ML20039D117
| ML20039D117 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 12/28/1981 |
| From: | Crutchfield D Office of Nuclear Reactor Regulation |
| To: | Counsil W CONNECTICUT YANKEE ATOMIC POWER CO. |
| References | |
| TASK-05-10.B, TASK-05-11.B, TASK-07-03, TASK-5-10.B, TASK-5-11.B, TASK-7-3, TASK-RR LSO5-81-12-089, LSO5-81-12-89, NUDOCS 8112310334 | |
| Download: ML20039D117 (9) | |
Text
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- r December 28, 1981
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m Docket No. 50-213 A
LS05-81-12-089 EECEtVED L 2 DEC301981> @
c Mr. W. G. Counsil. Vice President sesm"spesamY Nuclear Engineering and Operations 1,
Mc Connecticut Yankee Atomic Power Co.
f, Post Office Box 270 Hartford, Connecticut 061 01
Dear Mr. Counsil:
SUBJECT:
HADDAM NECK - SEP TOPICS V-10.B RHR SYSTEM RELIABILITY, V-ll.B RHR INTERLOCK REQUIREMENTS AND VII-3 SYSTEMS REQUIRED FOR SAFE SHUTDOWN (SAFE SHUTDOWN SYSTEMS REPORT)
In response to your letter of November 10, 1981, the staff has re-evaluated the need for independent, diverse interlocks on the RHR-to-RCS isolation valves. The staff concludes that the key lock switches and administrative controls and the pressure interlock on the inboard valves provide an adequate level of protection against overpressurization of the residual heat recoval system.
Revised pages of the safe shutdown systems report are enclosed and should, be substituted for the corresponding pages ir. the enclosure to our September 9,1981 letter. The safe shutdown systems evaluation is now considered to be complete. The remaining open items, as listed in Enclosure 2, will be addressed in the integrated assessment.
Sincerely, Dennis M. Crutchfield, Chief Operating Reactors Branch Mo. 5 Division of Licensing i
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'f December 28, 1981
%,.....f Docket No. 50-213 LS05-81-12-089 Mr. '
G. Counsil, Vice President Nuc'2ar Engineering and Operations Connecticut Yankee Atomic Power Co.
Post Office Box 270 Hartford, Connecticut 06101
Dear Mr. Counsil:
SUBJECT:
HADDAM NECK - SEP TOPICS V-10.B RHR SYSTEM RELIABILITY.
V-ll.B RHR INTERLOCK REQUIREMENTS AND VII-3 SYSTEMS REQUIRED FOR SAFE SHUTDOWN (SAFE SHUTDOWN SYSTEMS REPORT)
In response to your letter of. November 1.0, 1 981, the staff has re-evaluated the need for independent, diverse interlocks on the RHR-to-RCS isolation
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valves.
The staff concludes that the key lock switches and administrative controls and the pressure interlock on the inboard valves provide an adequate level of protection against overpressurization of the residual heat removal system.
Revised pages of the safe shutdown systems report are enclosed and should be substituted for the corresponding pages in the enclosure to our September 9,1981 letter.
The safe shutdown systems evaluation is now considered to be complete. The remaining open items, as listed in Enclosure 2, will be addressed in the integrated assessment.
Sincerely,
- k. i$h h.,
YY Dennis M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing
Enclosures:
As stated cc w/ enclosures:
See next page D
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HADDAM NECK Docket No. 50-213 Mr. W. G. Counsil CC Day, Berry & Howard Counselors at Law One Constitution Plaza Hartford, Connecticut 06103 Superintendent Haddam Neck Plant RFD #1 Post Office Box 127E East Hampton, Connectic~ut 06424 Mr. Richard R. Laudenat Manager, Generation Facilities Licensing Northeast Utilities Service Company P. O. Box 270 Hartford, Connecticut 06101
. Russell Library 119 Broad Street Middletowa, Connecticut 06457 Board of Selectmen Town Hall Haddam, Connecticut 06103 Connecticut Energy Agency ATTN: Assistant Director Research and Policy Development Department of Planning and Energy Policy 20 Grand Street Hartford, Connecticut 06106 U. S. Environmental Protection Agency Region I Office ATTN: EIS COORDINATOR JFK Federal Building Boston, Massachusetts 02203 Resident Inspector p
Haddam Neck Nuclear Power Station c/o U. S. NRC East Haddam Post Office East Haddam, Connecticut 06423 0
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9 ENCLOSURE 1 REVISED PAGES TO HADDAM NECK SAFE SHUTDOWN SYSTEMS REPORT e
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4.
SPECIFIC RESIDUAL HEAT REMOYAL AND OTHER REQUIREMENTS OF BRANCH TECHNICAL POSITION 5-1 Branch Technical Position 5-1 contains detailed functional requirements for specific systems used during safe shutdown.
Each specific requirement is
, presented below with a description of the applicable Haddam Neck system or area of operation.
4.1 RHR SYSTEM ISOLATION REQUIREMENTS Requirement:
"B.1 The following shall be provided in the suction side of the RHR system to isolate it from the RCS.
(a)
Isolation shall be provided by at least two power-operated valves in series.
The valve positions shall be indicated in the control room.
(b) The valves shall have independent diverse interlocks to prevent the valves from being opened unless the RCS pressure is below the RHR system design. pressure.
Failure of a power supply shall not cause any valve to change position.
(c) The valves shall have independent diverse interlocks to protect against one or both valves being open during an RCS increase above the design pressure of the RHR system."
Evaluation:
(a) Haddam Neck RHR station line has two power-operated valves in series.
Positions of both valves are indicated in the control room.
(b) The upstream (i.e., closest to the RCS) valve, MOV-780, has an interlock which prevents its opening unless RCS pressure (as sensed by the four RCS pressure channels) is less than 400 psig.
The other (downstream) valve, MOV-781, is provided with an administratively controlled key lock.
By procedure, the RHR valves are not opened unless RCS pressure is below 400 psig.
Both motor-operated valves fail "as is" on loss of power.
(c) Neither of the two suction valves has an interlock to protectively
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close an open valve when the RCS pressure rises above the design pressure of B-61 Haddam Neck Safe Shutdown Revised 12/81
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i the RHR system. However, the overpressure protection system (OPS) includes a 400-psig alarm to warn the operator that RCS pressure is increasing, enabling the operator to terminate the pressure increase or isolate the RHR system.
Requirement:
"B2.
One of the following shall be provided on the discharge side of the' RHR system to isolate it from the RCS; (a) The valves, position indicators, and'inte'rlo'cks'describsdfin Item B.1 (a)-(c).
(b) One or more check valves in series with a normally closed power-operated valve with its position indicated in the control room.
If the RHR system discharge line is used for an ECCS function, the power-operated valve should be opened upon receipt of a safety injection signal once the reactor coolant pressure has decreased below the ECCS design pressure.
(c) Three check valves in series, or (d) Two check valves.in series, provided that there are design provisions to permit periodic testing of the check valves for leak tightness and the testing is performed at least annualTy."
Evaluation:
The Haddam Neck RHR system has two discharge paths which require isolation from RCS pressure: the normal RHR return to the RCS (via two power-operated isolation valves), and the discharge to the ECCS core deluge supply lines (via a single check valve. in series with a power-operated isolation valve).
The normal RHR raturn to the RCS must meet the criteria of Item 2(a).
Features related to compliance are as follows:
1.
This discharge line has two power-operated isolation valves, MOV-804 and M0V-805, and positions of both valves are indicated in the control room.
2.~ An interlock prevents the upstream valve, MOV-804, from opening until RCS pressure (as sensed by four RCS pressure channels) is less than 400 psig. The downstream valve, MOV-805, is provided with an 9
administratively controlled key lock. Both valves fail "as is" on i
loss of power.
s B-62 Haddam Neck Safe Shutdown Revised 12/81 E
i The staff has concluded the following:
1.
The lack of independent diverse interlocks for the isolation valves to prevent the valves from being opened unless the RCS pressure is ~
below the RHR system design pressure is acceptable because in addi-tion to the single pressure interlock, the other two valves are
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key-lock type under ad..inistrative controls.
By procedure, none of
.the RHR valves is opened unless RCS pressure is below 400 psig. -
2.
The lack of valve closure if RCS pressure rises above PHR system design pressure is acceptable because it is compensated by admini-strative and procedural controls of these valves and the warning alarm provided by OPS.
3.
The acceptability of the opening of power-operated ' valves (with ECCS functions) upon receipt of an SI signal before RCS pressure falls below ECCS design presture will be evaluated in the integrated assessment.
4.2 PRESSURE, RELIEF REQUIREMENTS The RHR system shall satisfy the following pressure relief requirements.
Recuirement:
"C.1 To protect the RHP, system against accidental overpressurization when it~is in operation (not isolated frem the RCS), prssure relief in the RHR system shall be provided with relieving capacity '
in accordance with the ASME Boiler and pressure Vessel Code.
The most limiting pressure transient during the plant operating condi-tion when the RHR system 'is not isolated from the RCS shalf be-
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considered when selecting the pressure relieving, capacity of the,
RHR system.
For example, during shutdown cooling in a PWR with no steam bubble in the pressurizer, inadvertent operation operation of an additional charging pump or inadvertent opening of an ECCS accumulator valve should be considered in selection of design bases."
Evaluation:
The RHR relief valve has a setpoint of 500 psig and a relief capacity of
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960 gpa [10]. This relief valve was not sized to accommodate the highest pressure transients postulated to, occur during RHR cooling of the RCS.
However, the Licensee analyzed these potentially most severe pressure transients during the NRC generic review of RCS overpressurization events
[11].
To prevent or mitigate these transients, the Licensee has made several procedural and hardware modifications. The hardware modifications are the B-64 Haddam Nick Safe Shutdown Revised 12/81
2.
the need for interlocks on the RHR-to-core deluge motor-operated valves to prevent opening until. RCS pressure is below RHR design pressure 5.3 Topic V-il.B RHR Interlock Requirements The safety objective of this topic is identical to that of Topic V-11 A.
The staff conclusi~ ns regarding the Haddam Neck valve interlocks are discussed.
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in, Sections 4.1 and 5.2.
Ih addition to these requirements, and as a matter to be resolved separately from the SEP, the NRC staff has determined that certain isolation valve configurations in systems connecting the high-pressure primary coolant system (PCS) to lower-pressure systems extending outside containment are potentially significant contributors to an intersystem LOCA.
Such configurations have been found to represent a significant factor in the risk computed for core melt accidents (WASH-1400, Event V). The sequence of events leading to the core melt is initiated by the failure of two in-series check valves to function as a pressure isolation barrier between the high-pressure PCS and a lower-pressure system extending beyond containment.
This causes an overpressurization and rupture of the low-pressure system, which results in a LOCA that bypassess containment.
The NRC has determined that the probability of failure of these check valves as a pressure isolation barrier can be significantly reduced if the pressure at each valve is continuously monitored or if each valvesis periodically inspected by leak testing, ultrasonic examination, or radiographic inspection.
The NRC has established a program to provide increased assurance that such multiple isolation barriers are in place in all operating light water reactor plants.
This program has been designated Multiplant Action Item MP B-45.
B-74 Haddam Neck Safe Shutdown Revised 12/81
EMCLOSURE 2 Conclusions 1.
Because of the potential for Residual Heat Removal (RHR) overpressur-
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ization, the staff has determined that the following modifications should be considered for backfit during the integrated plant safety assessment:
... ' 4 a.
Interlocks on the RHR-to-core deluge motor-operated valves to
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- prevent opening until RCS pressure is below design pressure.
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b.
% fication of the technical specifications to requir6 placing the overpressure protection system in operation whenever RHR cooling' ic in progress.
2.
The staff concludes that the Haddam Neck systems fulfill the safety objective of reliable plant shutdown capability using safety-grade
, equipment provided that plant operating procedures are modified to in-(-,
struct operators how to perform shutdown and cooldown functions with the systems identified in the minimum systems list.
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3.
The staff noted during the safe. shutdown evaluation that no Technical Specification. requirement governs the allowed outage time of an ECCS
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train.
The need for this requirement will be evaluated under SEP Topic XVI, " Technical Specifications".
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4.
Based on our review, the staff concludes that procedural shortcomings
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exist with respect to shutdown from outside the control room in the areas of maintenance of batteries for portable instruments, the assign-M.
ment of shutdown duties for shift personnel and emergency communications methods.
The licensee should modify his procedures to alleviate these shortcomings.
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5.
A passive failure of the common pump suction header, discharge header, or
' e the non-essential condensate service line, to which the AFS suction line is attached, would prevent the AFS from supplying feedwater to the steam generators even without an assumed consurrent single active, failure. The low probability of a passive failure in the low pressure suction line or
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in the discharge line, which is periodically tested onder the Licensee's inservice inspection program, alleviates the need for any immediate cor-rective me.:sures.
The staff intends to examine the need for a long-term
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improvement in the redundancy of the AFS at the Haddaq Neck plant.
This will be considered separately from the SEP as part of the TMI Task Action Plan (NUREG-0737), Unresolved Safety Issues A-45 and A-46, and Multi-plant Action Plan issue C-14.
We note that the licensee has committed to pro-
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vide an isolation valve in the common cross connect line and a bypass f.; f T :
valve around the suction line isolation valve by January 1,1982.
These
.N modifications will enhance the reliability of the auxiliary feedwater
.M systems.
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