ML20197J072
| ML20197J072 | |
| Person / Time | |
|---|---|
| Issue date: | 09/06/1984 |
| From: | Bernero R Office of Nuclear Reactor Regulation |
| To: | Eisenhut D Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8410010093 | |
| Download: ML20197J072 (3) | |
Text
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UNITED STATES F
NUCLEAR REGULATORY COMMISSION
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ggp g g.1984 MEMORANDUM FOR:
Darrell G. Eisenhut, Director Division of Licensing, NRR FROM:
Robert M. Bernero, Director Division of Systems Integration, NRR
SUBJECT:
RESOLUTION OF GENERIC ISSUE 50, REACTOR VESSEL LEVEL INSTRUMENTATION IN BWRS A CRGR submittal to address the resolution of Generic Issue 50 was sent to Harold Denton on March 12, 1984.
In a subsequent briefing, he requested that the BWR Owners be asked to voluntarily implement the proposed modifications.
David Helwig, Chairman of the BWR Owners' Group, reported that a pool of the owners indicated that none of the owners objected to two of the three categories of improvements; two-thirds of
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the owners objected to implementation of the third category of improvements (this category would satisfy what has been labeled by the owners as the "Michelson concern").
On August 9,1984, I proposed to Harold Denton that Generic Issue 50 be I
. resolved by voluntary implementation of the first two categories of improvements; the third category, the Michelson concern will be retained as a new generic issue to be resolved in FY85.
He agreed.
This should allow Generic. Issue 50 to be resolved in FY84.
l Enclosed is a proposed generic letter which should be sent to the BWR l
. owners indicated.
If any additional information or clarification is needed, please contact Wayne Hodges (29410).
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Robert M. Bernero, Director Division of Systems, Integration, NRR
Enclosure:
As stated cc:
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MEMORANDUM FOR:
All Boiling Water Reactor Licensees of Operating Reactors (Except Lacrosse, Big Rock Point, Humboldt Bay and Dresden-1)
Gentlemen:
SUBJECT:
REACTOR VESSEL WATER LEVEL INSTRUMENTATION IN BWRs (GENERIC LETTER 84-
)
The water level instrumentation in a BWR is relied upon for controlling feedwater, actuating emergency systems, and for providing the operators information which is used as basis for actions to assure adequate core cooling.
Many of the actions in the emergency procedures guidelines are keyed to reactor water level.
The NRC staff has reviewed the S. Levy, Inc. report SLI-8211, " Review of BWR Reactor Vessel Water Level Measurement System" which was commissioned by the BWR Owner's Group.
The BWR Owners and S. Levy are to be commended for doing an excellent job of identifying potential problems with water level instrumentation and proposing solutions to those problems.
The report provides a generic evaluation of water level instrumentation adequacy of BWR/2 through BWR/6 plants.
SLI-8211 has also identified several improvements in BWR water level measurement and instrumentation systems which will improve the reliability and accuracy of those systems.
We believe that procedural changes identified in the emergency procedure guidelines are adequate for the short term, but permanent physical improvements should be made on a deliberate schedule to reduce the burden on the operator.
Three categories of improvements, which we believe to be prudent, are discussed below.
It is the staff's understanding, based on discussions with the Chairman of the BWR Owners' Group, none of the BWR Owners object to voluntary implementation of the first.two categories.
We commend your willingness to do.this.
Implementation of the first two categories of improvements will assure that the level; instrumentation will perform adequately as inadequate core cooling instrumentation required by NUREG-0737 Item II.F.2.
We request that you provide us with a description of how you plan to implement these ieprovements and your proposed schedule.
The third category of improvements is not as significant as the first two categories and 16 still being evaluated by the staff.
First, we understand that each licensee will consider improvements to its plant (s)thatwillreducelevelindicationerrorscausedbyhjghdrywell temperature. These improvements include preventing overheating of the reference legs or reducing their vertical drops in the drywell (Vertical drop should be measured from the condensation pot to the drywell exit
point.
Maximum allowable drop would allow an indicated level at the bottom of the normal operating range when actual level is just above lower tap for worst flashing condition).
Those plants for which the vertical drop in the drysell has already been minimized will not have to make additional changes for the drywell heating effect.
Second, the review of plant experience indicates that mechanical level indication equipment is more vulnerable to failures or malfunctions than analog equipment.
A number of plants have already connected analog trip units to their level transmitters to improve reliability and accuracy.
We understand that those plants which use mechancial level indication will replace the mechanical level indication equipment with analog level transmitters unless their operating experience supports high reliability of their mechanical indicators.
Third, for those plants in which operator action may be required to mitigate the consequences of a break in a reference leg and a single failure in a protection system channel associated with an intact reference leg, we understand that changes to the protection system logic may be needed.
These changes will generally result in additional transmitters to satisfy the single failure criterion.
This improvement may be needed in plants where an analysis has demonstrated a
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vulnerability.
This request for information was approved by the Office of Management and Budget under clearance number 3150-0065 which expires Septeober 30, 1985.
Sincerely, Darrell G. Eisenhut, Director Division of Licensing Office of Nuclear Regulatory Regulation e
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