency Core Cooling System Suction Header j
i The following report is being submitted in response to your request for infor-nation as outlined in Directorate of Regulatory Operations Bulletin 72-1.
At Monticello, a general visual inspection of the torus externale is performed after each plunt shut dcyn involving relief valve operation. On Tuesday, May-23, 1972 such an inspection revealed a damaged bolt in one of the vertict.1 support sections for the 20" torus cuction ring header. The nut had backed off and the bolt was moderately boved and exhibited crushed threr.ds in the load-bearing area.
On Thursday, June 1,1972 six bolto were removed for examination and replaced with SAE Orade 9 belto. Subsequent inspections vere performed on June 5 and 6, l
2972 of the entire 20" torus auction ring header support assembly system, with photographs taken for documentation.
On Jiu2e 8,1972 come reinspection was performed to complete the photographic records. All bolts were replaced with l
SAE Orade 8 and 9 bolts and all support assemblien vere examined for conformance with the original design.
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9102120608 720622 PDR ADOCK 05000263-G PM
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NORTe.' R N OTATEC POWER Coh. ANY Mr b 11 Orier July 5,1972 The cupport structure and bolting arrangement are exhibited in Figures 1 and 2.
For clarity, the boltira arrangement hac been identified as " upper vertical, lower vertical, outboard horizontal and inboard horizontal".
The sixteen mitered sec-tions of the torac have been numbered arbitrarily for ease of inspection location as indicsted on Figure 1.
Of thece sections only twelve are support assembly locations. As specified b,s the Chicago Bridge and Iron Company the bolting chould consist of 3/k" IILX IID BOLTS, 2 3/4" in length and 3/4" RDG HEXIOCK hVE both meeting Ar#.E specification A307 Tne "as found" bolting consisted of 3/4" HEX HD BOLTS, 2 3/4" in length, full
'j threaded and without lock nuto.
No identification markings were stamped on the bolto to crecify grade. Le bolta exhibited thread damage on the bearing surface vtcying from crushed threads to moderate thread damage.
In several instances localized thread damage was apparent due to the irregularity of a torch cut hole.
Of the 48 bolts, only one other exhibited bowing and that to a slicht extent.
An indicated in Table 1, nine sec tions had torch cut holes in the bracket guacet plate, pipe web or' support straps.
The torch cut holec were in addition to the drilled hole. A hydraulic Jack van required for removal of the outboard horizontal bolts in cection nine and section three, indicating horizontal comprescive loading on the torus at thece points.
A qualitative judgment baced on the jack cize and diccuccion with the personnel.who perfermed thic work indicates the horizontal load-(
ing force at these pointo was in the range of one to two thousand pounds.
A vicual inspection of the veldn van completed on June 8th.
The torus butt plates and padeyes were velded all around with a 1/4" fillet.
The pipe webs were spaced velds with 1/4" fillets on both sideo providing approxitately 15" of lineal veld.
he only discrepancies noted were that the web vac not flush with the ring header in five sections. All velds were c.agnetic particle inspected by Twin City Testing and Er.cinecting laboratory Inc. and no defecto or discontinuities were found.
Static loads on each vertical nanger have been measured and range i' rom 0 to 8340 poundo.
As of June 8,1972, all the cupport bolts for the 20" torus cuetion ring header were replaced with SAE grada 8 or 9; 3/4" IIIM HD partially thrcaded bolts having no threads in the chear load area.
'1he bolts were locked with double nuts.
General Electric and Chicago Bridge and Iron are providing services to return the support accembly cyctem to the original design. A static load analysis of vertical loading hah been completed to provide a basis for adjusting the cystem to balnneed loading on the support accemblics. Welding and inspection procedures for repair of bolt holes are currently being reviewed.
It in intended that all boltire vill be replaced with ACME A325 HEX HD 3/4" DOLTS with no threads in the load-bearing area, and lock nuts will be provided. Any replacement of support otrapo vill be ende using original specification caterial. We currently anticipate completion of all work by the end of July 1972.
Yours ven truly, LJ achter, Vice President System Operation & Power Productie taw /ma l
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A.4 7 section - Torus Suction Hoador suppor_t, structure F/G u.QE 2
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Upper Lownr Outboard Inboard Seetion Ver i ied Veriic ed Horirontal Liorirenta1 1
Torch cut
' Drilled Drilled Drilled and pariially dr illed 2
Drilled One Torch Web Drilled Drilled cut. One and Strap Torch dr illed Cut.
3 Drilled One Drilled and One Drilled and Web Drilled one lorch Cut ono Torch Cut and Strap Torched 4
Torus Suct ion Header Supply Line - ib Addi t ional Suppo,r,t,s, 5
Dr illed Drilled Dr'illed Drilled and Partial Torch Cut 6
Drilled Drilled Drilled Drilled i
7 Drillea Drilled Drilled Drilled l
8 lety;_ Su-i i en Hende r honolyllry,.3jj_f_ddmqral_Succo r ts 9
Drilled Torch Cut Drilled Web and Strap Torch Cut 10 Drilled Drilled Drilled Drilled 11 Drilled One Drilled One Drilled Drilled and one Torch and one Torch Cut Cut 12 Toros Suction Hender Supplylinf__ tJ _A_ddiiient,1 Supporis 2
13 Cne Torch One Torch One Torch Drilled Cut and One Cut and One Cut and One Drilled Drilled Dr ill ed i
14 Drilled One Torch One lorch Drilled l
Ct.t and One Cut and One Drilled Drilled i
l 15 Dr illed Three Torch Drilled Drilled Cut Holes 16
. Torus Suction Header Sunniv Line No Addiiinnal Suncoris l
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