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Cracking under pressure

Scottish CND report on reactor problems on Polaris submarines




1.1 nuclear powered submarines accidents 3

1.2 earlier problems with PWR 1 4

1.3 problems on ageing submarines 5


2.1 submarines affected 6

2.2 nature of reactor defect 8

2.3 dangers of loss of coolant accident 9


3.1 development of techniques 10

3.2 conduct of inspections 11

3.3 repairs 12

3.4 hazards posed to workers 12



4.2 use of Resolution class 13

4.3 comparison of Resolution and other classes 14



5.2 Resolution class 1992 - 1997 15


6.1 concern about emergency cooling system 15

6.2 incident on HMS RESOLUTION January 1988 16


ANNEX A nuclear powered submarine accidents 19

ANNEX B problems with PWR 1 20

ANNEX C status of ten older submarines 21

ANNEX D refits of Resolution class 22

ANNEX E deployment of Resolution class 1990/92 22

ANNEX F availability of Polaris subs. 1985/97 24

ANNEX G anonymous information given to SCND 25

notes and references 26


There is a serious defect which affects the reactors on nuclear powered submarines in the Royal Navy. The measures which have been taken to adjust to this problem have been inadequate. Polaris submarines have been used on operational patrols when on safety grounds they should have been kept in port.

A substantial weight of evidence has been assembled from a variety of sources. Submarine movements have been monitored and analysed. Individuals with knowledge of these matters have volunteered information. There has been a thorough search through published work covering both the recent situation and the accident record of British nuclear powered submarines.

This report has been compiled by Scottish CND and Faslane Peace Camp. Both groups are committed to creating a country free from nuclear weapons. However, the concerns expressed are shared by a wider cross-section of people, including some of those who have served and are serving on these submarines.

John Ainslie,

Scottish CND,

1st June 1992


DED Docking and Essential Defects

MoD Ministry of Defence

MODIX Reactor pipework decontamination process

PWR Pressurised Water Reactor

RRA Rolls Royce and Associates Ltd

SCRAM rapid insertion of control rods

VSEL Vickers Shipbuilders & Engineering Ltd

page 2 1. BACKGROUND


The Royal Navy operates a fleet of nuclear powered submarines, including the Resolution class which carry Polaris missiles. The reactors on these submarines are significantly smaller than land based reactors, however they are exposed to greater dangers. Nuclear powered submarines from both the American and former Soviet navies have been lost at sea. Although no Royal Navy nuclear powered submarine has been lost, several have been involved in major accidents [1].

a. Fire

Any fire on a submarine has the potential to become a major incident. Even if it is some distance from the reactor compartment, a fire can have serious implications for the safe operation of the nuclear plant. There have been at least 19 fires on nuclear powered submarines of the Royal Navy between 1963 and 1992 [Annex A.1].

There was a major fire on board HMS WARSPITE on 2ndMay1976 at Liverpool docks. A coupling failed and sprayed oil over the diesel generator room. This room provides power for elements of the adjacent reactor compartment. The fire lasted for five hours and lagging was still smoking many hours later. Five people were taken to hospital and one Marine Engineer Artificer was seriously injured. It was reported that Merseyside Fire Brigade who attended the scene were kept on stand-by for 2 weeks [2]. A generator had to be welded onto the outside of the casing of the submarine. Damage was so extensive that repairs took 105 weeks to complete and cost 8.8m [3].

On 30th April 1992 there was an electrical explosion in the switchroom of HMS TURBULENT which was preparing to leave Devonport. This resulted in a fire in the compartment, next to the reactor. The nuclear plant was working at the time of the explosion but was shut down automatically. The fireman in charge at the scene said that his men were met with a wall of intense heat and that the fire took 3 hours to extinguish. He also reported that the cramped conditions made their task particularly difficult. Due to a failure in the ventillation system fumes spread throughout the boat and 24 casualties suffering from smoke inhalation were taken to hospital [4].

b. Collision

There have been at least 6 collisions involving British nuclear powered submarines between 1963 and 1992 [Annex A.2]. Land based reactors are only exposed to the more remote hazard of an aircraft colliding with the plant.

At Faslane in January 1973 HMS REVENGE, which was being taken out of the dry dock, collided with HMS REPULSE. The hydroplanes on HMS REPULSE were damaged and had to be replaced immediately [5]. HMS REVENGE was probably carrying a full

complement of missiles and nuclear warheads at the time.

page 3 HMS SCEPTRE collided with a Soviet submarine while both vessels were submerged in the Barents sea in the early 1980s. The propeller of the Soviet submarine scratched the casing of HMS SCEPTRE. In order to regain power, the reactor on the British submarine was given a "battleshort". The automatic shutdown or SCRAM of a submarine reactor can result in the submarine going into an uncontrolled dive [6]. A "battleshort" is a manual override of reactor safety systems.

c. Fishing boats

The MoD has detailed 12 incidents between 1980 and 1990 involving Royal Navy submarines and fishing vessels [AnnexA.3]. There have been others before and since. The sinking of the ANTARES by HMS TRENCHANT on 22nd November 1990 showed that the Captain of a submerged submarine may not have a clear picture of the position of vessels on the surface [7]. Operational Polaris submarines do not use active sonar for fear of revealing their position. Passive sonar is used but the information which it provides is less precise.

d. Grounding

There have been a number of occasions when submarines have been grounded [Annex A.4]. It is believed that a grounding incident in 1986 led to the premature decommissioning of the USSNathanael Green [8]. It is likely that the shock of a grounding incident would lead to a reactor shut down. Water for the Emergency Cooling System may only be available from ballast tanks if the vessel is grounded.

e. Breakdown at sea

Mechanical breakdowns at sea are quite common and can present a hazard. Five such occasions have been noted [Annex A.5]. One of the most dramatic involved HMS REVENGE. There was a major steam leak in the turbo generator room. One member of the crew crawled along a foot wide catwalk beneath a hot cloud of escaping high pressure steam searching for the leak. It was said that his action prevented a major disaster. In May 1978 he was one of two submariners presented with awards for gallantry relating to this incident [9].

f. Loss of power

There are automatic systems which shut down the reactor to prevent a melt down. Emergency shut downs or SCRAMs occurred on 106 occasions on Royal Navy submarines between 1975 and 1979. This included 50 accidental SCRAMs, 29 of which were due to human error [10]. A sudden loss of power can threaten the safety of the submarine [11].


a. Background

British research into Pressurised Water Reactors [PWR] began at Harwell in 1954. Rolls Royce and Associates [RRA] was formed in 1959 to facilitate the transfer of technology from

page 4 the United States to Britain [12]. The Dounreay Submarine Prototype Reactor was established at HMS Vulcan in 1962. This incorporated features of both British PWR development and the American Westinghouse S5W design.

The first United States Navy submarine to be powered with this Westinghouse reactor was commissioned in 1959. The Royal Navy was supplied with a similar reactor for HMS DREADNOUGHT, which was commissioned four years later. Under the sales agreement the United States undertook to provide information relating to problems encountered with the reactor on HMSDREADNOUGHT during its lifetime. However, having supplied the initial reactor and design details, the United States was not willing to supply information about modifications [14]. There has not been a continuous sharing of expertise. RRA has relied on its own experience based on the performance of the unique prototype at Dounreay and the reactors in service on Royal Navy submarines.

b. Refits and DEDs

Major work on the reactor of a nuclear powered submarine is carried out during refits. The reactor is refuelled and essential repairs are carried out. 1/5 of the 1000 butt welds in the reactor compartment may require cutting and rewelding [15].

18 months before a refit inspections are carried out on the submarine to assess what work will be required [16]. It might be expected that reactor defects would be detected at this stage or when the vessel arrives at the dockyard. However it is apparent that on several occasions significant reactor defects have only been discovered during the closing stages of a refit. Problems were detected during final power testing on HMS RESOLUTION in 1976, on HMS RENOWN at the end of a refit in 1980, during a Docking and Essential Defects [DED] on HMS WARSPITE in 1984 and at the end of a refit on HMSVALIANT in 1988 [AnnexB.1].

RRA has facilities to develop and practice repair techniques at Dounreay and elsewhere [17]. Nevertheless there have been cases where serious reactor problems have been detected for which no tried and tested repair methods were available. There are references to "innovative engineering" on HMSWARSPITE during a DED in 1984, a "major innovative repair" on HMS REPULSE in 1986 and "novel tasks" carried out on the reactor of HMS VALIANT in 1988 [Annex B.1].

c. Problems encountered while in service

HMS VALIANT was at sea off the coast of Cornwall in May 1981 when there were difficulties with the reactor. On returning to Devonport it was discovered that there were small cracks in part of the Primary Coolant Circuit. 6 months earlier the reactor on board HMS DREADNOUGHT was shut down because of major machinery damage. HMS DREADNOUGHT was subsequently decommissioned. Problems on the two vessels may have been related [Annex B.2].

page 5 There were problems with the materials used in the seals of valves. Corrosion of seals could have led to a major and catastrophic loss of coolant. No assistance was provided from the United States Navy which had been aware of the problem [18].


a. Design life

It is clear that the original design life of Resolution class submarines was 20 years [19]. With regard to Vanguard class submarines the plant life for PWR 2 is the same as the planned submarine life [20]. It is reasonable to assume that in the 1960s the MoD asked RRA to supply a reactor system which would operate safely for 20 years. This design life expired in the Valiant class in 1987, Resolution class in 1989 and Churchill class in 1992.

b. Problems encountered

Systems on board the submarine were designed with this lifespan in mind. In addition to reactor fractures it is apparent that there have been a series of defects affecting ageing nuclear powered submarines. These problems are liable to multiply the longer a vessel is in service and could affect the safety of reactor operations.

As a submarine becomes older, restrictions are placed on how deep the vessel can dive. It is believed that Resolution class submarines have had difficulty in passing diving trials.

There were noise problems on HMS RESOLUTION which resulted in a visit to Rosyth in 1986/87 for special repairs. Regular visits to Loch Goil indicate that there may also have been noise problems with HMS REVENGE from 1990 to 1992.

HMS REPULSE was engaged in a month of trials operating from Coulport in Spring 1992 suggesting that there may have been problems with the vessel.



a. Valiant class

In December 1989 a major defect was discovered in the reactor on HMS WARSPITE during a refit at Devonport [1]. There has been conflicting information on whether or not a cost effective repair was possible [2]. In September 1990 it was announced that the vessel would be decommissioned.

HMS VALIANT was berthed at Faslane from January 1990 to June1991. The submarine was then in use for less than a year. In April 1992 there was a formal farewell for the vessel before she sailed to Rosyth [3]. It is likely that the submarine is due to be decommissioned.

page 6 b. Resolution class

HMS RENOWN arrived at Rosyth for her third refit in October 1987 [4]. By early 1990 the submarine had been taken out of the refuelling dock and was almost ready to leave. It was then decided to carry out extra work on the reactor. Either fractures were found or it was decided that major preventative action was required to ensure they would not appear [5]. This work has taken more than 2 years. As well as the fracture problem there have been a series of other defects. The total time required for the refit has been revised from two years to five years [6].

On 9th December 1991 it was announced that HMS REVENGE would not be given the third refit scheduled but would be scrapped [7]. There had been indications earlier in the year that this would happen.

It is reasonable to assume that the probability of the defect occurring will increase with the number of years the reactor has been in operation. The length of service of individual submarines can be estimated by deducting time spent in refits from the total time since a vessel was first commissioned [AnnexD.2]. This calculation shows service life as: HMSRENOWN 15years 11 months, HMSREVENGE 18 years 5 months, HMS REPULSE 18 years 8 months, and HMS RESOLUTION 20 years. There was serious concern about HMS RENOWN which has spent the shortest time in service and so there ought to be even greater concern about the other three Polaris boats.

c. Churchill Class

The defect found on HMS WARSPITE was also found on HMSCHURCHILL. HMS CHURCHILL was in refit at Rosyth where she remains. In September 1990 it was announced that the boat would be decommissioned. The problem with the boat was only revealed in June 1991, by the House of Commons Defence Committee [8].

The decommissioning of HMS CONQUEROR was announced in July 1990 and the submarine was towed out of Faslane on 30 August 1990 [9]. While there has been no indication of the problem with HMSCONQUEROR it is clear that a serious fault was discovered shortly after the defect was found on HMS WARSPITE.

HMS COURAGEOUS was berthed at Faslane from January 1990 until July 1991. The boat was then in use for less than one year. In April 1992 she was flying a decommissioning flag immediately before sailing to Devonport Dockyard [10].

There are now no Valiant or Churchill class submarines in service. While this was explained as due to defence cuts, the material state of the vessels was a major factor [11]

d. Swiftsure Class

HMS SWIFTSURE is currently in Rosyth dockyard. While it is possible that a refit may be taking place, the concensus of opinion is that the boat will be decommissioned.

page 7 HMS SPARTAN, HMS SCEPTRE and HMS SUPERB have all been berthed at Faslane for long periods of time during 1991 and 1992 [12]. This may have been to enable detailed inspections to take place.

e. Trafalgar class

When the defect was first noticed in January 1990, Trafalgar class submarines were being used to carry out tasks previously assigned to other vessels. There have been no obvious signs that these newest submarines are affected. However the MoD has said that when the defect was found on HMS WARSPITE an inspection process was begun affecting all nuclear powered submarines [13].

f. Vanguard class

The new Vanguard class submarines which will carry Trident missiles have a completely new reactor, the PWR 2. However when questioned about the possibility of the defect having implications for Vanguard class, the MoD have not given the categorical denial of any risk which might have been expected [14].

g. Submarines most at risk

There is some concern about the nuclear reactors on all nuclear powered submarines, which has necessitated a comprehensive inspection programme. However there are indications that the ten oldest submarines were most at risk.

It has been said that a substantial change in design was made after the first ten PWR reactors were built [15]. RRA carried out research into a problem affecting ten boats [para2.2]. Of these ten submarines eight are not currently in service: HMSVALIANT, WARSPITE, RENOWN, REVENGE, CHURCHILL, CONQUEROR, COURAGEOUS and SWIFTSURE. Only HMS REPULSE and RESOLUTION are currently in use [Annex C].


It is apparent that fractures were discovered in the Primary Cooling circuit of the PWR 1 reactors. The weak points in the circuit are welds joining two different alloys. There are a number of factors which can weaken the welds. Firstly, radiation has a detremental effect. Secondly, fluctuations in temperature can make the metal more brittle. Thirdly, poor water chemistry in the coolant circuit can contribute to corrosion [16].

In Spring 1991 a worker at VSEL in Barrow was commended for a project completed for RRA. A large volume of welding was carried out in order to replicate techniques which had been used in the 1950s and 1960s. A weld was made between two different types of steel. The 500kg test piece had to be continuously heated to 150 C. A photograph shows that it could be a junction on the Primary Circuit of the PWR 1

page 8 reactor. The welder said that 40 such welds had been completed in the 1960s. This could refer to 4 welds on each of the 10 earliest PWR 1 reactors [17]. It is believed that a different type of welding was used on the Dounreay Submarine Prototype and so this particular problem may not have been encountered in advance.

The primary coolant enters the pressure vessel of the PWR 1 reactor through 2 pipes, circulates around the fuel rods and then leaves the pressure vessel by 2 further pipes, each of which leads to one of the Steam Generators.

The defect is present on the 2 pipes through which primary coolant flows from the Pressure Vessel to the two Steam Generators. These are refered to as the "hot legs" of a PWR. The problem could appear at the junctions with the Pressure Vessel, or the junctions with the Steam Generator.

The welds to the Pressure Vessel are exposed to direct radiation from the fuel rods. This is liable to weaken them. This problem has been described as both acute and very difficult to repair [18]. It has been reported that Engineers from RRA were developing advanced techniques in order to carry out work inside the Pressure Vessel of a submarine berthed at Faslane during 1991.

There have been several reports that there is a problem at the Steam Generator junction. Inside the Steam Generator one large bore header feeds into a large number of small bore tubes. There appears to be a problem where the pipe from the Pressure Vessel joins the header. It is difficult to gain access to this area [19].

Reports of work carried out on HMS VALIANT at Rosyth in 1988 may be relevant. A difficult problem was encountered at the end of the refit which required RRA to design a remote tool to carry out a repair on the Steam Generating system. The task was not in the work specification and the problem had not been encountered before. There were difficulties in gaining access to the area concerned [20]. The refit was extended by 6 months to complete the task. A submariner has suggested that the defect discovered on HMS WARSPITE in 1989 was first encountered on HMS VALIANT [21].


If there is a significant risk of fractures then the probability of a major rupture occurring in the primary circuit is substantially increased. A major rupture would result in the release of a large amount of radioactive primary coolant into the reactor compartment and other parts of the submarine.

The consequences of an accident are described in the Clyde Public Safety Scheme:

"A more serious kind of accident would begin with a leak in the primary coolant system brought about for example by pipe

page 9 failure. As a result of the loss of coolant water the fuel cladding could eventually melt, releasing radioactive fission products into the compartment containing the reactor ..... If, following these events, the submarine's primary containment were itself to fail to some degree fission products would become dispersed throughout the submarine" [22].

There is also a possibility of more extensive damage. During the initial rupture there would be a steam explosion. If this was very severe it could result in damage to the Reactor Pressure Vessel and a major disaster [23].

A major rupture of the Primary Circuit would endanger the lives of those on board the vessel, particularly if the accident took place at sea. If the accident could not be effectively contained there would be a significant radiation risk to the general public. The problem could be complicated by a failure in the Emergency Cooling System.

RRA have conducted experiments into Loss of Coolant Accidents using the decontaminated Dounreay Submarine Prototype, with an electrical heater replacing the reactor core [24]. It can be assumed that these have been used to support safety cases made between 1990 and 1992.



On 18 January 1990 HMS RESOLUTION returned to Faslane after 4days of a 10 day exercise [1]. By the end of January all Valiant, Churchill and Resolution class submarines were either berthed or in refit, except for one Resolution class on patrol. The MoD said that submarines would be inspected when they returned from patrol [2]. HMS WARSPITE was used as a test bed for inspection techniques. A two stage inspection process was implemented. By November 1990 the second stage had not been carried out on HMS VALIANT, HMS COURAGEOUS, HMSSWIFTSURE or HMS SOVEREIGN [3].

Inspection involved highly complex work and there have been problems with access to the affected area [4]. This has contributed to the time taken [5].

The ability to carry out a complex task on a PWR 1 reactor is restricted by the level of radioactivity in the compartment. This can be reduced by decontamination processes. A major source of radioactivity is the build up of crud on the inside of the Primary Circuit which increases with the service life of the reactor [6]. In April 1980 HMSREVENGE began a refit at Rosyth. Levels of radiation were such that it was calculated that the refit could take 3 years [7]. As an

alternative it was decided to decontaminate the Primary Circuit pipework. This process produced 7.3 curies of radioactive waste [8]. The original process was replaced by a new process in 1985 which was used at the first stage of refits from 1986 onwards [9].

page 10 Detailed inspection would be most easily carried out on reactors which were undergoing refit and which had been decontaminated. This would apply to HMS WARSPITE, HMSCHURCHILL and HMS RENOWN. It would appear that the fault was found on at least two and possibly all three.

The ability to carry out a detailed inspection, other than after decontamination, should be questioned. The MODIX process has only been used at dockyards and takes 3 months [10]. There is no evidence to suggest that reactors at Naval Bases have been decontaminated to facilitate inspection work.

The use of remote technology to conduct work in PWR 1 reactors has in the past been problematic [11]. The compartment is cramped and initial attempts to use remote machinery during refits were not successful. On at least one occasion a job which should have been done by machine was done by hand [12].

The inspection techniques may not be able to adequately judge the seriousness of the problem. Restrictions were placed on visits to foreign ports because of a concern that problems with cracks might be worse than assumed [13].

In order to provide adequate safety, inspection techniques would have to prove a high level of success in detecting fractures at an early stage and before they constituted a serious safety hazard. The length and nature of planned reactor operations following the inspection would have to be taken into account.


It is apparent that thorough inspection techniques were not available during the first half of 1990. Despite this, all three available Resolution class submarines were sent on patrol [Annex E].

It would appear that in the case of HMS REPULSE a routine inspection did not detect any problems and the submarine was sent out on patrol. After the vessel returned to Faslane in July 1990 a fault in the reactor was discovered. It is not unreasonable to assume that the defect was present before and during the patrol.

Between July 1990 and July 1991 HMS RESOLUTION was used so extensively for patrolling that the longest period spent at Faslane was only 54 days. As the reactor had to be allowed to "cool down" it is unlikely that this was long enough to carry out a thorough inspection. It would appear that HMSRESOLUTION was sent out on two very long patrols without a detailed inspection of the reactor having been completed. In addition, after returning from a 108 day patrol in June 1991 the submarine spent only 7 days at Faslane before being sent out for a further 30 days on patrol. After this HMSRESOLUTION spent 5 months at Faslane during which time a number of containers belonging to RRA were seen alongside. This suggests that a detailed inspection was carried out in the Autumn of 1991.

page 11 The exposure of workers during inspections will vary with each reactor. The level of radioactivity increases with the service life of the reactor. While there is no public information about this, it is known that HMS REVENGE came out of refit in January 1983, HMS RESOLUTION came out of refit in September 1984, and HMS REPULSE came out of refit in October1986 [Annex C.1]. It could be assumed that it would be most difficult to carry out an inspection of HMS REVENGE.


It is likely that a range of repairs have been attempted. An effective repair may have been carried out on HMS RENOWN at Rosyth by fixing trouser leg seals [14]. It has taken over 2years to complete this work. This reactor would have been relatively easy to work on as pipework had been decontaminated in 1987 and the vessel was in a dry dock at Rosyth dockyard.

It is unlikely that other repairs have been as effective. Some form of repair was carried out on the Steam Generator of HMSVALIANT in a 6 month period at Rosyth in 1988. Some form of repair has been made to HMS REPULSE over a 13month period at Faslane. Further work was carried out one month after the vessel returned from patrol [15].

There were reports that a pipe was ground down on HMS REVENGE following the discovery of a reactor problem in February 1990 [16]. A proper repair of the defect had not been developped at this time and would have taken longer to complete.

In 1991 two different treatments of the defect were being considered and the experts were not certain which would be the most effective [17].


There is a marked increase in the levels of radiation to which workers were exposed at Faslane in 1990 in comparison with previous years [18]. This would appear to be in connection with inspection and repair work carried out to keep vessels at sea. There are reports that workers sent from Rosyth to Faslane were exposed to high levels of radiation in order to complete work on reactors on time during 1991 [19]. There may have been a conflict between pressures to keep one Polaris boat at sea and maintaining low levels of exposure to workers.



HMS VALIANT and HMS COURAGEOUS continued in service from 1990 until 1992. Both vessels were berthed at Faslane from the beginning of 1990 for 17 months. The crews were reduced as if the vessels were in refit [1]. In April 1991 the future of both submarines was uncertain. It was suggested that they might be retained in order to provide training opportunities for submariners [2]. Containers belonging to RRA were alongside these vessels during 1991, probably carrying out inspections. HMS VALIANT went out to sea in June 1991 and

page 12 HMS COURAGEOUS in July1991. They later put to sea on several occasions, possibly to provide training for submariners. They were not used for any long patrols. In April 1992 both vessels were sailed into dockyards, probably for decommissioning.

Restrictions were placed on visits to foreign ports by nuclear powered submarines, because of concern that a nuclear accident might occur [3]. Resolution class boats do not make such visits, except to the United States.


a. Work Up Exercises

The normal routine before the start of an operational patrol is that the submarine carries out a 10 day work up exercise [4]. This is required both to ensure that the equipment on the vessel is functioning correctly and to exercise personnel in their individual tasks and as a crew. There is a short period between the end of the exercise and the departure on patrol which is used to work on any problems encountered at sea.

Between July 1990 and January 1992 the only exercise carried out by HMSREVENGE was for 4 days in November 1990. No exercises were carried out before patrols in May and July 1991. No exercise was carried out before the patrols by HMSRESOLUTION in June and December 1991 [Annex E].

The length of the exercise period required for both the vessel and crew are longer if a submarine has not been in service for some time [5]. HMS REPULSE was berthed at Faslane for 13 months. A long trials period would have been expected to follow this. The 23 day exercise period was shorter than might be expected.

b. Change Over

It takes approximately 7 days for a submarine to reach its patrol area. The submarine going out should reach its patrol area before the submarine being relieved returns to base. Between July 1990 and January 1992, change over periods were 4 or 5 days and in one case 12hours [Annex E].

c. Length of Patrols

Prior to 1989 patrols were of a regular length of around 8weeks [6]. During 1990 and 1991 patrols varied in length between 16 days and 109 days [Annex E]. The long patrols were only 4 days shorter than the longest patrol ever completed by a Royal Navy nuclear powered submarine [7].

d. Proportion of boats at sea.

In the past there were said to be an average of 1.44 Polaris boats at sea [8]. From January to December 1991 there were an average of 1.16 Polaris boats at sea Annex E].


Changes to operational practice suggest that the MoD is conscious that each of the Resolution class boats could be affected by the defect. There has been a deliberate policy of restricting the operation of Resolution class submarines to the minimum required to maintain one boat at sea at all times. This has still required extensive use of all three boats and is in contrast with the greater degree of caution exercised in the operation of HMS VALIANT and HMS COURAGEOUS. The hunter killer submarines have only been used in a limited role, after inspection techniques were developed.



Prior to 1990 the longest period of service completed by a Resolution class submarine between refits was of 7 years and 5 months completed by HMS RENOWN between 1980 and 1987 [1]. In 1977 a new type of reactor core was installed in the Dounreay Submarine Prototype. This core was fully burned up by 1985 after having been in operation for less than 8 years [2].

HMS REVENGE completed her second refit in January 1983 and it is reasonable to assume that it was planned that the third

refit would be underway by Spring 1990 [3]. This would have meant 7years service between refits.

The refit of HMS RENOWN was extended by three years and HMSREPULSE was out of action for much of 1990 and 1991. As a result HMS REVENGE was kept in use for longer than originally planned. HMS REVENGE completed her final patrol 9years and 6 month after the submarine came out of refit. While actual reactor service life is not the same as years of service this is the best guide publicly available.

It would appear that extended service did have an effect on the reactor. It has been said that the third refit of HMS REVENGE would have taken 3 years, instead of the normal 2years [4]. There have been reports of problems in operating the Control Rod Drive Mechanisms on the reactor. There have also been reports of regular losses of power.

There is reason to believe that serious problems were encountered at sea on board HMS REVENGE during an 11week patrol between December1990 and February1991. During this time there were recurring problems with the reactor on HMSREVENGE, which may have lost power on 24 occasions. Safety mechanisms were overridden to regain power.

The fuel rods were in use beyond the end of their intended life. When the reactor was running there would be a build up of fission products which would cause a shut down. This may have happened so frequently on HMS REVENGE that reactor power was only available for less than 7days at a time. The operators should have been able to predict each loss of power. It would then take several tense hours to restart the reactor because of the effects of "xenon poisoning" [5].

page 14 A large amount of power is required to start the reactor and battery supplies are limited. These can only be recharged by diesel when the vessel is close to the surface. It is possible that circumstances arose in which safety mechanisms were overridden to regain power. It is possible for a shut down of the reactor to lead to an uncontrolled deep dive of a submerged submarine [6].

When HMS REVENGE was due to go to sea again at the end of May1991, it would appear that she was not fit to complete a long patrol. She was sent out to sea for 17 days during which time HMSRESOLUTION was resupplied, changed crews and returned to sea [Annex E].

Reactor problems are likely to have recurred during the last long patrol from June to September 1991. When the submarine returned to Faslane on 23rdSeptember 1991 there was a request that the Mechanical Engineering Officer from the alternate crew be alongside when the vessel arrived. This officer is responsible for reactor operations. Immediately after the submarine berthed a number of reactor personnel went down into the reactor area.

Because of unidentified problems with HMS REPULSE, HMSREVENGE was sent out on a final short patrol in March 1992. All missiles were offloaded from the vessel in April 1992.

5.2 RESOLUTION CLASS 1992 - 1997

a. Nine year commissions

Forward planning of the deployment of Resolution class submarines of the Polaris force is not public knowledge. Nevertheless it is possible to project what this is likely to be on the basis of earlier information. It would appear that the planned life of Polaris submarines between refits in the late 1980s and 1990s was 7 years. On this basis HMS RESOLUTION should have been decommissioned in late 1991 or early 1992. However the schedule has been upset by the extended refit on HMS RENOWN. It is likely that the Royal Navy is planning to continue running HMSRESOLUTION and HMSREPULSE for 9 years [Annex F]. This could result in a whole series of problems on these vessels, including the difficulties which were experienced on HMS REVENGE.

b. Two/three boat availability

Polaris submarines have in the past only become operational after completing a 9 month post-refit trials period which culminates in missile tests in Florida. Refits at Rosyth are "back to back" [Annex D]. This means that there have been periods of around 9 months when one submarine is on trials, one is in refit and only two are available for operations. The Royal Navy are not confident that a continuous patrol can be maintained with only two boats for longer than 9 months [7].

page 15 There were only two boats in use from July 1990 to July 1991 when HMSREPULSE was out of action. With the decommissioning of HMS REVENGE in April 1992 there are again only two boats available. This will remain the case until post refit trials are completed on HMSRENOWN, which may not be until Summer 1993 [8]. If it is planned to try to keep three boats available from 1993 onwards, this can only be achieved by further extending the use of HMS RESOLUTION and HMSREPULSE.



Anonymous information obtained by Scottish CND on two occasions suggests that while there are fractures in the primary circuit these are only part of the problem. The real danger is that in the event of these fractures causing a loss of coolant accident, the safety mechanisms would not operate as intended. On one occasion it was said that the Emergency Cooling System does not work. On a second occasion it was said that the main danger is final coolant failure, which could refer to failures in the Emergency Cooling System [Annex G].

Any doubts about the reliability or effectiveness of the Emergency Cooling System is cause for serious concern. The proper functioning of this system is essential for safe operation of nuclear reactors on submarines. Any doubts over the effectiveness of this system would bear heavily on safety calculations made over the operation of submarines which may be subject to fractures in the primary circuit and to the operation of reactor cores beyond their planned service life.


In the information refered to above there were references to an incident which could have resulted in a melt down. It is almost certain that this refers to an incident on HMSRESOLUTION on 26 January 1988.

HMS RESOLUTION had completed a work up exercise and was berthed at Faslane making last minute preparations before going out on patrol. The reactor would have been at high pressure and may have been in the process of being brought up to power. It was reported that the electricity supply to the reactor coolant pumps was shut off, two back up pumps failed as did a further emergency power supply. Two crewmen raced to start up a diesel generator [1].

It is likely that there have been a number of similar occasions when there has been a loss of power, and/or failure of coolant pumps on board nuclear powered submarines. Although not unique the incident was serious. The MoD was misleading the public in describing this as a "minor electrical malfunction" [2]. Any sudden loss of coolant flow in the primary coolant circuit a PWR nuclear reactor is a serious incident.

page 16 7. CONCLUSION

There have been at least 45 serious incidents involving Royal Navy nuclear powered submarines, including fires, collisions and encounters with fishing boats. A submarine is not a safe place to put a nuclear reactor.

Submarines of the Valiant, Resolution and Churchill classes have all now past the end of the life for which they were designed. Those vessels which have been kept in service have experienced a series of problems.

There have been unofficial reports that fractures have been found in welds in the primary coolant circuit of PWR 1 nuclear reactors. It is reasonable to assume that this is the defect which led to HMS WARSPITE and HMS CHURCHILL being decommissioned. Four other submarines with similar reactors have also been withdrawn from service. It is clear that all Polaris submarines are affected by this defect.

On several occasions in the past reactor problems have only been identified at one of the nuclear submarine dockyards where such faults are rectified. Work at Rosyth to tackle the primary coolant circuit defect on HMS RENOWN has taken 2years to complete. Inspection and repair work which has been attempted on other vessels at Faslane will not have been effective. It will have been hampered by radiation levels in reactor compartments.

The nature of the fault may be such that detailed inspections will not detect the fractures in time. Inspections in themselves are unlikely to be sufficient.

Fractures in the Primary Coolant Circuit could lead to a major Loss of Coolant Accident and casualties amongst the submarine crew. There is the chance of an even more serious nuclear disaster. The consequences would be worse if, as has been suggested, the Emergency Cooling System is unreliable.

While there is concern about all Royal Navy nuclear powered submarines, the older vessels are particularly at risk. The implications of the defect have placed severe constraints on the operation of Valiant and Churchill class boats. All vessels of these classes have now been withdrawn from service.

Polaris submarines have been equally at risk from the same defect but have been used very extensively. Normal routines have been abandoned in order to maintain one Polaris submarine at sea at all times. HMSRESOLUTION spent 20 weeks at sea in a 21 week period in 1991. There were serious problems in maintaining power on board HMS REVENGE when the submarine was kept in service for nine years instead of seven. The MoD can only continue to maintain one Polaris submarine at sea into the mid 1990s by operating HMS RESOLUTION and HMSREPULSE for two years beyond their intended decommissioning date.

page 17 Because of the dangers inherent in operating nuclear reactors on board submerged warships, safety considerations should be paramount. In the interest of safety, remedial action should have been carried out at one of the dockyards before any of the older submarines was used. Submarines should certainly not have been sent on long patrols before detailed inspections had been completed.

These dangerous practices are the result of an overriding operational requirement to keep one Polaris boat at sea at all times. There is no longer any strategic rationale to support this practice [1]. The lives of submariners and the safety of the general public are being put at risk to sustain a policy which is now irrelevant.

page 18 NOTES



1 2 US and 5 Soviet nuclear powered submarines have been

lost at sea, NP3, p7; RN does not have the unimpeachable

nuclear safety record claimed, HC 69 90/91 p10.

2 Guardian 3 May 76, Times 3 May 76

3 HC 362 80/81 p115

4 Western Morning News 1, 2 May, Plymouth Evening Herald 30 Apr, 1 May

5 Not reported as a collision but fire damage. Hydroplanes

taken from HMS RENOWN in Rosyth, HA 19 Jan 73, DP 2 Feb 73.

Several reliable sources have confirmed this was a collision.

6 D Forghan, weapons officer, HMS SCEPTRE, this week, 19 Sep 91;

7 HC 369 90/91, p60, 62

8 NP3, p2

9 HA 23 Feb 79

10 Naval Nuclear Bases, p4

11 JE Moore & R Compton Hall, Submarine Warfare, Michael Joseph,

1986, p39.

12 HC 369 90/91, p86f

13 HC 316 88/89, p40f

14 HC 36 80/81,

15 Spotlight Feb 84

16 Spotlight Sep 79

17 HC369 90/91, p86f

18 This Week, 19 Sep 91

19 HC 399 72/73 px

20 HC 36 80/81 p201


1 Independent 31 Jan 90, HC 69 90/91, p27

2 HC 369 90/91 p 64; "RRA can't repair" Observer 11 Nov 90

3 Sightings from Faslane Peace Camp

4 HC 337 91/92 p3, DP Oct 87

5 Scotsman 28 Sep 91; this week, 19 Sep 91

6 HC 337 91/92 p3,5

7 HC 337 91/92 p38

8 HC 69 90/91, p30

9 HC 369 90/91 p 64

10 HC 69 90/91 p30

11 Sightings from Faslane Peace Camp

12 Sightings from Faslane Peace Camp

13 HC 337 91/92 p 37

14 HC 69 90/91 p 20

15 Reactor System Defects

16 R Farmer, This Week, 19 Sep 91; Independent 11 May 91;

Reactor System Defects.

17 VSEL Link Jun 91

18 Reactor System Defects

19 Independent 11 May 91

20 Sunday Mail 22 Feb 88; DP 4 Mar 88

21 letter from submariner, Reactor System Defects, p6


23 Naval Nuclear Bases, p3

24 HC369 90/91 p86f

page 31 SECTION 3

1 Daily Record, 22 Jan 90

2 Scotsman 31 Jan 903 HC 69 90/91, p19, 27

4 Times 29 Oct 91

5 HC 69 90/91, p27

6 Spotlight Mar 83

7 Spotlight Jun 80

8 Statistical Bulletin radioactive discarges in Scotland,

1980-84, Scottish Office

9 HC 361 88/89 p41

10 HC 479 90/91, pxiii

11 Spotlight Feb 84

12 Welding of handhole toroid on Steam Generator of

HMS RESOLUTION, Spotlight Nov 83.

13 R Farmer, This Week, 19 Sep 91

14 Scotsman 28 Sep 91

15 5 containers from RRA were alongside HMS REPULSE at

Faslane, late Jan & early Feb 92

16 Independent, 19 Nov 90

17 R Farmer, This Week, 19 Sep 91

18 HC 369 90/91, p53

19 Guardian 1 Oct 91


1 Nov 90, HC 69 90/91, p19

2 Apr 91, HC 369 90/91, p12f

3 This Week, 19 Sep 91; HC 337 91/92 p xiv

4 J Crane, The Submarine, BBC, 1984, p180f

5 HC 369 90/91, p35

6 The submarine, p197; FW Lipscomb, The British Submarine,

Conway Maritime Press, 1975, p 231

7 The submarine, p9

8 SIPRI yearbook 1986, p61


1 DP 9 May 80, 2 Oct 87;

New cores exceeded the previous limit of 6 years,

HC 479 84/5, q1897

2 Nuclear Engineering International, Mar 88

3 HA 26 Nov 82; HC 337 91/92 p 3

4 Navy News Jan 92

5 Independent 11 May 91, Scotsman 28 Sep 91

6 Submarine Warfare, p39

7 Scotsman 10 Dec 91


1 Observer 14 Feb 88

2 Guardian 15 Feb 88


1 There is no longer a need to be ready for a bolt from the blue

attack according to Michael Clarke, Director, Centre for Defence

Studies, Scotsman 7 May 1992.