ML19208D909
| ML19208D909 | |
| Person / Time | |
|---|---|
| Issue date: | 06/14/1978 |
| From: | NRC OFFICE OF INSPECTION & ENFORCEMENT (IE) |
| To: | |
| References | |
| IEB-78-09, IEB-78-9, NUDOCS 7910010736 | |
| Download: ML19208D909 (5) | |
Text
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UNITED STATES NUCLEAR REGULATORY COF041SSION OFFICE OF INSPECTION AND ENFORCEMENT WASHINGTON, D. C.
20555 June 14, 1978 IE Bulletin No. 78-09 BWR DRYWELL LEAKAGE PATHS ASSOCIATED WITH INADEQUATE DRYWELL CLOSURES Description of Circumstanct s:
Upon completion of the E. I. llatch 1 plant refueling, the drywell head was reinstalled on April 1,1578 and a local leak rate test (LLRT) was successfully passed, providing no indication of a potential problem at the tice.
Subsequently, during the containment integrated leak rate test (CILRT) at the E. I. Hatch I plant on April 6,1978, high J eakage around the drywell head was experienced. After the high leakage 2 ate vas detected, the containment was depressurized. Prior to detensioning the drywell head bolts, a feeler gauge was used to determine that the clearance was greater where the leakage was occurring.
Upon retorquing the drywell head for a second LLRT and CILRT, the tightening sequence was started at the area of 3cakage and torque va.'.ucs of 1800 foot-pounds were used. Feeler gauge readings between the head and drywell were recorded. The second LLRT was passed successfully and no leakage w_s indicated around the drywell head during the second and successful CILRT conducted at 59 psig.
Another instance was identified during the CILRT a' "llstone Unit 1 on November 22-23, 1976, when both the drywell head and the drvaell head manway cover " lifted" during a Type A test subsequent to successful Typ e B (LLRT) te s t s.
Based on this experience, it appears that the LLRT following each reinsta11ation of the drywell head or other closures, such as after a routine refueling or other similar activity, cannot be the sole basis fcr assuring a suitable degree of drywell closure leak tightness.
It appears that there n2st be controls to ensure that drywell closures are nade in a reproducible manner.
Action to be taken by all BWR power reactor facilities wit): an operating license or construction permit:
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IE nulletin No. 78-09 June 14, 1978 1.
Determine if the procedural controls utiliz't
.t your facility are adequate to assure that drywell head reinstallations achieve a degree of Icak tightness equivalent to that attained during the installation immediately preceding the last successful CILRT.
This determination should include, but not be limited to, con-sideration of the following:
Comparison of the applied bolt torque (or for turn-of-the-nut a.
technique, the number of flats on each nut / bolt after metal-to-metal contact has been achieved) af ter any head reinstal-lation to that used during the reinstallation verified by CILRT, including any additional local retightening needed to reach LLRT acceptance criteria.
b.
Comparison of head-flange clearances after any head reinstal-lation, to that used during the reinstallation verified by CILRT.
Determination of the suitability of the drywell head c.
gaskets for reuse.
d.
Determination of the maximum allowable bolt torques to avoid bolt overstressing onditions.
e.
Determination of any special handling arrangements, tightening sequence, gasket preparation, or other special considerations caused by unique facility circumstances such as a warped drywell head.
2.
Should your determination called for in Item 1 above demonstrate a need for procedural revisions, your response to this Bulletin should include a description of the changes to be cade and a timetable for their implementation which must occur prior to the next dryvell head closure.
3.
Identify other bolted containment closures that would tend to vnseat on positive internal pressure and describe what actions are taken to ensure that adequate leak tightness would exist at an internal pressure of Pa.
4.
Within 45 calendar days of the date of issue of this bulletin, report in writing to the Director of the appropriate NRC Regional Office, the results of your review and your plan of action with regard to Item 1 through 3.
A copy of your report should be 2 of 3 e
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IE tulletin No. 78-09 June 14, 1978 sent to the United States Nuclear Regulatory Commission, Of fice of Inspection and Enforcement, Division of Reactor Operations Inspection, k'ashington, D. C.
20555.
For all BWR power reactor facilities with a construction permit, this Bulletin is for information only and no written response is required.
Approval by CAO, B150225 (R0072); clearance expires 7/31/80. Approval was given under a blanket clearance specifically for identified generic problems.
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IE Bulletin No. 78-09 June 14, 1978 LISTING OF BULLETINS ISSUED IN 1978 Bulletin Subject Date Issued Issued To No.
78-01 Flanzabic Contact -
1/16/78 All Power Reactor Arm Retainers in G.E.
Facilities with an CR120A Relays OL or CP 78-02 Terninal Block 1/30/78 All Power Reactor Qualification Facilities with an OL or CP 78-03 Potential Explosive 2/8/78 All EWR Power i
Gas Mixture Accumula-Reactor Facilities tions Associated with with an OL or CP BWR Offgas System Operations 78-04 Environmental Quali-2/21/78 All Power Reactor fication of Certain Facilities with an Stem Mounted Limit OL or CP Switches Inside Reactor Containment 78-05 Malfunctioning of 4/14/78 All Power Reactor Circuit Breaker Facilities with an Auxiliary Contact OL or CP Mechanis -General Model CR105X 78-06 Defective Cutler-Hac.mer 5/31/78 All Power Reactor Hammer, Type M Relays Facilities with an with DC Coils OL or CP 78-07 Protection afforded 6/12/78 All Power Reactor by Air-Line Respirators Facilities with an and Supplied-Air Hoods OL, all class E and F Research Reactors with an OL, all Fuel Cycle Facilities with an OL, and all Priority 1 Material Licensees Page 1 of 2 I
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6 IE Bulletin No. 78-09 June 14, 1978 LISTING OF BULLETINS ISSUED IN 1978 Bulletin Subj ect Date Issued Issued To No.
78-08 Radiation Levels from 6/12/78 All Power and Fuel Element Transfer Research Reactor Tubes Facilities with a Fuel Element Transfer Tube and an OL l
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