ML19332B070
| ML19332B070 | |
| Person / Time | |
|---|---|
| Site: | Pilgrim |
| Issue date: | 08/12/1980 |
| From: | Andognini G BOSTON EDISON CO. |
| To: | Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I) |
| References | |
| 80-186, IEB-80-17, NUDOCS 8009190940 | |
| Download: ML19332B070 (4) | |
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d SOSTON EDIMON COMPANY GENERAL OFF8CES 800 BOYLSTON STREET B O S T O N. M AES ACNU SETTS D219 9 G. CamL ANDOGNINt
.1 Su,EmINTENDENT August 12, 1980 NuCLEA. o,E Ar.oNS oE A=vurNT BECo Ltr. #80-186 Mr. Boyce H. Grier, Director l
Office of Inspection ar.d Enforcement Region I U.S. Nuclear Regulatory Commission 631 Park Avenue King of Prussia, PA.
19406 License No. DPR-35 Docket No. 50-293 Ir. formation Concerning IE Bulletin #80-17
References:
a) BECo letter (G.C. Andognini) to NRC (B.H. Grier) 3 titled " Response to Supplement #1 to IE Bulletin
- 80-17" dated August 8, 1980.
b)
BECo letter (G.C. Andognini) to NRC (B.H. Grier) titled " Response II to IE Bulletin #80-17" dated July 21, 1980, c) Meeting with BECo and NRC Staff members on August 5, 1980 at Region I, King of Prussia, PA. (Subj ect -
IE Bulletin #80-17)
De r Mr. Grier:
As reflected in the above listed references, Boston Edison Company has committed to provide further information relative to IE Bulletin #80-17 " Failure of 76 of 185 I
Control Rods to Fully Insert During a Scram at a BWR".
This letter therefore provides you with that information as follows and serves to close out all outstanding responses due on IE Bulletin #80-17 to date.
I In Reference a) we stated that our response to Item A.1 of IE Bulletin #80-17 Supplement 1 was not completed and would be forwarded by August 12, 1980. This response is presented below:
A.(1) Provide to the NRC Regional Office an analysis of the adequacy of the "as-built" SDV system and associated vent and drain systems, including any identified design deficiencies.
Include copies of verified "as-built" iso-metric drawings of the SDV and detailed descriptions of the remainder of the system, verified to be correct, as part of this analysis.
Response
"As-built" isometric. drawings of the SDV are included as Attachment "B"
to this letter.
80091;90 h o
CO3 TON EDISDN COMPANY Mr. Boyce H. Grier, Director August 12, 1980 Page 2 The SDV and vent and_ drain systems were examined via "as-built" (confir-mation by walkdown) to determine if any failure mechanisms could be postulated which might prevent a full scram similar to the Browns Ferry 3 incident.
The results of that examination revealed that there can not currently be perceived, a credible failure modefassuming a single f ailure which cascades into multiple failures) by which the aforementioned event can occur.
This takes into consideration that at Pilgrin Unit #1 there are the following:
a) continuous atmospheric venting of the SDV, b) a dedicated SDV instrument volume drain line, c) UT test points on each 6" header *
- At the present rime, daily checks are performed by plant personnel, using a portable, digital UT and additionallyr. hecks will be performed after scrams and before start-ups.
Investigation of the worst case scenario 1.e., a liquid loop seal in the 2" drain line (approximately 150') between the 6" west header (comparable to the east header at Browns Ferry 3) and the scram instrument volume; again revealed that there would still be sufficient volume in the west 6" header, itself, to accomodate incoming water as a result of a full scram (based on approximately 2.5 gals / drive during the scram stroke).
Reference b) identifie'd Item 6C of IE Bulletin #80-17 as requiring more time for completion.
Our response is presented as follows:
6 (C) Perform a 50.59 review to increase SLCS flow to the maximum consistent with safety (2 pumps, unless unsafe)
Response
Boston Edison Company has performed a 50.59 review to determine if sim-ultaneous operation of both installed SLCS pumps would reduce safety margins as previously analyzed.
The results of our review indicate that 2 pump SLCS operation is an unreviewed safety question as defined in 10CFR50.59.
Initial hardware changes would require (1) the installation of individual manual control switches on panel C905, (2) an interlocking circuit and cable routing modifications to remove undesirable failure modes, and (3) an upward adjustment to the setpoints of the SLCS relief valves.
Further_ analysis is also necessary to determine the effects of 2 pu=p operation on flux stability and the operating conditions necessary for initiation.
Without substantial redesign the current 2 pump system could not be single-active failure proof, which was an original design basis.
Reference c) consisted of a meeting between Boston Edison Company and members of the IE and NRR Staff to discuss the. Pilgrim Station as-installed configuration of the SDV and other matters associated with IE Bu11etin ' #80-17.
During this meeting it was determined that further information was necessary to respond to all the NRC concerns.
COCTON EDICON COMPANY Mr. B.H. Grier, Director August 12, 1980 Page 3 This information is offered as follows:
9 oAttachment A provides the design specifications for the new vacuum breakers installed downstream of the SDV vent valves, o Attachment B provides "as-built" isometric drawings for the SDV system and associated vent and drain systems.
Included are the lengths of run and slopes for all piping
- involved, oIn reference to our letter dated August 1, 1980 (Response III to IE Bulletin #80-17) the revised information to item 2(f) as well as further information to item 2(h) is provided as follows:
2.(f) " Measure the delay time from the scram initiation to closure of the SDV vent and drain valves utilizying the stem mounted position' switches".
Response
A Brush Recorder was used to monitor delay times for each scram.
The times measured from scram initiation to valve closure were:
Scram Signal to Closure of (in seconds)
Drain Valve Vent Valve (A)
Vent Valve (B)
Manual Scram 7.1 14.1 8.9 Auto Scram 7.2 16.7 9.2 2.(h) " Measure the time to drain the SDV down to a repeatable reference level".
Response
Additional information to our previous response includes tha following:
The delay times prior to scram signal reset were 16 minutes 13 seconds for the manual scram and 23 minutes 55 seconds for the auto scram.
The lines were determined to be full via UT of the lines.
o Item #3 of IE Bulletin #80-17 requested Licensees to commit to verify that there is no significant amount of water in the SDV and associated piping following any scram.
Since no previous correspondence has documented our committment to perform this veri-fication, please be advised th&_ 'rocedures have been written to accomplish a UT of the lines following all scrams.
oThe UT testing perforred for each scram test as uc11 as the daily monitoring is in accordance with General Electric's procedure as transmitted to all BWR Plant Super-intendents on July 3, 1980. Additionally, measurements are taken at 25 different points per each system loop.
o Initial system design specifications for drain times on the SDV are not available and no tests were performed for SDV draining times during startup.
Among the documents reviewed to possibly attain this information were:
-NEDO-20252, February 1974,"Startup Test Results of Pilgrim Nuclear Power Station Unit #1".
DO 3 TUN EDICON COMPANY Mr. B. H. Crier, Director August 12, 1980 Page 4
-- Control Rod Drive System", STD&A Summary Test Report, 100% Load Line.
Pilgrim Nuc1 car Power Station Unit #1, Final Safety Analysis Report o The total volume of the SDV piping = 542.44 gallons = 72.52 cubic feet.
This volume was calculated by the sum of each of the following:
- Scram Instrument Volume Tank
- Scram Drain Line to CV-302-22 (Drain Valve)
- Scram Header Vent Lines to CV-302-21A (Vent Valve)
- Scram Header Vent Lines to CV-302-21B (Vent Valve)
- Scram Discharge Header to the Withdraw Valves at the CRD Control Nodules.
Should you have any further questions or concerns relative to the SDV and associated systems at Pilgrim Station, please do not hesitate to contact us.
Very truly yours, O
(
Attachments JDK/gn cc: Director, Office of Inspection and Enforcement Division of Safeguards Inspection Washington, D. C.
20555 Mr. Vince Panciera Reactor Systems Branch Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D. C.
20555