ML20211B712
| ML20211B712 | |
| Person / Time | |
|---|---|
| Site: | Haddam Neck File:Connecticut Yankee Atomic Power Co icon.png |
| Issue date: | 05/28/1986 |
| From: | Stello V NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Dodd C SENATE |
| Shared Package | |
| ML20211B715 | List: |
| References | |
| NUDOCS 8606110869 | |
| Download: ML20211B712 (3) | |
Text
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~'>.... ;uS The Honorable Christopher J. Dodd United States Senate Washington, D.C. 20510
Dear Senator Dodd:
In response to your letter of May 9, 1986, we have enclosed the temporary exemption issued to the Connecticut Yankee Atomic Power Company (CYAPC0) and the associated NRC staff safety evaluation report related to a recently identified single-failure vulnerabfiity at the Haddam Neck plant. The enclosure provides a detailed description of the technical basis upon which the NRC staff concluded that plant operation will not present an undue risk to,the public health and safety until CYAPC0 can develop r.nd implement a permanent design change to correct this vulnerability. '
On' March 25, 1986, while the plant was shutdown for refueling, CYAPC0 informed the NRC of the results of recent analyses which identified a limited range of pipe ruptures (equivalent to a 1.9 to 2.7 inch diameter opening) in loop no. 2 (Haddam Neck has four steam generator loop 3) that could potentially lead to core uncovery and subsequent overheating. The size and location of the postulated pipe rupture are such that flow from the plant's high-pressure cooling system would be diverted out the break, while there would not be sufficient loss of reactor coolant to allow the low-pressure cooling systems to provide the necessary cooling flow.
Despite the low likelihood'of this postulated event, CYAPC0 evaluated various corrective measures which could be implemented promptly to ensure that adequate cooling flow can be provided'for such events. CYAPC0 then proposed a procedure by which the operators vould alige o alternate high-pressure injection system.
In addition, other procedural n." W ! were identified which can mitigate the potential for, and consequen.e r, ,e postulated break.
The alignment of this alternate system requires that one valve be closed and another valve be opened. Failure to reposition either of these valves, when required, would prevent the alternate system from providing the necessary cooling flow. General Design Criterion 35 of Appendix A to 10 CFR 50 requires that the emergency core cooling systems be able to accomplish the safety function assuming a single failure. Thus, the reliance on these valves, even for a limited range of breaks, requires an exemption. The staff has concluded that there is reasonable assurance that these actions can be accomplished and, on that basis, concluded that the temporary exemption should be granted.
In view of the brief explanation of these circumstances in the article Mr. Peeler referred to, his concern is understandable. The NRC staff has reviewed this matter in detail to ensure that plant operation would not pose 8606110869 DR 860528 ADOCK 05000213 PDR
an undue risk. (As a point of clarification, contrary to the implications of the newspaper article, neither the Senior Resident Inspector nor the NRC Project Manager have the authority to grant such exemptions; their concurrence is required, along with that of other responsible NRC technical, legal, and supervisory personnel.)
We continue to believe that this exemption is justified. We trust that this clarification will resolve your constituent's concern.
Sincerely, b) T. A, %
ctor Stello, Jr.
Executive Director for Operations
Enclosure:
Exemption from Sin le Failure Criterion (GDC 35 - Haddam Neck Plant DISTRIBUTION Docket file NRC PDR Local PDR T. Murley G. Cunningham "
l ED0 #1733 #
! ED0 Reading H. Denton/D. Eisenhut Reply to: Mr. Mann G. Lainas 60 Was n on Street D. Crutchfield Hartfor , CT 06106 E. Rossi ISAP Reading OELD l V. Stello l D. Mossburg (ED0 #1733) l M. Schaaf F. Akstulewicz
! P. Anderson C. Grimes F. Schroeder .
F. Miraglia X
- SEE PREVIOUS SHEET FOR CONCURRENCE.
- 47 ISAP:DPL-B* ISAP:DPL-B* DD:DPL-B* D:DPL-B* DD: D:Nd oc ,
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an undue risk. (As a point of clarification, contrary to the implications of the newspaper article, neither the Senior Resident Inspector nor the NRC ;
Project Manager have the authority to grant such exemptions; their concurrence I is required, along with that of other responsible NRC technical, legal, and I supervisory personnel.) I 1
We continue to believe that this exemption is justified. We trust that this l clarification will resolve your constituent's concern. l 1
l Victor Stello, Jr. l Executive Director for Operations
Enclosure:
ExemptionfromSing)leFailure Criterion (GDC 35 - Haddam Neck Plant DISTRIBUTION ,
Docket file !
NRC PDR I Local PDR l T. Murley ,
G. Cunningham EDO #1733
- E00 Reading H. Denton/D. Eisenhut Reply o
- MF. Ed Lnn G. Lainas -
60 Washington Street D. Crutchfield Hartford, CT 0G106 E. Rossi ISAP Reading OELD V. Stello l PPA 9'(ED0 #1733) l D. Mossburg M M. Schaaf F. Akstulewicz P. Anderson l C. Grimes F. Schroeder F. Miraglia ISAP:DPL- 31 ISAP:DP W i
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ENCLOSURE
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April 28,1986 Docket No.: 50-213 Mr. John F. Opeka, Senior Vice President Nuclear Engineering and Operations Connecticut Yankee Atomic Power Company Post Office Box 270 Hartford, Connecticut 06I41-0270
Dear Mr. Opeka:
SUBJECT:
EXEMPTION FROM SINGLE FAILURE CRITERION (G0C 35) -
HADDAM NECK PLANT The Commission has issued the enclosed exemption from the single failure requirements of General Design Criteria No. 35 of 10 CFR 50, Appendix A, and the April 22, Interim 1986. Acceptece Criteria in response to your letter dated This exemption, which is being forwarded to the Office of the Fedrmal Register for publication, pertains to the requirement that the single system failure criterion be assumed in all emergency core cooling evaluations.
In particular, it exempts two valves, in the suction line for the high pressure safety injection system, located outside the containment, from single failure considerations in the event a small break break loss-of-coolant accident should occur during the period of cycle 14 operation.
Sincerely, t
gr lf0 l Frank MNiragl a, Director Cr.: L uie: Division of PWR-Licensing - 8 A: stated cr: See next page b$h 'f' l
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O Mr. John F. Opeka Connecticut Yankee Atomic Power Company Haddam Neck Plant cc:
Gerald Garfield, Esquire Day, Berry & Howard Kevin McCarthy, Director Counselors at Law Radiation Control Unit City Place Department of Environmental Hartford, Connecticut 06103-3499 Prote~ction State Office Building Superintendent Hartford, Connecticut 06106 Haddam Neck Plant RDF #1 Richard M. Kacich, Supervisor Post Office Box 127E Operating Nuclear Plant Licensing East Hampton, Connecticut 06424 Northeast Utilities Service Company Post Office Box 270 Edward J. Mroczka Hartford, Connecticut 06141-0270 Vice President, Nuclear Operations Northeast Utilities Service Company Post Office Box 270 .
Hartford, Connecticut 06141-0270 Board of Selectmen Tcur. !!all Haddam, Connecticut 06103 State of Connecticut Office of Policy and Management ATTN: Under Secretary Energy Division 80 Washington Street Hartford, Connecticut 06106 Resident Inspector Haddam Neck Nuclear Power Station
\ clo U.S. NRC i East Haddam Post Office East Haddam, Connecticut 06423 Regional Administrator, Region I U.S. Nuclear Regulatory Commission j
631 Park Avenue King of Prussia, Pennsylvania 19406 l
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UNITED STATES OF AMERICA '
NUCLEAR REGULATORY COMMISSION In the matter of ) Docket No. 50-213
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CONNECTICUT YANKEE ATOMIC )
POWER COMPANY
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HADDAM NECK PLANT
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EXEMPTION I.
The Connecticut Yankee Atomic Power Company (CYAPC0 or the Licensee) is the holder of Operating License No. DPR-61 which authorizes operation o^f Haddam Neck Plant. The License provides, among other things, that the Haddam Neck Plant is subject to all rules, regulations, and Orders of the Commission now or hereafter in effect.
The plant is a single-unit pressurized water reactor at the Licensee's site located in Middlesex County, Connecticut.
II.
On March 25,1986, (CYAPCO) reported that the results of analyses of a of a small limited range of break sizes in one loop of reactor coolant system (RCS) for which safety injectior flow during only the high pressure recirculation mode may be insufficient to provide adequate core cooling.
By letter dated April 10,1986, CYAPC0 identified measures to provide adequate core cooling in the event of a small-break loss-of-coolant accident (LOCA).
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CYAPCO's proposed immediate corrective action measures included the use of the high pressure safety injection (HPSI) system, the residual heat removal (RHR) system and certain operator actions. However, CYAPC0 noted that two valves, which are used during the HPSI recirculation mode, do not meet the prescribed single failure requirements.
Provisions requiring consideration of single failures in this context are set forth both in GDC 35 and the Interim Acceptance Criteria. GDC 35 provides, in applicable part, as follows:
A system to provide abundant emergency core cooling shall be provided ... to assure that for onsite electric power system operation (assuming offsite power is not available) and for offsite electric power system operation (assuming onsite power is not available) the system safety function can be accomplished, assuming a single failure.
Further, the Interim Acceptance Criteria, to which Haddam Neck was originally evaluated, provide as follows:
The combination of systems used for analyses should be derived from a failure mode and effects analyses, using the single failure criterion.
(Interim Acceptance Criteria for Emergency Core Cooling Systems for Light Water Power Reactors, Appendix A, Part 3, 36 FR 12249.)
l III For2 the following cases, a small break LOCA with a break size between 0.02 ft and 0.045 ft 2 in the number 2 cold leg between the charging entry nozzle and the reactor vessel or in the charging line downstream from the inline check valve, adequate recirculation flow might not be delivered to the core. 2 If the break is less than 0.02 ft , the charging pumps provide adequate makeup flow, and if the break is greater than 0.045 ft2 , the reactor coolant system (RCS) would depressurize rapidly enough to use the RHR pumps.
By letter dated April 10,1986, CYAPC0 proposed a HPSI pump recirculation mode to provide adequate flow to the core for the above cases of small break LOCAs until CYAPC0 could identify and establish a permanent resolution.
By letter dated April 22,1986, CYAPC0 requested a temporary
exemption from the single failure criteria for two valves outside of containment that would be used under procedurally defined conditions to respond to small break LOCAs. On April 23, 1986, the staff and CYAPC0 met to discuss this exemption. During this meeting, CYAPCO agreed there were several actions that could be taken to improve the emergency procedures the operators would follow to respond to such events. By letter dated April 25, 1986, CYAPC0 formalized several commitments made during this meeting, including the conduct of special training to assure operator awareness of both the actions to be taken and the reasons behind those actions.
To operate a HPSI in a high pressure recirculation mode, the HPSI system must be realigned from the RWST to the RHR pump discharge. This requires closing valve SI-MOV-24 to isolate the RWST, and opening valve RH-M0V-784 to align suction from the RHR system which draws from the containment sump .
These valves do not meet the prescribed single failure requirement. These valves are outside of containment and can be aligned manually if necessary.
Even if these valves cannot be aligned, the HPSI or charging pumps could inject water from the RWST at a rate sufficient to cool the core for several hours.
The operator will assure the core is being adequately cooled by monitoring the core exit thermocouples and reactor vessel level instrumentation.
The injection from the RWST at low flow can provide adequate time for the operator to depressurize the RCS, allowing the RHR pumps to be used in the recirculation mode.
The licensee has recently tested the valves in the HPSI suction line and determined them to be operable. Also, CYAPC0 has committed to impose a monthly surveillance and cycling requirement for these valves to provide assurance of valve operability. Additionally, during this refueling, CYAPC0 conducted a 100% ultrasonic examination of the welds in the piping between the last check valve in loop 2 charging and the RCS main loop, including the joint to which the piping segments are connected. The probability of breaks in this piping is greatest at the weld locations. This examination provides further evidence that the probability of a break occurring in this piping remains remote.
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. l Based on all of the above, the staff concludes that the measures taken by CYAPC0 will provide reasonable assurance that adequate core cooling for a small break LOCA at the Haddam Neck Plant can be accomplished.
The NRC staff's consideration of the safety aspects of the requested exemption has been discussed in detail above. The high pressure recirculation mode using the charging pumps has been found to be deficient for a narrow spectrum of breaks, whereas the safety benefits derived from using the HPSI pumps recirculation made represent a capability for a much broader range of postulated breaks. CYAPCO has estimated that the implementation of the proposed interim response measure (use of HPSI pumps during recirculation) decreases the overall core melt frequency associated with small and medium break LOCAs at Haddam Neck by approximately 27 percent over the original design.
Thus, the licensee has concluded that the granting of the requested exemption will be a net benefit to plant safety.
CYAPC0 has significantly upgraded their accident analyses for the Haddam Neck Plant in the past few years. This upgrade involved reanalyses of large and small break LOCA events, and non-LOCA events, including analyses performed in connection with the response to TMI Action Plan Items II.K.3.5. II.K.3.30, and II.K.3.31. In the recently completed probabilistic safety study (PSS) for the Haddam Neck Plant, CYAPC0 identified the ECCS system sensitivity to breaks in loop 2 or the charging line during the recirculation phase of a small break LOCA.
The present condition was identified as a result of CYAPCO's own ir.itiatives to reevaluate Haddam Neck's LOCA analyses. Once identified, CYAPC0 has shown diligence and willingness to resolve this. safety issue. In the proposed immediate corrective action, CYAPC0 identified a non-conformance with the prescribed single failure requirement. CYAPC0 promptly evaluated this
' non-conformance and provided an exemption request with a basis for operation while in non-conformance with the single failure requirement. The staff has concluded that CYAPC0 has been expeditious in its efforts to satisfy the ECCS requirements, including the IAC.
i Based on its review, the staff concludes that issuance of this temporary exemption will have no significant effect on plant safety. Further, the licensee has shown good faith in rectifying the problem and in attempting to comply with the Commission's regulations as promptly as practicabl>.
-S-IV Pursuant to 10 CFR 51.32, the Commission has determined that the granting of this exemption will have no significant impact on the environment (51 FR 15708).
Accordingly, the Commission has determined that, pursuant to 10 CFR 50.12(a)(2)(v), the requested temporary exemption is authorized by law and will not endanger life or property or the common defense and security.
Therefore, the Commission hereby grants the temporary exemption from the requirements of General Design Criteria 35 of Appendix A to 10 CFR Part 50 ano tne Interim Acceptance Criteria for valves RH-MOV-784 and SI-MOV-24 for the period of cycle 14 operation. By September 1986, CYAPC0 shall provide a description of the long-term resolution of this issue and a schedule for completion of any plant modifications. Thereafter, the Director of the Office of Nuclear Reactor Regulation may extend the period of this exemption for good cause shown.
A copy of the Safety Evaluation dated April 28, 1986, related to this action is available for public inspection at the Comission's Public Document Room,1717 H Street, N.W., Washington, D.C., and at the local Public Document Room, incated at the Russell Library,123 Broad Street, Middletown, Connecticut 06457. A copy may be obtained upon written request addressed to the U.S. Nuclear Regulatory Commission, Washington, D.C.
20555, Attention: Director Division of PWR Licen' sing-8.
This Exemption is effective upon issuance.
Mtc at Bethesda, Maryland this 28thday of April 1986.
FOR THE NUCLEAR REGULATORY COMMISSION d^ WC Frank J. hragli'a, rector Division of PWR Licensing - 8 Office of Nuclear Reactor Regulation l
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SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGUL RELATIVE TO TEMPORARY EXEMPTION FROM SINGLE FAILURE REQ HADDAM NECK PLANT ,
DOCKET NO. 50-213
~ 1. 0 INTRODUCTION The licensee for the Haddam Neck plant recently identified a range of break sizes in one reactor system cold leg for which adequate small break LOCA protection was not assured.
Before startup of the plant from the current refueling outage, the licensee proposes to implement a temporary fix that will provide protection for all break sizes and locations. The temporary fix involves utilizing a mode of ECCS operation that does not meet the single failure requirements of GDC 35 of 10 CFR Part 50, Appendix A, or the Interim Acceptance Criteria for Emergency Core Cooling Systems. Haddam Neck is not required to conform to the final ECCS rule, as described in 10 CFR 50.46, or Appendix X to '
10 CFR 50, since these apply only to plants with zirconium alloy fuel cladding and Haddam Neck utilizes stainless steel fuel cladding.
2.0 EXEMPTION REQUESTED By letter dated April 10,1986, CYAPC0 proposed a HPSI pump recirculation mode to provide adequate core cooling for a limited range of small break LOCAs.
CYAPCO's proposed interim fix requires realigning the HPSI pumps from the RWST to the RHR pump discharge. Two valves which are used during this realignment do not meet the prescribed single failure requirements.
CYAPC0 request a temporary exemption from the single failure requirements for the HPSI pump recirculation mode of operation to mitigate the consequences of a small break LOCA.
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3.0 DISCUSSION At a minimum, the RWST contains 230,000 gallons,of borated' ater.
Recirculation is begun by procedure after 100,000 gallons have been injected. This leaves 130,000 gallons, of which approximately 100,000 gallons could be injected, as needed, if difficulties are encountered in initiating or maintaining recirculation from the sump.
Both high and low pressure recirculation flow is provided. Low pressure flow is from the containment sump through the RHR pumps and heat exchangers and into the core deluge lines. High pressure flow is provided by aligning the suction of the charging pumps to the RHR heat exchanger discharge. The charging flow is injected into the cold leg of loop 2.
For a range of small break sizes, the reactor system pressure would remain above the RHR pump discharge head so that recirculation would only be accomplished by the charging pumps.
The licensee's ECCS evaluations have concluded that the recirculation flow from one charging pump (360 gpm) is adequate to maintain core cooling following a small break LOCA.
Large and intermediate break sizes would allow the reactor system to depressurize sufficiently for low pressure recirculation to be effective. .However, if a small break were to occur in the number 2 cold leg between the charging nozzle and the reactor vessel or in the charging line downstream from the inline check valve, adequate recirculation flow might not be delivered to the core.
4.0 EVALUATION The licensee has developed a procedure by which recirculation flow could be established using either of the two high pressure safety injection (HPSI) pumps in tandem with the RHR pumps. The HpSI path would be used instead of the charging path for break sizes which depressurize the reactor system below 1500 psig.
Steam formation cannot occur within the reactor core above 1500 psig for small break LOCA's and maintenance of the reactor system pressure above 1500 psig indicates that the charging system is providing adequate core cooling.
One HPSI pump can deliver considerably more flow to the cold legs than the charging pumps; therefore, the safety injection capacity assumptions of the original IAC ECCS analysis will be maintained. lo enhance HPSI recirculation flow, reactor system depressurization will be increased by opening a PORV on the pressurizer.
Opening the PORV might cause additional water to be lost from the reactor system. This is not of concern since the pressurizer surge line leading from the hot leg to the pressurizer is well above the core. Before the core could begin to uncover, the level in the reactor system would have to drop below the surge line elevation. At that point, only steam could flow from above the core into the pressurizer and out the PORV. The HPSI flow capacity is in excess of the requirements for core coverage under these conditions.
The licensee evaluated the consequences of a break in one of the HPSI injection lines because the location of a small break LOCA cannot be readily established from instrument readings. If the break were between the injection nozzle and the first check valve, water from the HPSI pump might not reach the reactor system. The HPSI injection line is larger than the charging line and the licensee determined that a rupture of a HPSI line would depressurize the reactor system below 150 psig before the start of recirculation. At this pressure, the RHR pumps would be able to inject into the reactor system through a different nozzle and provide adequate cooling.
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However, use of the HPSI pumps in the recirculation mode is susceptible to single failure. The valve aligning the pump suction to the RHR pump discharge must be opened and the valve aligning the pump suction to the RWST must be closed. These valves are outside containment and can be aligned manually if required.
The licensee has recently tested the valves and determined them to be operable.
In addition, the licensee has committed to a valve testing program with independent verification at 30-day intervals during operation.
Implementation of this testing program will require a technical specification change to be submitted later.
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In the event the above measures are not sufficient to keep the core covered, the licensee has committed to provide additional defense in depth measures to ensure core cooling, which will be written into the plant emergency procedures before restart. These procedures will provide for injection of the additional water remaining in the RWST at a rate sufficient to provide core cooling until the reactor system can be depressurized allos:ing the RHR pumps to provide recirculation.
The operator can monitor core cooling at Haddam Neck using core exit thermocouples and reactor vessel level instrumentation. Sufficient water remains in the RWST following the initial injection of 100,000 gallons to provide core cooling for several hours, thus providing adequate time for operator action.
5.0 CONCLUSION
The staff concludes that the' protective measures described by the licensee increase plant safety and that core cooling at Haddam Neck will be adequate following a small break LOCA.
Dated: April 28,1986 Principal Contributor: W. L.,Jensen l
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% g EDO PRINCIPAL CORRESPONDENCE CONTROL FROM: DUE: 05/29/86 EDO CONTROL: 001733 DOC DT: 05/09/86 SEN. CHRISTOPHER J. DODD FINAL REPLY:
TO:
KAMMERER FOR SIGNATURE OF ** GREEN ** SECY NO: 86-467 EXECUTIVE DIRECTOR DESC: ROUTINO:
ENCLOSES LTR FM PHILIP H. PEELER, UNITED RETAIL & MURLEY INDUSTRIAL UNION EXPRESSING CONCERN RE ACTION GCUNNINGHAM TAKEN BY NRC TO GRANT SAFETY EXEMPTION TO HADDAM NECK PLANT DATE: 05/14/86 ASSIONED TO: NRR CONTACT: DENTON SPECI A' INSTRUCTIONS OR REMARKS:
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NRR RECEIVED: 5/15/86 / s ACTION: OPLB:MIRAGLIA j'
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NRR ROUTING:' DENTON/EISENHUT PPAS M0SSBURG L
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r OFFICE OF THE SECRETARY CORRESPONDENCE CONTROL TICKET PAPER NUMBER: CRC-86-0467 LOGGING DATE: May 13 86 ACTION OFFICE: EDO i
AUTHOR: C.J. Dodd--Const Ref AFFILIATION: U.S. SENATE LETTER DATE: May 9 86 FILE CODE: C&R-2 BP
SUBJECT:
Express concern about action taken by the NRC to grant a safety exemption to the Ct Yankee Power plant ACTION: Direct Reply DISTRIBUTION: OCA to Ack SPECIAL HANDLING: None NOTES: Philip H. Peeler DATE DUE: May 23 86 SIGNATURE: . DATE SIGNED: j AFFILIATION:
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og1733 Rec'd Ott, EDO %I Date T ' / V - 76 l 1;raa . /J N /./
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