NRC Generic Letter 1980-17
| ML031350308 | |
| Person / Time | |
|---|---|
| Issue date: | 03/24/1980 |
| From: | Ziemann D Office of Nuclear Reactor Regulation |
| To: | |
| References | |
| GL-80-017, NUDOCS 8004240497 | |
| Download: ML031350308 (8) | |
DISTRIBUTION
Docket MAycock FBC PDR FSchroeder Local PDR VNoonan ORB Reading WHazelton NRR Reading RKlecker MAR 2 4 1980 D. Eisenhut REJohnson RVollmer NRandall Docket No. 50-245 OELD PCheck OI&E (3) GLaninas DLzi emann FCLemenson HSmith BGrimes Mr. IW.G. Counsil, Vice President JJShea ,TSPeais Nuclear Engineering and Operations NSIC RBosnak sTERA JPKnight Northeast Nuclear Energy Com.lpany ACRS (16)
Post Office Box 270 DRoss Hartford, Connecticut 06101 DCrutchfield DIR, IE ( )
CHHofmayer DShapaker Dear Mr. Counsil: RSnaider SHAnouer RE: ,MiODIFICATIONS TO COILING WATER REACTOR CONTROL ROD DRIVE SYSTEMS
Enclosed you uill find a copy of our January 28, 1980 letter to General Electric which discusses the NRC staff's conclusions regarding proposed control rod drive (CRD) system modifications related to the eli;ination of cracking in the CRD return line nozzle. You will also find a copy of our February 11, 1980 letter to GE regarding additional analyses of boiloff rates and CRD system makeup.capability. This letter also re- sponds to a GE-proposed draft procedure for optimizing CRD pump floi: to the reactor vessel.
You should especially note our request that modifications not be per- formied on operating reactors until complete guidance has been issued in
-NUREG-0619. I-e anticipate issuing this document in its 'For Coiuvent"
for, in April 1980. Haiever, if an operating reactor Is scheduled for a refueling outage in the near future, and if applicable CRD syster- n7odifications or adjustments are scheduled prior to the final issuance of NUREG-0619, please obtain NRC guidance by contacting your Project manager. The staff will provide assistance as necessary.
Sincerely, Original Si'qu by ly Dennis L. Ziemann, Chief /
Operating Reactors Branch gE
Division of Operating Reactors Enclosures:
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-2 March 24, 1980
Mr. iW.G. Counsil cc William H. Cuddy, Esquire Connecticut Energy Agency Day, Berry & Howard ATTN: Assistant Director Counselors at Law Research and Policy One Constitution Plaza . Development Hartford, Connecticut 06103 Department of Planning and Energy Policy Anthony Z. Roisman 20 Grand Street Natural Resources Defense Council Hartford, Connecticut 06106
917 15th Street, N. W.
Washington, D. C. 20005 Director, Technical Assessment Division Northeast Nuclear Energy Company Office of Radiation Programs ATTh: Superintendent (AW-459)
Millstone Plant U. S. Environmental Protection P. 0. Box 128 Agency Waterford, Connecticut 06385 Crystal Mall #2 Arlington, Virginia 20460
Mr. James R. Himmelwright Northeast Utilities Service Company U. S. Environmental Protection P. 0. Box 270 Agency Hartford, Connecticut 06101 Region I Office ATTN: EIS COORDINATOR
Resident Inspector JFK Federal Building c/o U. S. NRC Boston, Massachusetts 02203 P. 0. Box Drawer KK
Niantic, Connecticut 06357 Waterford Public Library Rope Ferry Road, Route 156 Waterford, Connecticut 06385 First Selectman of the Town of Waterford Hall of Records
200 Boston Post Road Waterford, Connecticut 06385
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4 Fe,~L .UNITED STATES
NUCLEAR REGULATORY COMMISSION
W QWASHIN0GTON., O.. C205 January 28, 1980
Generic Technical Activity A-lO
Mr. Richard Gridley, Manager Fuel and Services Licensing General Electric Company
175 Curtner Avenue San Jose, California 95215 Dear Mr. Gridley:
Since the initial discovery of cracking in boiling water reactor (BWR)
control rod drive return line (CRDRL) nozzles in early 1977, General Electric (GE) has proposed a number of solutions to the problem in the course of which several documents were submitted for NRC staff review.
These documents were as follows:
1. Letter of March 14, 1979, G. G. Sherwood (GE) to Y. Stello and R. Mattson (NRC) regarding calculation of CRD system return flow capacity;
2. Letter of April 9, 1979, 6. G. Sherwood (GE) to V. Stello and R. Mattson (NRC) forwarding results of CRD system solenoid valve endurance testing;
3. Letter of May 1, 1979, G. 6. Sherwood (GE) to V. Stello and R. Mattson (NRC) forwarding results of CRD system solenoid valve performance testing; and
4. Letter of November 2, 1979, 6. 6. Sherwood (GE) to R. P. Snaider (NRC) forwarding additional information as requested regarding CRD
hydraulic system performance, especially with regard to corrosion products emanating from carbon steel piping.
All concerned the GE rationale for the latest proposed system modification to prevent nozzle cracking; namely, total removal of the CRDRL and cutting and capping of the CRDRL nozzle. Previous submittals had presented the bases for the other modification proposals discussed herein.
are I l I
Mr. Richard Gridley - 2 -January 28, 1980
Specifically, your March 14, 1979 letter discussed the GE analysis performed after the NRC's selection of a base case for use in comparing capability to inject high pressure water into the reactor vessel when other water sources Ferry Unit were isolated. This base case was the 1975 incident at Browns No. I, during which the CRD system sometimes was one of the only capable '
sources of high pressure water injection to keep the reactort core covered. The capability had not been directly staff recognizes that the pressure of thisHowever, assumed in any previous safety analysis. the critical need for the
1979 incident at the Oyster Creek system was again revealed during the earlyincident Nuclear Generating Station. During this the reactor vessel also was isolated from other sources of high pressure water and the CRD system of the active fuel.
makeup capability helped prevent uncovering Your analysis of March 14, 1979, included several assumptions which the NRC
staff has found acceptable. Principal among atthese was that concurrent operation of the two CRD pumps was possible any plant. This of course supply limitations and no pump implies that there will be no electrical that will be reached. Licensees net positive suction.head (XPSH) limits this to be valid, by testing, and applicants will be required to demonstrate pri6r to our approving CRD return line removal.
The letters of April 9, and May 1, 1979, discussed the solenoid valve testing program Initiated in response to earlier NRC concerns. The original rerouting determined that return flow to analysis of CRDRL removal without would enter CRD cooling water lines the reactor vessel from drive operation themselves. During and return to the vessel through the CRD mechanisms path would be a reverse the actual testing, however, you discovered that directional control valves of the flow path through the insert exhaust The long-term cycling of the control non-actuated Hydraulic Control Units.
valves in the reverse direction was a cause of NRC concert, with regard to CRD hydraulic system.
possible deleterious effects upon the operation of the In response to this concern, GE tested ten valves which had been removed from an operating reactor on which the return line had been isolated for six months. These valves were then compared against tests performed on flow characteristics five new valves. The results showed that the reverse of the valves to the point of all valves were similar and that degradation during long-tern of causing system malfunction would not be expected The NRC staff is satisfied with these normal operation of the system.
results.
Siculated life cycle testing also was performed on five valves, resulting in the determination that no adverse effects were caused by the backflow.
The NRC staff has found this acceptable.
Mr.'Richard Gridley - 3- January 28, 1980
your final letter of November 2, 1979, discussed in detail your response to staff concerns regarding possible degradation of the CRD system and individual CRO mechanisms because of corrosion problems from carton steel piping. Certain modifications were suggested to solve these problems.
You also discussed your recomnendations regarding the installation of pressure equalizing valves in the CRD system to prevent, under a hypo- thetical transient, a large pressure differential across the CRO system which could result in excessively fast movement of a selected control rod. The valves also prevent flow from the carbon steel piping of the normal exhaust water heaoer to the drive cooling water header.
We have reviewed your submittals and have concluded the following:
1. Only licensees of the following classes of plants and will be allowed at this time to implement the recommendation to cut cap with no re- routing of tne CRDRL and without further analysis. Each applicable plant must demonstrate, by testing, concurrent two CR0 pump operation (with one exception), satisfactory CRD system operation, required flow capability, and each will be required to install the system modifications listed in 4. below.
a. 218' BWR/6 b. 251. BWR/6 c. 183' BWR/4 (only one pump needed to satisfy base case requirement)
d. 251' BWR/4 No modifications should be performed on operating reactors prior to issuance of the *For Comment' issue of MUREG-0619, scheduled for release inJanuary 1980.
2. We do not accept the hypothesis that the calculations for the above plants were bounding. Therefore, prior to our approval of modification of other plant-classes, we shall require analysis similar to that per- formed on the plant classes of l. above. The same testing and system modifications will also be required.
3. We found the 251 8WR/5 (the fifth class analyzed in the March 14, 1979 letter) presently to be unacceptable for modification in that its calcu- lated flow fell below the acceptable base case value. be acceptable. Further analysts or plant-specific testing-could prove flow capacity to
Mr. Richard Gridley _ 4 - January 28, 1980
on all
4. We will require that the following modifications be i1plemented rerouting and those plants requesting the removal of the CRDRL without which reroute but choose to operate with CRD return line flow valved out;
a. Installation of equalizing valves between the cooling water header and the exhaust water header.
-b. Flush ports installed at high and low points of exhaust water header piping run if carbon steel piping is retained; and c. Replacement of carbon steel pipe in the flow stabilizer loop with stainless steel and rerouting directly to the cooling water header.
for
5. Each licensee must establish readily-available operating procedures achieving maximum CRD flow to an otherwise isolated reactor vessel.
6. Licensees who choose to reroute the CRDRL, either with or without continuous return line flow to the system being tapped into, must water add the GE-reconmended pressure control station to the cooling station acts to buffer hydraulic perturbations from header. This in any connected system in order to prevent pressure fluctuations the CR0 system.
nothings Modification 4.c is based upon our decision not to accept the ado in your November a, 1979 letter. We consider the alternative addressed and one Smore absolute solution' (your characterization] to be the correct absolute with this *more agree with your recommendation, made in accordance We do not
-solutions, that the carbon steel piping should be eliminated. corrosion accept the option of filter installation as a means of trapping a deleterious effect on the CRD mechanisms. Our con- particles that have water header cern is that improperly maintained filters on the cooling of multiple could result in heatup of drive mechanisms and the possibility drive failures of a type not previously analyzed.
GE recom- Note that we have discussed only the acceptability of the latest mendation discussed in the four letters. We continue to accept CRDRL
the return re-routing to a line outside containment that in turn provides in other flow to the reactor vessel (valving out after re-routing results
4. 6. above). We also find acceptable, as a strictly requirements - see and require this will interim measure, the valving out of the CRDRL. However, line inspection, during each refueling outage, of that portion of the will containing stagnant water. No matter which option is chosen, we CRORL
require complete inspection, by dye penetrant techniques, of.the of nozzle, the apron area beneath the nozzle, and the subsequent removal any cracks found during the inspection.
Mr. Richard Gridley 5 - January 28, 1980
For the BWRs undergoing licensing review and designed and constructed without the CRDRL and its nozzle or modified with the CRDRL cut and capped without rerouting, we will require testing (similar to that for operating plants) to prove satisfactory system operation, return flow capability equal to or In excess of the base case requirement discussed above, and two pump operation.
Applicable modifications of 4. above also cust be implemented. We shall require the establishment of operating procedures for achieving maximum CRD
flow to an othervise isolated vessel. Calculations with regard to base case return flow requirements should be submitted, but in lieu of such calculations, the staff may accept reference to a bounding analysis if necessary Justification is provided.
Additional guidance on this subject will be contained in NUREG-0619. This document is tenatively scheduled for publication in February 1980.
incerely, ss Givisio. 1ng irector Di ~sion a Operating Reactors Office of Muclear Reactor Regulation
K...' UNITED STATES
NUCLEAR REGULATORY, COMMISSION
WASHINGTON. D.C.20555 February 11. 1980
Generic Task No. A-10
Mr. Richard Gridley, Manager Fuel & Services Licensing General Electric Company
175 Curtner Avenue San Jose, California 95125 Dear Mr. Gridley:
By letter dated November 27, 1979,.you forwarded results of analyses of boil-off rates and.Control Rod Drive (CRD) System Pump makeup capability for plants not previously addressed in earlier related submittals. The letter also included a draft procedure for optimizing CRD pump flow to the reactor vessel.
The November 27," 1979 letter was not included in the NRC's Unresolved Safety Issue A-10 review and the analyzed classes of plants will not be included in NUREG-06l9, which resolves A-10 and is tentatively scheduled for issuance in "For Commrent" form by February 29, 1980. However, we see no reason why licensees and applicants cannot use the results in the plant-specific analyses (and testing) required by NUREG-0619. Significantly more detail will be required in their submittals, however, particularly with regard to the assump- tions utilized in derivation of the various flow rates.
We concur that the GE-proposed procedure for optimization of CRD system flow to the pressure vessel provides a necessary first step toward reaching the desired goal. However, in our opinion it is too cumbersome with regard to measurement of pump discharge flow. When faced with the-need to maintain
.water level upon loss of other capable high pressure water injection systems, the operator simply cannot be burdened with the need to refer to pump curves or the need to consider what, if any, other portions of system flow are not included in a respanned flow meter.
We believe that operators should be provided one or two meters capable of reliable direct measurement of one and ~wo pump flow.
Siyicerely, Darrel G.ienhut, Acting Director Divisio o'Oerating Reactors Office of Nuclear Reactor Regulation